In northwestern North America, stickleback in small, shallow lakes have evolved a deep-bodied (benthic) form specialized for feeding on benthic invertebrates, while those in deep, oligotrophic lakes evolved a slender form (limnetic) adapted for feeding on plankton. Research in our laboratory has demonstrated that benthic populations retain ancestral tendencies to form bottom-feeding foraging groups that cannibalize young in nests when they are discovered. Courtship in benthic populations is typically initiated by females who swim to the male and press their abdomens against the male’s dorsal spines initiating the relatively inconspicuous dorsal pricking behavior that makes up most courtship in these populations. In contrast, limnetics have lost ancestral cannibalistic tendencies, and males initiate courtship with the very conspicuous zig-zag dance.
Ongoing research by Stella Richard is aimed at understanding ecotypic differences in the endocrine stress responses of males confronted by these foraging groups. Benthic males tend to be drab during courtship, whereas limnetic males typically have red throats and iridescent blue-green backs. Ancestral populations in the Pacific Northwest tend to exhibit intermediate and plastic (below) phenotypes in nature. We have also shown that benthic males retain ancestral diversionary displays in response to the approach of groups, and that these displays appear to include co-opted and ritualized elements of behavior used in other contexts. Current collaborative research with Anna Greenwood and Katie Peichel is aimed at understanding the genomic bases of this remarkable behavior.