Female Bush-Crickets, Pholidoptera griseoaptera, that have Received Smaller Ejaculates Show a Higher Mating Rate in the Field

Abstract

Females of numerous insect species are known to be polyandrous, but there have been relatively few studies of factors associated with the degree of polyandry in females in the field. Number of copulations by females is negatively associated with ejaculate size across bush-cricket species. Assessing intraspecific variability is important when looking for and interpreting trait evolution. Therefore the aim of this study was to test the association between ejaculate size (i.e. volume of spermatodose-spermatophore- like structure formed within the spermatheca) and mating rate (i.e. number of spermatodoses) of females of Pholidoptera griseoaptera, while accounting for female body size (pronotum length) and age (number of hind leg's cuticular bands). The results based on field-caught individuals suggested that there were statistically significant nega- tive association between smallest and mean spermatodose volume, respectively, and number of copulations in this nuptial gift-giving bush-cricket species. This is in accor- dance with interspecific associations between ejaculate size and polyandry. However, lower slope of the intraspecific relationship may suggest lower importance of the ejaculate size in explaining females' mating rate variability in this nuptial gift-giving species.