Behavioural mechanisms of sexual isolation involving multiple modalities and their inheritance

Abstract

Speciation research dissects the genetics and evolution of reproductive barriers between parental species. Hybrids are the “gatekeepers” of gene flow, so it is also important to understand the behavioural mechanisms and genetics of any potential isolation from their parental species. We tested the role of multiple behavioural barriers in reproductive isolation among closely related field crickets and their hybrids (Teleogryllus oceanicus and Teleogryllus commodus). These species hybridize in the laboratory, but the behaviour of hybrids is unusual and there is little evidence for gene flow in the wild. We found that heterospecific pairs exhibited reduced rates of courtship behaviour due to discrimination by both sexes, and that this behavioural isolation was symmetrical. However, hybrids were not sexually selected against and exhibited high rates of courtship behaviour even though hybrid females are sterile. Using reciprocal hybrid crosses, we characterized patterns of interspecific divergence and inheritance in key sexual traits that might underlie the mating patterns we found: calling song, courtship song and cuticular hydrocarbons (CHCs). Song traits exhibited both sex linkage and transgressive segregation, whereas CHCs exhibited only the latter. Calculations of the strength of isolation exerted by these sexual traits suggest that close‐range signals are as important as long‐distance signals in contributing to interspecific sexual isolation. The surprisingly weak mating barriers observed between hybrids and parental species highlight the need to examine reproductive isolating mechanisms and their genetic bases across different potential stages of introgressive hybridization.

Vocal divergence is concordant with genomic evidence for strong reproductive isolation in grasshopper mice (Onychomys)

“…Whereas speciation research has traditionally focused on single types of isolating mechanisms in a given system (e.g., genetic incompatibilities or ecological isolation; Coyne & Orr, ), recent work in invertebrates emphasizes the importance of multiple isolating mechanisms acting in concert (Dutta, Balakrishnan, & Tregenza, ; Gilman, Fowler‐Finn, & Hebets, ; Moran, Hunt, Mitchell, Ritchie, & Bailey, ). Here, we show that, contrary to prior suggestions (Sullivan et al, ), hybridization between O. arenicola and O. torridus either does not occur or is so rare that it is below the detection limits of our sample sizes.…”

Sexual selection and population divergence III: Interspecific and intraspecific variation in mating signals

“…Little is known about these species' interactions in sympatry, because research has focused almost exclusively on allopatric populations (e.g. Bailey & Macleod, 2013; Moran, Hunt, Mitchell, Ritchie, & Bailey, 2019; Pitchers et al., 2013; Simmons, Zuk, & Rotenberry, 2001). However, there is no evidence for contemporary gene flow (Moran et al., 2018) which could be due to successful reinforcement or reproductive isolation prior to secondary contact.…”

“…Male calling song plays a critical role in maintaining the boundary between T. commodus and T. oceanicus (Bailey & Macleod, 2013; Hill, Loftus‐Hills, & Gartside, 1972; Moran et al., 2019). In both species, calling song is a nondirectional, long‐range signal that transmits across distances orders of magnitude further than those involved in physical interactions (i.e.…”

“…Terminology for song parameters was coordinated to enable comparison between the two species and follows Moran et al. (2019)…”

Genomic signals of admixture and reinforcement between two closely related species of European sepsid flies

“…In recent years, multiple approaches have been employed to explore the importance of interspecific gene flow in sympatry vs. allopatry (e.g. Nakazato, Warren, & Moyle, 2010;Nadeau et al, 2013;Brandvain et al, 2014;Bouchemousse et al, 2016;Feulner & Seehausen, 2019;Kastally, Trasoletti, & Mardulyn, 2019;Moran et al, 2019). The objective of our study is to assess the extent of genome-wide admixture between S. cynipsea and S. neocynipsea in Europe by applying a version of the ABBA-BABA test for historical gene flow (Green et al, 2010;Durand et al, 2011;Soraggi et al, 2018) that can exploit genomewide allele frequency data of single nucleotide polymorphisms (SNPs).…”