[en] Herbivorous reef fishes have evolved to occupy a central role in controlling both the distribution of algae and the flow of energy in coral reef food webs. Today, these fauna and the ecosystems they
maintain have become increasingly threatened by anthropogenic stressors. Developing an understanding of how the diversification dynamics of these lineages responded to historic climatic shifts provides critical insight into the expectations of herbivorous fish diversity under current models of climatic change. We combined molecular, paleontological, and morphological data to assess the
diversification dynamics of rabbitfishes (Siganidae) and surgeonfishes (Acanthuridae), two major clades of herbivorous fishes that have been of central ecological importance over the past 50
million years. By combining landmark-based geometric morphometric data of 396 extant and fossil species images with a time-calibrated phylogeny, we found diversification of both clades
reflected the expectations of an extinction recovery model following the collapse of the West Tethys Sea. The two groups however exhibit differing tempos of speciation as well as extant morphospace
occupancies relative to Eocene species. Our results indicate the viability of multiple evolutionary pathways leading to lineage persistence in the wake of environmental change. However, given
modern-day trends in habitat degradation, they also forewarn of future patterns of diversity not dissimilar to those of the post Tethyian collapse favoring fewer, more generalized herbivores on reefs unlike those of the present.
