G5 Doctoral dissertation (article)
Mechanisms underlying speciation and adaptation processes in two closely related Drosophila virilis group species (2021)
Lajiutumiseen ja sopeutumiseen liittyvät tekijät kahdella lähisukuisella Drosophila virilis -ryhmän lajilla

Poikela, N. (2021). Mechanisms underlying speciation and adaptation processes in two closely related Drosophila virilis group species [Doctoral dissertation]. Jyväskylän yliopisto. JYU Dissertations, 367. http://urn.fi/URN:ISBN:978-951-39-8581-3

JYU authors or editors

Publication details

All authors or editors: Poikela, Noora

eISBN: 978-951-39-8581-3

Journal or series: JYU Dissertations

eISSN: 2489-9003

Publication year: 2021

Number in series: 367

Number of pages in the book: 1 verkkoaineisto (51 sivua, 60 sivua useina numerointijaksoina, 45 numeroimatonta sivua)

Publisher: Jyväskylän yliopisto

Place of Publication: Jyväskylä

Publication country: Finland

Publication language: English

Persistent website address: http://urn.fi/URN:ISBN:978-951-39-8581-3

Publication open access: Openly available

Publication channel open access: Open Access channel

Abstract

Speciation is a slow process that proceeds through populations’ ecological divergence and the development of reproductive barriers. Populations living in the same area (sympatry) are susceptible to the disruptive effects of gene flow and recombination, which can slow down or prevent their divergence. Accordingly, natural selection may favour genetic mechanisms, like chromosomal inversions, which protect divergent loci from the homogenising effects of gene exchange and promote speciation. In this dissertation, I investigated the central aspects of speciation and adaptation using two closely related fly species, Drosophila montana and D. flavomontana. In the first chapter, I found the reproductive barriers between these species to be strong, but not complete. In D. flavomontana, the prezygotic barriers showed signs of reinforcement in sympatric populations, the type of barriers varying according to the length of species coexistence and/or species abundancies. The second chapter showed ecological isolation between D. montana and D. flavomontana to be enhanced by multiple environmental variables and to be largely based on species differences in cold tolerance. The third chapter suggested that chromosomal inversions had originated already before the species’ split, where they may have played an important role in the development of early reproductive barriers and/or ecological differences between local populations of the ancestral form. The last chapter, where I performed repeated interspecific backcrosses, indicated that the X chromosomal inversions, together with an incompatibility locus residing within them, effectively prevent gene flow from D. montana to D. flavomontana. Overall, this dissertation gives a comprehensive overview of the mechanisms underlying speciation and adaptation processes in these two species. It supports the existing speciation theories, but also brings up new perspectives, and shows that finding the final answers in speciation research is extremely challenging.

Keywords: evolution; natural selection; speciation; adaptation (change); hybridisation; cold resistance; population genetics; sex chromosomes; Drosophilidae; doctoral dissertations

Free keywords: chromosomal inversions; cold tolerance; Drosophila; genetic incompatibilities; reinforcement; reproductive barriers; speciation

Contributing organizations

Ministry reporting: Yes

Reporting Year: 2021