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  • 1.
    Amcoff, Mirjam
    et al.
    Uppsala universitet, Institutionen för ekologi och evolution.
    Arnqvist, Göran
    Uppsala universitet, Institutionen för ekologi och evolution.
    Kolm, Niclas
    Uppsala universitet, Institutionen för ekologi och evolution.
    Courtship signalling with a labile bilateral signal: males show their best side2009In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 63, no 12, p. 1717-1725Article in journal (Refereed)
    Abstract [en]

    Asymmetries in courtship signals can result from both developmental instability during ontogeny and from temporary or permanent damage following mating, fighting, or interactions with predators. These two types of asymmetries, which can be divided into fluctuating asymmetry (FA) and damage asymmetry (DA), have both been suggested to play an important role in mate choice as potential honest indicators of phenotypic and/or genetic quality, while at the same time, DA may affect ornament asymmetry in a random manner. Interestingly, despite the massive research effort that has been devoted to the study of asymmetry during the past decades, very little is known about how an individual's behaviour relates to asymmetry. Here, we measure and characterise asymmetry in morphological courtship signals in Corynopoma riisei, a fish where males carry elaborate paddle-like appendices on each side of the body that they display in front of females during courtship. Moreover, we investigate whether male courtship display, employing this bilateral morphological trait, reflects trait asymmetry. Finally, we assess whether males respond to phenotypic manipulations of DA with corresponding changes in courtship behaviour. We show that male display behaviour is asymmetric in a manner that reflects asymmetry of their morphological courtship trait and that male display behaviour responds to manipulations of asymmetry of these paddles. Our results thus suggest that males preferentially use their best side and, hence, that males respond adaptively to temporary changes in signal trait asymmetry.

  • 2.
    Amcoff, Mirjam
    et al.
    Uppsala universitet, Zooekologi.
    Gonzalez-Voyer, A.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Evolution of egg dummies in Tanganyikan cichlid fishes: the roles of parental care and sexual selection2013In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 26, no 11, p. 2369-2382Article, review/survey (Refereed)
    Abstract [en]

    Sexual selection has been suggested to be an important driver of speciation in cichlid fishes of the Great Lakes of Africa, and the presence of male egg dummies is proposed to have played a key role. Here, we investigate how mouthbrooding and egg dummies have evolved in Tanganyikan cichlids, the lineage which seeded the other African radiations, with a special emphasis on the egg dummies. Using modern phylogenetic comparative analyses and a phylogeny including 86% of the 200 described species, we provide formal evidence demonstrating correlated evolution between mouthbrooding and egg dummies in Tanganyikan cichlids. These results concur with existing evidence, suggesting that egg dummies have evolved through sensory exploitation. We also demonstrate that there is a strong evolutionary correlation between the presence of egg dummies and both pre- and post-copulatory sexual selection. Moreover, egg dummy evolution was contingent on the intensity of pre- and post-copulatory sexual selection in Tanganyikan cichlids. In sum, our results provide evidence supporting the hypothesis of egg dummies evolving through sensory exploitation and highlight the role of sexual selection in favouring the evolution and maintenance of this trait.

  • 3.
    Amcoff, Mirjam
    et al.
    Uppsala universitet, Zooekologi.
    Hallsson, Lara R.
    Winberg, Svante
    Uppsala universitet, Fysiologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Male Courtship Pheromones Affect Female Behaviour in the Swordtail Characin (Corynopoma riisei)2014In: Ethology, ISSN 0179-1613, E-ISSN 1439-0310, Vol. 120, no 5, p. 463-470Article in journal (Refereed)
    Abstract [en]

    Pheromones constitute an important cue used by both males and females during courtship. Here, we investigate the effect of male pheromones on female behaviour in the swordtail characin (Corynopoma riisei), a species of fish where males have a caudal pheromone gland which has been suggested to affect female behaviour during courtship. We subjected female C.riisei to male courtship pheromones and investigated the effect on both female behaviour and brain serotonergic activity levels compared to a control group. While no difference in serotonergic activity was found, the pheromone-treated females showed lower stress levels compared to the control group. Furthermore, pheromone-treated females increased locomotor activity over time, while a decrease in locomotor activity was observed in the control group. These results suggest that the male courtship pheromones may serve to reduce female stress and increase female activity, possibly to aid males in gaining access to females and facilitating sperm transfer.

  • 4.
    Amcoff, Mirjam
    et al.
    Uppsala universitet, Zooekologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    A test of sensory exploitation in the swordtail characin (Corynopoma riisei) based on colour matchingbetween female prey and a male ornament2014In: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, Vol. 97, no 3, p. 247-254Article in journal (Refereed)
    Abstract [en]

    The sensory exploitation hypothesis states that pre-existing biases in female sensory systems may generate strong selection on male signals to match such biases. As environmental conditions differ between populations, sexual preferences resulting from natural selection are expected to vary as well. The swordtail characin (Corynopoma riisei) is a species in which males carry a flag-like ornament growing from the operculum that has been proposed to function as a prey mimic to attract females. Here, we investigated if female plasticity in feeding preferences is associated with plasticity in preference for an artificial male ornament in this species. Females were trained for 10 days by offering them differently coloured food items and were then tested for changes in preferences for differently coloured artificial male ornaments according to foraging experience. We found a rapid and pronounced change in female preference for the colouration of the artificial ornament according to food training. Thus our results support the possibility that sensory exploitation may act as a driving force for female preferences for male ornaments in this species.

  • 5.
    Amcoff, Mirjam
    et al.
    Uppsala universitet, Zooekologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Does female feeding motivation affect the response to a food-mimicking male ornament in the swordtail characin Corynopoma riisei?2013In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 83, no 2, p. 343-354Article in journal (Refereed)
    Abstract [en]

    Female response to various aspects of male trait morphology and the effect of female feeding motivation were investigated in the swordtail characin Corynopoma riisei, a species where males are equipped with a flag-like food-mimicking ornament that grows from the operculum. Unfed females responded more strongly to the male ornament and showed a stronger preference for larger ornaments than did fed females. Females were shown not to discriminate between artificial male ornaments of either undamaged or damaged shape.

  • 6.
    Amcoff, Mirjam
    et al.
    Uppsala University, Sweden.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Multiple male sexual signals and female responsiveness in the swordtail characin, Corynopoma riisei2015In: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, Vol. 98, no 7, p. 1731-1740Article in journal (Refereed)
    Abstract [en]

    In the courtship process, multiple signals are often used between the signaller and the receiver. Here we describe female response to multiple male visual morphological and behavioural signals in the swordtail characin, Corynopoma riisei. The swordtail characin is a species in which males display several morphological ornaments as well as a rich courtship repertoire. Our results show that high courtship intensity was associated with an increased female response towards the male ornament, increased number of mating attempts and a reduction in female aggression. The morphological aspects investigated here did not seem to correlate with female response. This may indicate that, when both behaviour and morphology are considered simultaneously, courtship behaviour may have priority over morphological cues in this species.

  • 7.
    Amcoff, Mirjam
    et al.
    Uppsala universitet, Zooekologi.
    Lindqvist, Charlotte
    Uppsala universitet, Zooekologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Sensory exploitation and plasticity in female mate choice in the swordtail characin2013In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 85, no 5, p. 891-898Article in journal (Refereed)
    Abstract [en]

    Despite extensive research in the field of sexual selection, the evolutionary origin and maintenance of preferences for sexual ornaments are still debated. Recent studies have pointed out that plasticity in mate choice might be more common than previously thought, but little is still known about the factors that affect such plasticity. The swordtail characin, Corynopoma riisei, is a tropical fish species in which males use a food-mimicking ornament to attract females. We tested whether ecological factors, more specifically prior foraging experience, can affect female preference for male ornaments. For this, we habituated females on a diet consisting of either red-coloured food or standard-coloured green food items and then we tested whether female preferences for artificially red-coloured male ornaments matched their previous foraging experience. We found a strong effect of food treatment: females trained on red food showed a stronger response to males with red-coloured ornaments than females trained on green food. Our results show that ecological variation can generate divergence of female preferences for male ornaments and that the response in preference to environmental change can be rapid if the bias is partly learnt.

  • 8.
    Arnqvist, Göran
    et al.
    Uppsala universitet, Zooekologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Population differentiation in the swordtail characin (Corynopoma riisei): a role for sensory drive?2010In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 23, no 9, p. 1907-1918Article, review/survey (Refereed)
    Abstract [en]

    Sensory drive, where the efficacy of a sexual signal depends on the environment in which it is employed, is a potential mechanism behind divergent evolution of secondary sexual traits. Male swordtail characins are equipped with a narrow and transparent extension of the gill cover with a flag-like structure at its tip. This opercular flag mimics a prey item and is employed by males as a 'lure' to attract the attention of females during mating attempts. We conducted a study of genetic and morphological differentiation across swordtail characin populations throughout their native range in Trinidad. The morphology of the opercular flag varied across populations and several aspects of this variation match the predicted hallmarks of sensory drive. First, morphological differentiation of the flag across populations was unrelated to genetic similarity at neutral genetic markers. Second, the shape of the flag covaried with those aspects of body shape that should reflect adaptation to different feeding regimes. Third, and most importantly, the shape of the flag covaried across populations with those environmental characteristics that should most closely reflect differences in local prey abundance. Overall, our results are consistent with a scenario where the evolution of this male sexual signal tracks food-related shifts in female sensory biases across populations, thus providing at least provisional support for a role for sensory drive in population differentiation.

  • 9. Bloch, Natasha
    et al.
    Corral-López, Alberto
    Stockholm University, Faculty of Science, Department of Zoology.
    Buechel, Severine D.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Mank, Judith E.
    Early neurogenomic response associated with variation in guppy female mate preference2018In: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 2, no 11, p. 1772-1781Article in journal (Refereed)
    Abstract [en]

    Understanding the evolution of mate choice requires dissecting the mechanisms of female preference, particularly how these differ among social contexts and preference phenotypes. Here, we studied the female neurogenomic response after only 10 min of mate exposure in both a sensory component (optic tectum) and a decision-making component (telencephalon) of the brain. By comparing the transcriptional response between females with and without preferences for colourful males, we identified unique neurogenomic elements associated with the female preference phenotype that are not present in females without preference. A network analysis revealed different properties for this response at the sensory-processing and the decision-making levels, and we show that this response is highly centralized in the telencephalon. Furthermore, we identified an additional set of genes that vary in expression across social contexts, beyond mate evaluation. We show that transcription factors among these loci are predicted to regulate the transcriptional response of the genes we found to be associated with female preference.

  • 10.
    Buechel, Séverine D.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Booksmythe, Isobel
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Jennions, Michael D.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Artificial selection on male genitalia length alters female brain size2016In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 283, no 1843, article id 20161796Article in journal (Refereed)
    Abstract [en]

    Male harassment is a classic example of how sexual conflict over mating leads to sex-specific behavioural adaptations. Females often suffer significant costs from males attempting forced copulations, and the sexes can be in an arms race over male coercion. Yet, despite recent recognition that divergent sex-specific interests in reproduction can affect brain evolution, sexual conflict has not been addressed in this context. Here, we investigate whether artificial selection on a correlate of male success at coercion, genital length, affects brain anatomy in males and females. We analysed the brains of eastern mosquitofish (Gambusia holbrooki), which had been artificially selected for long or short gonopodium, thereby mimicking selection arising from differing levels of male harassment. By analogy to how prey species often have relatively larger brains than their predators, we found that female, but not male, brain size was greater following selection for a longer gonopodium. Brain subregion volumes remained unchanged. These results suggest that there is a positive genetic correlation between male gonopodium length and female brain size, which is possibly linked to increased female cognitive ability to avoid male coercion. We propose that sexual conflict is an important factor in the evolution of brain anatomy and cognitive ability.

  • 11.
    Buechel, Séverine D.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Boussard, Annika
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    van der Bijl, Wouter
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Brain size affects performance in a reversal-learning test2018In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 285, no 1871, article id 20172031Article in journal (Refereed)
    Abstract [en]

    It has become increasingly clear that a larger brain can confer cognitive benefits. Yet not all of the numerous aspects of cognition seem to be affected by brain size. Recent evidence suggests that some more basic forms of cognition, for instance colour vision, are not influenced by brain size. We therefore hypothesize that a larger brain is especially beneficial for distinct and gradually more complex aspects of cognition. To test this hypothesis, we assessed the performance of brain size selected female guppies (Poecilia reticulata) in two distinct aspects of cognition that differ in cognitive complexity. In a standard reversal-learning test we first investigated basic learning ability with a colour discrimination test, then reversed the reward contingency to specifically test for cognitive flexibility. We found that large-brained females outperformed small-brained females in the reversed-learning part of the test but not in the colour discrimination part of the test. Large-brained individuals are hence cognitively more flexible, which probably yields fitness benefits, as they may adapt more quickly to social and/or ecological cognitive challenges. Our results also suggest that a larger brain becomes especially advantageous with increasing cognitive complexity. These findings corroborate the significance of brain size for cognitive evolution.

  • 12.
    Buechel, Séverine D.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Noreikiene, Kristina
    DeFaveri, Jacquelin
    Toli, Elisavet
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Merilä, Juha
    Variation in sexual brain size dimorphism over the breeding cycle in the three-spined stickleback2019In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 222, no 7, article id UNSP jeb194464Article in journal (Refereed)
    Abstract [en]

    Snapshot analyses have demonstrated dramatic intraspecific variation in the degree of brain sexual size dimorphism (SSD). Although brain SSDis believed to be generated by the sex-specific cognitive demands of reproduction, the relative roles of developmental and population-specific contributions to variation in brain SSD remain little studied. Using a common garden experiment, we tested for sex-specific changes in brain anatomy over the breeding cycle in three-spined stickleback (Gasterosteus aculeatus) sampled from four locations in northern Europe. We found that the male brain increased in size (ca. 24%) significantly more than the female brain towards breeding, and that the resulting brain SSD was similar (ca. 20%) for all populations over the breeding cycle. Our findings support the notion that the stickleback brain is highly plastic and changes over the breeding cycle, especially in males, likely as an adaptive response to the cognitive demands of reproduction (e.g. nest construction and parental care). The results also provide evidence to suggest that breeding-related changes in brain size may be the reason for the widely varying estimates of brain SSD across studies of this species, cautioning against interpreting brain size measurements from a single time point as fixed/static.

  • 13. Chen, Yu-Chia
    et al.
    Harrison, Peter W.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology, Ethology. Uppsala University, Sweden.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology, Ethology. Uppsala University, Sweden.
    Mank, Judith E.
    Panula, Pertti
    Expression change in Angiopoietin-1 underlies change in relative brain size in fish2015In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1810, article id 20150872Article in journal (Refereed)
    Abstract [en]

    Brain size varies substantially across the animal kingdom and is often associated with cognitive ability; however, the genetic architecture underpinning natural variation in these key traits is virtually unknown. In order to identify the genetic architecture and loci underlying variation in brain size, we analysed both coding sequence and expression for all the loci expressed in the telencephalon in replicate populations of guppies (Poecilia reticulata) artificially selected for large and small relative brain size. A single gene, Angiopoietin-1 (Ang-1), a regulator of angiogenesis and suspected driver of neural development, was differentially expressed between large-and small-brain populations. Zebra fish (Danio rerio) morphants showed that mild knock down of Ang-1 produces a small-brained phenotype that could be rescued with Ang-1 mRNA. Translation inhibition of Ang-1 resulted in smaller brains in larvae and increased expression of Notch-1, which regulates differentiation of neural stem cells. In situ analysis of newborn large-and small-brained guppies revealed matching expression patterns of Ang-1 and Notch-1 to those observed in zebrafish larvae. Taken together, our results suggest that the genetic architecture affecting brain size in our population may be surprisingly simple, and Ang-1 may be a potentially important locus in the evolution of vertebrate brain size and cognitive ability.

  • 14.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bloch, Natasha I.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    van der Bijl, Wouter
    Stockholm University, Faculty of Science, Department of Zoology.
    Buechel, Severine D.
    Stockholm University, Faculty of Science, Department of Zoology.
    Mank, Judith E.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Female brain size affects the assessment of male attractiveness during mate choice2017In: Science Advances, ISSN 0036-8156, E-ISSN 2375-2548, Vol. 3, no 3, article id e1601990Article in journal (Refereed)
    Abstract [en]

    Mate choice decisions are central in sexual selection theory aimed to understand how sexual traits evolve and their role in evolutionary diversification. We test the hypothesis that brain size and cognitive ability are important for accurate assessment of partner quality and that variation in brain size and cognitive ability underlies variation in mate choice. We compared sexual preference in guppy female lines selected for divergence in relative brain size, which we have previously shown to have substantial differences in cognitive ability. In a dichotomous choice test, large-brained and wild-type females showed strong preference for males with color traits that predict attractiveness in this species. In contrast, small-brained females showed no preference for males with these traits. In-depth analysis of optomotor response to color cues and gene expression of key opsins in the eye revealed that the observed differences were not due to differences in visual perception of color, indicating that differences in the ability to process indicators of attractiveness are responsible. We thus provide the first experimental support that individual variation in brain size affects mate choice decisions and conclude that differences in cognitive ability may be an important underlying mechanism behind variation in female mate choice.

  • 15.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Van der Bijl, Wouter
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    No association between brain size and male sexual behavior in the guppy2015In: Current Zoology, ISSN 1674-5507, Vol. 61, no 2, p. 265-273Article in journal (Refereed)
    Abstract [en]

    Animal behavior is remarkably variable at all taxonomic levels. Over the last decades, research on animal behavior has focused on understanding ultimate processes. Yet, it has progressively become more evident that to fully understand behavioral variation, ultimate explanations need to be complemented with proximate ones. In particular, the mechanisms generating variation in sexual behavior remain an open question. Variation in aspects of brain morphology has been suggested as a plausible mechanism underlying this variation. However, our knowledge of this potential association is based almost exclusively on comparative analyses. Experimental studies are needed to establish causality and bridge the gap between micro-and macroevolutionary mechanisms concerning the link between brain and sexual behavior. We used male guppies that had been artificially selected for large or small relative brain size to study this association. We paired males with females and scored the full known set of male and female sexual behaviors described in guppies. We found several previously demonstrated associations between male traits, male behavior and female behavior. Females responded more strongly towards males that courted more and males with more orange coloration. Also, larger males and males with less conspicuous coloration attempted more coerced copulations. However, courting, frequency of coerced copulation attempts, total intensity of sexual behavior, and female response did not differ between large-and small-brained males. Our data suggest that relative brain size is an unlikely mechanism underlying variation in sexual behavior of the male guppy. We discuss these findings in the context of the conditions under which relative brain size might affect male sexual behavior

  • 16.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Garate-Olaizola, Maddi
    Stockholm University, Faculty of Science, Department of Zoology.
    Buechel, Severine D.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    On the role of body size, brain size, and eye size in visual acuity2017In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 71, no 12, article id UNSP 179Article in journal (Refereed)
    Abstract [en]

    The visual system is highly variable across species, and such variability is a key factor influencing animal behavior. Variation in the visual system, for instance, can influence the outcome of learning tasks when visual stimuli are used. We illustrate this issue in guppies (Poecilia reticulata) artificially selected for large and small relative brain size with pronounced behavioral differences in learning experiments and mate choice tests. We performed a study of the visual system by quantifying eye size and optomotor response of large-brained and small-brained guppies. This represents the first experimental test of the link between brain size evolution and visual acuity. We found that female guppies have larger eyes than male guppies, both in absolute terms and in relation to their body size. Likewise, individuals selected for larger brains had slightly larger eyes but not better visual acuity than small-brained guppies. However, body size was positively associated with visual acuity. We discuss our findings in relation to previous macroevolutionary studies on the evolution of brain morphology, eye morphology, visual acuity, and ecological variables, while stressing the importance of accounting for sensory abilities in behavioral studies.

  • 17.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Garate-Olaizola, Maddi
    Buechel, Severine
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    On the role of body size, brain size and eye size in visual acuityManuscript (preprint) (Other academic)
  • 18.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Brain size affects the judgment of female quality during male mate choiceManuscript (preprint) (Other academic)
  • 19.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Selection for relative brain size affects context-dependent male preference for, but not discrimination of, female body size in guppies2018In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 221, no 12, article id jeb175240Article in journal (Refereed)
    Abstract [en]

    Understanding what drives animal decisions is fundamental in evolutionary biology, and mate choice decisions are arguably some of the most important in any individual's life. As cognitive ability can impact decision making, elucidating the link between mate choice and cognitive ability is necessary to fully understand mate choice. To experimentally study this link, we used guppies (Poecilia reticulata) artificially selected for divergence in relative brain size and with previously demonstrated differences in cognitive ability. A previous test in our female guppy selection lines demonstrated the impact of brain size and cognitive ability on information processing during female mate choice decisions. Here, we evaluated the effect of brain size and cognitive ability on male mate choice decisions. Specifically, we investigated the preference of large-brained, small-brained and non-selected guppy males for female body size, a key indicator of female fecundity in this species. For this, male preference was quantified in dichotomous choice tests when presented with dyads of females with small, medium and large body size differences. All types of males showed a preference for larger females but no effect of brain size was found in the ability to discriminate between differently sized females. However, we found that non-selected and large-brained males, but not small-brained males, showed a context-dependent preference for larger females depending on the difference in female size. Our results have two important implications. First, they provide further evidence that male mate choice also occurs in a species in which secondary sexual omamentation is present only in males. Second, they show that brain size and cognitive ability have important effects on individual variation in mating preference and sexually selected traits.

  • 20.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University College of London, UK.
    Romensky, Maksym
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology. Wageningen University, The Netherlands.
    Buechel, Severine D.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Brain size affects responsiveness in mating behaviour to variation in predation pressure and sex ratio2020In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 33, no 2, p. 165-177Article in journal (Refereed)
    Abstract [en]

    Despite ongoing advances in sexual selection theory, the evolution of mating decisions remains enigmatic. Cognitive processes often require simultaneous processing of multiple sources of information from environmental and social cues. However, little experimental data exist on how cognitive ability affects such fitness-associated aspects of behaviour. Using advanced tracking techniques, we studied mating behaviours of guppies artificially selected for divergence in relative brain size, with known differences in cognitive ability, when predation threat and sex ratio was varied. In females, we found a general increase in copulation behaviour in when the sex ratio was female biased, but only large-brained females responded with greater willingness to copulate under a low predation threat. In males, we found that small-brained individuals courted more intensively and displayed more aggressive behaviours than large-brained individuals. However, there were no differences in female response to males with different brain size. These results provide further evidence of a role for female brain size in optimal decision-making in a mating context. In addition, our results indicate that brain size may affect mating display skill in male guppies. We suggest that it is important to consider the association between brain size, cognitive ability and sexual behaviour when studying how morphological and behavioural traits evolve in wild populations.

  • 21.
    Corral-López, Alberto
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Romensky, Maksym
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Buechel, Severine
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Brain size, environmental complexity and mating behaviourManuscript (preprint) (Other academic)
  • 22.
    Emerson, B. C.
    et al.
    University of East Anglia, UK.
    Kolm, Niclas
    University of East Anglia, UK; University of Edinburgh, UK.
    Ecology: Is speciation driven by species diversity? Reply.2005In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 438, no 7064, p. E2-Article in journal (Refereed)
  • 23.
    Emerson, B. C.
    et al.
    University of East Anglia, UK.
    Kolm, Niclas
    University of East Anglia, UK; University of Edinburgh, UK.
    Species diversity can drive speciation2005In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 434, no 7036, p. 1015-1017Article in journal (Refereed)
    Abstract [en]

    A fundamental question in evolutionary ecology and conservation biology is: why do some areas contain greater species diversity than others? Island biogeographic theory has identified the roles of immigration and extinction in relation to area size and proximity to source areas(1,2), and the role of speciation is also recognized as an important factor(3-6). However, one as yet unexplored possibility is that species diversity itself might help to promote speciation, and indeed the central tenets of island biogeographic theory support such a prediction. Here we use data for plants and arthropods of the volcanic archipelagos of the Canary and Hawaiian Islands to address whether there is a positive relationship between species diversity and rate of diversification. Our index of diversification for each island is the proportion of species that are endemic, and we test our prediction that this increases with increasing species number. We show that even after controlling for several important physical features of islands, diversification is strongly related to species number.

  • 24. Emerson, Brent C.
    et al.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Response to comments on Species diversity can drive speciation2007In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 30, no 3, p. 334-338Article in journal (Refereed)
  • 25. Emerson, Brent C.
    et al.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Species diversity can drive speciation: reply2007In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 88, no 8, p. 2135-2138Article in journal (Refereed)
  • 26. Fitzpatrick, J. L.
    et al.
    Almbro, Maria
    University of Western Australia, WA, Australia.
    Gonzalez-Voyer, A.
    Hamada, S.
    Pennington, C.
    Scanlan, J.
    Kolm, Niclas
    Sexual selection uncouples the evolution of brain and body size in pinnipeds2012In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 25, no 7, p. 1321-1330Article in journal (Refereed)
    Abstract [en]

    The size of the vertebrate brain is shaped by a variety of selective forces. Although larger brains (correcting for body size) are thought to confer fitness advantages, energetic limitations of this costly organ may lead to trade-offs, for example as recently suggested between sexual traits and neural tissue. Here, we examine the patterns of selection on male and female brain size in pinnipeds, a group where the strength of sexual selection differs markedly among species and between the sexes. Relative brain size was negatively associated with the intensity of sexual selection in males but not females. However, analyses of the rates of body and brain size evolution showed that this apparent trade-off between sexual selection and brain mass is driven by selection for increasing body mass rather than by an actual reduction in male brain size. Our results suggest that sexual selection has important effects on the allometric relationships of neural development.

  • 27. Fitzpatrick, J. L.
    et al.
    Almbro, Maria
    University of Western Australia, WA, Australia.
    Gonzalez-Voyer, A.
    Kolm, Niclas
    Simmons, L. W.
    Male Contest Competition And The Coevolution Of Weaponry And Testes In Pinnipeds2012In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 66, no 11, p. 3595-3604Article in journal (Refereed)
    Abstract [en]

    Male reproductive success is influenced by competitive interactions during precopulatory and postcopulatory selective episodes. Consequently, males can gain reproductive advantages during precopulatory contest competition by investing in weaponry and during postcopulatory sperm competition by investing in ejaculates. However, recent theory predicts male expenditure on weaponry and ejaculates should be subject to a trade-off, and should vary under increasing risk and intensity of sperm competition. Here, we provide the first comparative analysis of the prediction that expenditure on weaponry should be negatively associated with expenditure on testes mass. Specifically, we assess how sexual selection influences the evolution of primary and secondary sexual traits among pinnipeds (seals, sea lions, and walruses). Using recently developed comparative methods, we demonstrate that sexual selection promotes rapid divergence in body mass, sexual size dimorphism (SSD), and genital morphology. We then show that genital length appears to be positively associated with the strength of postcopulatory sexual selection. However, subsequent analyses reveal that both genital length and testes mass are negatively associated with investment in precopulatory weaponry. Thus, our results are congruent with recent theoretical predictions of contest-based sperm competition models. We discuss the possible role of trade-offs and allometry in influencing patterns of reproductive trait evolution in pinnipeds.

  • 28. Fitzpatrick, John L.
    et al.
    Montgomerie, Robert
    Desjardins, Julie K.
    Stiver, Kelly A.
    Kolm, Niclas
    Uppsala universitet, Institutionen för ekologi och evolution.
    Balshine, Sigal
    Female promiscuity promotes the evolution of faster sperm in cichlid fishes2009In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 106, no 4, p. 1128-1132Article in journal (Refereed)
    Abstract [en]

    Sperm competition, the contest among ejaculates from rival males to fertilize ova of a female, is a common and powerful evolutionary force influencing ejaculate traits. During competitive interactions between ejaculates, longer and faster spermatozoa are expected to have an edge; however, to date, there has been mixed support for this key prediction from sperm competition theory. Here, we use the spectacular radiation of cichlid fishes from Lake Tanganyika to examine sperm characteristics in 29 closely related species. We provide phylogenetically robust evidence that species experiencing greater levels of sperm competition have faster-swimming sperm. We also show that sperm competition selects for increases in the number, size, and longevity of spermatozoa in the ejaculate of a male, and, contrary to expectations from theory, we find no evidence of trade-offs among sperm traits in an interspecific analysis. Also, sperm swimming speed is positively correlated with sperm length among, but not within, species. These different responses to sperm competition at intra-and interspecific levels provide a simple, powerful explanation for equivocal results from previous studies. Using phylogenetic analyses, we also reconstructed the probable evolutionary route of trait evolution in this taxon, and show that, in response to increases in the magnitude of sperm competition, the evolution of sperm traits in this clade began with the evolution of faster (thus, more competitive) sperm.

  • 29.
    Fong, Stephanie
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Buechel, Séverine D.
    Stockholm University, Faculty of Science, Department of Zoology.
    Boussard, Annika
    Stockholm University, Faculty of Science, Department of Zoology.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Plastic changes in brain morphology in relation to learning and environmental enrichment in the guppy (Poecilia reticulata)2019In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 222, no 10, article id UNSP jeb200402Article in journal (Refereed)
    Abstract [en]

    Despite the common assumption that the brain is malleable to surrounding conditions mainly during ontogeny, plastic neural changes can occur also in adulthood. One of the driving forces responsible for alterations in brain morphology is increasing environmental complexity that may demand enhanced cognitive abilities (e.g. attention, memory and learning). However, studies looking at the relationship between brain morphology and learning are scarce. Here, we tested the effects of both learning and environmental enrichment on neural plasticity in guppies (Poecilia reticulata), by means of either a reversal-learning test or a spatial-learning test. Given considerable evidence supporting environmentally induced plastic alterations, two separate control groups that were not subjected to any cognitive test were included to account for potential changes induced by the experimental setup alone. We did not find any effect of learning on any of our brain measurements. However, we found strong evidence for an environmental effect, where fish given access to the spatial-learning environment had larger relative brain size and optic tectum size in relation to those exposed to the reversal-learning environment. Our results demonstrate the plasticity of the adult brain to respond adaptively mainly to environmental conditions, providing support for the environmental enhancement theory.

  • 30. Garamszegi, László Zsolt
    et al.
    Temrin, Hans
    Stockholm University, Faculty of Science, Department of Zoology.
    Kubinyi, Enikő
    Miklósi, Ádám
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    The role of common ancestry and gene flow in the evolution of human-directed play behaviour in dogs2019In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101Article in journal (Refereed)
    Abstract [en]

    Among-population variance of phenotypic traits is of high relevance for understanding evolutionary mechanisms that operate in relatively short timescales, but various sources of nonindependence, such as common ancestry and gene flow, can hamper the interpretations. In this comparative analysis of 138 dog breeds, we demonstrate how such confounders can independently shape the evolution of a behavioural trait (human-directed play behaviour from the Dog Mentality Assessment project). We combined information on genetic relatedness and haplotype sharing to reflect common ancestry and gene flow, respectively, and entered these into a phylogenetic mixed model to partition the among-breed variance of human-directed play behaviour while also accounting for within-breed variance. We found that 75% of the among-breed variance was explained by overall genetic relatedness among breeds, whereas 15% could be attributed to haplotype sharing that arises from gene flow. Therefore, most of the differences in human-directed play behaviour among breeds have likely been caused by constraints of common ancestry as a likely consequence of past selection regimes. On the other hand, gene flow caused by crosses among breeds has played a minor, but not negligible role. Our study serves as an example of an analytical approach that can be applied to comparative situations where the effects of shared origin and gene flow require quantification and appropriate statistical control in a within-species/among-population framework. Altogether, our results suggest that the evolutionary history of dog breeds has left remarkable signatures on the among-breed variation of a behavioural phenotype.

  • 31.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Institutionen för ekologi och evolution.
    Fitzpatrick, John L.
    Kolm, Niclas
    Uppsala universitet, Institutionen för ekologi och evolution.
    Sexual selection determines parental care patterns in cichlid fishes2008In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 62, no 8, p. 2015-2026Article in journal (Refereed)
    Abstract [en]

    Despite a massive research effort, our understanding of why, in most vertebrates, males compete for mates and females care for offspring remains incomplete. Two alternative hypotheses have been proposed to explain the direction of causality between parental care and sexual selection. Traditionally, sexual selection has been explained as a consequence of relative parental investment, where the sex investing less will compete for the sex investing more. However, a more recent model suggests that parental care patterns result from sexual selection acting on one sex favoring mating competition and lower parental investment. Using species-level comparative analyses on Tanganyikan cichlid fishes we tested these alternative hypotheses employing a proxy of sexual selection based on mating system, sexual dichromatism, and dimorphism data. First, while controlling for female reproductive investment, we found that species with intense sexual selection were associated with female-only care whereas species with moderate sexual selection were associated with biparental care. Second, using contingency analyses, we found that, contrary to the traditional view, evolutionary changes in parental care type are dependent on the intensity of sexual selection. Hence, our results support the hypothesis that sexual selection determines parental care patterns in Tanganyikan cichlid fishes.

  • 32.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Zooekologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Rates of phenotypic evolution of ecological characters and sexual traits during the Tanganyikan cichlid adaptive radiation2011In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 24, no 11, p. 2378-2388Article in journal (Refereed)
    Abstract [en]

    Theory suggests that sexual traits evolve faster than ecological characters. However, characteristics of a species niche may also influence evolution of sexual traits. Hence, a pending question is whether ecological characters and sexual traits present similar tempo and mode of evolution during periods of rapid ecological divergence, such as adaptive radiation. Here, we use recently developed phylogenetic comparative methods to analyse the temporal dynamics of evolution for ecological and sexual traits in Tanganyikan cichlids. Our results indicate that whereas disparity in ecological characters was concentrated early in the radiation, disparity in sexual traits remained high throughout the radiation. Thus, closely related Tanganyikan cichlids presented higher disparity in sexual traits than ecological characters. Sexual traits were also under stronger selection than ecological characters. In sum, our results suggest that ecological characters and sexual traits present distinct evolutionary patterns, and that sexual traits can evolve faster than ecological characters, even during adaptive radiation.

  • 33.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Evolutionsbiologi.
    Kolm, Niclas
    Uppsala universitet, Evolutionsbiologi.
    Sex, Ecology and the Brain: Evolutionary Correlates of Brain Structure Volumes in Tanganyikan Cichlids2010In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 5, no 12, p. e14355-Article in journal (Refereed)
    Abstract [en]

    Analyses of the macroevolutionary correlates of brain structure volumes allow pinpointing of selective pressures influencing specific structures. Here we use a multiple regression framework, including phylogenetic information, to analyze brain structure evolution in 43 Tanganyikan cichlid species. We analyzed the effect of ecological and sexually selected traits for species averages, the effect of ecological traits for each sex separately and the influence of sexual selection on structure dimorphism. Our results indicate that both ecological and sexually selected traits have influenced brain structure evolution. The patterns observed in males and females generally followed those observed at the species level. Interestingly, our results suggest that strong sexual selection is associated with reduced structure volumes, since all correlations between sexually selected traits and structure volumes were negative and the only statistically significant association between sexual selection and structure dimorphism was also negative. Finally, we previously found that monoparental female care was associated with increased brain size. However, here cerebellum and hypothalamus volumes, after controlling for brain size, associated negatively with female-only care. Thus, in accord with the mosaic model of brain evolution, brain structure volumes may not respond proportionately to changes in brain size. Indeed selection favoring larger brains can simultaneously lead to a reduction in relative structure volumes.

  • 34.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Zooekologi.
    Winberg, Svante
    Uppsala universitet, Fysiologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Brain structure evolution in a basal vertebrate clade: evidence from phylogenetic comparative analysis of cichlid fishes2009In: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 9, p. 238-Article in journal (Refereed)
    Abstract [en]

     Background: The vertebrate brain is composed of several interconnected, functionally distinct structures and much debate has surrounded the basic question of how these structures evolve. On the one hand, according to the 'mosaic evolution hypothesis', because of the elevated metabolic cost of brain tissue, selection is expected to target specific structures mediating the cognitive abilities which are being favored. On the other hand, the 'concerted evolution hypothesis' argues that developmental constraints limit such mosaic evolution and instead the size of the entire brain varies in response to selection on any of its constituent parts. To date, analyses of these hypotheses of brain evolution have been limited to mammals and birds; excluding Actinopterygii, the basal and most diverse class of vertebrates. Using a combination of recently developed phylogenetic multivariate allometry analyses and comparative methods that can identify distinct rates of evolution, even in highly correlated traits, we studied brain structure evolution in a highly variable clade of ray-finned fishes; the Tanganyikan cichlids.

    Results: Total brain size explained 86% of the variance in brain structure volume in cichlids, a lower proportion than what has previously been reported for mammals. Brain structures showed variation in pair-wise allometry suggesting some degree of independence in evolutionary changes in size. This result is supported by variation among structures on the strength of their loadings on the principal size axis of the allometric analysis. The rate of evolution analyses generally supported the results of the multivariate allometry analyses, showing variation among several structures in their evolutionary patterns. The olfactory bulbs and hypothalamus were found to evolve faster than other structures while the dorsal medulla presented the slowest evolutionary rate.

    Conclusion: Our results favor a mosaic model of brain evolution, as certain structures are evolving in a modular fashion, with a small but non-negligible influence of concerted evolution in cichlid fishes. Interestingly, one of the structures presenting distinct evolutionary patterns within cichlids, the olfactory bulbs, has also been shown to evolve differently from other structures in mammals. Hence, our results for a basal vertebrate clade also point towards a conserved developmental plan for all vertebrates.

  • 35.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Zooekologi.
    Winberg, Svante
    Uppsala universitet, Fysiologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Distinct Evolutionary Patterns of Brain and Body Size During Adaptive Radiation2009In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 63, no 9, p. 2266-2274Article in journal (Refereed)
    Abstract [en]

    Morphological traits are often genetically and/or phenotypically correlated with each other and such covariation can have an important influence on the evolution of individual traits. The strong positive relationship between brain size and body size in vertebrates has attracted a lot of interest, and much debate has surrounded the study of the factors responsible for the allometric relationship between these two traits. Here, we use comparative analyses of the Tanganyikan cichlid adaptive radiation to investigate the patterns of evolution for brain size and body size separately. We found that body size exhibited recent bursts of rapid evolution, a pattern that is consistent with divergence linked to ecological specialization. Brain weight on the other hand, showed no bursts of divergence but rather evolved in a gradual manner. Our results thus show that even highly genetically correlated traits can present markedly different patterns of evolution, hence interpreting patterns of evolution of traits from correlations in extant taxa can be misleading. Furthermore, our results suggest, contrary to expectations from theory, that brain size does not play a key role during adaptive radiation.

  • 36.
    Gonzalez-Voyer, Alejandro
    et al.
    Uppsala universitet, Zooekologi.
    Winberg, Svante
    Uppsala universitet, Fysiologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Social fishes and single mothers: brain evolution in African cichlids2009In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 276, no 1654, p. 161-167Article in journal (Refereed)
    Abstract [en]

    As with any organ, differences in brain size-after adequate control of allometry-are assumed to be a response to selection. With over 200 species and an astonishing diversity in niche preferences and social organization, Tanganyikan cichlids present an excellent opportunity to study brain evolution. We used phylogenetic comparative analyses of sexed adults from 39 Tanganyikan cichlid species in a multiple regression framework to investigate the influence of ecology, sexual selection and parental care patterns on whole brain size, as well as to analyse sex-specific effects. First, using species-specific measures, we analysed the influence of diet, habitat, form of care (mouthbrooding or substrate guarding), care type (biparental or female only) and intensity of sexual selection on brain size, while controlling for body size. Then, we repeated the analyses for male and female brain size separately. Type of diet and care type were significantly correlated with whole brain size. Sex-specific analyses showed that female brain size correlated significantly with care type while male brain size was uncorrelated with care type. Our results suggest that more complex social interactions associated with diet select for larger brains and further that the burden of uniparental care exerts high cognitive demands on females.

  • 37. Hayward, A.
    et al.
    Tsuboi, M.
    Owusu, C.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Buechel, Severine D.
    Stockholm University, Faculty of Science, Department of Zoology.
    Zidar, J.
    Cornwallis, C. K.
    Lovlie, H.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Evolutionary associations between host traits and parasite load: insights from Lake Tanganyika cichlids2017In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 30, no 6, p. 1056-1067Article in journal (Refereed)
    Abstract [en]

    Parasite diversity and abundance (parasite load) vary greatly among host species. However, the influence of host traits on variation in parasitism remains poorly understood. Comparative studies of parasite load have largely examined measures of parasite species richness and are predominantly based on records obtained from published data. Consequently, little is known about the relationships between host traits and other aspects of parasite load, such as parasite abundance, prevalence and aggregation. Meanwhile, understanding of parasite species richness may be clouded by limitations associated with data collation from multiple independent sources. We conducted a field study of Lake Tanganyika cichlid fishes and their helminth parasites. Using a Bayesian phylogenetic comparative framework, we tested evolutionary associations between five key host traits (body size, gut length, diet breadth, habitat complexity and number of sympatric hosts) predicted to influence parasitism, together with multiple measures of parasite load. We find that the number of host species that a particular host may encounter due to its habitat preferences emerges as a factor of general importance for parasite diversity, abundance and prevalence, but not parasite aggregation. In contrast, body size and gut size are positively related to aspects of parasite load within, but not between species. The influence of host phylogeny varies considerably among measures of parasite load, with the greatest influence exerted on parasite diversity. These results reveal that both host morphology and biotic interactions are key determinants of host-parasite associations and that consideration of multiple aspects of parasite load is required to fully understand patterns in parasitism.

  • 38.
    Herbert-Read, James E.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala University, Sweden.
    Rosén, Emil
    Szorkovszky, Alex
    Ioannou, Christos C.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Perna, Andrea
    Ramnarine, Indar W.
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Krause, Jens
    Sumpter, David J. T.
    How predation shapes the social interaction rules of shoaling fish2017In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 284, no 1861, article id 20171126Article in journal (Refereed)
    Abstract [en]

    Predation is thought to shape the macroscopic properties of animal groups, making moving groups more cohesive and coordinated. Precisely how predation has shaped individuals' fine-scale social interactions in natural populations, however, is unknown. Using high-resolution tracking data of shoaling fish (Poecilia reticulata) from populations differing in natural predation pressure, we show how predation adapts individuals' social interaction rules. Fish originating from high predation environments formed larger, more cohesive, but not more polarized groups than fish from low predation environments. Using a new approach to detect the discrete points in time when individuals decide to update their movements based on the available social cues, we determine how these collective properties emerge from individuals' microscopic social interactions. We first confirm predictions that predation shapes the attraction-repulsion dynamic of these fish, reducing the critical distance at which neighbours move apart, or come back together. While we find strong evidence that fish align with their near neighbours, we do not find that predation shapes the strength or likelihood of these alignment tendencies. We also find that predation sharpens individuals' acceleration and deceleration responses, implying key perceptual and energetic differences associated with how individuals move in different predation regimes. Our results reveal how predation can shape the social interactions of individuals in groups, ultimately driving differences in groups' collective behaviour.

  • 39. Herczeg, Gábor
    et al.
    Urszán, Tamás J.
    Orf, Stephanie
    Nagy, Gergely
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Brain size predicts behavioural plasticity in guppies (Poecilia reticulata): An experiment2019In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 32, no 3, p. 218-226Article in journal (Refereed)
    Abstract [en]

    Understanding how animal personality (consistent between-individual behavioural differences) arises has become a central topic in behavioural sciences. This endeavour is complicated by the fact that not only the mean behaviour of individuals (behavioural type) but also the strength of their reaction to environmental change (behavioural plasticity) varies consistently. Personality and cognitive abilities are linked, and we suggest that behavioural plasticity could also be explained by differences in brain size (a proxy for cognitive abilities), since accurate decisions are likely essential to make behavioural plasticity beneficial. We test this idea in guppies (Poecilia reticulata), artificially selected for large and small brain size, which show clear cognitive differences between selection lines. To test whether those lines differed in behavioural plasticity, we reared them in groups in structurally enriched environments and then placed adults individually into empty tanks, where we presented them daily with visual predator cues and monitored their behaviour for 20 days with video-aided motion tracking. We found that individuals differed consistently in activity and risk-taking, as well as in behavioural plasticity. In activity, only the large-brained lines demonstrated habituation (increased activity) to the new environment, whereas in risk-taking, we found sensitization (decreased risk-taking) in both brain size lines. We conclude that brain size, potentially via increasing cognitive abilities, may increase behavioural plasticity, which in turn can improve habituation to novel environments. However, the effects seem to be behaviour-specific. Our results suggest that brain size likely explains some of the variation in behavioural plasticity found at the intraspecific level.

  • 40. Herczeg, Gábor
    et al.
    Urszán, Tamás János
    Orf, Stephanie
    Nagy, Gergely
    Kotrschal, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Yes, correct context is indeed the key: An answer to Haave-Audet et al. 20192019In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 32, no 12, p. 1450-1455Article in journal (Refereed)
    Abstract [en]

    We published a study recently testing the link between brain size and behavioural plasticity using brain size selected guppy (Poecilia reticulata) lines (2019, Journal of Evolutionary Biology, 32, 218-226). Only large-brained fish showed habituation to a new, but actually harmless environment perceived as risky, by increasing movement activity over the 20-day observation period. We concluded that Our results suggest that brain size likely explains some of the variation in behavioural plasticity found at the intraspecific level. In a commentary published in the same journal, Haave-Audet et al. challenged the main message of our study, stating that (a) relative brain size is not a suitable proxy for cognitive ability and (b) habituation measured by us is likely not adaptive and costly. In our response, we first show that a decade's work has proven repeatedly that relative brain size is indeed positively linked to cognitive performance in our model system. Second, we discuss how switching from stressed to unstressed behaviour in stressful situations without real risk is likely adaptive. Finally, we point out that the main cost of behavioural plasticity in our case is the development and maintenance of the neural system needed for information processing, and not the expression of plasticity. We hope that our discussion with Haave-Audet et al. helps clarifying some central issues in this emerging research field.

  • 41. Hoffman, Eric A.
    et al.
    Arquello, J. Roman
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Berglund, Anders
    Uppsala universitet, Zooekologi.
    Jones, Adam G.
    Eleven polymorphic microsatellite loci in a coral reef fish, Pterapogon kauderni2004In: Molecular Ecology Notes, ISSN 1471-8278, E-ISSN 1471-8286, Vol. 4, no 3, p. 342-344Article in journal (Refereed)
    Abstract [en]

    We describe the isolation and characterization of 11 polymorphic tetranucleotide microsatellite loci from a male mouthbrooding coral reef fish, the Banggai cardinalfish Pterapogon kauderni. In a sample of 37 fish from a natural population, polymorphism at these loci ranged from two to 15 alleles, with expected heterozygosities ranging from 0.107 to 0.928, enabling high-resolution genetic studies of this coral reef fish.

  • 42. Hoffman, Eric A.
    et al.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Berglund, Anders
    Uppsala universitet, Zooekologi.
    Arquello, J. Roman
    Jones, A dam G.
    Genetic structure in the coral-reef-associated Banggai cardinalfish, Pterapogon kauderni2005In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 14, no 5, p. 1367-1375Article in journal (Refereed)
    Abstract [en]

    In this study, we used 11 polymorphic microsatellite loci to show that oceanic distances as small as 2–5 km are sufficient to produce high levels of population genetic structure (multilocus FST as high as 0.22) in the Banggai cardinalfish(Pterapogon kauderni), a heavily exploited reef fish lacking a pelagic larval dispersal phase. Global FST among all populations, separated by a maximum distance of 203 km, was 0.18 (RST = 0.35). Moreover, two lines of evidence suggest that estimates of FST may actually underestimate the true level of genetic structure. First, within-locus FST values were consistently close to the theoretical maximum set by the average within-population heterozygosity. Second, the allele size permutation test showed that RST values were significantly larger than FST values, indicating that populations have been isolated long enough for mutation to have played a role in generating allelic variation among populations. The high level of microspatial structure observed in this marine fish indicates that life history traits such as lack of pelagic larval phase and a good homing ability do indeed play a role in shaping population genetic structure in the marine realm.

  • 43.
    Höglund, Erik
    et al.
    Uppsala universitet, Limnologi.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Winberg, Svante
    Uppsala universitet, Jämförande fysiologi.
    Stress-induced changes in brain serotonergic activity, plasma cortisol and aggressive behavior in Arctic charr (Salvelinus alpinus) is counteracted by L-DOPA2001In: Physiology and Behavior, ISSN 0031-9384, E-ISSN 1873-507X, Vol. 74, no 3, p. 381-389Article in journal (Refereed)
    Abstract [en]

    Arctic charr (Salvelinus alpinus) were tested for aggressive behavior using intruder tests, before and after 2 days of dyadic social interaction. Following social interaction, half of the dominant and half of the subordinate fish were given l-DOPA (10 mg/kg, orally), whereas the remaining dominant and subordinate fish were given vehicle. One hour following drug treatment, the fish were tested for aggressive behavior again in a third and final intruder test, after which blood plasma and brain tissue were sampled for analysis of plasma cortisol concentrations and brain levels of monoamines and monoamine metabolites. Subordinate fish showed a reduction in the number of attacks launched against the intruder, as well as an increase in attack latency, as compared to prior to dyadic social interactions. Social subordination also resulted in an elevation of brain serotonergic activity. Fish receiving l-DOPA prior to the final intruder test showed shorter attack latency than vehicle controls. Drug treatment was a stressful experience and vehicle controls showed elevated plasma cortisol levels and longer attack latency as compared to before treatment. l-DOPA-treated fish showed lower plasma levels of cortisol and lower serotonergic activity in certain brain areas than vehicle controls. These results suggest that l-DOPA counteracts the stress-induced inhibition of aggressive behavior, and at the same time inhibits stress-induced effects on brain serotonergic activity and plasma cortisol concentrations.

  • 44.
    Kolm, N
    et al.
    Uppsala universitet, Institutionen för ekologi och evolution.
    Goodwin, NB
    Balshine, S
    Reynolds, JD
    Life history evolution in cichlids 1: Revisiting the evolution of life histories in relation to parental care2006In: Journal of Evolutionary Biology, Vol. 19, p. 66-75Article in journal (Refereed)
  • 45.
    Kolm, N
    et al.
    Uppsala universitet, Institutionen för ekologi och evolution.
    Goodwin, NB
    Balshine, S
    Reynolds, JD
    Life history evolution in cichlids 2: directional evolution of the trade-off between egg number and egg size2006In: Journal of Evolutionary Biology, Vol. 19, p. 76-84Article in journal (Refereed)
  • 46.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Female courtship in the Banggai cardinalfish: honest signals of egg maturity and reproductive output?2004In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 56, no 1, p. 59-64Article in journal (Refereed)
    Abstract [en]

    Despite the vast literature on male courtship behaviour, little is known about the function and information content of female courtship behaviour. Female courtship behaviour may be important in many species, particularly where both sexes invest heavily in the offspring, and if such behaviours contain honest information regarding a female’s potential reproductive investment, they may be particularly important in male mate choice. Using observations of two female courtship behaviours (the “rush” and the “twitch”) from experimental pairings in the Banggai cardinalfish (Pterapogon kauderni), I addressed the question of whether these courtship behaviours contained information on female reproductive output (clutch weight) and egg maturity (proximity to spawning), traits commonly associated with male mate choice. I especially focused on the importance of these courtship behaviours in relation to other female characters, such as size and condition, using multiple regression. I found that one of these behaviours, the rush, was strongly associated with fecundity, whereas size, condition and the twitch were not. Further, I found that the “twitch” behaviour was associated with how close to actual spawning a female was. The results suggest that female courtship behaviour may convey highly important information in a mate choice context. I discuss the adaptive value of honest information in female courtship behaviour in light of these results.

  • 47.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Females produce larger eggs for large males in a paternal mouthbrooding fish2001In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 268, no 1482, p. 2229-2234Article in journal (Refereed)
    Abstract [en]

    When individuals receive different returns from their reproductive investment dependent on mate quality, they are expected to invest more when breeding with higher quality mates. A number of studies over the past decade have shown that females may alter their reproductive effort depending on the quality/attractiveness of their mate. However, to date, despite extensive work on parental investment, such a differential allocation has not been demonstrated in fish. Indeed, so far only two studies from any taxon have suggested that females alter the quality of individual offspring according to the quality/attractiveness of their mate. The banggai cardinal fish is an obligate paternal mouth brooder where females lay few large eggs. It has previously been shown that male size determines clutch weight irrespective of female size in this species. In this study, I investigated whether females perform more courtship displays towards larger males and whether females allocate their reproductive effort depending on the size of their mate by experimentally assigning females to either large or small males. I found that females displayed more towards larger males, thereby suggesting a female preference for larger males. Further, females produced heavier eggs and heavier clutches but not more eggs when paired with large males. My experiments show that females in this species adjust their offspring weight and, thus, presumably offspring quality according to the size of their mate.

  • 48.
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Male size determines reproductive output in a paternal mouthbrooding fish2002In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 63, no 4, p. 727-733Article in journal (Refereed)
    Abstract [en]

    Size can have strong effects on reproductive success in both males and females, and in many species large individuals are preferred as mates. To estimate the potential benefits from mate choice for size in both sexes, I studied the effects of the size of each sex on the reproductive output of pairs of Banggai cardinalfish, Pterapogon kauderni, a sexually monomorphic obligate paternal mouthbrooder. When pairs were allowed to form freely, a size-assortative mating pattern was observed and larger pairs had a higher reproductive output as determined by total clutch weight and egg size. To separate the potential benefits from mate choice for size for each sex, I subsequently used these pairs to form reversed size-assortative pairs, that is, the largest male paired to the smallest female and vice versa. I found a positive correlation between male size and clutch size: relatively heavier clutches were found in pairs where females were given a larger male. This suggests that the size of the male influences clutch weight. For egg size, however, the size of both sexes seemed important. The study reveals the benefits of mutual mate choice on size in this species: larger females provide larger eggs and larger males can brood heavier clutches. Furthermore, these results suggest that females differentially allocate resources into the eggs according to the size of the mate.

  • 49.
    Kolm, Niclas
    et al.
    Uppsala universitet, Zooekologi.
    Ahnesjö, Ingrid
    Uppsala universitet, Zooekologi.
    Do egg size and parental care coevolve in fish?2005In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 66, no 6, p. 1499-1515Article in journal (Refereed)
    Abstract [en]

    A phenomenon that has attracted a substantial theoretical and empirical interest is the positive relationship between egg size and the extent of parental care in fishes. Interestingly, despite the effort put into solving the causality behind this relationship over the past two decades it remains largely unsolved. Moreover, how general the positive relationship between egg size and parental care is among fishes is also poorly understood. In order to stimulate research exploring egg size and parental care variation in fishes, the potential selective forces from both natural and sexual selection on egg size and parental care are discussed. Recent empirical findings on how oxygen requirements and developmental times may differ between differently sized eggs are incorporated into a critical view of the current theory of this field. Furthermore, it is suggested that the up to now neglected effects of sexual selection, through both mate choice and sexual conflict, can have strong effects on the relationship between egg size and parental care in fishes. In light of the recent developments of comparative and experimental methods, future approaches that may improve the understanding of the relationship between egg size and care in fishes are suggested.

  • 50.
    Kolm, Niclas
    et al.
    Uppsala universitet, Zooekologi.
    Amcoff, Mirjam
    Uppsala universitet, Zooekologi.
    Mann, Richard P.
    Uppsala universitet, Analys och tillämpad matematik.
    Arnqvist, Göran
    Uppsala universitet, Zooekologi.
    Diversification of a Food-Mimicking Male Ornament via Sensory Drive2012In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 22, no 15, p. 1440-1443Article in journal (Refereed)
    Abstract [en]

    The evolutionary divergence of sexual signals is often important during the formation of new animal species, but our understanding of the origin of signal diversity is limited [1, 2]. Sensory drive, the optimization of communication signal efficiency through matching to the local environment, has been highlighted as a potential promoter of diversification and speciation [3]. The swordtail characin (Corynopoma riisei) is a tropical fish in which males display a flag-like ornament that elicits female foraging behavior during courtship. We show that the shape of the male ornament covaries with female diet across natural populations. More specifically, natural populations in which the female diet is more dominated by ants exhibit male ornaments more similar to the shape of an ant. Feeding experiments confirm that females habituated to a diet of ants prefer to bite at male ornaments from populations with a diet more dominated by ants. Our results show that the male ornament functions as a "fishing lure" that is diversifying in shape to match local variation in female search images employed during foraging. This direct link between variation in female feeding ecology and the evolutionary diversification of male sexual ornaments suggests that sensory drive may be a common engine of signal divergence.

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