Geographic Patterns of Body-Mass Diversity in Mexican Mammals

Arita, Héctor T.; Figueroa, Fernanda

doi:10.2307/3546497

Cited by 20 publications

(17 citation statements)

References 59 publications

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“…However, body size distribution of southern African insectivorous bats was scale-dependant, becoming progressively more right-skewed and less evenly spaced from local to regional levels. The right-skewed body size distribution at the greatest regional scale is consistent with body size distributions of non-volant and volant New World mammals at regional and continental scales [25], [66], [67]. Our results are also consistent with the observation that body sizes of non-volant mammals tend to be evenly distributed at a local scale [66], [67].…”

Section: Discussionsupporting

confidence: 88%

The Relative Influence of Competition and Prey Defenses on the Phenotypic Structure of Insectivorous Bat Ensembles in Southern Africa

Schoeman

Jacobs

2008

PLoS ONE

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Deterministic filters such as competition and prey defences should have a strong influence on the community structure of animals such as insectivorous bats that have life histories characterized by low fecundity, low predation risk, long life expectancy, and stable populations. We investigated the relative influence of these two deterministic filters on the phenotypic structure of insectivorous bat ensembles in southern Africa. We used null models to simulate the random phenotypic patterns expected in the absence of competition or prey defences and analysed the deviations of the observed phenotypic pattern from these expected random patterns. The phenotypic structure at local scales exhibited non-random patterns consistent with both competition and prey defense hypotheses. There was evidence that competition influenced body size distribution across ensembles. Competition also influenced wing and echolocation patterns in ensembles and in functional foraging groups with high species richness or abundance. At the same time, prey defense filters influenced echolocation patterns in two species-poor ensembles. Non-random patterns remained evident even after we removed the influence of body size from wing morphology and echolocation parameters taking phylogeny into account. However, abiotic filters such as geographic distribution ranges of small and large-bodied species, extinction risk, and the physics of flight and sound probably also interacted with biotic filters at local and/or regional scales to influence the community structure of sympatric bats in southern Africa. Future studies should investigate alternative parameters that define bat community structure such as diet and abundance to better determine the influence of competition and prey defences on the structure of insectivorous bat ensembles in southern Africa.

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Section: Discussionsupporting

confidence: 88%

The Relative Influence of Competition and Prey Defenses on the Phenotypic Structure of Insectivorous Bat Ensembles in Southern Africa

Schoeman

Jacobs

2008

PLoS ONE

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“…At lower taxonomic levels (Kozłowski & Gawelczyk, 2002), and at smaller spatial scales (Gaston & Blackburn, 2000), BSFDs are more variable, ranging in the latter case from right‐skewed to lognormal and from unimodal to multimodal. Whilst BSFDs of some local assemblages can be well predicted by a random draw from the regional body size distribution, in other local assemblages they are less right‐skewed than expected on this basis (Brown & Nicoletto, 1991; Arita & Figueroa, 1999; Bakker & Kelt, 2000).…”

Section: Introductionmentioning

confidence: 87%

Environmental factors, regional body size distributions and spatial variation in body size of local avian assemblages

Greve

Gaston

Rensburg

et al. 2008

Global Ecology and Biogeography

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Aim To determine how well variation in median body size of avian assemblages is predicted by (1) the environmental models usually employed in analyses of Bergmann's rule and (2) random sampling from the regional body size frequency distribution. If body size frequency distributions of local assemblages represent a random sample of a regional frequency distribution, then geographical variation in body sizes of assemblages might be a consequence of the determinants of spatial variation in species richness rather than direct influences on body size per se. Location Southern Africa. Methods Median body masses (as a measure of body size) of avian assemblages were calculated for quarter‐degree grid cells across South Africa and Lesotho. The relationship between median body mass and four environmental variables (minimum and maximum monthly temperatures, precipitation and seasonality in the normalized difference vegetation index, as a measure of seasonality in productivity) was examined using general linear models first without taking spatial autocorrelation into account, and then accounting for it by fitting an exponential spatial covariance structure. Model fit was assessed using the Akaike information criterion and Akaike weights. At each species richness value, random assemblages were sampled by either drawing species randomly from the regional body mass frequency distribution, or drawing species from the regional body mass frequency distribution with a probability proportional to their geographical distribution in the area. The ability of randomizations to predict actual body masses was examined using two‐tailed Fisher exact tests. Results Seasonality in productivity was the only environmental variable that remained a significant predictor of body mass variation in spatially explicit models, though the positive relationship was weak. When species richness was included in the models it remained the only significant predictor of size variation. Randomizations predicted median body mass poorly at low species richness, but well at high richness. Main conclusions Environmental models that have previously been proposed explain little of the variation in body mass across avian assemblages in South Africa. However, much of the variation in the median mass of assemblages could be predicted by randomly drawing species from the regional body mass frequency distribution, particularly using randomizations in which all species were drawn from the regional body mass frequency distribution with equal probability and at high species richness values. This outcome emphasizes the need to consider null expectations in investigations of the geographical variation in body size together with the probable environmental mechanisms underlying spatial variation in average size. Moreover, it suggests that in the South African avifauna, spatial variation in the body sizes of assemblages may be determined indirectly by the factors that influence geographical variation in species richness.

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“…This region showed a high heterogeneity (SD of altitude, 530.6 m; SD of temperature, 2.5°C; SD of rainfall, 762.0 mm; n = 56 stations). The scaling of body-mass diversity in this region has been analysed elsewhere (Arita and Figueroa 1999). The fourth quadrat, located in the mostly flat Yucatan Peninsula, is fully Neotropical and showed low levels of heterogeneity (SD of altitude, 47.7 m; SD of temperature, 0.8°C; SD of rainfall, 228.9 mm; n = 40 stations).…”

Section: Methodsmentioning

confidence: 99%

Geographic range, turnover rate and the scaling of species diversity

Arita

Rodríguez²

2002

Ecography

105

101

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The study of the relative roles of local and regional processes in determining the scaling of species diversity is a very active field in current ecology. The importance of species turnover and the species‐range‐size frequency distributions in determining how local and regional species diversity are linked has been recognised by recent approaches. Here we present a model, based on a system of fully nested sampling quadrats, to analyse species diversity at several scales. Using a recursive procedure that incorporates increasingly smaller scales and a multiplicative formula for relating local and regional diversity, the model allows the simultaneous depiction of alpha, beta and gamma diversity in a single “species‐scale plot”. Species diversity is defined as the number of ranges that are intersected by sampling quadrats of various sizes. The size, shape and location of individual species ranges determine diversity at any scale, but the average point diversity, measured at hypothetical zero‐area localities, is determined solely by the size of individual ranges, regardless of their shape and location. The model predicts that if the species‐area relationship is a power function, then beta diversity must be scale invariant if measured at constant scale increments. Applying the model to the mammal fauna of four Mexican regions with contrasting environmental conditions, we found that: 1) the species‐range‐size frequency distribution at the scale of the Mexican regions differs from the log‐normal pattern reported for the national and continental scales. 2) Beta diversity is not scale‐invariant within each region, implying that the species‐area relationship (SAR) does not follow a power function. 3) There is geographic variation in beta diversity. 4) The scaling of diversity is directly linked to patterns of species turnover rate, and ultimately determined by patterns in the geographic distribution of species. The model shows that regional species diversity and the average distribution range of species are the two basic data necessary to predict patterns in the scaling of species diversity.

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Geographic Patterns of Body-Mass Diversity in Mexican Mammals

Cited by 20 publications

References 59 publications

The Relative Influence of Competition and Prey Defenses on the Phenotypic Structure of Insectivorous Bat Ensembles in Southern Africa

The Relative Influence of Competition and Prey Defenses on the Phenotypic Structure of Insectivorous Bat Ensembles in Southern Africa

Environmental factors, regional body size distributions and spatial variation in body size of local avian assemblages

Geographic range, turnover rate and the scaling of species diversity

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