AbstractSexual selection in mate‐guarding Crustacea may involve several processes: male choice, male‐male competition, and female choice. To evaluate the relative importance of the different processes in mate choice of the aquatic isopodI. baiticawe studied 1) the mate‐choice criteria of males, 2) effects of sex ratio on the outcome of the mating contest, and 3) the role of size in male‐male interactions. When given a choice between a small and a large female, males most often chose the one that matured earlier for parturial ecdysis. Maturity was a more important choice criterion than female size, but these also correlated positively. Large males had a mating advantage in both male‐ and female‐biased sex ratios; pairing was size‐assortative only in the male‐biased ratio where guarding was also longer. If an extra male was placed with a precopulatory pair, 30 take‐overs occurred, large males surpassing. Present and earlier work suggests that male size is an asset in both intra‐ and intersexual interactions. There is little or no direct phenotypic sexual selection on female size: sexual selection for large males presumably contributes to the evolution of sexual size dimo
展开▼
