A Framework for Simultaneous Tests of Abiotic, Biotic, and Historical Drivers of Species Distributions: Empirical Tests for North American Wood Warblers Based on Climate and Pollen.

Understanding how abiotic, biotic, and historical factors shape species distributions remains a central question in ecology, but studies linking biotic factors to continental-scale patterns remain scarce. Here, we present a novel framework for simultaneously testing patterns expected when abiotic, biotic, or historical factors drive species range limits. We use ecological niche models to produce empirical estimates of the "biotic, abiotic, and movement" paradigm (BAM diagrams), which previously has been used only theoretically. On the basis of climatic and pollen data as well as explicit consideration of dispersal limitations, we implement the framework for a group of North American birds (Oreothlypis warblers) with clear habitat associations. Because the pollen-based predictor variables characterize vegetation, they represent biotic factors needed by each bird species. Although continental-scale patterns of distribution are traditionally attributed to abiotic factors, only one species matched the hypothesis of solely abiotic drivers. In contrast, pollen-based models indicate biotic drivers for two species, correctly predicting their absence in climatically suitable areas. These results highlight the feasibility of considering and quantifying the potential effects of biotic interactions on species ranges, especially when interactions can be decoupled from abiotic factors. Furthermore, the availability of pollen data now and in the Holocene highlights the potential of these data to be used to predict range shifts of other organisms tightly dependent on particular vegetation types.

Paraphyly of Cinclodes fuscus (Aves: Passeriformes: Furnariidae): implications for taxonomy and biogeography.

The Andes are a hotspot of global avian diversity, but studies on the historical diversification of Andean birds remain relatively scarce. Evolutionary studies on avian lineages with Andean-Patagonian distributions have focused on reconstructing species-level phylogenies, whereas no detailed phylogeographic studies on widespread species have been conducted. Here, we describe phylogeographic patterns in the Bar-winged Cinclodes (Cinclodes fuscus), a widespread and common species of ovenbird (Furnariidae) that breeds from Tierra del Fuego to the northern Andes. Traditionally, C. fuscus has been considered a single species composed of nine subspecies, but its long and narrow range suggests the possibility of considerable genetic variation among populations. Sequences of two mitochondrial genes revealed three discrete and geographically coherent groups of C. fuscus, occupying the southern, central, and northern Andes. Surprisingly, phylogenetic analyses indicated that these groups were more closely related to other species of Cinclodes than to each other. Relationships of the southern and northern C. fuscus clades to other species of Cinclodes were straightforward; in combination with available information on plumage, behavioral, and vocal variation, this suggests that each should be recognized as a distinct biological species. The central Andean group was paraphyletic with respect to C. oustaleti, and relationships among these taxa and C. olrogi were poorly resolved. We suggest that the central Andean C. fuscus should also be considered a different species, pending new information to clarify species limits in this group. These new phylogenetic data, along with recently developed methods, allowed us to review the biogeography of the genus, confirming southern South America and the central Andes as important areas for the diversification of these birds.