Dominant climate influences on North American bird distributions

Abstract

Aim Geographic distributions of species are constrained by several factors acting at different scales, with climate assumed to be a major determinant at broad extents. Recent studies, however, have challenged this statement and indicated that climate may not dominate among the factors governing geographic distributions of species. Here, we argue that these results are misleading due to the lack of consideration of the geographic area that has been accessible to the species.Location North America. MethodsWe generated null distributions for 75 North American endemic and 19 non-endemic bird species. For each species, climatic envelopes of observed and null distributions were modelled using neural networks and generalized linear models, and seven climatic predictors. Values of the area under the receiver-operating characteristic curve (AUC) based on models of observed distributions were compared with corresponding AUC values for the null distributions. ResultsMore than 82% of the endemic species showed AUC higher for the observed than for the null distributions, while 63% of the non-endemic species showed such a pattern. Main conclusionsWe demonstrate a dominant climatic signal in shaping North American bird distributions. Our results attest to the importance of climate in determining species distributions and support the use of climate-envelope models for estimating potential distributional areas at the appropriate spatial scales.

Uses and misuses of bioclimatic envelope modeling

“…For example, Beale and colleagues (2008) evaluated climatic determination of European bird species' ranges, and purported to find negligible climatic determination; however, a parallel study using identical methods but improved distributional data for European bird species ) found widespread climatic determination. An analogous study applied to North American birds but conducted at an extent that included much more endemism (Jime´nez-Valverde et al 2011a) also found strong evidence of climatic determination in the distributions of birds. Failures of attribution may also arise because the climatic variables selected are not those directly limiting the distribution of the species in question (e.g., Ashcroft et al 2011, Austin andVan Niel 2011), as will frequently be the case with species having distributions that are structured by barriers to dispersal or by factors operating at different spatial extents or resolutions from those used in modeling.…”

Incorporating uncertainty in predictive species distribution modelling

“…Equally, there is no certainty that species with only partial ranges within a study area do not reach tolerance limits within the area (figure 1, cf. [42,43]): geographical distribution and distribution within niche space are different phenomena. Modelling the fundamental niche from geographical data is harder than modelling the realized niche, but doing so avoids some problems highlighted above.…”

Species’ Geographic Distributions Through Time: Playing Catch-up with Changing Climates

“…This conclusion, however, was based on analyses fraught with complications (Araújo et al 2009;), particularly as regards exclusion of distributional limits of the species in question from the area of analysis. A study developed in parallel to the original one, but in a geographic arena that holds much more species endemism, yielded opposite results (Jiménez-Valverde et al 2010), suggesting that the original work was flawed, probably in large part owing to artificial delimitation of the study area to western Europe.…”