Origin of sexual isolation in Drosophila ananassae due to founder effects

Abstract

The origin of sexual isolation is the central event in the evolution of biological species and plays a key role in maintaining biological diversity. Three mass culture stocks of D. ananassae originating from different geographic localities showing no isolation with each other were subjected to different degrees of bottlenecks i.e. one pair, five pairs and ten pairs. These drift lines were passed through flush-crash cycle at every generation with same initial number of founders, and maintained for twenty-seven generations and then the pattern of matings was tested among these nine drift lines involving 36 crosses in total. In 23 of 36 crosses, the difference between homogamic and heterogamic matings was significant and isolation indices were significantly more than zero in one direction only providing evidence for asymmetrical sexual isolation. Further, when Bonferroni test for pair-wise analysis was employed, significant differences between homogamic and heterogamic matings were found in 25 crosses. These findings provide evidence for origin of sexual isolation by founder effects in D. ananassae.

The Genetic Basis of Female Mate Preference and Species Isolation inDrosophila

“…While the contribution of natural selection has been wellsupported, the impact of genetic drift has been debated within the literature. For example, a computer model exploring the development of behavioral isolation via sexual selection [16] and research that employed extreme bottlenecking [17] both showed that genetic drift can rapidly lead to some level of sexual isolation. On the other hand, speciation by genetic drift has been shown to be unlikely to occur [18, 19] because genes for mating behavior are most likely either pleiotropic and directly under natural selection, or are closely linked to genes that are under selection and therefore would not simply be fixed by a random process [20].…”

Species Differentiation on a Dynamic Landscape: Shifts in Metapopulation Genetic Structure Using the Chronology of the Hawaiian Archipelago

“…However, recent studies suggest that the effects of purging are unpredictable and rarely strong enough to eliminate inbreeding depression (Boakes et al 2007). Despite a lack of empirical support for the role of bottlenecks in facilitating differentiation in natural populations (but see for laboratory populations, Regan et al 2003; Nanda and Singh 2011) some theoretical evidence exists to suggest that bottlenecks may play a substantial role in the speciation process (Templeton 2008), though the genetic basis is still unclear and the ecological context is critical.…”

Disruptive selection for sternopleural bristle phenotypes inDrosophila ananassae

“…The degree of sexual isolation is stronger in isofemale lines than in natural populations and may involve genetic bottlenecks (Singh and Chatterjee 1985). It has also been demonstrated that there is an instability of the mate recognition system in D. ananassae (Singh and Chatterjee 1985;Nanda and Singh 2011a, 2011b, 2011c. Thoday and Gibson (1962) showed divergence for a polygenic character and ethological isolations were produced simultaneously by disruptive selection for a morphological character (sternopleural chaeta number) in D. melanogaster.…”