His research is focused on developing and using phylogenetic hypotheses and information from the fossil record to study the evolutionary biology of ray-finned fishes. He has published on detailed phylogenetic analyses of Antarctic notothenioids and North American endemic darters, using time-calibrated phylogenies to studying adaptive radiation and the geography of speciation. Recent studies have been directed towards the phylogeny and patterns of lineage diversification among all major lineages of ray-finned fishes.