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It is thought that species abundance is correlated with environmental suitability and that environmental variables, scale, and type of model fitting can confound this relationship. We performed a meta-analysis to 1) test whether species abundance is positively correlated with environmental suitability derived from correlative ecological niche models (ENM), 2) test whether studies encompassing large areas within a species range (> 50%) exhibited higher AS correlations than studies encompassing small areas within a species range (< 50%), 3) assess which modelling method provided higher AS correlation, and 4) compare strength of the AS relationship between studies using only climatic variables and those that used both climatic and other environmental variables to derive suitability. We used correlation coefficients to measure the relationship between abundance and environmental suitability derived from ENM. Each correlation coefficient was considered an effect size in a random-effects multivariate meta-analysis. In all cases we found a significantly positive relationship between abundance and suitability. This relationship was consistent regardless of scale of study, ENM method, or set of variables used to derive suitability. There was no difference in strength of correlation between studies focusing on large or small areas within a species’ range or among ENM methods. Studies using other variables in combination with climate exhibited higher AS correlations than studies using only climatic variables. We conclude that occurrence data can be a reasonable proxy for abundance, especially for vertebrates, and the use of local variables increases the strength of the AS relationship. Use of ENMs can significantly decrease survey costs and allow the study of large-scale abundance patterns using less information. Including only climatic variables in ENM may confound the relationship between abundance and suitability when compared to studies including variables taken locally. However, modelers and conservationists must be aware that high environmental suitability does not always indicate high abundance.

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 important effect than TFS in determining diversity gradients of New World bats. Indeed, relative effects of different historical mechanisms, as well as relative effects of historical and contemporary environmental determinants, are probably context-dependent. Future research should move away from attempting to identify the mechanism with primacy and instead attempt to understand the particular contexts in which different mechanisms have greater influence on diversity gradients.

Identifying biological processes that structure natural communities has long interested ecologists. Community structure may be determined by various processes, including differential responses of species to environmental characteristics, regional-level spatial influences such as dispersal, or stochasticity generated from ecological drift. Few studies have used the metacommunity paradigm (interacting communities linked by dispersal) to investigate avian community composition along an urban gradient, yet such a theoretical construct may provide insights into species turnover even in unnatural settings such as rural to urban gradients. We measured the influence of spatial and environmental characteristics on two aspects of avian community structure across a gradient of urbanization: 1) taxonomic composition and 2) functional richness based on diet, foraging strategies, nesting locations and morphology. We also measured the relationship between species traits and environmental variables with an RLQ-fourth corner analysis. Together, environmental and spatial processes were significantly related to taxonomic structure and functional richness, but spatial variables accounted for more variation than environmental variables. Fine spatial scales were positively correlated with insectivorous birds and negatively correlated with body and wing size. Urbanization was positively correlated with birds that forage at the canopy level, while emergent wetlands were negatively correlated with birds that nested in cliffs and frugivorous birds. Functional richness and urbanization were significantly related to fine spatial variables. Spatial and environmental factors played an important role in taxonomic and functional structure in avian metacommunity structure. This study highlights the importance of studying multiple aspects of biodiversity, such as taxonomic and functional dimensions, especially when examining effects of complementary spatial and environmental processes.

The degree to which Grinnellian and Eltonian niche characteristics influence species distribution may depend on latitude. Tropical regions are environmentally stable and resource-rich, whereas temperate regions are comparatively less environmentally stable (e.g., environmental filtering). Moreover, phylogenetic niche conservatism could influence distributions by inhibiting the ability for species to colonize environmentally different locations. Herein, we examine relationships between niche characteristics, passerine distributions, and phylogenetic niche conservatism across the latitudinal gradient. We used environmental and climatic variables to characterize Grinnellian niches and diets to characterize Eltonian niches. We conducted variation partitioning with retained components from ordination methods to evaluate the degree of association of Grinnellian and Eltonian niche characteristics with passerine distribution across latitudes. We examined the relationship between phylogenetic signal and niche characteristics with a phylogenetic regression. Passerine distributions were more related to environmental gradients than resources across latitudes. While niche conservatism was prevalent in Eltonian niche characteristics, phylogeny was related to Grinnellian niche characteristics in only 46% of biomes. There was no latitudinal gradient in phylogenetic niche conservatism or the degree to which Eltonian and Grinnellian niche characteristics relate to passerine distribution. Niche conservatism, albeit weak, was present for Grinnellian niche characteristics, thus potentially influencing the expansion of passerine distributions into the northern hemisphere.

Biodiversity is a complex and multidimensional concept that characterizes variation of life on Earth. Nonetheless, most studies have examined only a few, if not just one, dimension in isolation. Herein we conduct analyses that explicitly incorporate correlations among multiple dimensions of biodiversity by characterizing morphological, phylogenetic, and functional structure of bat communities from Atlantic Forest of South America and examine degree of redundancy among these sets of descriptors. Second, we examine dimensionality (i.e. number of orthogonal dimensions) of community structure by quantitatively determining if these different sets of descriptors correspond to unique dimensions. We assess if dimensionality measured from empirical communities differs from that based on communities randomly assembled from a regional species pool. Finally, we examine whether different indices of community structure respond differently to environmental gradients spanning Atlantic Forest. We find that Atlantic Forest bat communities are highly variable in terms of morphological, phylogenetic, and functional structure. Different sets of community structure indices exhibited substantive correlations. Accordingly, dimensionality was lower than the set of six different descriptors or even the three different biological dimensions represented. Nonetheless, observed dimensionality was greater than that expected from a null model of assembly. Only abundance-based indices of phylogenetic structure exhibited significant environmental gradients. Temperature seasonality was the strongest predictor of phylogenetic structure, with overdispersed communities characterizing more seasonal environments and underdispersed communities occurring in areas of lower variation in temperature. Dimensionality of community structure is low with phylogenetic structure exhibiting the strongest patterns, probably because phylogeny reflects many different ecological aspects of the phenotype that are not restricted to just one index of structure. Temperature seasonality is an important determinant of phylogenetic structure of bat communities in Atlantic Forest. This research helps us to better understand the factors underlying the distribution of biodiversity, which is increasingly important for endangered ecoregions such as Atlantic Forest.

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.

One of the more vexing issues in ecology is how historical processes affect contemporary patterns of biodiversity. Accordingly, few models have been presented. Two corollary models (centre of origin, time-for-speciation) can be used to make quantitative predictions characterizing the tropical niche conservatism hypothesis and describe diversification as diffusion and subsequent cladogenesis of species away from the place of origin of a higher taxon in the tropics. Predictions derived from such models are: (i) species richness declines toward the periphery of the range of a higher taxon; (ii) taxa are more derived toward the periphery than the centre; (iii) ages of taxa are lower toward the periphery than the centre; and (iv) ages and measures of derivedness are less variable toward the periphery of the range of a higher taxon. I tested these predictions to better understand the formation of one of the most ubiquitous patterns of biodiversity-the latitudinal gradient in species richness. Results indicate well-supported predictions for New World leaf-nosed bats and that diversification has had strong influences on latitudinal gradients of species richness. A better understanding of how evolutionary diversification of taxa contributes to formation of patterns of species richness along environmental gradients is necessary to fully understand spatial variation in biodiversity.

We examine Robert MacArthur’s hypothesis that niche breadth is positively associated with latitude (the latitude–niche breadth hypothesis). This idea has been influential and long standing, yet no studies have evaluated its generality or the validity of its assumptions. We review the theoretical arguments suggesting a positive relationship between niche breadth and latitude. We also use available evidence to evaluate the assumptions and predictions of MacArthur’s latitude–niche breadth hypothesis. We find that neither the assumptions nor the predictions of the hypothesis are supported by data. We propose an alternative hypothesis linking latitude with niche breadth. Unlike previous ideas, our conceptual framework does not require equilibrial assumptions and is based on recently uncovered patterns of species interactions.

Species with low effective population sizes are at greater risk of extinction because of reduced genetic diversity. Such species are more vulnerable to chance events that decrease population sizes (e.g. demographic stochasticity). Dipodomys elator , (Texas kangaroo rat) is a kangaroo rat that is classified as threatened in Texas and field surveys from the past 50 years indicate that the distribution of this species has decreased. This suggests geographic range reductions that could have caused population fluctuations, potentially impacting effective population size. Conversely, the more common and widespread D . ordii (Ord’s kangaroo rat) is thought to exhibit relative geographic and demographic stability. We assessed the genetic variation of D . elator and D . ordii samples using 3RAD, a modified restriction site associated sequencing approach. We hypothesized that D . elator would show lower levels of nucleotide diversity, observed heterozygosity, and effective population size when compared to D . ordii . We were also interested in identifying population structure within contemporary samples of D . elator and detecting genetic variation between temporal samples to understand demographic dynamics. We analyzed up to 61,000 single nucleotide polymorphisms. We found that genetic variability and effective population size in contemporary D . elator populations is lower than that of D . ordii . There is slight, if any, population structure within contemporary D . elator samples, and we found low genetic differentiation between spatial or temporal historical samples. This indicates little change in nuclear genetic diversity over 30 years. Results suggest that genetic diversity of D . elator has remained stable despite reduced population size and/or abundance, which may indicate a metapopulation-like system, whose fluctuations might counteract species extinction.

The lowland tapir (Tapirus terrestris) is a megaherbivore integral to ecosystem functioning in South America's tropical landscapes but is increasingly threatened by habitat loss and fragmentation. This study assessed occupancy, detectability, and activity patterns of lowland tapirs across the Orinoquia region of Colombia. We deployed 360 camera traps over 32,000 trap‐days from 2015 to 2023 across nine study areas, evaluating the influence of habitat characteristics and anthropogenic factors on the tapir presence using hierarchical occupancy models. Our results revealed a naïve occupancy of 0.40 and an overall detectability of 0.46. Model‐averaged estimates identified dense forest cover as a critical positive predictor of tapir occupancy (Ψ = 0.58, CI: 0.39–0.64), while proximity to water resources similarly enhanced both occupancy and detectability. Conversely, anthropogenic landscapes such as pastures negatively impacted occupancy probabilities (Ψ = 0.45, CI: 0.40–0.51), whereas crop areas, primarily those used for household consumption, showed a surprising positive association. Taken together, these results indicate higher occupancy in dense forest and near streams, lower occupancy in pastures, no strong positive effect of gallery/riparian belts, and a context‐dependent positive association with smallholder crops. Our findings underscore the importance of dense forests and water bodies for tapir conservation and suggest that effective management strategies must address habitat fragmentation and human–wildlife conflicts. Future conservation efforts should include intensive monitoring, community‐based participatory approaches, and consideration of climate change impacts to ensure the long‐term survival of tapir populations in this rapidly changing landscape. RESUMEN La danta de tierras bajas (Tapirus terrestris) es un megaherbívoro que hace parte integral de la funcionalidad ecológica de los paisajes tropicales de Sur América, el cual se encuentra altamente amenazado como consecuencia de la pérdida y fragmentación de los hábitats. Este estudio buscó determinar la ocupación, detectabilidad y patrones de actividad de la danta de tierras bajas a través de la región de la Orinoquia colombiana. Fueron instaladas 360 cámaras trampa durante 32,000 días efectivos de muestreo entre 2015 y 2023. En total fueron evaluadas nueve áreas de estudio donde se determinó la influencia de las características de hábitat y factores antropogénicos sobre la presencia de las dantas por medio de la implementación de modelos de ocupación jerárquicos. Los resultados revelaron una ocupación naïve de 0.40 y una detectabilidad de 0.46. Las estimaciones promediadas del modelo identificaron el bosque denso como un predictor positivo crítico en la ocupación de la danta (Ψ = 0.58, CI: 0.39–0.64), así como la proximidad a los recursos hídricos mejoró de forma similar tanto la ocupación como la detectabilidad. Por el contrario, los paisajes antropogénicos como los pastos impactaron negativamente en las probabilidades de ocupación (Ψ = 0.45, CI: 0.40–0.51). Las áreas de cultivo, principalmente aquellas utilizadas para el consumo doméstico, mostraron una sorprendente asociación positiva. En conjunto, estos resultados indican una mayor ocupación en bosques densos y zonas cercanas a cuerpos de agua, una menor ocupación en pastizales, la ausencia de un efecto positivo marcado de los bosques de galería o ribereños, y una asociación positiva dependiente del contexto con cultivos de pequeña escala. Las carreteras aparecieron como barreras de dispersión significativas, reduciendo la detectabilidad. Nuestros resultados subrayan la importancia de los bosques densos y los cuerpos de agua para la conservación de la danta y sugieren que las estrategias de gestión efectivas deben abordar la fragmentación de los hábitats, la expansión de las carreteras y los conflictos entre el hombre y la fauna. Los futuros esfuerzos de conservación deberían incluir un seguimiento intensivo, enfoques participativos basados en la comunidad y la consideración de los impactos del cambio climático para asegurar la supervivencia a largo plazo de las poblaciones de dantas en este paisaje rápidamente cambiante. Our study reveals that lowland tapir (Tapirus terrestris ) occupancy in Colombia's Orinoquia region is strongly influenced by dense forests and proximity to water bodies, while anthropogenic factors such as pastures and road networks negatively impact their presence. Using an extensive 8 year camera trap dataset and hierarchical occupancy models, we demonstrate that habitat fragmentation and land‐use change shape tapir distribution, with certain crop types unexpectedly supporting their persistence. These findings underscore the urgent need for conservation strategies that prioritize habitat connectivity, community‐based management, and climate‐resilient approaches to ensure the long‐term survival of this keystone megaherbivore.