Premating Reproductive Barriers between Hybridising Cricket Species Differing in Their Degree of Polyandry

Abstract

Understanding speciation hinges on understanding how reproductive barriers arise between incompletely isolated populations. Despite their crucial role in speciation, prezygotic barriers are relatively poorly understood and hard to predict. We use two closely related cricket species, Gryllus bimaculatus and G. campestris, to experimentally investigate premating barriers during three sequential mate choice steps. Furthermore, we experimentally show a significant difference in polyandry levels between the two species and subsequently test the hypothesis that females of the more polyandrous species, G. bimaculatus, will be less discriminating against heterospecific males and hence hybridise more readily. During close-range mating behaviour experiments, males showed relatively weak species discrimination but females discriminated very strongly. In line with our predictions, this discrimination is asymmetric, with the more polyandrous G. bimaculatus mating heterospecifically and G. campestris females never mating heterospecifically. Our study shows clear differences in the strength of reproductive isolation during the mate choice process depending on sex and species, which may have important consequences for the evolution of reproductive barriers.

Genetic identification of a non-native species introgression into wild population of the field cricket Gryllus campestris (Orthoptera: Gryllidae) in Central Europe

“…The latter species' range in Europe is mainly restricted to the Mediterranean coastal regions. Both species share common life histories, utilizing similar habitats and have recently been studied for patterns of reproductive barrier development that may have caused their speciation and prevent hybridization Veen et al, 2011Veen et al, , 2013. Contact zones between these two fi eld cricket species exist in south-eastern Spain and probably also in Italy and further east, although geographical barriers like the Cantabrian Mountains probably prevent secondary contact (Bazyluk & Liana, 2000;Veen et al, 2013 and references therein).…”

“…Contact zones between these two fi eld cricket species exist in south-eastern Spain and probably also in Italy and further east, although geographical barriers like the Cantabrian Mountains probably prevent secondary contact (Bazyluk & Liana, 2000;Veen et al, 2013 and references therein). In contact zones of the two species, the possibility of introgression exists, and it has indeed been experimentally demonstrated that they can hybridize (Veen et al, 2011Tyler et al, 2013). The intensity of inter-specifi c crossing in the natural environment remains unknown, though earlier studies suggest that gene fl ow between these two species ought to be highly restricted via multiple reproductive barriers .…”

“…The topic has also been recently intensively studied using molecular (DNA) markers (Harrison, 1983;Harrison et al, 1987;Maroja et al, 2009Maroja et al, , 2014Veen et al, 2011Veen et al, , 2013Larson et al, 2012;Andrés et al, 2013;Tyler et al, 2013). These studies aimed to discover reproductive barriers acting at pre-and post-mating stages.…”

“…In contrast, G. bimaculatus females hybridize more readily, which is explained by their higher degree of polyandry (Veen et al, 2011Tyler et al, 2013). Hybrid females prefer mating with G. bimaculatus males, while hybrid males have reduced attractiveness in general, as fact that should restrict further gene fl ow .…”

“…Hybrid females prefer mating with G. bimaculatus males, while hybrid males have reduced attractiveness in general, as fact that should restrict further gene fl ow . These particular studies showed that in the case of hybridization, the interspecifi c introgression should occur mainly through G. bimaculatus females and G. campestris males (Veen et al, 2011. In such circumstances, the mtDNA haplotype of a relatively small group of introduced individuals could spread within the natural population due to genetic drift.…”