Meeting Abstract
The loss of a complex adaptive trait is typically associated with a move of a species to a new environment. This move results in changes in multiple traits, thus confounding genetic dissection of the loss. One way to address this is by examining sexually dimorphic species, here the ostracod crustacean Euphilomedes carcharodonta. Eye loss in Euphilomedes adults is restricted to females, who are largely benthic, compared to benthic/pelagic males. Comparisons between male and female eye development show that a handful of key regulatory genes are expressed at lower levels in developing female eyes. Moreover, both males and females exhibit heterochrony with regards to their eye development compared to other species of ostracods. This suggests that eye loss in this species requires two steps: 1) A heterochronic shift suppressing embryonic eye development, affecting both males and females 2) Redeployment of embryonic developmental regulators in male eyes to de-suppress eye development. This complex evolutionary history can be explained by dispersal mechanisms in males compared to females. Males appear to disperse, using their eyes in the water column to avoid predators, while females tend to be benthic and likely have much lower dispersal. We show that blindfolded males disperse and move towards females at similar rates to mock blindfolded males. This suggests that niche segregation, and not mate choice/acquisition, is driving the dimorphism.
