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Life history evolution during a climate-driven butterfly range expansion
Stockholm University, Faculty of Science, Department of Zoology.ORCID iD: 0000-0002-4628-0584
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Climate change pushes species polewards and upwards – as temperatures rise, species move to areas that were previously too cold for them. During range expansions, species encounter unfamiliar environmental conditions, which may require evolutionary adaptation, but expanding populations may often be hampered by their genetic and demographic properties. Whether range-expanding populations can adapt may greatly affect species distributions, but the question is largely unexplored for native species expanding in response to climate change. 

In seasonal environments, organisms must endure harsh conditions and synchronise growth and reproduction with the presence of food and mates. To time their life cycles, many animals and plants use seasonal changes in daylength. Insects typically overwinter in diapause (dormancy with paused development and suppressed metabolism), which is induced by short days well before winter. But across-latitude differences in daylength pose challenges for latitudinal range expansions. I focus on whether traits related to seasonal timing and winter survival have evolved during range expansion of the wall brown butterfly (Lasiommata megera) in Sweden.

In Chapter I, I confirmed that the wall brown has, in 2000–2020, expanded northwards along the eastern and western coasts of Sweden, and in Chapter II, I demonstrated that these parallel expansions have proceeded independently from the south, in isolation from each other. Laboratory experiments in Chapter I revealed that caterpillars from northern populations have evolved to correctly interpret their local daylength cues. This rapid evolution, repeated along two range expansions, indicates that latitudinal differences in daylength may seldom hinder insect range expansions. In Chapter II, I found that northern range margin populations have lower genetic variation than southern ones but are unlikely to have received much locally maladaptive gene flow from the south. Further, a genomic scan suggested that the parallel phenotypic changes have evolved through non-parallel genetic changes. In Chapter III, a laboratory experiment showed lack of local adaptation to different winters, in contrast to the rapid evolution of diapause timing. Overall winter survival was low in the coldest treatment, indicating that winter temperatures limit the range.

In Chapter IV, I studied diapause induction, growth rate, and winter survival in a field setting. Almost all individuals entered diapause, with only minimal impact from the among-population differences found in Chapter I. These evolved differences could stem from natural selection on earlier parts of the generation, which experience longer days than our experiment captured. Further, individuals of northern descent grew faster than those from the south. This could help them grow large enough before winter, yet pre-winter mass did not affect winter survival. This time, natural selection may favour high growth rates in late-hatching individuals with less time to grow before winter. Like in Chapter III, there was no evidence for evolution of improved winter survival, and survival dropped markedly when transplanting individuals outside of the current range.

Despite rapid evolution in two traits, cold winters limit the wall brown’s expansion. To predict range expansions, we must pinpoint their drivers, study trait evolution relevant to these drivers, and recognize that traits that are crucial in different seasons may vary in evolvability.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University , 2024. , p. 52
Keywords [en]
climate change, diapause, genomics, insect cold tolerance, life cycle, local adaptation, parallel evolution, photoperiodism, reciprocal transplant
National Category
Ecology Evolutionary Biology Zoology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-227080ISBN: 978-91-8014-693-7 (print)ISBN: 978-91-8014-694-4 (electronic)OAI: oai:DiVA.org:su-227080DiVA, id: diva2:1842272
Public defence
2024-04-12, Vivi Täckholmsalen (Q-salen), NPQ-huset, Svante Arrhenius väg 20 and online via Zoom, public link is available at the department website, Stockholm, 14:00 (English)
Opponent
Supervisors
Available from: 2024-03-20 Created: 2024-03-04 Last updated: 2024-03-11Bibliographically approved
List of papers
1. Local adaptation to seasonal cues at the fronts of two parallel, climate-induced butterfly range expansions
Open this publication in new window or tab >>Local adaptation to seasonal cues at the fronts of two parallel, climate-induced butterfly range expansions
2022 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 25, no 9, p. 2022-2033Article in journal (Refereed) Published
Abstract [en]

Climate change allows species to expand polewards, but non-changing environmental features may limit expansions. Daylength is unaffected by climate and drives life cycle timing in many animals and plants. Because daylength varies over latitudes, poleward-expanding populations must adapt to new daylength conditions. We studied local adaptation to daylength in the butterfly Lasiommata megera, which is expanding northwards along several routes in Europe. Using common garden laboratory experiments with controlled daylengths, we compared diapause induction between populations from the southern-Swedish core range and recently established marginal populations from two independent expansion fronts in Sweden. Caterpillars from the northern populations entered diapause in clearly longer daylengths than those from southern populations, with the exception of caterpillars from one geographically isolated population. The northern populations have repeatedly and rapidly adapted to their local daylengths, indicating that the common use of daylength as seasonal cue need not strongly limit climate-induced insect range expansions.

Keywords
climate change, diapause, Lepidoptera, Nymphalidae, phenotypic plasticity, photoperiodism, reaction norm, seasonal adaptation
National Category
Biological Sciences Ecology
Research subject
Ecology and Evolution
Identifiers
urn:nbn:se:su:diva-209490 (URN)10.1111/ele.14085 (DOI)000840397700001 ()35965449 (PubMedID)2-s2.0-85135788453 (Scopus ID)
Funder
Carl Tryggers foundation Swedish Research Council, 2017‐04500
Available from: 2022-09-21 Created: 2022-09-21 Last updated: 2024-03-04Bibliographically approved
2. Repeated evolution of seasonal plasticity during a climate-driven butterfly range expansion is not associated with parallel genomic signatures of selection
Open this publication in new window or tab >>Repeated evolution of seasonal plasticity during a climate-driven butterfly range expansion is not associated with parallel genomic signatures of selection
(English)Manuscript (preprint) (Other academic)
National Category
Evolutionary Biology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-227079 (URN)
Available from: 2024-02-28 Created: 2024-02-28 Last updated: 2024-03-06Bibliographically approved
3. A range-expanding butterfly is susceptible to cold and long winters but shows no signs of local adaptation to winter conditions
Open this publication in new window or tab >>A range-expanding butterfly is susceptible to cold and long winters but shows no signs of local adaptation to winter conditions
2023 (English)In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 37, no 12, p. 3064-3078Article in journal (Refereed) Published
Abstract [en]
  1. Numerous species shift or expand their ranges poleward in response to climate change. Even when expanding species follow their climatic niches, expanding range margin populations are likely to face unfamiliar environmental conditions and thus natural selection for local adaptation.
  2. The wall brown butterfly (Lasiommata megera) has expanded northward in Sweden in the years 2000–2020, most likely as a result of climate change, and has previously been shown to have evolved local adaptations to northern daylength conditions. This evolution has occurred despite hypothesised genetic constraints to adaptation at range margins.
  3. We studied local adaptation to winter conditions in four of the previously-studied L. megera populations, using a common garden laboratory experiment with a warm and short, an intermediate, and a cold and long winter treatment. We compared the winter and post-winter survival of caterpillars from two southern core range and two northern range margin populations in Sweden.
  4. During the experiment, we measured metabolic rates of a subset of diapausing caterpillars to test whether populations differ in metabolic suppression during diapause. Further, we measured supercooling points, which reflect lower lethal temperature in L. megera, of the same subset of caterpillars. We also compared supercooling points between L. megera and three closely related species with more northern distributions.
  5. Few individuals survived the coldest treatment all the way to successful adult emergence, so L. megera seems susceptible to cold winters. Individuals of northern descent did not survive cold winters any better than individuals from southern populations. Similarly, there were no signs of local adaptation in metabolic rates or supercooling points. The comparison among species did not reveal any clear relationship between geographical distribution and supercooling point.
  6. Although northern winters probably exert strong selection on L. megera, we provide comprehensive evidence for the lack of local adaptation to winter conditions. This contrasts with the previous finding of quickly evolved local adaptation in diapause timing, highlighting the need to consider how traits associated with different seasons differ in how they may evolve and facilitate climate change-induced range expansions.
Keywords
cold tolerance, diapause, ecophysiology, Lepidoptera: Nymphalidae, Satyrinae
National Category
Ecology Zoology
Identifiers
urn:nbn:se:su:diva-223873 (URN)10.1111/1365-2435.14445 (DOI)001083745600001 ()2-s2.0-85173639106 (Scopus ID)
Available from: 2023-11-21 Created: 2023-11-21 Last updated: 2024-03-04Bibliographically approved
4. Winters restrict a climate change-driven butterfly range expansion despite rapid evolution of two seasonal timing traits
Open this publication in new window or tab >>Winters restrict a climate change-driven butterfly range expansion despite rapid evolution of two seasonal timing traits
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-227078 (URN)
Available from: 2024-02-28 Created: 2024-02-28 Last updated: 2024-03-06Bibliographically approved

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