Meeting Abstract

14.5  Friday, Jan. 4  Multiple fitness peaks on the adaptive landscape drive the evolution of novel ecological niches within a recent sympatric adaptive radiation of Cyprinodon pupfishes MARTIN, CH*; WAINWRIGHT, PC; University of California, Davis; University of California, Davis chmartin@ucdavis.edu

Multiple fitness peaks corresponding to ecological opportunities are thought to be the major force driving niche diversification during adaptive radiation. Here we measured a large portion of the adaptive landscape within a 10,000-year-old radiation of Cyprinodon pupfishes endemic to San Salvador Island, Bahamas from the growth and survival of 1,865 F2 hybrids placed in field enclosures in two lakes. We found that hybrid phenotypes corresponding to the abundant generalist species sit atop an isolated fitness peak separated by a valley from a higher fitness peak corresponding to the hard-shelled prey specialist species. We confirmed experimentally the presence of multiple fitness peaks in sympatry driven by increased competition in high-density field enclosures, strongly supporting the early burst model of adaptive radiation. Furthermore, this striking multi-peak landscape explains both the rarity of trophic specialists across the Caribbean due to stabilizing selection on generalist founding populations and the rapid increase in morphological diversification rates of specialists due to the higher fitness of the specialist peak.