Phylogenetic insights into the history and diversification of fishes on reefs

Abstract

Studies of the phylogenetic history of fishes on reefs and the impact of reefs on fish diversification have, to date, been limited to relatively small clades. We take advantage of a recent multi-locus, time-calibrated phylogeny of acanthomorph fishes and a broad-scale morphological dataset of body shape in reef acanthomorphs to explore the history and diversification of fish on reefs at the family level. We find that no reef family exhibits exceptional species diversity for their stem age and some, such as Aulostomidae, Zanclidae, Menidae, and Triodontidae may in fact be species poor. The inferred history of reef colonization is highly dependent on how a reef family is defined; one classification scheme raises the possibility that most modern acanthomorph families originated on reefs. We find that most reef families occupy surprisingly distinct regions of morphospace and yet, some of the most diverse reef families occupy central and highly overlapping positions within the body shape morphospace. To the extent that proximity in morphospace reflects ecological similarity, these results imply that most reef fish families have diversified in adaptive zones away from other families. In contrast, a few of the most successful (e.g., Labridae and Pomacentridae) have achieved dominance while potentially facing stronger interactions with other lineages. Finally, we find no relationship between species diversity and body shape diversity. Assuming neither are diversity dependent, this result suggests that morphological and ecological diversification within families of reef fish may not be linked to the accumulation of species. Time-calibrated phylogenies provide the means for generating a greater understanding of the macroevolutionary processes influencing reef fish diversification, but we are currently limited by the lack of robust crown-group ages for many reef fish families.