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Abstract Prezygotic isolation is often stronger between sympatric as opposed to allopatric taxa, but the underlying cause can be difficult to infer from comparative studies alone. Experimental evolution, where evolutionary responses to treatments manipulating the presence/absence of heterospecific individuals are tracked, can provide a powerful complementary approach. We used experimental evolution to investigate a naturally occurring pattern of reproductive character displacement in the mushroom-feeding fly, Drosophila subquinaria. In nature, female D. subquinaria from populations sympatric with the closely related Drosophila recens discriminate more strongly against heterospecific males than do females from allopatric populations. Starting with 16 replicate allopatric populations of D. subquinaria, we manipulated the presence/absence of D. recens during mating (experimental sympatry vs. control) and, when present, we allowed hybrids to live or kill them each generation. Across 12 generations, heterospecific offspring production from no-choice mating trials between D. subquinaria females and D. recens males declined in both experimental sympatry treatments relative to the control, suggesting increased sexual isolation. Male cuticular hydrocarbon profiles also evolved, but only in the hybrids killed treatment. Our results strongly imply that the existing reproductive character displacement in wild D. subquinaria populations was an evolutionary response to selection arising from secondary contact with D. recens.
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Absence of female preference and the origin of a unisexual species, the Amazon molly ( Poecilia formosa )
Abstract The role of hybridization as a formative process in evolution has received much attention in the past few decades. A particularly fascinating outcome of hybrid speciation is the formation of asexual hybrid species. The Amazon molly (Poecilia formosa) is such a hybrid and originated from aP. mexicanamother and aP. latipinnafather. Consequently, a heterospecific mating must have occurred leading to the Amazon molly, indicating a breakdown of any potential prezygotic isolation between parental species. Here we studied the female mate preferences of extantP. mexicanaandP. latipinnafrom several populations using standard binary choice tests with males of both sexual species that were matched for size.Poecilia mexicanaandP. latipinnacan be crossed in the lab, however, the offspring are not asexual, but sexual F1s. In our study, we generated F1s and tested their mating preferences with sexual males of bothP. mexicanaandP. latipinnaagainst F1males. Overall, our results show that in extantP. mexicanaandP. latipinnano female preference for conspecific males was detectable. Consequently, heterospecific matings are possible and not hindered by any apparent behavioral prezygotic isolation. If female preferences in these species were comparable around the time the Amazon molly originated as a hybrid species ca. 100,000 years ago, matings leading to hybrids would be very likely. F1females also have no discernable mating preferences for either sexual males or F1males. Such lack of prezygotic behavioral isolation could potentially lead to F2individuals, backcrosses, and introgression.
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- Award ID(s):
- 1916519
- PAR ID:
- 10506314
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Ethology
- Volume:
- 130
- Issue:
- 8
- ISSN:
- 0179-1613
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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