Meeting Abstract
One of the most poorly understood evolutionary processes is the evolution of novelty. How do new species colonize novel ecological niches (i.e. empty fitness peaks) or begin to use existing structures for novel functions? The microendemic origin of sympatric scale-eating and molluscivore pupfishes on a single Bahamian island within a vast ocean of ecological opportunity across Caribbean hypersaline lakes provides an intriguing case study of this process. Repeated measurements of the fitness landscape in this environment based on hybrid survival and growth in field enclosures indicate that a complex adaptive landscape with multiple fitness peaks is driving diversification in this system. Traditionally, negative frequency-dependent competition is thought to underlie such disruptive selection. However, the stability of these fitness peaks across lakes, time periods, and different frequencies of competitors suggests that performance shapes the large-scale features of the adaptive landscape. Excessive gene misexpression in hybrids and reduced hatch rates also provide intriguing clues that genetic incompatibilities in these young species may impair the performance of hybrids, regardless of the number of competitors within field enclosures, and contribute to the long-term stability of interspecific fitness peaks in contrast to intrapopulation frequency-dependent dynamics. The origins of microendemic adaptive radiation may lie at the intersection of ecological opportunity, performance, complex fitness landscapes, and diverse sources of genetic variation.
