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  • 1. Fitzpatrick, Luisa J.
    et al.
    Gasparini, Clelia
    Fitzpatrick, John L.
    University of Manchester, UK.
    Evans, Jonathan P.
    Male-female relatedness and patterns of male reproductive investment in guppies2014In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 10, no 5Article in journal (Refereed)
    Abstract [en]

    Inbreeding can cause reductions in fitness, driving the evolution of pre- and postcopulatory inbreeding avoidance mechanisms. There is now considerable evidence for such processes in females, but few studies have focused on males, particularly in the context of postcopulatory inbreeding avoidance. Here, we address this topic by exposing male guppies (Poecilia reticulata) to either full-sibling or unrelated females and determining whether they adjust investment in courtship and ejaculates. Our results revealed that males reduce their courtship but concomitantly exhibit short-term increases in ejaculate quality when paired with siblings. In conjunction with prior work reporting cryptic female preferences for unrelated sperm, our present findings reveal possible sexually antagonistic counter-adaptations that may offset postcopulatory inbreeding avoidance by females.

  • 2. Gil-Romera, Graciela
    et al.
    Adolf, Carole
    Benito, Blas M.
    Bittner, Lucas
    Johansson, Maria U.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Grady, David A.
    Lamb, Henry F.
    Lemma, Bruk
    Fekadu, Mekbib
    Glaser, Bruno
    Mekonnen, Betelhem
    Sevilla-Callejo, Miguel
    Zech, Michael
    Zech, Wolfgang
    Miehe, Georg
    Long-term fire resilience of the Ericaceous Belt, Bale Mountains, Ethiopia2019In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 15, no 7, article id 20190357Article in journal (Refereed)
    Abstract [en]

    Fire is the most frequent disturbance in the Ericaceous Belt (ca 3000-1300 m.a.s.l.), one of the most important plant communities of tropical African mountains. Through resprouting after fire, Erica establishes a positive fire feedback under certain burning regimes. However, present-day human activity in the Bale Mountains of Ethiopia includes fire and grating systems that may have a negative impact on the resilience of the ericaceous ecosystem. Current knowledge of Erica-fire relationships is based on studies of modern vegetation, lacking a longer time perspective that can shed light on baseline conditions for the fire feedback. We hypothesite that fire has influenced Erica communities in the Bale Mountains at millennial time-scales. To test this, we (1) identity the tire history ot the Bale Mountains through a pollen and charcoal record from Garba Guracha, a lake at 3950 m.a.s.l., and (2) describe the long-term bidirectional feedback between wildfire and Erica, which may control the ecosystem's resilience. Our results support fire occurrence in the area since ca 14 000 years ago, with particularly intense burning during the early Holocene, 10.8-6.0 cal ka BP. We show that a positive feedback between Erica abundance and fire occurrence was in operation throughout the Lateglacial and Holocene, and interpret the Ericaceous Bolt of the Ethiopian mountains as a long-term fire resilient ecosystem. We propose that controlled burning should be an integral part of landscape management in the Bale Mountains National Park.

  • 3.
    Kotrschal, Alexander
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Corral-Lopez, Alberto
    Stockholm University, Faculty of Science, Department of Zoology.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology.
    Large brains, short life: selection on brain size impacts intrinsic lifespan2019In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 15, no 5, article id 20190137Article in journal (Refereed)
    Abstract [en]

    The relationship between brain size and ageing is a paradox. The cognitive benefits of large brains should protect from extrinsic mortality and thus indirectly select for slower ageing. However, the substantial energetic cost of neural tissue may also impact the energetic budget of large-brained organisms, causing less investment in somatic maintenance and thereby faster ageing. While the positive association between brain size and survival in the wild is well established, no studies exist on the direct effects of brain size on ageing. Here we test how brain size influences intrinsic ageing in guppy (Poecilia reticulata) brain size selection lines with 12% difference in relative brain size. Measuring survival under benign conditions, we find that large-brained animals live 22% shorter than small-brained animals and the effect is similar in both males and females. Our results suggest a trade-off between investment into brain size and somatic maintenance. This implies that the link between brain size and ageing is contingent on the mechanism of mortality, and selection for positive correlations between brain size and ageing should occur mainly under cognition-driven survival benefits from increased brain size. We show that accelerated ageing can be a cost of evolving a larger brain.

  • 4.
    Lehmann, Philipp
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Stellenbosch University, South Africa .
    Javal, Marion
    Terblanche, John S.
    Oxygen limitation is not the cause of death during lethal heat exposure in an insect2019In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 15, no 1, article id 20180701Article in journal (Refereed)
    Abstract [en]

    Oxygen- and capacity-limited thermal tolerance (OCLTT) is a controversial hypothesis claiming to explain variation in, and mechanistically determine, animal thermal limits. The lack of support from Insecta is typically argued to be a consequence of their high-performance respiratory systems. However, no studies have reported internal body oxygen levels during thermal ramping so it is unclear if changes in ambient gas are partially or fully offset by a compensatory respiratory system. Here we provide such an assessment by simultaneously recording haemolymph oxygen (pO(2)) levels-as an approximation of tissue oxygenation-while experimentally manipulating ambient oxygen and subjecting organisms to thermal extremes in a series of thermolimit respirometry experiments using pupae of the butterfly Pieris napi. The main results are that while P. napi undergo large changes in haemolymph pO(2) that are positively correlated with experimental oxygen levels, haemolymph pO(2) is similar pre-and post-death during thermal assays. OCLTT predicts that reduction in body oxygen level should lead to a reduction in CTmax. Despite finding the former, there was no change in CTmax across a wide range of body oxygen levels. Thus, we argue that oxygen availability is not a functional determinant of the upper thermal limits in pupae of P. napi.

  • 5.
    Lindenfors, Patrik
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Neocortex evolution in primates: the 'social brain' is for females2005In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 1, p. 407-410Article in journal (Refereed)
    Abstract [en]

    According to the social intelligence hypothesis, relative neocortex size should be directly related to the degree of social complexity. This hypothesis has found support in a number of comparative studies of group size. The relationship between neocortex and sociality is thought to exist either because relative neocortex size limits group size or because a larger group size selects for a larger neocortex. However, research on primate social evolution has indicated that male and female group sizes evolve in relation to different demands. While females mostly group according to conditions set by the environment, males instead simply go where the females are. Thus, any hypothesis relating to primate social evolution has to analyse its relationship with male and female group sizes separately. Since sex-specific neocortex sizes in primates are unavailable in sufficient quantity, I here instead present results from phylogenetic comparative analyses of unsexed relative neocortex sizes and female and male group sizes. These analyses show that while relative neocortex size is positively correlated with female group size, it is negatively, or not at all correlated with male group size. This indicates that the social intelligence hypothesis only applies to female sociality.

  • 6. Maklakov, Alexei A.
    et al.
    Immler, Simone
    Gonzalez-Voyer, Alejandro
    Rönn, Johanna
    Kolm, Niclas
    Uppsala universitet, Zooekologi.
    Brains and the city in passerine birds: re-analysis and confirmation of the original result2013In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 9, no 6, article id 20130859Article in journal (Refereed)
    Abstract [en]

    Our original paper [1] included two Bayesian analyses [2] of the association between brain size and the probability of a passerine species of bird breeding in the city centre—at the level of families and at the level of individual species—with both analyses suggesting the same pattern. It has since been brought to our attention that in one of the analyses at the level of individual species, the residual variance was not fixed to 1 resulting in overestimation of the variance. We re-ran the analysis using fixed residual variance and the results support the original conclusion that relative brain size is associated with breeding in the city centre (ln brain size: posterior mean, 324.53, 95% credibility interval, 52.61–601.35; ln body size: posterior mean, −276.22, 95% credibility interval, −490.60 to −70.32). Furthermore, we applied a complimentary approach using logistic regression to test whether brain size predicts breeding in the city centre (yes/no) without accounting for phylogeny. This analysis also resulted in a significant positive association between brain size and breeding in city centres (likelihood ratio tests: ln brain size: d.f. = 1, χ2 = 11.08, p = 0.0009; ln body size: d.f. = 1, χ2 = 11.26, p = 0.0008). Thus, our results are confirmed by both phylogenetic and non-phylogenetic analyses.

  • 7.
    Maklakov, Alexei
    et al.
    Uppsala Universitet.
    Immler, Simone
    Uppsala Universitet.
    Gonzalez-Voyer, Alejandro
    Rönn, Johanna
    Uppsala universitet.
    Kolm, Niclas
    Brains and the city: big-brained passerine birds succeed in urban environments2011In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 7, no 5, p. 730-732Article in journal (Refereed)
    Abstract [en]

    Urban regions are among the most human-altered environments on Earth and they are poised for rapid expansion following population growth and migration. Identifying the biological traits that determine which species are likely to succeed in urbanized habitats is important for predicting global trends in biodiversity. We provide the first evidence for the intuitive yet untested hypothesis that relative brain size is a key factor predisposing animals to successful establishment in cities. We apply phylogenetic mixed modelling in a Bayesian framework to show that passerine species that succeed in colonizing at least one of 12 European cities are more likely to belong to big-brained lineages than species avoiding these urban areas. These data support findings linking relative brain size with the ability to persist in novel and changing environments in vertebrate populations, and have important implications for our understanding of recent trends in biodiversity.

  • 8. Ollivier, Morgane
    et al.
    Tresset, Anne
    Frantz, Laurent A. F.
    Bréhard, Stéphanie
    Bălăşescu, Adrian
    Mashkour, Marjan
    Boroneanţ, Adina
    Pionnier-Capitan, Maud
    Lebrasseur, Ophélie
    Arbogast, Rose-Marie
    Bartosiewicz, László
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies.
    Debue, Karyne
    Rabinovich, Rivka
    Sablin, Mikhail V.
    Larson, Greger
    Hänni, Catherine
    Hitte, Christophe
    Vigne, Jean-Denis
    Dogs accompanied humans during the Neolithic expansion into Europe2018In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 14, no 10, article id 20180286Article in journal (Refereed)
    Abstract [en]

    Near Eastern Neolithic farmers introduced several species of domestic plants and animals as they dispersed into Europe. Dogs were the only domestic species present in both Europe and the Near East prior to the Neolithic. Here, we assessed whether early Near Eastern dogs possessed a unique mitochondrial lineage that differentiated them from Mesolithic European populations. We then analysed mitochondrial DNA sequences from 99 ancient European and Near Eastern dogs spanning the Upper Palaeolithic to the Bronze Age to assess if incoming farmers brought Near Eastern dogs with them, or instead primarily adopted indigenous European dogs after they arrived. Our results show that European pre-Neolithic dogs all possessed the mitochondrial haplogroup C, and that the Neolithic and Post-Neolithic dogs associated with farmers from Southeastern Europe mainly possessed haplogroup D. Thus, the appearance of haplogroup D most probably resulted from the dissemination of dogs from the Near East into Europe. In Western and Northern Europe, the turnover is incomplete and haplogroup C persists well into the Chalcolithic at least. These results suggest that dogs were an integral component of the Neolithic farming package and a mitochondrial lineage associated with the Near East was introduced into Europe alongside pigs, cows, sheep and goats. It got diluted into the native dog population when reaching the Western and Northern margins of Europe.

  • 9.
    Peña, Carlos
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Wahlberg, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Prehistorical climate change increased diversification of a group of butterflies2008In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 4, p. 274-278Article in journal (Refereed)
  • 10.
    Rydin, Catarina
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bolinder, Kristina
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Moonlight pollination in the gymnosperm Ephedra (Gnetales)2015In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 11, no 4, article id 20140993Article in journal (Refereed)
    Abstract [en]

    Most gymnosperms are wind-pollinated, but some are insect-pollinated, and in Ephedra (Gnetales), both wind pollination and insect pollination occur. Little is, however, known about mechanisms and evolution of pollination syndromes in gymnosperms. Based on four seasons of field studies, we show an unexpected correlation between pollination and the phases of the moon in one of our studied species, Ephedra foeminea. It is pollinated by dipterans and lepidopterans, most of them nocturnal, and its pollination coincides with the full moon of July. This may be adaptive in two ways. Many nocturnal insects navigate using the moon. Further, the spectacular reflection of the full-moonlight in the pollination drops is the only apparent means of nocturnal attraction of insects in these plants. In the sympatric but wind-pollinated Ephedra distachya, pollination is not correlated to the full moon but occurs at approximately the same dates every year. The lunar correlation has probably been lost in most species of Ephedra subsequent an evolutionary shift to wind pollination in the clade. When the services of insects are no longer needed for successful pollination, the adaptive value of correlating pollination with the full moon is lost, and conceivably also the trait.

  • 11. Tsuboi, Masahito
    et al.
    Gonzalez-Voyer, Alejandro
    Stockholm University, Faculty of Science, Department of Zoology, Ethology. Universidad Nacional Autonoma de Mexico, Mexico.
    Kolm, Niclas
    Stockholm University, Faculty of Science, Department of Zoology, Ethology.
    Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids2015In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 11, no 5, article id 20141053Article in journal (Refereed)
    Abstract [en]

    Functional coupling, where a singlemorphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with biparental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution.

  • 12.
    Uggla, Caroline
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Andersson, Gunnar
    Stockholm University, Faculty of Social Sciences, Department of Sociology.
    Higher divorce risk when mates are plentiful? Evidence from Denmark2018In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 14, no 9, article id 20180475Article in journal (Refereed)
    Abstract [en]

    Work from social and biological sciences has shown that adult sex ratios are associated with relationship behaviours. When partners are abundant, opportunities for mate switching may increase and relationship stability decrease. To date, most of the human literature has used regional areas at various levels of aggregation to define partner markets. But, in developed countries, many individuals of reproductive age spend a considerable amount of time outside their residential areas, and other measures may better capture the opportunities to meet a (new) partner. Here, we use Danish register data to test whether the sex ratio of the occupational sector is linked to divorce. Our data cover individuals in Denmark who married during 1981-2002 and we control for age at and duration of marriage, education and parity. Results support the prediction that a higher proportion of opposite-sex individuals in one's occupational sector is associated with higher divorce risk. This holds for both men and women, but associations are somewhat stronger for men and vary by education. Our results highlight the need to study demographic behaviours of men and women simultaneously, and to consider partner markets beyond geographical areas so that differing strategies for males and females may be examined.

  • 13.
    Valdiosera, C.
    et al.
    Centro UCM-ISCIII de Evolucio´n y Comportamiento Humanos,C/Sinesio Delgado 4, 28029 Madrid, Spain.
    Garcia, N.
    Centro UCM-ISCIII de Evolucio´n y Comportamiento Humanos,C/Sinesio Delgado 4, 28029 Madrid, Spain.
    Dalen, L.
    Stockholm University, Faculty of Science, Department of Zoology.
    Smith, C.
    Departamento de Paleobiologı´a, Museo Nacional de Ciencias Naturales.
    Kahlke, R. D.
    Forschungsstation für Quartärpalä ontologie Weimar, ForschungsinstitutSenckenberg, Am Jakobskirchhof 4, 99423 Weimar, Germany.
    Liden, K.
    Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies. Stockholm University, Faculty of Humanities, Department of Archaeology and Classical Studies, Archaeological Research Laboratory.
    Angerbjörn, A.
    Stockholm University, Faculty of Science, Department of Zoology.
    Arsuaga, J. L.
    Centro UCM-ISCIII de Evolucio´n y Comportamiento Humanos,C/Sinesio Delgado 4, 28029 Madrid, Spain.
    Götherström, A.
    Department of Evolutionary Biology, Uppsala University.
    Typing single polymorphic nucleotides in mitochondrial DNA as a way to access Middle Pleistocene DNA2006In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 2, no 4, p. 601-603Article in journal (Refereed)
    Abstract [en]

    In this study, we have used a technique designed to target short fragments containing informative mitochondrial substitutions to extend the temporal limits of DNA recovery and study the molecular phylogeny of Ursus deningeri. We present a cladistic analysis using DNA recovered from 400 kyr old U. deningeri remains, which demonstrates U. deningeri's relation to Ursus spelaeus. This study extends the limits of recovery from skeletal remains by almost 300 kyr. Plant material from permafrost environments has yielded DNA of this age in earlier studies, and our data suggest that DNA in teeth from cave environments may be equally well preserved.

  • 14. Wedell, Nina
    et al.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Bergström, Jonas
    Stockholm University, Faculty of Science, Department of Zoology.
    Coevolution of non-fertile sperm and female receptivity in a butterfly.2009In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 5, no 5, p. 678-81Article in journal (Refereed)
    Abstract [en]

    Sexual conflict can promote rapid evolution of male and female reproductive traits. Males of many polyandrous butterflies transfer nutrients at mating that enhances female fecundity, but generates sexual conflict over female remating due to sperm competition. Butterflies produce both normal fertilizing sperm and large numbers of non-fertile sperm. In the green-veined white butterfly, Pieris napi, non-fertile sperm fill the females' sperm storage organ, switching off receptivity and thereby reducing female remating. There is genetic variation in the number of non-fertile sperm stored, which directly relates to the female's refractory period. There is also genetic variation in males' sperm production. Here, we show that females' refractory period and males' sperm production are genetically correlated using quantitative genetic and selection experiments. Thus selection on male manipulation may increase the frequency of susceptible females to such manipulations as a correlated response and vice versa.

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