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Errbii M, Gadau J, Becker K, Schrader L, Oettler J. Causes and consequences of a complex recombinational landscape in the ant Cardiocondyla obscurior. Genome Res 2024; 34:863-876. [PMID: 38839375 PMCID: PMC11293551 DOI: 10.1101/gr.278392.123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 05/30/2024] [Indexed: 06/07/2024]
Abstract
Eusocial Hymenoptera have the highest recombination rates among all multicellular animals studied so far, but it is unclear why this is and how this affects the biology of individual species. A high-resolution linkage map for the ant Cardiocondyla obscurior corroborates genome-wide high recombination rates reported for ants (8.1 cM/Mb). However, recombination is locally suppressed in regions that are enriched with TEs, that have strong haplotype divergence, or that show signatures of epistatic selection in C. obscurior The results do not support the hypotheses that high recombination rates are linked to phenotypic plasticity or to modulating selection efficiency. Instead, genetic diversity and the frequency of structural variants correlate positively with local recombination rates, potentially compensating for the low levels of genetic variation expected in haplodiploid social Hymenoptera with low effective population size. Ultimately, the data show that recombination contributes to within-population polymorphism and to the divergence of the lineages within C. obscurior.
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Affiliation(s)
- Mohammed Errbii
- Institute for Evolution and Biodiversity, University of Münster, 48149 Münster, Germany
| | - Jürgen Gadau
- Institute for Evolution and Biodiversity, University of Münster, 48149 Münster, Germany
| | - Kerstin Becker
- Cologne Center for Genomics (CCG), Medical Faculty, University of Cologne, 50931 Cologne, Germany
| | - Lukas Schrader
- Institute for Evolution and Biodiversity, University of Münster, 48149 Münster, Germany;
| | - Jan Oettler
- Lehrstuhl für Zoologie/Evolutionsbiologie, University Regensburg, 93053 Regensburg, Germany
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2
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Brülhart J, Süß A, Oettler J, Heinze J, Schultner E. Sex- and caste-specific developmental responses to juvenile hormone in an ant with maternal caste determination. J Exp Biol 2024; 227:jeb247396. [PMID: 38779857 PMCID: PMC11418025 DOI: 10.1242/jeb.247396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 05/16/2024] [Indexed: 05/25/2024]
Abstract
Juvenile hormone is considered to be a master regulator of polyphenism in social insects. In the ant Cardiocondyla obscurior, whether a female egg develops into a queen or a worker is determined maternally and caste-specific differentiation occurs in embryos, so that queens and workers can be distinguished in a non-invasive manner from late embryogenesis onwards. This ant also exhibits two male morphs - winged and wingless males. Here, we used topical treatment with juvenile hormone III and its synthetic analogue methoprene, a method that influences caste determination and differentiation in some ant species, to investigate whether hormone manipulation affects the development and growth of male, queen- and worker-destined embryos and larvae. We found no effect of hormone treatment on female caste ratios or body sizes in any of the treated stages, even though individuals reacted to heightened hormone availability with increased expression of krüppel-homolog 1, a conserved JH first-response gene. In contrast, hormone treatment resulted in the emergence of significantly larger males, although male morph fate was not affected. These results show that in C. obscurior, maternal caste determination leads to irreversible and highly canalized caste-specific development and growth.
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Affiliation(s)
- Jeanne Brülhart
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Anja Süß
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Jan Oettler
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Jürgen Heinze
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
| | - Eva Schultner
- Zoologie/Evolutionsbiologie, Universität Regensburg, 93053 Regensburg, Germany
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3
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Seistrup AS, Choppin M, Govind S, Feldmeyer B, Kever M, Karaulanov E, Séguret A, Karunanithi S, Almeida MV, Ketting RF, Foitzik S. Age- and caste-independent piRNAs in the germline and miRNA profiles linked to caste and fecundity in the ant Temnothorax rugatulus. Mol Ecol 2023; 32:6027-6043. [PMID: 37830492 DOI: 10.1111/mec.17162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 09/26/2023] [Indexed: 10/14/2023]
Abstract
Social insects are models for studies of phenotypic plasticity. Ant queens and workers vary in fecundity and lifespan, which are enhanced and extended in queens. Yet, the regulatory mechanisms underlying this variation are not well understood. Ant queens live and reproduce for years, so that they need to protect their germline from transposable element (TE) activity, which may be redundant in short-lived, often sterile workers. We analysed the expression of two protective classes of small RNAs, microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs), in various tissues, castes and age classes of the ant Temnothorax rugatulus. In queens, piRNAs were highly abundant in ovaries with TEs being their clear targets, with reduced but still detectable piRNA-specific ping-pong signatures in thorax and brains. piRNA pathway activity varied little with age in queens. Moreover, the reduced ovaries of workers also exhibited similar piRNA activity and this not only in young, fertile workers, but also in older foragers with regressed ovaries. Therefore, these ants protect their germline through piRNA activity, regardless of ovarian development, age or caste, even in sterile workers often considered the soma of the superorganism. Our tissue-specific miRNA analysis detected the expression of 304 miRNAs, of which 105 were expressed in all tissues, 10 enriched in the brain, three in the thorax, whereas 83 were ovarian-specific. We identified ovarian miRNAs whose expression was related to caste, fecundity and age, and which likely regulate group-specific gene expression. sRNA shifts in young- to middle-aged queens were minor, suggesting delayed senescence in this reproductive caste.
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Affiliation(s)
- Ann-Sophie Seistrup
- Institute of Molecular Biology, Mainz, Germany
- International PhD Programme on Gene Regulation, Epigenetics & Genome Stability, Mainz, Germany
| | - Marina Choppin
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Shamitha Govind
- Institute of Molecular Biology, Mainz, Germany
- International PhD Programme on Gene Regulation, Epigenetics & Genome Stability, Mainz, Germany
| | - Barbara Feldmeyer
- Senckenberg Biodiversity and Climate Research Centre (SBiK-F), Molecular Ecology, Frankfurt, Germany
| | - Marion Kever
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
| | | | - Alice Séguret
- School of Biological Sciences, University of Bristol, Bristol, UK
| | | | - Miguel V Almeida
- Institute of Molecular Biology, Mainz, Germany
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - René F Ketting
- Institute of Molecular Biology, Mainz, Germany
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Susanne Foitzik
- Institute of Organismic and Molecular Evolution, Johannes Gutenberg University Mainz, Mainz, Germany
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4
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Ozan M, Helanterä H, d'Ettorre P, Sundström L. Queen fecundity, worker entourage and cuticular chemistry in the ant Formica fusca. Proc Biol Sci 2023; 290:20230861. [PMID: 37554034 PMCID: PMC10410219 DOI: 10.1098/rspb.2023.0861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 07/06/2023] [Indexed: 08/10/2023] Open
Abstract
Cooperative breeding entails conflicts over reproductive shares that may be settled in different ways. In ants, where several queens simultaneously reproduce in a colony, both queens and workers may influence the reproductive apportionment and offspring quality. Queens may vary in their intrinsic fecundity, which may influence the size of the worker entourage attending individual queens, and this may eventually dictate the reproductive output of a queen. We tested whether the reproductive success of queens is affected by the size of their worker entourage, their fecundity at the onset of the reproductive season, and whether the queen cuticular hydrocarbon profile carries information on fecundity. We show that in the ant Formica fusca both queen fecundity and egg hatching success increase with the size of their entourage, and that newly hatched larvae produced by initially highly fecund queens are smaller. Furthermore, higher relatedness among workers increased queen fecundity. Finally, the queens that received a large worker entourage differed in the cuticular chemistry from those that received a small worker entourage. Our results thus show that workers play a pivotal role in determining queen fitness, that high intracolony relatedness among workers enhances the overall reproductive output in the colony, and that queen fecundity is reflected in their cuticular hydrocarbon profile.
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Affiliation(s)
- Martina Ozan
- Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, 00014, Finland
- Tvärminne Zoological Station, University of Helsinki, J.A. Palménintie 260, 10900 Hanko, Finland
| | - Heikki Helanterä
- Tvärminne Zoological Station, University of Helsinki, J.A. Palménintie 260, 10900 Hanko, Finland
- Faculty of Science, Ecology and Genetics Research Unit, University of Oulu, 90014, Finland
| | - Patrizia d'Ettorre
- Laboratoire d'Ethologie Expérimentale et Comparée, UR 4443, Université Sorbonne Paris Nord, Villetaneuse, France
- Institut Universitaire de France (IUF), Paris, France
| | - Liselotte Sundström
- Organismal and Evolutionary Biology, Faculty of Biological and Environmental Sciences, University of Helsinki, 00014, Finland
- Tvärminne Zoological Station, University of Helsinki, J.A. Palménintie 260, 10900 Hanko, Finland
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Mueller UG, Himler AG, Farrior CE. Life history, nest longevity, sex ratio, and nest architecture of the fungus-growing ant Mycetosoritis hartmanni (Formicidae: Attina). PLoS One 2023; 18:e0289146. [PMID: 37494382 PMCID: PMC10370743 DOI: 10.1371/journal.pone.0289146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 07/12/2023] [Indexed: 07/28/2023] Open
Abstract
Mycetosoritis hartmanni is a rarely collected fungus-farming ant of North America. We describe life history and nest architecture for a M. hartmanni population in central Texas, USA. Colonies are monogynous with typically less than 100 workers (average 47.6 workers, maximum 148 workers). Nests occur always in sand and have a uniform architecture with 1-3 underground garden chambers arranged along a vertical tunnel, with the deepest gardens 50-70 cm deep. Foragers are active primarily between April and October. After reduced activity between November and February, egg laying by queens resumes in April, and the first worker pupae develop in early June. Reproductive females and males are reared primarily in July and August, with proportionally more females produced early in summer (protogyny). Mating flights and founding of new nests by mated females occur in late June to August, but may extend through September. For a cohort of 150 established nests (nests that had survived at least one year after nest founding), the estimated mortality rate was 0.41-0.53, the estimated average lifespan for these nests was 1.9-2.5 years, and the longest-living nests were observed to live for 6 years. These life-history parameters for M. hartmanni in central Texas are consistent with information from additional M. hartmanni nests observed throughout the range of this species from eastern Louisiana to southern Texas. Throughout its range in the USA, M. hartmanni can be locally very abundant in sun-exposed, sandy soil. Abundance of M. hartmanni seems so far relatively unaffected by invasive fire ants, and at present M. hartmanni does not appear to be an endangered species.
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Affiliation(s)
- Ulrich G Mueller
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States of America
| | - Anna G Himler
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States of America
- Department of Biology, College of Idaho, Caldwell, ID, United States of America
| | - Caroline E Farrior
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States of America
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6
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Collins DH, Prince DC, Donelan JL, Chapman T, Bourke AFG. Costs of reproduction are present but latent in eusocial bumblebee queens. BMC Biol 2023; 21:153. [PMID: 37430246 DOI: 10.1186/s12915-023-01648-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 06/12/2023] [Indexed: 07/12/2023] Open
Abstract
BACKGROUND The standard evolutionary theory of ageing proposes that ageing occurs because of a trade-off between reproduction and longevity. Eusocial insect queens exhibit positive fecundity-longevity associations and so have been suggested to be counter-examples through not expressing costs of reproduction and through remodelling conserved genetic and endocrine networks regulating ageing and reproduction. If so, eusocial evolution from solitary ancestors with negative fecundity-longevity associations must have involved a stage at which costs of reproduction were suppressed and fecundity and longevity became positively associated. Using the bumblebee (Bombus terrestris), we experimentally tested whether queens in annual eusocial insects at an intermediate level of eusocial complexity experience costs of reproduction, and, using mRNA-seq, the extent to which they exhibit a remodelling of relevant genetic and endocrine networks. Specifically, we tested whether costs of reproduction are present but latent, or whether a remodelling of relevant genetic and endocrine networks has already occurred allowing queens to reproduce without costs. RESULTS We experimentally increased queens' costs of reproduction by removing their eggs, which caused queens to increase their egg-laying rate. Treatment queens had significantly reduced longevity relative to control queens whose egg-laying rate was not increased. Reduced longevity in treatment queens was not caused by increased worker-to-queen aggression or by increased overall activity in queens. In addition, treatment and control queens differed in age-related gene expression based on mRNA-seq in both their overall expression profiles and the expression of ageing-related genes. Remarkably, these differences appeared to occur principally with respect to relative age, not chronological age. CONCLUSIONS This study represents the first simultaneously phenotypic and transcriptomic experimental test for a longevity cost of reproduction in eusocial insect queens. The results support the occurrence of costs of reproduction in annual eusocial insects of intermediate social complexity and suggest that reproductive costs are present but latent in queens of such species, i.e. that these queens exhibit condition-dependent positive fecundity-longevity associations. They also raise the possibility that a partial remodelling of genetic and endocrine networks underpinning ageing may have occurred in intermediately eusocial species such that, in unmanipulated conditions, age-related gene expression depends more on chronological than relative age.
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Affiliation(s)
- David H Collins
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
| | - David C Prince
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Jenny L Donelan
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Tracey Chapman
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Andrew F G Bourke
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
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7
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Schultner E, Wallner T, Dofka B, Brülhart J, Heinze J, Freitak D, Pokorny T, Oettler J. Queens control caste allocation in the ant Cardiocondyla obscurior. Proc Biol Sci 2023; 290:20221784. [PMID: 36750190 PMCID: PMC9904955 DOI: 10.1098/rspb.2022.1784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 01/17/2023] [Indexed: 02/09/2023] Open
Abstract
Social insect queens and workers can engage in conflict over reproductive allocation when they have different fitness optima. Here, we show that queens have control over queen-worker caste allocation in the ant Cardiocondyla obscurior, a species in which workers lack reproductive organs. We describe crystalline deposits that distinguish castes from the egg stage onwards, providing the first report of a discrete trait that can be used to identify ant caste throughout pre-imaginal development. The comparison of queen and worker-destined eggs and larvae revealed size and weight differences in late development, but no discernible differences in traits that may be used in social interactions, including hair morphology and cuticular odours. In line with a lack of caste-specific traits, adult workers treated developing queens and workers indiscriminately. Together with previous studies demonstrating queen control over sex allocation, these results show that queens control reproductive allocation in C. obscurior and suggest that the fitness interests of colony members are aligned to optimize resource allocation in this ant.
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Affiliation(s)
- Eva Schultner
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Tobias Wallner
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Benjamin Dofka
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Jeanne Brülhart
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Jürgen Heinze
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Dalial Freitak
- Institute for Biology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
| | - Tamara Pokorny
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | - Jan Oettler
- Zoology/Evolutionary Biology, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
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Kreider JJ, Kramer BH, Komdeur J, Pen I. The evolution of ageing in cooperative breeders. Evol Lett 2022; 6:450-459. [PMID: 36579168 PMCID: PMC9783459 DOI: 10.1002/evl3.307] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 10/24/2022] [Accepted: 11/06/2022] [Indexed: 12/03/2022] Open
Abstract
Cooperatively breeding animals live longer than their solitary counterparts. This has been suggested for birds, mole rats, and social insects. A common explanation for these long lifespans is that cooperative breeding evolves more readily in long-lived species because lower mortality reduces the rate of territory turnover and thus leads to a limitation of breeding territories. Here, we reverse this argument and show that-rather than being a cause for its evolution-long lifespans are an evolutionary consequence of cooperative breeding. In evolutionary individual-based simulations, we show that natural selection favors a delayed onset of senescence in cooperative breeders, relative to solitary breeders, because cooperative breeders have a delayed age of first reproduction as helpers wait in a reproductive queue to obtain breeder status. Especially long lifespans evolve in cooperative breeders in which queue positions depend on the helpers' age rank among the helpers within the breeding territory. Furthermore, we show that lower genetic relatedness among group members leads to the evolution of longer lifespans. This is because selection against higher mortality is weaker when mortality reduces competition for breeding between relatives. Our results link the evolutionary theory of ageing with kin selection theory, demonstrating that the evolution of ageing in cooperative breeders is driven by the timing of reproduction and kin structure within breeding territories.
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Affiliation(s)
- Jan J. Kreider
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands,Behavioural and Physiological Ecology, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Boris H. Kramer
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Jan Komdeur
- Behavioural and Physiological Ecology, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Ido Pen
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
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Vidal M, Heinze J. Assisted dispersal and reproductive success in an ant species with matchmaking. Ecol Evol 2022; 12:e9236. [PMID: 36016821 PMCID: PMC9398888 DOI: 10.1002/ece3.9236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/28/2022] [Accepted: 08/01/2022] [Indexed: 11/27/2022] Open
Abstract
Workers of the ant Cardiocondyla elegans drop female sexuals into the nest entrance of other colonies to promote outbreeding with unrelated, wingless males. Corroborating the results from previous years, we document that carrier and carried female sexuals are typically related and that the transfer initially occurs mostly from their joint natal colonies to unrelated colonies. Female sexuals mate multiply with up to seven genetically distinguishable males. Contrary to our expectation, the colony growth rate of multiple-mated and outbred female sexuals was lower than that of inbred or single-mated females, leading to the question of why female sexuals mate multiply at all. Despite the obvious costs, multiple mating might be a way for female sexuals to "pay rent" for hibernation in an alien nest. We argue that in addition to evade inbreeding depression from regular sibling mating over many generations, assisted dispersal might also be a strategy for minimizing the risk of losing all reproductive investment when nests are flooded in winter.
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Affiliation(s)
- Mathilde Vidal
- LS Zoologie/EvolutionsbiologieUniversität RegensburgRegensburgGermany
| | - Jürgen Heinze
- LS Zoologie/EvolutionsbiologieUniversität RegensburgRegensburgGermany
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