Does hunger lead to hybridization in a genus of sexually cannibalistic insects (Orthoptera: Prophalangopsidae)?

Allochronic isolation can be a strong mechanism for reproductive isolation and speciation. However, imperfect allochrony and the expression of phenological plasticity can erode temporal barriers to gene flow and result in hybridization between divergent lineages. Here, we combine behavioural ecology and genomics to investigate this scenario in two closely related species of grigs in the genus Cyphoderris. These species exhibit a unique mating system whereby females feed on the fleshy hind wings of the male during copulation, and copulation with conspecific males is more likely in food-restricted females than in well-fed females. In western Canada, Cyphoderris buckelli and Cyphoderris monstrosa are sympatric but largely allochronically separated, with C. buckelli breeding earlier. However, their breeding seasons can overlap, leading to potential for older C. buckelli females to mate with young C. monstrosa males to obtain resources via sexual cannibalism. We used behavioural assays to test whether female feeding status affects the propensity for interspecific mating between C. buckelli females and C. monstrosa males. We then tested for hybridization and gene exchange in wild populations of both species, using morphology, mitochondrial DNA and genome-wide nuclear markers. We found that interspecific courtship and mating can occur, but the relationship between food restriction and increased propensity for hybridization was not significant. Although we observed intraspecific population genetic structure in both species, we found no signatures of hybridization in the morphological or genetic datasets, which suggests that postmating reproductive barriers might be preventing successful hybridization in the wild.

Previous Interspecific Courtship Impairs Female Receptivity to Conspecifics in the Parasitoid Wasp Nasonia longicornis But Not in N. vitripennis

Interspecific sexual interactions are not uncommon in animals. In sympatry, females often face the risk of accidentally mating with a heterospecific male. Based on the actual risks imposed by the environment at a given time and place, females should be able to adjust their mate acceptance in order to avoid interspecific copulations as well as accidentally refusing to mate with a conspecific. We investigate the ability of females of the two parasitoid wasp species Nasonia vitripennis (Nv) and N. longicornis (Nl) to adjust their mate acceptance in response to previous unsuccessful courtship by heterospecific males. We show that Nl females are more reluctant to mate with a conspecific male when having been courted previously by a heterospecific male, but Nv females are not. We argue that this strategy is reasonable for Nl females but not for Nv females, which follow a different strategy to avoid the fitness costs imposed by heterospecific copulations.

Courtship behavior of phycitid moths. II. Behavioral and pheromonal isolation of Plodia interpunctella and Cadra cautella in the laboratory

Interspecific courtship was observed between the Indian meal moth, Plodia interpunctella, and the almond moth, Cadra cautella. Successful cross-mating did not occur, however, because of the following isolation mechanisms: (1) incompatible courtship behavior, (2) male sex pheromone as a species recognition signal, (3) inhibition of males to female sex pheromone stimulation, and (4) mechanical or physiological barriers to insemination.Male Indian meal moths were strongly excited by calling almond moth females and courted them vigorously. However, because the courtship behavior of this combination was incompatible, copulation did not occur. Occasionally courtship continued to a later stage in the sequence but then the female rejected the male apparently because he releases an inappropriate aphrodisiac from his scent scales.In the reciprocal cross, fully two-thirds of the almond moth males failed to be sufficiently excited by Indian meal moth females to court them. Most of these males were inhibited, as indicated by their subsequent lack of response to pheromone extracts from their own female. Those males which were excited by Indian meal moth females courted them successfully and copulated, but insemination apparently did not occur. In a few cases the females rejected the males, as in the reverse cross.