Genetic data and niche differences suggest that disjunct populations of Diglossa brunneiventris are not sister lineages

Disjunct distributions within a species are of great interest in systematics and biogeography. This separation can function as a barrier to gene flow when the distance among populations exceeds the dispersal capacity of individuals, and depending on the duration of the barrier, it may eventually lead to speciation. Here, we describe patterns of geographic differentiation of 2 disjunct populations of Diglossa brunneiventris separated by ∼1,000 km along the Andes. Diglossa brunneiventris vuilleumieriis isolated in northern Colombia, while Diglossa brunneiventris brunneiventris has a seemingly continuous distribution across Peru, Bolivia, and Chile. We sequenced mitochondrial and nuclear DNA of the 2 D. brunneiventris subspecies to evaluate whether they form a monophyletic clade, while including the other 3 species within the carbonaria complex (D. gloriosa, D. humeralis, and D. carbonaria). We also constructed ecological niche models for each D. brunneiventris subspecies to compare their climatic niches. We found that when using all available molecular data, the 2 D. brunneiventris subspecies are not sister lineages. In fact, each subspecies is more closely related to other species in the carbonaria complex. Our niche modeling analyses showed that the subspecies are occupying almost entirely different climatic niches. An additional and not expected result was that the carbonaria complex might encompass more cryptic species than previously considered. We suggest reevaluating the taxonomic status of these brunneiventris populations, especially the northern subspecies, given its highly restricted range and potential threatened status.LAY SUMMARYDiglossa brunneiventris has two disjunct populations separated by more than 1,000 km along the Andes (longer than the span of Ecuador).Although similar in coloration, the two populations exhibit differences in body size and wing length.Whether these two populations belong to the same species and how recently they were separated are still open questions.We provide molecular and climatic evidence that suggests the two populations are not sister taxa.Genetic evidence suggests the northern population is related to populations of Diglossa humeralis from the Eastern Andes in Colombia, while the southern population is more related to populations of D. humeralis from Ecuador and southern Colombia.The northern population has a restricted and fragmented range and its conservation status depends on evidence for its recognition as an independent lineage.