Phylogenetics and the study of adaptive radiations

One of my motivations for building the “big darter” tree is to investigate patterns of diversification in darters that may result from adaptive radiation.  Results from our studies have broad implications to the study of evolutionary radiations, because the study of adaptive radiation in clades with a continental distribution is rare and the best studied adaptive radiations involve fairly recent evolutionary ages.  We intend to expand our study to include other marine and freshwater fish clades.

I am interested in developing novel approaches to study evolutionary radiations using phylogenetics.  Specifically, I am investigating strategies to use phylogenies in a multifaceted approach that will identify monophyletic lineages, detect shits in habitat or resource utilization in clades, assess the tempo of diversification, and track patterns of morphological disparity.

One of the expectations from Simpson’s formulation of adaptive radiation that we are testing is the hypothesis that lineages exhibiting relatively high degrees of morphological and ecological disparity will also exhibit higher rates of lineage diversification.

University of California, Davis graduate student Rose Carlson is collaborating with me on several darter projects, including a study of the relationship between rate of change of morphological characters with known functional consequences and co-occurrence of closely related darter species.

Yale E&EB graduate student Christen Bossu is using the “big darter” tree to investigate the evolution of dichromatism in darters and any effects on rates of diversification.

Yale E&EB graduate student Richard Harrington is examining the dietary resource axis in darters by investigating evolutionary trends in the width of dietary niches among species, and the relationship between interspecific dietary niche overlap and evolutionary age.

One of the most important and general results from our work on darters to date is the demonstration that allopatric speciation can happen rapidly, and rapid diversification is not synonymous with sympatric speciation.Another equally important contribution of the “big darter” tree is the discovery that much of the diversification of darters has occurred within, as opposed to between, disjunct areas of the Central Highlands in eastern North America.