Applying a regional community concept to forest birds of eastern North America

Abstract

The regional community concept embraces the idea that species interactions across large areas shape both the geographic/ecological distributions and the local abundances of populations. Within this framework, I analyzed the distribution and abundance of 79 species of land birds across 142 ca. 10-ha census plots from standardized breeding bird censuses in deciduous and mixed forests of eastern North America. To characterize the regional ecological space, plots were ordinated on the basis of species abundances. Within the regional community defined by these synthetic axes, the distribution and abundance of individual species did not appear to be shaped by competition or to reflect the adaptations of individuals: (i) local abundance and population extent across the ordination axes were unrelated, (ii) pairwise correlation coefficients of species abundances were centered on 0, (iii) average species distribution and abundance were independent of the number of close relatives, and (iv) distribution and abundance exhibited no evolutionary (phylogenetic) conservatism. To explain these seemingly random patterns, I speculate that species are approximately evenly matched competitors over much of the region and that their distributions and relative abundances are determined by the labile coevolutionary outcomes of interactions with specialized pathogens. Thus, despite the appearance that random processes determine patterns in the distribution and abundance of populations in the regional community, it is plausible that speciesspecific deterministic interactions are responsible. Although competition is a dominant force in ecological communities, variation in the distribution and abundance of individual species might instead reflect the outcome of interactions with specialized antagonists, including pathogens.niche | population distribution | community assembly | macroecology | variance in abundance B iological communities comprise large numbers of potentially interacting species. Although ecologists broadly embrace this concept of community (1, 2), they are not agreed on the integrity of communities as ecological entities or the scale on which communities can be perceived (3). Interactions between populations in local assemblages are evident through natural (4, 5) and experimental (2, 6) manipulations, but dispersal of individuals across space also connects and integrates assemblage dynamics within the larger region. The local presence and relative abundance of species integrate processes of evolutionary diversification and ecological interaction operating at large spatial and temporal scales (7). Accordingly, ecological communities make sense only as regional entities. Nonetheless, factors that influence the numbers and distributions of species within the regional community are poorly understood.The distribution and abundance of a species have two components (8). The individual component reflects adaptations to use substrates and exploit resources within the individual's activity space, which is also influenced by its tolera...

Species richness and morphological diversity of passerine birds

“…For example, SDs of the PC scores for 34 species in eucalypt woodland near Armidale, northeastern New South Wales, Australia (51), 43 species in deciduous forest in Connecticut (Plot CT2778262 of the Breeding Bird Census) (see ref. 52), and 139 species in a flood-plain forest plot in Amazonian Peru (50), approximate those of the larger region in which each of these local areas occurs ( Fig. 3 and SI Appendix, Relationship of regional to local morphological variance).…”

The Unified Neutral Theory of Biodiversity and Biogeography at Age Ten

“…This vigorous debate has now spanned a decade (see [14,15,30,49,[84][85][86][87][88][89]] for reviews and opinions on both sides). We suggest that the time has now come to put both the theory and its criticisms into perspective and move forward.…”

The case for ecological neutral theory

“…Gone are the days when proponents and opponents of neutral theory could build their cases on good or bad fits of one particular neutral model to some empirical species abundance distribution [1][2][3][4][5]. Here, we complement the recent reviews [6][7][8][9] and opinions [10][11][12][13][14] with our own opinion on how neutral theory can aid progress in ecological research. The opposition to neutral theory in ecology is not surprising given its radical assumption and we view such criticism as necessary for neutral theory to grow.…”

“…For example, a dispersal kernel contains valuable information [39] about the chance of a dispersing seed reaching certain distances from its origin; however, it must be stochastic because the deterministic alternative is impractical. In the case of ecological drift, Ricklefs [14] suggests that 'deterministic influences of specialized pathogens' are the cause of patterns resembling those arising from stochastic neutral theory. We agree with the essential idea that neutral drift can result from deterministic processes that are complex and not well understood.…”