Latitudinal gradients in the phenetic diversity of New World bat communities (original) (raw)
Related papers
Oikos, 2006
Latitudinal gradients of species richness: a test of the geographic area hypothesis at two ecological scales. Á/ Oikos 112: 163 Á/173. The geographic area hypothesis advances area as the primary cause of latitudinal gradients in diversity. The greater area of tropical zones, it suggests, stimulates speciation, inhibits extinction, and leads to increased species richness compared to the situation in smaller temperate and boreal zones. Because bats exhibit exceptionally strong latitudinal gradients of richness at multiple spatial scales in the New World, they are an appropriate system with which to test the geographic area hypothesis. We used range maps for 250 species of New World bats to estimate species richness in biogeographic zones at two hierarchical spatial scales: biome types and provinces. We then conducted a series of regression analyses to evaluate the ability of area to account for latitudinal gradients in species richness. However, spillover (zonal bleeding) of tropical species into extra-tropical zones may mask the species-area relationship and alter perceptions of the latitudinal gradient. To address this issue, we conducted additional analyses excluding tropical species, using a series of increasingly inclusive definitions of tropical ranges. Ecogeographic zones of the New World are not larger at tropical versus extra-tropical latitudes. Moreover, spillover of tropical species into ecogeographic zones within extra-tropical regions generally does not diminish the association between richness and area. Nonetheless, the latitudinal gradient of species richness is strong and significant at both ecogeographic scales. Clearly, area does not drive the latitudinal gradient of bat species richness in the New World. In fact, area represents a source of noise rather than a dominant signal at the focal scale of biome types and provinces in the Western Hemisphere.
Journal of Biogeography, 2004
Aims (i) To describe at the level of local communities latitudinal gradients in the species richness of different families of New World bats and to explore the generality of such gradients. (ii) To characterize the relative effects of changes in the richness of each family to the richness of entire communities. (iii) To determine differences in the rate and direction of latitudinal gradients in species richness within families. (iv) To evaluate how differences among families regarding latitudinal gradients in species richness influence the latitudinal gradient in species richness of entire communities. Location Continental New World ranging from the northern continental United States (Iowa, 42°N) to eastern Paraguay (Canindeyú , 24°S). Methods Data on the species composition of communities came from 32 intensively sampled sites. Analyses focused on species richness of five of nine New World bat families. Multivariate analysis of variance and discriminant function analysis determined and described differences among temperate, subtropical, and tropical climatic zones regarding the species richness of bat families. Simple linear regression described latitudinal gradients in species richness of families. Path analysis was used to describe: (i) the direct effect of latitude on species richness of communities, (ii) the indirect effects of latitude on the species richness of communities through its effect on the species richness of each family, (iii) the relative effects of latitude on the species richness of bat families, and (iv) the relative contribution of each family to variation in the species richness of communities.
A latitudinal gradient in dimensionality of biodiversity
Ecography, 2018
Biodiversity is multifaceted and represents numerous dimensions expressing variation in richness and abundances of species, ecosystem functions, phylogenetic relationships, morphology, traits and interactions. Such dimensions are correlated to varying degrees and recent research has attempted to better understand behavior of such correlations. We define dimensionality of biodiversity as degree of redundancy in variation among multiple dimensions of biodiversity. One fundamental question regarding biodiversity is whether its dimensionality is spatially structured, also exhibiting geographic gradients. We examine if redundancy among dimensions of biodiversity changes latitudinally thereby contributing to increased tropical complexity. Geographic range maps of bats were overlaid on a 100 100 km grid of the New World to determine species composition of each cell. Species richness and three measures each of phylogenetic, functional and phenetic diversity were calculated. Dimensionality was estimated as evenness of eigenvalues generated from a principal components analysis (PCA) of multiple measures of biodiversity. High dimensionality is characterized by low correlations among biodiversity measures and high evenness of eigenvalues from PCA, whereas low dimensionality is characterized by high correlations and low evenness of eigenvalues. Latitudinal gradients of dimensionality were determined by regression analysis. Slope of the empirical relationship was compared to slopes generated from two null models that randomized the distribution of species. Dimensionality of biodiversity does indeed exhibit a latitudinal gradient, decreasing with increasing latitude. This empirical gradient was stronger than expected by the random distribution of species. Additionally, spatial variation in dimensionality of biodiversity could not be explained by a similar underlying pattern in variation of environmental conditions. Correlations among different dimensions of biodiversity vary spatially, and interpretations of such correlations should be geographically explicit. Mechanisms proposed to explain latitudinal gradients need not only account for gradients of biodiversity, but gradients in dimensionality as well. A gradient in dimensionality suggests that conservation strategies that rely on maximization of a single metric, such as species richness, might be of varying utility in different geographic contexts.
PLoS ONE, 2013
Inference involving diversity gradients typically is gathered by mechanistic tests involving single dimensions of biodiversity such as species richness. Nonetheless, because traits such as geographic range size, trophic status or phenotypic characteristics are tied to a particular species, mechanistic effects driving broad diversity patterns should manifest across numerous dimensions of biodiversity. We develop an approach of stronger inference based on numerous dimensions of biodiversity and apply it to evaluate one such putative mechanism: the mid-domain effect (MDE). Species composition of 10,000-km 2 grid cells was determined by overlaying geographic range maps of 133 noctilionoid bat taxa. We determined empirical diversity gradients in the Neotropics by calculating species richness and three indices each of phylogenetic, functional and phenetic diversity for each grid cell. We also created 1,000 simulated gradients of each examined metric of biodiversity based on a MDE model to estimate patterns expected if species distributions were randomly placed within the Neotropics. For each simulation run, we regressed the observed gradient onto the MDE-expected gradient. If a MDE drives empirical gradients, then coefficients of determination from such an analysis should be high, the intercept no different from zero and the slope no different than unity. Species richness gradients predicted by the MDE fit empirical patterns. The MDE produced strong spatially structured gradients of taxonomic, phylogenetic, functional and phenetic diversity. Nonetheless, expected values generated from the MDE for most dimensions of biodiversity exhibited poor fit to most empirical patterns. The MDE cannot account for most empirical patterns of biodiversity. Fuller understanding of latitudinal gradients will come from simultaneous examination of relative effects of random, environmental and historical mechanisms to better understand distribution and abundance of the current biota.
Latitudinal Gradients of Biodiversity: Pattern, Process, Scale, and Synthesis
Annual Review of Ecology, Evolution, and Systematics, 2003
▪ The latitudinal gradient of decreasing richness from tropical to extratropical areas is ecology's longest recognized pattern. Nonetheless, notable exceptions to the general pattern exist, and it is well recognized that patterns may be dependent on characteristics of spatial scale and taxonomic hierarchy. We conducted an extensive survey of the literature and provide a synthetic assessment of the degree to which variation in patterns (positive linear, negative linear, modal, or nonsignificant) is a consequence of characteristics of scale (extent or focus) or taxon. In addition, we considered latitudinal gradients with respect to generic and familial richness, as well as species evenness and diversity. We provide a classification of the over 30 hypotheses advanced to account for the latitudinal gradient, and we discuss seven hypotheses with most promise for advancing ecological, biogeographic, and evolutionary understanding. We conclude with a forward-looking synthesis and lis...
The diversity field of New World leaf-nosed bats (Phyllostomidae)
Global Ecology and Biogeography, 2009
Aim To analyse how the patterns of species richness for the whole family Phyllostomidae determine the structure of diversity fields (sets of species-richness values) within the ranges of individual bat species.Location The range of the family Phyllostomidae in North and South America.Methods We generated a database of the occurrence of 143 phyllostomid bat species in 6794 quadrats, analysing the species-richness frequency distribution for all sites, and for subsets of sites defined by the geographic ranges of species. Range–diversity plots, depicting simultaneously the size and the mean species richness of ranges, were built to explore the patterns of co-occurrence in widespread and restricted species. We compared the empirical patterns against two null models: (1) with scattered (non-cohesive) ranges, and (2) with cohesive ranges modelled with the spreading-dye algorithm. Diversity fields were analysed with richness maps for individual species and with comparisons of species-richness frequency distributions.Results Overall richness frequency distribution showed a multimodal pattern, whereas simulated distributions showed lower values of variance, and were unimodal (for model 1) and bimodal (for model 2). Range–diversity plots for the empirical data and for the cohesive-ranges simulation showed a strong tendency of species to co-occur in high-diversity sites. The scattered-ranges simulation showed no such tendency. Diversity fields varied according to idiosyncratic features of species generating particular geographic patterns and richness frequency distributions.Main conclusions Phyllostomid bats show a higher level of co-occurrence than expected from null models. That tendency in turn implies a higher variance in species richness among sites, generating a wider species-richness frequency distribution. The diversity field of individual species results from the size, shape and location of ranges, but also depends on the general pattern of richness for the whole family.
Multiple dimensions of bat biodiversity along an extensive tropical elevational gradient
The Journal of animal ecology, 2014
Research concerning spatial dynamics of biodiversity generally has been limited to considerations of the taxonomic dimension, which is insensitive to interspecific variation in ecological or evolutionary characteristics that play important roles in species assembly and provide linkages to ecosystem services. Consequently, the assumption that the taxonomic dimension is a good surrogate for other dimensions remains unconfirmed.We assessed variation in taxonomic (species richness) as well as phylogenetic and functional (Rao's quadratic entropy, a measurement of dispersion) dimensions of bat biodiversity along an elevational gradient in the Manu Biosphere Reserve of Peru. Phylogenetic dispersion was based on relatedness of species derived from a mammalian supertree. Functional dispersion was estimated separately for each of six functional components that reflect particular niche axes (e.g. diet, foraging strategy, body size) and for all functional components combined.Species richness declined non-linearly with elevation, whereas phylogenetic dispersion and functional dispersion based on all functional components were not significantly associated with elevation (orthogonal polynomial regression). Moreover, considerable heterogeneity in the form of elevational relationships existed among functional components. After accounting for variation in species richness, dispersion of phylogenetic, diet and foraging strategy attributes were significantly greater than expected at high elevations, whereas dispersion of body size was significantly less than expected at high elevations.Species richness was a poor surrogate for phylogenetic or functional dispersion. Functional dispersion based on multiple components obscured patterns detected by particular components and hindered identification of mechanistic explanations for elevational variation in biodiversity.Variation in phylogenetic dispersion effectively captured the composite variation represented by all functional components, suggesting a phylogenetic signal in functional attributes.Mechanisms that give rise to variation in richness do not fully account for variation in phylogenetic or functional characteristics of assemblages. Greater than expected phylogenetic, diet and foraging strategy dispersion at high elevations were associated with the loss of phylogenetically or functionally redundant species, suggesting that increasing interspecific competition with decreasing productivity resulted in competitive exclusion. In contrast, low dispersion of size attributes at high elevations suggests the importance of abiotic filtering that favors small-sized species that can more easily enter torpor.This article is protected by copyright. All rights reserved.