Sexual and postmating reproductive isolation between allopatric Drosophila montana populations suggest speciation potential

Abstract

BackgroundWidely distributed species with populations adapted to different environmental conditions can provide valuable opportunities for tracing the onset of reproductive incompatibilities and their role in the speciation process. Drosophila montana, a D. virilis group species found in high latitude boreal forests in Nearctic and Palearctic regions around the globe, could be an excellent model system for studying the early stages of speciation, as a wealth of information concerning this species' ecology, mating system, life history, genetics and phylogeography is available. However, reproductive barriers between populations have hereto not been investigated.ResultsWe report both pre- and postmating barriers to reproduction between flies from European (Finnish) and North American (Canadian) populations of Drosophila montana. Using a series of mate-choice designs, we show that flies from these two populations mate assortatively (i.e., exhibit significant sexual isolation) while emphasizing the importance of experimental design in these kinds of studies. We also assessed potential postmating isolation by quantifying egg and progeny production in intra- and interpopulation crosses and show a significant one-way reduction in progeny production, affecting both male and female offspring equally.ConclusionWe provide evidence that allopatric D. montana populations exhibit reproductive isolation and we discuss the potential mechanisms involved. Our data emphasize the importance of experimental design in studies on premating isolation between recently diverged taxa and suggest that postmating barriers may be due to postcopulatory-prezygotic mechanisms. D. montana populations seem to be evolving multiple barriers to gene flow in allopatry and our study lays the groundwork for future investigations of the genetic and phenotypic mechanisms underlying these barriers.

Patterns of Evolutionary Conservation of Microsatellites (SSRs) Suggest a Faster Rate of Genome Evolution in Hymenoptera Than in Diptera

“…Some Drosophila species from mountainous areas or from colder climates or such species with more extended life cycles (Begon 1976; Keightley 2000; Jennings et al 2011) are known to have fewer generations per year, similar to D. willistoni and the Hawaiian D. grimshawi for which we assumed five generations per year.…”

Comparison of sexual compatibility in crosses between the southern and northern populations of the cabbage beetle Colaphellus bowringi

“…Interestingly, TA female fecundity was lower in intra‐population crosses than in inter‐population crosses but without showing a significant difference. It is possible that larger XS males may contain more sperm or can stimulate ovulation and oviposition (Jennings et al ., ). Our experiments also showed that inter‐population crosses (XS female × TA male and TA female × XS male) resulted in significantly lower egg hatching rate and shorter female longevity than intra‐population crosses from both XS and TA populations (Figs.…”

Precopulatory mating and postzygotic isolation between two walnut‐infesting species of Rhagoletis from Mexican highlands

“…In contrast, R. ramosae females mated with males of both species. Sexual selection has been claimed to be one of the most important forces triggering divergence and speciation between populations with allopatric history (Ritchie, 2007;Jennings et al, 2011). Sexual selection has been claimed to be one of the most important forces triggering divergence and speciation between populations with allopatric history (Ritchie, 2007;Jennings et al, 2011).…”