The Combined Effects of Pre- and Post-Insemination Sexual Selection on Extreme Variation in Male Body Size

摘要: Orb-weaving spiders of the genus Nephila are notable for their sexual size dimorphism, with dwarf males and giant females. However, less well known is extreme polymorphism that characteristic some species. For example, adult male body in N. edulis varies by an order magnitude. Previous experiments reveal mating behaviour covaries size, suggesting variation maintained opposing pre- post-insemination selection pressures. Here, we test this idea allowing different sizes to compete directly simultaneously access Using sterile-male technique paternity assessment, show two competing drawn from extremes variations, split same way as intermediate sizes. The a large dropped 50% 30% on average if he competed against instead one small male. increased his frequency when there were more rivals but required much lower total duration copulation achieve share. These data consistent pressures at least partly explain size.