Incorporating color into integrative taxonomy: analysis of the varied tit (Sittiparus varius) complex in East Asia

Species designations are critically important scientific hypotheses that serve as the foundational units in a wide range of biological subdisciplines. A growing realization that some classes of data fail to delimit species under certain conditions has led to increasingly more integrative taxonomies, whereby species discovery and hypothesis testing are based on multiple kinds of data (e.g. morphological, molecular, behavioral, ecological, etc.). However, although most taxonomic descriptions have been based on morphology, some key morphological features, such as color, are rarely quantified and incorporated into integrative taxonomic studies. In this paper, we applied a new method of ultraviolet digital photography to measure plumage variation in a color-variable avian species complex, the varied tit (Sittiparus varius). Plumage measurements corroborated species limits defined by morphometric, mitochondrial DNA, and nuclear DNA disjunctions and provided the only evidence for recognizing t...