Meeting Abstract
Organismal form is shaped by natural selection through the lens of performance. Here I show that performance demands can also affect all levels of biological organization, from genetic architecture to fitness landscape to mate choice to diversification rate. My lab investigates the rare origins of pupfish adaptive radiation endemic to a single Bahamian island, including a large-jawed scale-eating specialist and a molluscivore with a novel nasal protrusion. Scale-eating exerts substantial performance demands for efficient high-speed strikes to remove small amounts of protein-rich mucus and scales. This results in a wider fitness valley, stronger pre-mating isolation, faster oral jaw diversification rate, and larger-effect genetic architecture underlying increases in jaw size. In contrast, molluscivory requires robust, shorter jaws to feed on non-evasive prey. This low-demand trophic performance results in a shallow, narrow fitness valley, weak pre-mating isolation, moderate jaw diversification rates, and a small-effect genetic architecture underlying shorter jaw lengths. Surprisingly, both specialist trophic morphologies benefited from past introgression of adaptive alleles from the distant Grand Bahama Bank. Thus, the performance demands of highly divergent trophic specialists have cascading effects on biological organization. Despite abundant ecological opportunity, these trophic specialists may have originated from the fortuitous assembly of different pools of standing genetic variation from across the Caribbean.
