Male body size effects on mating behaviour and paternity success in polyandrous Phytoseiulus persimilis and Neoseiulus californicus

Abstract: We hypothesize that the difference in body size plasticity of males of Phytoseiulus persimilis (low) and Neoseiulus californicus (high) is sexually selected because deviations from standard body size incur higher costs regarding mating success and lifetime reproductive success in P. persimilis than N. californicus. Accordingly, here we assessed whether in double-mating females (with standard-sized and small male mates) the paternity success of small relative to standard-sized males is lower in P. persimilis than N. californicus, independent of the mating sequence. We observed the mating behaviour of the female and her sequential mates (female re-mating proportion, mating duration) and analysed the paternity success of the two male mates via microsatellite genotyping of diploid daughters. In both species, the re-mating likelihood was higher when the first mate was a small male. Pooled over both male body size categories, the first mating duration was longer than the second mating duration in both species. Pooled over species, the duration of the first mating was not affected by male body size, whereas the duration of the second mating was longer when the second mates were standard-sized. In P. persimilis, the number of offspring sired by small first male mates was lower than that sired by standard-sized first male mates, whereas the number of offspring sired by the second mates was unaffected by male body size. Contrary, in N. californicus small and standard-sized male mates sired similar offspring numbers, independent if acting as first or second mates. These results corroborate our assumptions that male body size is more important to fitness in P. persimilis than N. californicus and that past sexual selection limited male body size plasticity more strongly in P. persimilis than N. californicus.Abstract only