Female-biased sexual size dimorphism exists as a widespread evolutionary pattern. Fertility selection favoring larger females with more reproductive capacity is the main explanation. However, increasing body size requires greater energy intake, which may impede the evolution of extreme sizes in women. Therefore, size increases may be possible through the evolution of more advantageous foraging tactics. Therefore, when combined with selection for larger males, selection on fecundity should result in greater SSD in species with more advantageous foraging strategies. Crab spiders are sit-and-wait predators that hunt in the substratum of some plants. Species that scavenge for flowers or use strategies to lure prey may have access to more food than other species. We extracted body size measurements for 614 crab spider species from 43 genera and classified them based on foraging strategy. Our findings showed that foraging strategies that provide higher energy input (EFS) result in greater SSD. Statistical estimates show that in EFS species, female cephalothorax width is 91% larger than male, whereas in non-EFS species, female is 26% larger than male. These differences may be due to females being larger and males being smaller. The effect on male size reduction is likely due to competitive competition, whereas the increase in female size is likely due to selection for fecundity. These results suggest that the shift to a more lucrative foraging strategy may have been an important event in the evolution of body size and SSD in crab spiders.
Rocha, P. A., and Gawryszewski, F. M. (2024). Foraging strategy as a pathway for the evolution of sexual size dimorphism. ecology and evolution, 14(11), e70100. https://doi.org/10.1002/ece3.70100
