Latitudinal Diversity Gradients in New World Bats: Are They a Consequence of Niche Conservatism? (original) (raw)
Related papers
Latitudinal gradients of genus richness and endemism and the diversification of New World bats
Several hypotheses have been advanced for the origin and diversification of the bat fauna of the New World. Traditional models considered one of the families (Vespertilionidae) to have had a North American origin, whilst the diversification of other seven families was thought to have occurred in South America. Present- day patterns of diversity are the result, according to these hypotheses, of the mixing of faunas, mostly coinciding with the Great American Biotic Interchange (GABI) of the Americas. Recent research has challenged the traditional model and has posited the possibility of dual centres of diversification (in South and North America) for families traditionally considered of strict South American origin. Here we examine the latitudinal patterns of bat diversity and endemism at the genus level and show that present-day patterns are more consistent with this dual-diversification hypothesis than with the traditional models. We document an asymmetrical latitudinal gradient of genus richness with a plateau near the equator, but with a decline in Central America and Mexico; however, in this area the relative number of genera, considering the species richness, is higher than expected by chance, as shown by a proper null model. The distribution and identity of endemic genera are consistent with models considering a North American origin for two of the families (Vespertilionidae and Natalidae), an early arrival to South America for another family (Molossidae), and a complex diversification process, involving two centres of diversification, for at least two of the families of the Noctilionoidea (Mormoopidae and Phyllostomidae) and possibly for the Emballonuridae. The recently identified Panamanian Realm (including southern Mexico and Central America) seems to have played a significant role in the diversification of New World bats.
The role of frugivory in the diversification of bats in the Neotropics
Aim: Ecological interactions are among the most important biotic factors influencing the processes of speciation and extinction. Our aim was to test whether diversification rates of New World Noctilionoidea bats are associated with specialization for frugivory, and how this pattern differs between the mainland and the West Indies. Location: The New World. Methods We reconstructed a time-calibrated molecular phylogenetic hypothesis for the New World genera of the superfamily Noctilionoidea. We compiled data on diet, morphology, geographical distribution and number of ecoregions in which each genus occurs. Then, using the phylogenetic tree constructed, we tested whether diversification was driven by diet (animalivorous and sanguinivorous versus nectarivorous and frugivorous) and specialization for frugivory. Afterwards, we conducted phylogenetic comparative analyses to identify correlates of species richness and net diversification rates. Results: The diversification rate was higher in mutualistic than in antagonistic clades in mainland and Antillean biogeographical scenarios, but only strictly frugivorous clades showed a markedly higher diversification rate than the rest of the genera. Geographical range and number of ecoregions were positively associated with species richness and diversification rate in continental and insular lineages. Lower body mass, lower forearm length and specialization for frugivory were significantly positively correlated with higher diversification rates in continental lineages, whereas these parameters were negatively correlated in Antillean lineages. Main conclusions: The direction of the relationship of intrinsic factors (specialization for frugivory and body size) with diversification of noctilionoid bats depends on the biogeographical context, whereas the direction of the relationship of extrinsic factors (geographical range and number of ecoregions) with diversification is consistent in both mainland and the West Indian lineages.
Proceedings of the Royal Society B: Biological Sciences, 2011
Determinants of contemporary patterns of diversity, particularly those spanning extensive latitudinal gradients, are some of the most intensely debated issues in ecology. Recently, focus has shifted from a contemporary environmental perspective to a historical one in an attempt to better understand the construction of latitudinal gradients. Although the vast majority of research on historical mechanisms has focused on tropical niche conservatism (TNC), other historical scenarios could produce similar latitudinal gradients. Herein, I formalize predictions to distinguish between two such historical processes—namely time for speciation (TFS) and TNC—and test relative support based on diversity gradients of New World bats. TFS and TNC are distinctly spatial and environmental mechanisms, respectively. Nonetheless, because of the way that environmental characteristics vary spatially, these two mechanisms are hard to distinguish. Evidence provided herein suggests that TNC has had a more im...
Explaining the causes of geographic gradients in biodiversity remains an elusive task. Traditionally, correlative approaches have been used to relate species richness with contemporary climate, without actually explaining the causal factors. Recent approaches propose simulation models as more appropriate tools for assessing potential causes of macroecological patterns. Here we developed stochastic models to assess the relative contribution of climate and niche conservatism in determining compositional similarity among sites (co-diversity) and geographic association among species (co-distribution) in the bat family Phyllostomidae. We used range-diversity plots and variance-ratio tests to describe and evaluate such patterns. Our results supported a strong effect of climate in determining cohesive ranges causing positive co-diversity and co-distribution. We also demonstrated a marginal effect of niche conservatism, as modeled here, among species in shaping these patterns. However, climate and niche conservatism are not sufficient and other processes are still required to explain observed patterns. Our study highlights the importance of historical processes and demonstrates the usefulness of a simulation framework in testing biogeographical hypothesis to understand the relationship between diversity and distribution.
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 synthesis of ecological and evolutionary determinants of bat diversity across spatial scales
BMC Ecology
Background: Diversity patterns result from ecological to evolutionary processes operating at different spatial and temporal scales. Species trait variation determine the spatial scales at which organisms perceive the environment. Despite this knowledge, the coupling of all these factors to understand how diversity is structured is still deficient. Here, we review the role of ecological and evolutionary processes operating across different hierarchically spatial scales to shape diversity patterns of bats-the second largest mammal order and the only mammals with real flight capability. Main body: We observed that flight development and its provision of increased dispersal ability influenced the diversification, life history, geographic distribution, and local interspecific interactions of bats, differently across multiple spatial scales. Niche packing combined with different flight, foraging and echolocation strategies and differential use of air space allowed the coexistence among bats as well as for an increased diversity supported by the environment. Considering distinct bat species distributions across space due to their functional characteristics, we assert that understanding such characteristics in Chiroptera improves the knowledge on ecological processes at different scales. We also point two main knowledge gaps that limit progress on the knowledge on scale-dependence of ecological and evolutionary processes in bats: a geographical bias, showing that research on bats is mainly done in the New World; and the lack of studies addressing the mesoscale (i.e. landscape and metacommunity scales). Conclusions: We propose that it is essential to couple spatial scales and different zoogeographical regions along with their functional traits, to address bat diversity patterns and understand how they are distributed across the environment. Understanding how bats perceive space is a complex task: all bats can fly, but their perception of space varies with their biological traits.
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.
Latitudinal gradients in the phenetic diversity of New World bat communities
Oikos, 2006
Although the examination of latitudinal gradients of species richness is common, little attention has been devoted to other components of biodiversity such as phenetic diversity. Because the phenotype reflects aspects of an organism's environment, ecological relationships and evolutionary history, measures of phenetic diversity likely provide complimentary information to that of species richness, and may provide unique insights for understanding the mechanistic basis to patterns of biodiversity. Herein, we evaluate latitudinal gradients in the phenetic diversity of 32 New World bat communities. Seven morphological characters were used to estimate phenotypic variation among bat species within local communities. Principal components analysis decomposed this variation into axes of size and shape. Three measures of phenetic diversity were calculated separately for size and for shape axes. The range of species scores on a particular axis described the amount of phenetic variation encompassed by species in a community. The standard deviation of minimum spanning-tree segment lengths described uniformity of species. Average nearestneighbor distances described local packing. We separately regressed these six measures on local species richness and latitude separately. Variation in species richness accounted for a significant amount of variation in each measure of phenetic diversity. Latitude also accounted for significant variation in phenetic diversity except for the standard deviation of minimum-spanning tree segment lengths and the average nearest-neighbor distance on the shape axis. More importantly, gradients in phenetic diversity were significantly different than would be expected as a consequence of latitudinal gradients in species richness. Nonetheless, when variation among communities regarding the richness and composition of their regional faunas was taken into consideration, differences between empirical and simulated gradients were nonsignificant. Thus, factors that determine the composition of regional faunas have a great impact on the phenetic diversity of communities and ultimately the latitudinal gradient in biodiversity.
Assemblages of bats are phylogenetically clustered on a regional scale
Basic and Applied Ecology, 2013
Phylogenetically related species are assumed to be ecologically similar. Ecological similarity might lead to competition and to low distributional overlap. Therefore, if competitive interactions drive assemblages, we expect a decrease in distributional overlap with increasing phylogenetic relatedness and phylogenetic over-dispersion in assemblages. We tested this hypothesis by evaluating the mean phylogenetic distance of bat assemblages within grid cells of ≈36 km 2 across Bavaria, Germany (887 grids; 20,023 records). To calculate phylogenetic distance between species, we used a phylogenetic tree derived from sequences of three mitochondrial genes (cytb, COI, ND1), two nuclear-protein-encoding genes (vWF, RAG2) and the genes encoding16S rRNA, 12S rRNA and tRNA-Val. Overall, bat species co-occurring within grid cells were more similar than expected from null models (phylogenetic clustering). This suggests that on the considered scale, bat assemblages are triggered more by environmental filters than by competition. Furthermore, mean phylogenetic distance decreased with the amount of anthropogenic habitats within grids. This contrasts with species richness of bats, which increased with anthropogenic habitats.