Interspecific patterns of species richness, geographic range size, and body size among New World venomous snakes

Many higher taxa exhibit latitudinal gradients in species richness, geographic range size, and body size. However, these variables are often interdependent, such that examinations of univariate or bivariate patterns alone may be misleading. Therefore, I examined latitudinal gradients in, and relationships between, species richness, geographic range size, and body size among 144 species of New World venomous snakes [families Elapidae (coral snakes) and Viperidae (pitvipers)]. Both lineages are monophyletic, collectively span 99° of latitude, and are extremely variable in body size and geographic range sizes. Coral snakes exhibit highest species richness near the equator, while pitviper species richness peaks in Central America. Species – range size distributions were strongly right-skewed for both families. There was little support for Bergmann's rule or Rapoport's rule for snakes of either family, as neither body size nor range size increased significantly with latitude. However, range area and median range latitude were positively correlated above 15° N, indicating a possible "Rapoport effect" at high northern latitudes. Geographic range size was positively associated with body size. Available continental area strongly influenced range size. Comparative (phylogenetically-based) analyses revealed that shared history is a poor predictor of range size variation within clades. Among vipers, trends in geographic range sizes may have been structured more by historical biogeography than by macroecological biotic factors.     

Broad‐scale geographic patterns in body size and hind wing development of western Palaearctic carabid beetles(Coleoptera: Carabidae)

Research into large‐scale ecological rules has a long tradition but has received increasing attention over the last two decades. Whereas environmental, especially climatic, influences on the geographic distribution of species traits such as body size are well understood in mammals and birds, our knowledge of the determinants and mechanisms which shape spatial patterns in invertebrate traits is still limited. This study analyzes macroecological patterns in two traits of the highly diverse invertebrate taxon of carabid beetles: body size and hind wing development, the latter being directly linked to species’ dispersal abilities. We tested for potential impacts of environmental variables (spatial, areal, topographic and climate‐related) representing both contemporary conditions and historical processes on large‐scale patterns in the two traits. Regression models revealed hump‐shaped relationships with latitude for both traits in the categories 1) all species, 2) widespread and 3) endemic (restricted‐range) species: body size and the proportion of flightless species increased from northern towards southern Europe and then decreased towards North Africa. The shared and independent influence of environmental factors was analyzed by variation partitioning. While contemporary environmental productivity and stability (represented by measures of ambient energy and water energy balance) had strong positive relationships with carabid body size, patterns in hind wing development were most notably influenced by topography (elevation range). Regions with high elevation range and low historical climate variability (since the last ice age), which likely offer long‐term stable habitats (i.e. glacial refugia), coincide with regions with high proportions of flightless species. Thus geographic patterns in carabid traits tend to be formed not only by recent climate but also by dispersal and historical climate and processes (i.e. glaciations and postglacial colonization).     

Abundance-occupancy dynamics in a human dominated environment: linking interspecific and intraspecific trends in British farmland and woodland birds

1. Range size, population size and body size, the key macroecological variables, vary temporally both within and across species in response to anthropogenic and natural environmental change. However, resulting temporal trends in the relationships between these variables (i.e. macroecological patterns) have received little attention. 2. Positive relationships between the local abundance and regional occupancy of species (abundance-occupancy relationships) are among the most pervasive of all macroecological patterns. In the absence of formal predictions of how abundance-occupancy relationships may vary temporally, we outline several scenarios of how changes in abundance within species might affect interspecific patterns. 3. We use data on the distribution and abundance of 73 farmland and 55 woodland bird species in Britain over a 32-year period encompassing substantial habitat modification to assess the likelihood of these scenarios. 4. In both farmland and woodland habitats, the interspecific abundance-occupancy relationship changed markedly over the period 1968-99, with a significant decline in the strength of the relationship. 5. Consideration of intraspecific dynamics shows that this has been due to a decoupling of abundance and occupancy particularly in rare and declining species. Insights into the intraspecific processes responsible for the interspecific trend are obtained by analysis of temporal trends in the distribution of individuals between sites, which show patterns consistent with habitat quality declines. 6. This study shows that a profitable approach to ascertaining the nature of human impacts is to link intra- and interspecific processes. In the case of British farmland and woodland birds, changes to the environment lead to species-specific responses in large-scale distributions. These species-specific changes are the driver of the observed changes in the form and strength of the interspecific relationship.     

Trait biogeography of marine copepods – an analysis across scales

Functional traits, rather than taxonomic identity, determine the fitness of individuals in their environment: traits of marine organisms are therefore expected to vary across the global ocean as a function of the environment. Here, we quantify such spatial and seasonal variations based on extensive empirical data and present the first global biogeography of key traits (body size, feeding mode, relative offspring size and myelination) for pelagic copepods, the major group of marine zooplankton. We identify strong patterns with latitude, season and between ocean basins that are partially (c. 50%) explained by key environmental drivers. Body size, for example decreases with temperature, confirming the temperature‐size rule, but surprisingly also with productivity, possibly driven by food‐chain length and size‐selective predation. Patterns unrelated to environmental predictors may originate from phylogenetic clustering. Our maps can be used as a test‐bed for trait‐based mechanistic models and to inspire next‐generation biogeochemical models.     

Climate effects on fish body size–trophic position relationship depend on ecosystem type

The energetic demand of consumers increases with body size and temperature. This implies that energetic constraints may limit the trophic position of larger consumers, which is expected to be lower in tropical than in temperate regions to compensate for energy limitation. Using a global dataset of 3635 marine and freshwater ray‐finned fish species, we addressed if and how climate affects the fish body size–trophic position relationship in both freshwater and marine ecosystems, while controlling for the effects of taxonomic affiliation. We observed significant fish body size–trophic position relationships for different ecosystems. However, only in freshwater systems larger tropical fish presented a significantly lower trophic position than their temperate counterparts. Climate did not affect the fish body size–trophic position relationship in marine systems. Our results suggest that larger tropical freshwater fish may compensate for higher energetic constraints feeding at lower trophic positions, compared to their temperate counterparts of similar body size. The lower latitudinal temperature range in marine ecosystems and/or their larger ecosystem size may attenuate and/or compensate for the energy limitation of larger marine fish. Based on our results, temperature may determine macroecological patterns of aquatic food webs, but its effect is contingent on ecosystem type. We suggest that freshwater ecosystems may be more sensitive to warming‐induced alterations in food web topology and food chain length than marine ecosystems.     

Tracing alpha, beta, and gamma diversity responses to environmental change in boreal lakes

Boreal lakes undergo broad-scale environmental change over time, but biodiversity responses to these changes, particularly at macroecological scales, are not well known. We studied long-term trends (1992–2009) of environmental variables and assessed α, β, and γ diversity responses of phytoplankton and littoral invertebrates to these changes. Diversity was assessed based on taxon richness (“richness”) and the exponentiated Shannon entropy (“diversity”). Almost all environmental variables underwent significant monotonic change over time, indicating mainly decreasing acidification, water clarity and nutrient concentrations in the lakes. These variables explained about 54 and 38 % of variance in regression models of invertebrates and phytoplankton, respectively. Despite this, most diversity-related variables fluctuated around a long-term mean. Only α and γ richness and diversity of invertebrates increased monotonically through time, and these patterns correlated significantly with local and regional abundances. Results suggest that biodiversity in boreal lakes is currently stable, with no evidence of regional biotic homogenization or local diversity loss. Results also show that richness trends between phytoplankton and invertebrates were widely uncorrelated, and the same was found for diversity trends. Also, within each taxonomic group, temporal patterns of richness and diversity were largely uncorrelated with each other. From an applied perspective, this suggest that long-term trends of biodiversity in boreal lakes at a macroecological scale cannot be accurately assessed without multiple lines of evidence, i.e. through the use of multiple taxa and diversity-related variables in the analyses.     

Body size–climate relationships of European spiders

Aim Geographic body size patterns of mammals and birds can be partly understood under the framework of Bergmann’s rule. Climatic influences on body size of invertebrates, however, appear highly variable and lack a comparable, generally applicable theoretical framework. We derived predictions for body size–climate relationships for spiders from the literature and tested them using three datasets of variable spatial extent and grain. Location Europe. Methods To distinguish climate from space, we compared clines in body size within three datasets with different degrees of co‐variation between latitude and climate. These datasets were: (1) regional spider faunas from 40 European countries and large islands; (2) local spider assemblages from standardized samples in 32 habitats across Europe; and (3) local spider assemblages from Central European habitats. In the latter dataset climatic conditions were determined more by habitat type than by geographic position, and therefore this dataset provided a non‐spatial gradient of various microclimates. Spider body size was studied in relation to latitude, temperature and water availability. Results In all three datasets the mean body size of spider assemblages increased from cool/moist to warm/dry environments. This increase could be accounted for by turnover from small‐bodied to large‐bodied spider families. Body size–climate relationships within families were inconsistent. Main conclusions Starvation resistance and accelerated maturation can be ruled out as explanations for the body size clines recorded, because they predict the inverse of the observed relationship between spider body size and temperature. The relationship between body size and climate was partly independent of geographic position. Thus, the restriction of large‐bodied spiders to their glacial refugia owing to dispersal limitations can be excluded. Our results are consistent with mechanisms invoking metabolic rate, desiccation resistance and community interactions to predict a decrease in body size from warm and dry to cool and moist conditions.     

Species richness, abundance, and body size relationships from a neotropical chironomid assemblage: Looking for patterns

We investigated two of the most studied relationships in the macroecological research program (species richness vs. body size and abundance vs. body size) of a local chironomid assemblage from southeastern Brazil. Although numerous studies have examined these relationships, few have investigated how they vary at different temporal scales. We used data from a forested stream to document and examine these patterns at monthly intervals. Both the species body size distribution and the abundance–body size relationship varied temporally. In some months the body size distribution was skewed to the right, whereas in others it approached normality. We found both linear relationships (with different values of slopes), and a polygonal pattern in the abundance–body size relationship. This temporal variation was not related to environmental variables. Our results suggest that body size relationships are temporally instable properties of this chironomid assemblage.     

An interspecific test of Bergmann's rule reveals inconsistent body size patterns across several lineages of water beetles (Coleoptera: Dytiscidae)

1. Bergmann's rule sensu lato, the ecogeographic pattern relating animals' body size with environmental temperature (or latitude), has been shown to be inconsistent among insect taxa. Body size clines remain largely unexplored in aquatic insects, which may show contrasting patterns to those found in terrestrial groups because of the physiological or mechanical constraints of the aquatic environment. 2. Bergmann's rule was tested using data on body size, phylogeny and distribution for 93 species belonging to four lineages of dytiscid water beetles. The relationship between size and latitude was explored at two taxonomic resolutions – within each independent lineage, and for the whole dataset – employing phylogenetic generalised least‐squares to control for phylogenetic inertia. The potential influence of habitat preference (lotic versus lentic) on body size clines was also considered. 3. Within‐lineage analyses showed negative relationships (i.e. converse Bergmann's rule), but only in two lineages (specifically in those that included both lotic and lentic species). By contrast, no relationship was found between body size and latitude for the whole dataset. 4. These results suggest that there may be no universal interspecific trends in latitudinal variation of body size in aquatic insects, even among closely related groups, and show the need to account for phylogenetic inertia. Furthermore, habitat preferences should be considered when exploring latitudinal clines in body size in aquatic taxa at the interspecific level.     

The birds and the seas: body size reconciles differences in the abundance–occupancy relationship across marine and terrestrial vertebrates

Despite some fundamental differences in production processes and the ecology of consumer species on land and in the sea, further understanding of pattern and process in both biomes might be gained by applying common methods of macroecological analysis. We develop methods that reconcile apparent differences in abundance and occupancy for marine and terrestrial vertebrates, as exemplified by fish and birds. These recognize and take account of those aspects of the life history and ecology of marine and terrestrial animals that influence their abundance, distribution and trophic role. When abundance and occupancy are averaged within species over time we show that variation within a region is less for birds than fish, but when abundance and occupancy are averaged over space, the difference between birds and fish disappears. Further, we develop size rather than species‐structured abundance–occupancy relationships for fish assemblages and demonstrate that patterns of intra‐size class variation that are very similar to intraspecific variation in bird species, over both time and space. We argue that this result reflects the relative importance of body size and species identity respectively in determining trophic roles in marine and terrestrial environments. Selection of the appropriate analytical unit on land (species) and in the sea (size) helps to reconcile apparently divergent macroecological patterns, especially when these are driven by contrasting patterns of energy acquisition and use.     

Connecting species richness, abundance and body size in deep-sea gastropods

Aim This paper examines species richness, abundance, and body size in deep‐sea gastropods and how they vary over depth, which is a strong correlate of nutrient input. Previous studies have documented the empirical relationships among these properties in terrestrial and coastal ecosystems, but a full understanding of how these patterns arise has yet to be obtained. Examining the relationships among macroecological variables is a logical progression in deep‐sea ecology, where patterns of body size, diversity, and abundance have been quantified separately but not linked together. Location 196–5042 m depth in the western North Atlantic. Method Individuals analysed represent all Vetigastropoda and Caenogastropoda (Class Gastropoda) with intact shells, excluding Ptenoglossa, collected by the Woods Hole Benthic Sampling Program (3424 individuals representing 80 species). Biovolume was measured for every individual separately (i.e. allowing the same species to occupy multiple size classes) and divided into log₂ body size bins. Analyses were conducted for all gastropods together and separated into orders and depth regions (representing different nutrient inputs). A kernel smoothing technique, Kolmogorov‐Smirnov test of fit, and OLS and RMA were used to characterize the patterns. Results Overall, the relationship between the number of individuals and species is right skewed. There is also a positive linear relationship between the number of individuals and the number of species, which is independent of body size. Variation among these relationships is seen among the three depth regions. At depths inferred to correspond with intermediate nutrient input levels, species are accumulated faster given the number of individuals and shift from a right‐skewed to a log‐normal distribution. Conclusion A strong link between body size, abundance, and species richness appears to be ubiquitous over a variety of taxa and environments, including the deep sea. However, the nature of these relationships is affected by the productivity regime and scale at which they are examined.     

Form–function relationships in a marine foundation species depend on scale: a shoot to global perspective from a distributed ecological experiment

Form–function relationships in plants underlie their ecosystem roles in supporting higher trophic levels through primary production, detrital pathways, and habitat provision. For widespread, phenotypically‐variable plants, productivity may differ not only across abiotic conditions, but also from distinct morphological or demographic traits. A single foundation species, eelgrass Zostera marina, typically dominates north temperate seagrass meadows, which we studied across 14 sites spanning 32–61°N latitude and two ocean basins. Body size varied by nearly two orders of magnitude through this range, and was largest at mid‐latitudes and in the Pacific Ocean. At the global scale, neither latitude, site‐level environmental conditions, nor body size helped predict productivity (relative growth rate 1–2% day^‐1 at most sites), suggesting a remarkable capacity of Z. marina to achieve similar productivity in summer. Furthermore, among a suite of stressors applied within sites, only ambient leaf damage reduced productivity; grazer reduction and nutrient addition had no effect on eelgrass size or growth. Scale‐dependence was evident in different allometric relationships within and across sites for productivity and for modules (leaf count) relative to size. Zostera marina provides a range of ecosystem functions related to both body size (habitat provision, water flow) and growth rates (food, carbon dynamics). Our observed decoupling of body size and maximum production suggests that geographic variation in these ecosystem functions may be independent, with a future need to resolve how local adaptation or plasticity of body size might actually enable more consistent peak productivity across disparate environmental conditions.     

The importance of phylogenetic scale in tests of Bergmann's and Rapoport's rules: lessons from a clade of South American lizards

We tested for the occurrence of Bergmann's rule, the pattern of increasing body size with latitude, and Rapoport's rule, the positive relationship between geographical range size and latitude, in 34 lineages of Liolaemus lizards that occupy arid regions of the Andean foothills. We tested the climatic-variability hypothesis (CVH) by examining the relationship between thermal tolerance breadth and distribution. Each of these analyses was performed varying the level of phylogenetic inclusiveness. Bergmann's rule and the CVH were supported, but Rapoport's rule was not. More variance in the data for Bergmann's rule and the CVH was explained using species belonging to the L. boulengeri series rather than all species, and inclusion of multiple outgroups tended to obscure these macroecological patterns. Evidence for Bergmann's rule and the predicted patterns from the CVH remained after application of phylogenetic comparative methods, indicating a greater role of ecological processes rather than phylogeny in shaping the current species distributions of these lizards.     

Range size in North American Enallagma damselflies correlates with wing size

1. Cross-species macroecological comparisons in freshwater invertebrates have been restricted by a lack of large-scale distributional data, and robust phylogenies. Here, we use data from the OdonataCentral database to explore body length–range size and wing length–range size relationships in damselflies from the genus Enallagma ; the recent publication of a phylogeny for this group meant that, as well as a cross-species analysis, we were able to assess relationships in a phylogenetically controlled manner.
2. For cross-species comparisons, only wing length showed significant (positive) regression relationships with range size and occupancy, although the inclusion of body length in multiple regressions increased the fit of the models. Damselflies with larger wings relative to their body length had larger distributions, a result confirmed by a significant positive relationship between range size and residuals from the regression of wing size on body size.
3. For the phylogenetically controlled analyses, only wing length contrast scores were significantly related to distribution patterns and entered into regression models; the significant positive relationships between wing length contrasts and both range size and occupancy contrasts suggested that evolutionary increases in wing length had occurred alongside range expansions.
4. Together these results suggest that species of Enallagma with larger wings (both absolute and relative to body length) tend to be more widely distributed in North America and that the evolution of wing size may have played a role in range expansion. No such relationships were evident for body size. We discuss the potential importance of wing morphometrics for studying the evolutionary ecology of freshwater insects.     

Body size explains interspecific variation in size–latitude relationships in geographically widespread beetle species

1. In most birds and mammals, larger individuals of the same species tend to be found at higher latitudes, but in insects, body size–latitude relationships are highly variable. 2. Recent studies have shown that larger‐bodied insect species are more likely to decrease in size when reared at increased temperature, compared with smaller‐sized species. These findings have led to the prediction that a positive relationship between body size and latitude should be more prevalent in larger‐bodied insect species. 3. This study measured the body size of > 4000 beetle specimens (12 species) collected throughout North America. Some beetle species increased in size with latitude, while others decreased. Importantly, mean species body size explained c. 30% of the interspecific variation in the size–latitude response. 4. As predicted, larger‐bodied beetle species were more likely to show a positive relationship between body size and latitude (Bergmann's rule), and smaller‐bodied species were more likely to show a negative body size–latitude relationship (inverse Bergmann's rule). 5. These body size–latitude patterns suggest that size‐specific responses to temperature may underlie global latitudinal distributions of body size in Coleoptera, as well as other insects.     

Abundance–occupancy relationships in deep sea wood fall communities

The generally positive relationship between the number of sites a species occupies and its average abundance within those sites provides an important link between population processes occurring at different spatial scales. Although such abundance–occupancy relationships (AORs) have been documented across a very wide range of taxa and in many different environments, little is known of such patterns in Earth's largest ecosystem, the deep sea. Wood falls – derived from natural or anthropogenic inputs of wood into the oceans – constitute an important deep‐sea habitat, habouring their own unique communities ultimately entirely dependent on the wood for chemical energy. In this study we take advantage of the unique features of an experimental wood fall deployment to examine AORs for the first time in deep‐sea invertebrates. The study design combines advantages of both experimental (tractability, control of key environmental parameters) and observational (natural colonisation by taxonomically diverse communities) studies. We show that the interspecific AOR is strongly positive across the 48 species occurring over 32 wood fall communities. The precise form of the AOR is mediated by both species‐level life history (body size) and by the colonisation stage at which communities were harvested, but not by environmental energy (wood fall size). Temporal dynamics within species are also generally consistent with positive intraspecific AORs. This support for positive AORs in the deep sea is an important extension of a macroecological generality into a new environment offering considerable potential for further testing and developing mechanistic macroecological theories.     

Climate‐driven body‐size trends in the ostracod fauna of the deep Indian Ocean

Abstract: Body size is a common focus of macroevolutionary, macroecological and palaeontological investigations. Here, we document body‐size evolution in 19 species‐level ostracod lineages from the deep Indian Ocean (Deep Sea Drilling Program Site 253) over the past 40 myr. Body‐size trajectories vary across taxa and time intervals, but most lineages (16/19) show net gains in body size. Because many modern ostracod taxa are larger in colder parts of their geographical range, we compared the timing and magnitude of these size changes to established Cenozoic deep‐water cooling patterns confirmed through δ¹⁸O measurements of benthic foraminifera in the samples studied. These data show a significant negative correlation between size changes and temperature changes (ostracods get larger as temperatures get colder), and that systematic size increases only occur during intervals of sustained cooling. In addition, statistical support for an explicit temperature‐tracking model exceeds that of purely directional evolution. We argue that this Cope’s Rule pattern is driven by secular changes in the environment, rather than any universal or intrinsic advantages to larger body sizes, and we note some difficulties in the attempts to link Cope’s Rule to observations made within a single generation.     

Global macroecology of bird assemblages in urbanized and semi‐natural ecosystems

Aim Despite the increasing pace of urbanization, little is known about how this process affects biodiversity globally. We investigate macroecological patterns of bird assemblages in urbanized areas relative to semi‐natural ecosystems. Location World‐wide. Methods We use a database of quantitative bird surveys to compare key assemblage structure parameters for plots in urbanized and semi‐natural ecosystems controlling for spatial autocorrelation and survey methodology. We use the term ‘urbanized’ instead of ‘urban’ ecosystems as many of the plots were not located in the centre of towns but in remnant habitat patches within conurbations. Results Some macroecological relationships were conserved in urbanized landscapes. Species–area, species–abundance and species–biomass relationships did not differ significantly between urbanized and non‐urbanized environments. However, there were differences in the relationships between productivity and assemblage structure. In forests, species richness increased with productivity; in both forests and open habitats, the evenness of species abundances declined as productivity increased. Among urbanized plots, instead, both species richness and the evenness of species abundances were independent of variation in productivity. Main conclusions Remnant habitats within urbanized areas are subject to many ecological alterations, yet key macroecological patterns differ remarkably little in urbanized versus non‐urbanized plots. Our results support the need for increased conservation activities in urbanized landscapes, particularly given the additional benefits of local experiences of biodiversity for the human population. With increasing urbanization world‐wide, broad‐scale efforts are needed to understand and manage the effects of this driver of change on biodiversity.     

Seeing the forest for the trees: partitioning ecological and phylogenetic components of Bergmann's rule in European Carnivora

Comparative methods have commonly been applied in macroecological research. However, few methods exist to map and analyze phylogenetic variation in geographical space. Here we develop a general analytical framework to partition the phylogenetic and ecological structures of macroecological patterns in geographic space. As an example, we apply the framework to evaluate interspecific patterns of body size geographic variation (Bergmann's rule) in European Carnivora. We model the components of variance attributable to ecological and phylogenetic effects, and to the shared influence of both factors. Spatial patterns in the ecological component are stronger than those in the original body size data. More importantly, the magnitude of intraspecific body size patterns (as measured by the correlation coefficient between body size and latitude) is significantly correlated with the ecological component across species, providing a unified interpretation for Bergmann's rule at multiple levels of biological hierarchy. This approach provides a better understanding of patterns in macroecological traits and allows improved understanding of their underlying ecological and evolutionary mechanisms.     

Latitudinal gradients in butterfly body sizes: is there a general pattern?

We tested for the existence of latitudinal gradients in the body sizes of butterflies in North America, Europe, Australia and the Afrotropics. We initially compared body sizes (measured as male forewing length) of all butterflies found in 5° latitudinal bands in each region, and then evaluated the relationship between body size and latitude statistically using the latitudinal midpoint of each species' distribution. Trends were examined for species in all butterfly families together and for each family separately. We found that gradients in body sizes were inconsistent in different geographical regions and butterfly families; in some cases species were larger towards the tropics, in some they were smaller, and in other cases there were no relationships. Most of the gradients, when they existed, reflected between-family effects arising from changes in the relative numbers of species in each family across regions. We conclude that general ecological explanations for geographical trends in butterfly body sizes are inappropriate, and gradients largely reflect historical patterns of speciation within and between taxa in each biogeographical realm. Thus, the robustness of body size gradients found in other insect groups should be confirmed in future studies by including more than one geographical region whenever possible.