Why focus on species?
Biodiversity is a measure of the variety of life. It can refer to variation on a number of levels, although species are the most common unit used to describe biodiversity. Therefore, to understand the evolutionary processes that generate biodiversity and the mechanisms that help to sustain it, I study species. Species-level phylogenetics adjoins more common family-level phylogenetic approaches that include representative taxa to evaluate relationships among clades of species, and phylogeographic studies of relationships among populations within species. Complete species-level sampling provides the opportunity to robustly identify sister-species relationships, more accurately estimate the timing of speciation, and establish geographical relationships of closely related species. These key pieces of information form a framework that can be used to investigate the evolutionary processes that promote biodiversity.
Figure from Hodge et al., 2013 showing the biodiversity of Pomacanthus species.