Benefits of size dimorphism and copulatory silk wrapping in the sexually cannibalistic nursery web spider, <i>Pisaurina mira</i>

Benefits of size dimorphism and copulatory silk wrapping in the sexually cannibalistic nursery web spider, Pisaurina mira" (2016). Eileen Hebets Publications. Paper 54. For most males, reproductive success is dependent on the ability to acquire mates and successfully fertilize a female's eggs [1,2]. Research across diverse animal taxa has documented elaborate courtship displays and seemingly coercive strategies that exist to secure matings (reviewed in [1–3]). In systems with the potential for high levels of sperm competition, males can increase fertilization success by preventing females from successfully re-mating through mate guarding or the production of sperm plugs and seminal toxins, among others (reviewed in [4]). For a small number of taxa in which females are sexually cannibalistic, however , males have an additional challenge—surviving a reproductive encounter. While cannibalism prior to sperm transfer results in zero male fitness, cannibalism after the transfer of sperm can be beneficial to a male [5,6]. Nonetheless, even post-copulatory sexual cannibalism carries a potentially high cost (e.g. reduced sperm transfer and loss of future reproductive opportunities) and can strongly influence the evolution of male mating strategies and associated morphologies [7,8]. Given the costs of sexual cannibalism, we expect positive selection for male traits/behaviors that reduce the likelihood of being eaten. Indeed, across cannibalistic spider taxa (Class Arach-nida, Order Araneae), sexual cannibalism is commonly associated with extreme morphologies and striking mating systems (reviewed in [9,10]). For example, sexual size dimorphism (SSD) is often associated with sexual cannibalism [11,12]. It has been suggested that longer male legs have been selected to avoid pre-copulatory cannibalism in a number of orb-weaving spiders [13]. Additionally, larger male fishing spiders (Dolomedes Abstract In sexually cannibalistic animals, male fitness is influenced not only by successful mate acquisition and egg fertilization, but also by avoiding being eaten. In the cannibalistic nursery web spider, Pisaurina mira, the legs of mature males are longer in relation to their body size than those of females, and males use these legs to aid in wrapping a female's legs with silk prior to and during copulation. We hypothesized that elongated male legs and silk wrapping provide benefits to males, in part through a reduced likelihood of sexual cannibalism. To test this, we paired females of random size with males from one of two treatment groups—those capable of silk wrapping versus those incapable of silk wrapping. We found that males with relatively longer legs and larger body size were more …