Remating responses are consistent with male postcopulatory manipulation but not reinforcement in D. pseudoobscura

Abstract

Reinforcement occurs when hybridization between closely related lineages produces low-fitness offspring, prompting selection for elevated reproductive isolation specifically in areas of sympatry. Both premating and postmating prezygotic behaviors have been shown to be the target of reinforcing selection, but it remains unclear whether remating behaviors experience reinforcement, although they can also influence offspring identity and limit formation of hybrids. Here, we evaluated evidence for reinforcing selection on remating behaviors in Drosophila pseudoobscura, by comparing remating traits in females from populations historically allopatric and sympatric with Drosophila persimilis. We found that the propensity to remate was not higher in sympatric females, compared to allopatric females, regardless of whether the first mated male was heterospecific or conspecific. Moreover, remating behavior did not contribute to interspecific reproductive isolation among any population; that is, females showed no higher propensity to remate following a heterospecific first mating than following a conspecific first mating. Instead, we found that females are less likely to remate after initial matings with unfamiliar males, regardless of species identity. This is consistent with one scenario of postmating sexual conflict in which females are poorly defended against postcopulatory manipulation by males with whom they have not coevolved. Our results are generally inconsistent with reinforcement on remating traits and suggest that this behavior might be more strongly shaped by the consequences of local antagonistic male-female interactions than interactions with heterospecifics.

Keywords: allopatry; coevolution; reproductive isolation; sexual conflict; speciation; sympatry.

Figure 1

Collection locations for Drosophila pseudoobscura and Drosophila persimilis study populations. Mt. Saint Helena and Sierra are sympatric locations (both species); Zion is an allopatric site (D. pseudoobscura only). Inset: North American range maps for the two species; the range of D. persimilis is entirely contained within the broader D. pseudoobscura range

Figure 2

Mating (panel a) and remating (panel b) probabilities of D. pseudoobscura females following first matings with males from their own population (Own pop), a different conspecific population (Diff pop), and heterospecific males. p‐Values are from logistic regressions (see Section “3”)

Figure 3

Survival curves showing remating latencies of allopatric (a) and sympatric female (b) D. pseudoobscura when mated to different classes of first males: Own (conspecific male from the same population as the female); Diff (conspecific male from a different population); Hetero (heterospecific male). Figure S1 shows survival curves of remating latency separately for each isofemale line