Adaptation and ecological speciation in seasonally varying environments at high latitudes: Drosophila virilis group

Abstract

Living in high latitudes and altitudes sets specific requirements on species’ ability to forecast seasonal changes and to respond to them in an appropriate way. Adaptation into diverse environmental conditions can also lead to ecological speciation through habitat isolation or by inducing changes in traits that influence assortative mating. In this review, we explain how the unique time-measuring systems of Drosophila virilis group species have enabled the species to occupy high latitudes and how the traits involved in species reproduction and survival exhibit strong linkage with latitudinally varying photoperiodic and climatic conditions. We also describe variation in reproductive barriers between the populations of two species with overlapping distributions and show how local adaptation and the reinforcement of prezygotic barriers have created partial reproductive isolation between conspecific populations. Finally, we consider the role of species-specific chromosomal inversions and the X chromosome in the development of reproductive barriers between diverging lineages.

Experimental introgression inDrosophila: asymmetric postzygotic isolation associated with chromosomal inversions and an incompatibility locus on the X chromosome

“…Two closely-related species of the Drosophila virilis group, D. montana and D. flavomontana , provide an excellent test case for studying the evolution of BDMIs. The species originate from the Rocky Mountains of North America, where the divergence of the montana complex species ( D. flavomontana, D. lacicola and D. borealis ) most likely occurred (Hoikkala & Poikela, 2022; Patterson, 1952; Throckmorton, 1982). D. montana has expanded around the northern hemisphere, whereas D. flavomontana has remained in North America (Hoikkala & Poikela, 2022).…”

“…The species originate from the Rocky Mountains of North America, where the divergence of the montana complex species ( D. flavomontana, D. lacicola and D. borealis ) most likely occurred (Hoikkala & Poikela, 2022; Patterson, 1952; Throckmorton, 1982). D. montana has expanded around the northern hemisphere, whereas D. flavomontana has remained in North America (Hoikkala & Poikela, 2022). D. montana lives generally in colder environments and uses different host trees than D. flavomontana (Patterson, 1952; Throckmorton, 1982).…”

Chromosomal inversions and the demography of speciation inDrosophila montanaandDrosophila flavomontana

“…Based on the polytene chromosome studies, these species have several alternatively fixed inversions (Stone et al 1960; Throckmorton 1982), but studies on the genomic divergence of the inversions are still lacking. Species of the montana complex ( D. montana , D. flavomontana, D. lacicola and D. borealis ) have diverged ∼3.8 Mya in the Rocky Mountains area (Patterson 1952; Throckmorton 1982; Hoikkala and Poikela 2022; Yusuf et al 2022), and presently D. montana and D. flavomontana inhabit variable climates in the Rocky Mountains and the western coast of North America (Hoikkala and Poikela 2022). In the mountains, D. montana has spread to higher altitudes than D. flavomontana , while on the western coast, where D. flavomontana has spread relatively recently, both species live at low altitudes (Fig.…”

“…In the mountains, D. montana has spread to higher altitudes than D. flavomontana , while on the western coast, where D. flavomontana has spread relatively recently, both species live at low altitudes (Fig. 1; (Patterson 1952; Poikela et al 2019; Hoikkala and Poikela 2022)). In both sites, populations of the two species can be regarded as sympatric or parapatric.…”

Divergence and introgression among the virilis group of Drosophila

“…The virilis group has been used extensively to study adaptation and speciation (Throckmorton 1982;Hoikkala and Poikela 2022). Postzygotic barriers have evolved to varying degrees (Throckmorton 1982;Orr and Coyne 1989) and postmating prezygotic (PMPZ) barriers have been shown to cause reductions in both interspecific and interpopulation fertilization (Sweigart 2010;Ahmed-Braimah 2016;Garlovsky and Snook 2018;Poikela et al 2019;Garlovsky et al 2020).…”