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How does sympatric evolution shape reproductive isolation in spider mites?
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Orientador(es)
Resumo(s)
In many species, negative interspecific sexual interactions owing to incomplete species recognition and
hybridization (i.e., reproductive interference) can lead to the rapid extinction/displacement of
populations. Nevertheless, if species persist long enough in sympatry, it may also drive the evolution of
stronger pre-zygotic isolation (e.g., reinforcement), thereby completing speciation, or, in the presence
of gene flow, it may instead select for weaker post-zygotic isolation, thereby reversing speciation.
Determining what reproductive barriers (pre-zygotic and/or post-zygotic) are more likely to evolve in
sympatry may thus allow better understanding the fate of interacting species.
In this project, I used a pair of hybridizing genetically divergent colour form populations of the
spider mite species Tetranychus urticae (green and red), which were previously shown to be fully postzygotically isolated. Following up to 69 generations of experimental evolution in sympatry or allopatry,
I performed three different experiments to assess, respectively, pre-mating, post-mating pre-zygotic and
early post-zygotic, as well as late post-zygotic barriers.
I found that none of the tested reproductive barriers evolved during experimental evolution, but
that green-form females evolved in sympatry differed from those evolved in allopatry. They had a lower
fecundity, their offspring had a higher juvenile mortality, and their sex-ratio was more skewed towards
females. Altogether, these results show that reproductive interference can quickly drive the evolution of
a species’ reproductive traits and sex allocation. However, I also found that, conversely to our previous
knowledge, late reproductive barriers were incomplete between all populations of the two forms.
Therefore, genetic analyses would be necessary to determine whether the observed evolutionary
responses result from selection, or are the by-product of gene flow in this system. Finally, these results
also call for further research on other possible evolutionary responses, as well as on the ecological
consequences of reproductive interference in natural populations.
Descrição
Tese de mestrado, Biologia da Conservação, 2022, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Isolamento reprodutivo interferência reprodutiva evolução experimental simpatria ácaros-aranha Teses de mestrado - 2022