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Geographical Range Size (geographical + range_size)

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Life Sciences	75%

Selected Abstracts

Latitudinal diversity gradients for brachiopod genera during late Palaeozoic time: links between climate, biogeography and evolutionary rates

GLOBAL ECOLOGY, Issue 4 2007
Matthew G. Powell
ABSTRACT Aim, The latitudinal diversity gradient, in which taxonomic richness is greatest at low latitudes and declines towards the poles, is a pervasive feature of the biota through geological time. This study utilizes fossil data to examine how the latitudinal diversity gradient and associated spatial patterns covaried through the major climate shifts at the onset and end of the late Palaeozoic ice age. Location, Data were acquired from fossil localities from around the world. Methods, Latitudinal patterns of diversity, mean geographical range size and macroevolutionary rates were constructed from a literature-derived data base of occurrences of fossil brachiopod genera in space and time. The literature search resulted in a total of 18,596 occurrences for 991 genera from 2320 localities. Results, Climate changes associated with the onset of the late Palaeozoic ice age (c. 327 Ma) altered the biogeographical structure of the brachiopod fauna by the preferential elimination of narrowly distributed, largely tropical genera when glaciation began. Because the oceans were left populated primarily with widespread genera, the slope of the diversity gradient became gentle at this time, and the gradient of average latitudinal range size weakened. In addition, because narrowly distributed genera had intrinsically high rates of origination and extinction, the gradients of both of these macroevolutionary rates were also reduced. These patterns were reversed when the ice age climate abated in early Permian time (c. 290 Ma): narrowly distributed genera rediversified at low latitudes, restoring steep gradients of diversity, average latitudinal range size and macroevolutionary rates. Main conclusions, During late Palaeozoic time, these latitudinal gradients for brachiopods may have been linked by the increased magnitude of seasonality during the late Palaeozoic ice age. Pronounced seasonality would have prevented the existence of genera with narrow latitudinal ranges. These results for the late Palaeozoic ice age suggest a climatic basis for the present-day latitudinal diversity gradient. [source]

Geographical range size heritability: what do neutral models with different modes of speciation predict?

GLOBAL ECOLOGY, Issue 3 2007
David Mouillot
ABSTRACT Aim, Phylogenetic conservatism or heritability of the geographical range sizes of species (i.e. the tendency for closely related species to share similar range sizes) has been predicted to occur because of the strong phylogenetic conservatism of niche traits. However, the extent of such heritability in range size is disputed and the role of biology in shaping this attribute remains unclear. Here, we investigate the level of heritability of geographical range sizes that is generated from neutral models assuming no biological differences between species. Methods, We used three different neutral models, which differ in their speciation mode, to simulate the life-history of 250,000 individuals in a square lattice of 50 × 50 cells. These individuals can speciate, reproduce, migrate and die in the metacommunity according to stochastic events. We ran each model for 3000 steps and recorded the range size of each species at each step. The heritability of geographical range size was assessed using an asymmetry coefficient between range sizes of sister species and using the coefficient of correlation between the range sizes of ancestors and their descendants. Results, Our results demonstrated the ability of neutral models to mimic some important observed patterns in the heritability of geographical range size. Consistently, sister species exhibited higher asymmetry in range sizes than expected by chance, and correlations between the range sizes of ancestor,descendant species pairs, although often weak, were almost invariably positive. Main conclusions, Our findings suggest that, even without any biological trait differences, statistically significant heritability in the geographical range sizes of species can be found. This heritability is weaker than that observed in some empirical studies, but suggests that even here a substantial component of heritability may not necessarily be associated with niche conservatism. We also conclude that both present-day and fossil data sets may provide similar information on the heritability of the geographical range sizes of species, while the omission of rare species will tend to overestimate this heritability. [source]

Dispersal and the interspecific abundance-occupancy relationship in British birds

GLOBAL ECOLOGY, Issue 5 2003
Kevin J. Gaston
ABSTRACT Aim To test the prediction that deviations of species from the positive interspecific relationship between abundance and occupancy (a measure of geographical range size) are related to differences in dispersal. Location Great Britain. Methods Quantitative data on the abundances, occupancy and dispersal distances of British birds are compared using phylogenetic comparative methods. Results Measures of natal and adult dispersal distance, and the intraspecific variance in these parameters, explain little variation in occupancy in addition to that accounted for by population size. Individual dispersal variables failed to explain significant variance when added individually to a model with population size as a predictor. Migrants and species using wet habitats tend to disperse further than residents and dry habitat species. Analysing these four groups separately revealed effects of dispersal only on the occupancy attained by dry habitat species. Conclusions The only consistent predictor of occupancy in these analyses was population size. [source]

Flea species richness and parameters of host body, host geography and host ,milieu'

JOURNAL OF ANIMAL ECOLOGY, Issue 6 2004
BORIS R. KRASNOV
Summary 1We have assessed how different host parameters affect species richness of flea assemblages using the independent contrasts method. Three groups of host parameters were examined. The first group included host body parameters (body size, basal and average daily metabolic rates), the second group included parameters of geographical range size and position of this range in relation to the equator (latitude) and the third group comprised parameters related to the number of sympatric closely related species. 2None of the host body parameters correlated with species richness of flea assemblages. 3Flea species richness increased with an increase in latitude of the geographical range centre of a host as well as with an increase in a composite variable that described the size of the geographical range. 4The number of sympatric closely related species both across the entire geographical range and locally was correlated positively with species richness of fleas. 5Our results show that species richness of ectoparasites is affected little by parameters of the host body and to a greater extent by parameters related to the host environment. [source]

Thermal tolerance and geographical range size in the Agabus brunneus group of European diving beetles (Coleoptera: Dytiscidae)

JOURNAL OF BIOGEOGRAPHY, Issue 2 2008
P. Calosi
Abstract Aim, Within clades, most taxa are rare, whilst few are common, a general pattern for which the causes remain poorly understood. Here we investigate the relationship between thermal performance (tolerance and acclimation ability) and the size of a species' geographical range for an assemblage of four ecologically similar European diving beetles (the Agabus brunneus group) to examine whether thermal physiology relates to latitudinal range extent, and whether Brown's hypothesis and the environmental variability hypothesis apply to these taxa. Location, Europe. Methods, In order to determine the species tolerances to either low or high temperatures we measured the lethal thermal limits of adults, previously acclimated at one of two temperatures, by means of thermal ramping experiments (± 1°C min,1). These measures of upper and lower thermal tolerances (UTT and LTT respectively) were then used to estimate each species' thermal tolerance range, as total thermal tolerance polygons and marginal UTT and LTT thermal polygons. Results, Overall, widespread species have higher UTTs and lower LTTs than restricted ones. Mean upper lethal limits of the Agabus brunneus group (43 to 46°C), are similar to those of insects living at similar latitudes, whilst mean lower lethal limits (,6 to ,9°C) are relatively high, suggesting that this group is not particularly cold-hardy compared with other mid-temperate-latitude insects. Widespread species possess the largest thermal tolerance ranges and have a relatively symmetrical tolerance to both high and low temperatures, when compared with range-restricted relatives. Over the temperature range employed, adults did not acclimate to either high or low temperatures, contrasting with many insect groups, and suggesting that physiological plasticity has a limited role in shaping distribution. Main conclusions, Absolute thermal niche appears to be a good predictor of latitudinal range, supporting both Brown's hypothesis and the environmental variability hypothesis. Restricted-range species may be more susceptible to the direct effect of climate change than widespread species, notwithstanding the possibility that even ,thermally-hardy', widespread species may be influenced by the indirect effects of climate change such as reduction in habitat availability in Mediterranean areas. [source]

Body size, biomic specialization and range size of African large mammals

JOURNAL OF BIOGEOGRAPHY, Issue 7 2005
Manuel Hernández Fernández
Abstract Aim, The goal of this paper is to examine the relationships between body size, biomic specialization and range size in the African large mammals, which are defined as all the African species corresponding to the orders Primates, Carnivora, Proboscidea, Perissodactyla, Hyracoidea, Tubulidentata, Artiodactyla and Pholidota. Location, The study used the large mammal assemblage from Africa. Methods, The degree of biomic specialization of African large mammals is investigated using the biomic specialization index (BSI) for each mammal species, based on the number of biomes it inhabits. Range size for each species is measured as the latitudinal extent of the geographical distribution of the species. We have analysed our data using both conventional cross-species analyses and phylogenetically independent contrasts. Results, There is a polygonal relationship between species biomic specialization and body size. While small and large species are biomic specialists, medium-sized species are distributed along the whole range of biomic specialization. The latitudinal extent,body size relationship is approximately triangular. Small-bodied species may have either large or small ranges, whereas large-bodied ones have only large ranges. A positive correlation between latitudinal extent and biomic specialization is evident, although their relationship is better described as triangular. Main conclusions, We found a polygonal relationship between species biomic specialization and body size, which agrees with previous arguments that small-bodied species have more limited dispersal and, therefore, they may come to occupy a lesser proportion of their potential inhabitable biomes. On the other hand, large-bodied species are constrained to inhabit biomes with a high productivity. A polygonal relationship between species latitudinal extent and body size in African large mammals agrees with previous studies of the relationship between range size and body size in other continents. The independent study of the macroecological pattern in biomic specialization highlights different factors that influence the body size,range size relationship. Although body size is usually implicated as a correlate of both specialization and geographical range size in large mammals, much of the variation in these variables cannot be attributed to size differences but to biome specific factors such as productivity, area, history, etc. [source]

The distribution,abundance (density) relationship: its form and causes in a tropical mammal order, Primates

JOURNAL OF BIOGEOGRAPHY, Issue 4 2005
A. H. Harcourt
Abstract Aim, Across a wide variety of organisms, taxa with high local densities (abundance) have large geographical ranges (distributions). We use primatology's detailed knowledge of its taxon to investigate the form and causes of the relationship in, unusually for macroecological analysis, a tropical taxon. Location, Africa, Central and South America, Asia, Madagascar. Methods, To investigate the form of the density,range relationship, we regressed local density on geographical range size, and also on female body mass, because in the Primates, density correlates strongly with mass. To investigate the biological causes of the relationship, we related (1) abundance (density × range size) and (2) residuals from the density,range regression lines to various measures of (i) resource use, (ii) reproductive rate and (iii) potential specialization. All data are from the literature. Analyses were done at the level of species (n = 140), genera (n = 60) and families/subfamilies (n = 17). We present various levels of results, including for all data, after omission of outlier data, after correction for phylogenetic dependence, and after Bonferroni correction of probabilities for multiple comparisons. Results, Regarding the form of the relationship, Madagascar primates are clear outliers (high densities in small ranges). Among the remaining three realms, the relation of density to range is weak or non-existent at the level of species and genera. However, it is strong, tight and linear at the level of families/subfamilies (r2 = 0.6, F1,10 = 19, P < 0.01). Although among primates, density is very significantly related to mass, at no taxonomic level is range size related to body mass. Consequently, removing the effects of mass makes little to no difference to density,range results. Regarding the biology of the relationship, only traits indicative of specialization are associated with abundance (meaning numbers): rare taxa are more specialized than are abundant taxa. The association is largely via range size, not density. Across families, no traits correlate significantly with the density,range relationship, nor with deviations from it, despite the strength of the relationship at this taxonomic level. Main conclusions, We suggest that in macroecology, analysis at taxonomic levels deeper than that of the relatively ephemeral species can be appropriate. We argue that the several purely methodological explanations for the positive density,range size relationship in primates can be rejected. Of the various biological hypotheses, those having to do with specialization,generalization seem the only applicable ones. The fact that the relationship is entirely via range size, not via density, means that while we might have a biology of range size, we do not yet have one of the density,geographical range relationship. It is probably time to search for multivariate explanations, rather than univariate ones. However, we can for the first time, for at least primates, suggest that any association of abundance or range size with specialization is via the number of different subtaxa, not the average degree of specialization of each subtaxon. The implication for conservation is obvious. [source]

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

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2005
F. B. CRUZ
Abstract 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. [source]

Phylogenetic autocorrelation and heritability of geographic range size, shape and position of fiddler crabs, genus Uca (Crustacea, Decapoda)

JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 2 2010
J. C. Nabout
Abstract The aim of this study was to evaluate the levels of phylogenetic heritability of the geographical range size, shape and position for 88 species of fiddler crabs of the world, using phylogenetic comparative methods and simulation procedures to evaluate their fit to the neutral model of Brownian motion. The geographical range maps were compiled from literature, and range size was based on the entire length of coastline occupied by each species, and the position of each range was calculated as its latitudinal and longitudinal midpoint. The range shape of each species was based in fractal dimension (box-counting technique). The evolutionary patterns in the geographical range metrics were explored by phylogenetic correlograms using Moran's I autocorrelation coefficients, autoregressive method (ARM) and phylogenetic eigenvector regression (PVR). The correlograms were compared with those obtained by simulations of Brownian motion processes across phylogenies. The distribution of geographical range size of fiddler crabs is right-skewed and weak phylogenetic autocorrelation was observed. On the other hand, there was a strong phylogenetic pattern in the position of the range (mainly along longitudinal axis). Indeed, the ARM and PVR evidenced, respectively, that ca. 86% and 91% of the longitudinal midpoint could be explained by phylogenetic relationships among the species. The strong longitudinal phylogenetic pattern may be due to vicariant allopatric speciation and geographically structured cladogenesis in the group. The traits analysed (geographical range size and position) did not follow a Brownian motion process, thus suggesting that both adaptive ecological and evolutionary processes must be invoked to explain their dynamics, not following a simple neutral inheritance in the fiddler-crab evolution. Resumen El objetivo de este trabajo fue estimar los niveles de herencia filogenética existentes en la posición geográfica, forma y el tamaño de rango geográfico en 88 especies de cangrejo violinista del mundo, mediante simulaciones y métodos comparativos filogenéticos para así evaluar su ajuste al modelo neutro de evolución browniana. Los mapas de rango geográfico se obtuvieron de la literatura. La forma de rango geográfico fue estimada en la dimensión fractal. Los patrones evolutivos en el tamaño y forma del rango geográfico y la posición geográfica fueron explorados mediante correlogramas filogenéticos utilizando el índice I de Moran, coeficientes autorregresivos (ARM) y regressión por autovetores filogenéticos (PVR). Estos correlogramas fueron comparados con aquellos obtenidos mediante la simulación de procesos de evolución browniana en las filogenias. El tamaño y forma de rango geográfico del cangrejo violinista mostró una distribución apuntada hacia la derecha aunque no se encontró autocorrelación filogenética. Por otra parte, se observó un marcado patrón filogenético para la posición geográfica del rango (principalmente a lo largo del eje longitudinal). De hecho, el ARM y PVR evidenció respectivamente que cerca del 86% y 91% de la localización del punto medio longitudinal del rango se puede explicar mediante las relaciones filogenéticas existentes entre las especies. El fuerte patrón filogenético en la longitud podría ser debido a especiación alopátrica y a una cladogénesis estructurada geográficamente para el grupo, tal y como se propuso en las hipótesis. Los rasgos analizados (rango geográfico y posición geográfica) no siguieron un proceso de evolución browniana, sugiriendo pues que tanto los procesos evolutivos como la adaptación ecológica deberían ser tenidos en cuenta para explicar sus dinámicas, ya que el transcurso de la evolución del cangrejo violinista no se explica mediante un simple modelo de herencia neutra. [source]

Life-history traits associated with fragmentation vulnerability of lizards in the Thousand Island Lake, China

ANIMAL CONSERVATION, Issue 4 2009
Y. Wang
Abstract Following habitat fragmentation, the remnant faunal community will undergo a period of species loss or ,relaxation.' Theory predicts that species with particular life-history traits, such as a small population size, small geographical range, low fecundity and large body size, should be more vulnerable to fragmentation. In this study, we investigated the relationships between the above life-history traits and the fragmentation vulnerability index (the number of islands occupied) of five lizard species inhabiting recently isolated land-bridge islands in the Thousand Island Lake, China. Data on life-history traits were collected from field surveys (population density) and from the literature (body size, clutch size and geographical range size). The species,area relationships for lizards sampled from the mainland versus on the islands differed significantly (i.e. the number of species inhabiting islands was decreased relative to similar-sized areas on the mainland), indicating that species extinction has occurred on all of the study islands following isolation. For the fragmentation vulnerability index, model selection based on Akaike's information criterion identified natural density at mainland sites as the best correlate of vulnerability to fragmentation, supporting the hypothesis that rare species are most vulnerable to local extinction and will be lost first from fragmented landscapes. In contrast, there was little evidence for an effect of lizards' snout,vent length, clutch size or geographical range size on fragmentation vulnerability. Identification of species traits that render some species more vulnerable to fragmentation than others has important implications for conservation and can be used to aid direct management efforts. [source]

Richness patterns, species distributions and the principle of extreme deconstruction

GLOBAL ECOLOGY, Issue 2 2009
Levi Carina Terribile
ABSTRACT Aim, To analyse the global patterns in species richness of Viperidae snakes through the deconstruction of richness into sets of species according to their distribution models, range size, body size and phylogenetic structure, and to test if environmental drivers explaining the geographical ranges of species are similar to those explaining richness patterns, something we called the extreme deconstruction principle. Location, Global. Methods, We generated a global dataset of 228 terrestrial viperid snakes, which included geographical ranges (mapped at 1° resolution, for a grid with 7331 cells world-wide), body sizes and phylogenetic relationships among species. We used logistic regression (generalized linear model; GLM) to model species geographical ranges with five environmental predictors. Sets of species richness were also generated for large and small-bodied species, for basal and derived species and for four classes of geographical range sizes. Richness patterns were also modelled against the five environmental variables through standard ordinary least squares (OLS) multiple regressions. These subsets are replications to test if environmental factors driving species geographical ranges can be directly associated with those explaining richness patterns. Results, Around 48% of the total variance in viperid richness was explained by the environmental model, but richness sets revealed different patterns across the world. The similarity between OLS coefficients and the primacy of variables across species geographical range GLMs was equal to 0.645 when analysing all viperid snakes. Thus, in general, when an environmental predictor it is important to model species geographical ranges, this predictor is also important when modelling richness, so that the extreme deconstruction principle holds. However, replicating this correlation using subsets of species within different categories in body size, range size and phylogenetic structure gave more variable results, with correlations between GLM and OLS coefficients varying from ,0.46 up to 0.83. Despite this, there is a relatively high correspondence (r = 0.73) between the similarity of GLM-OLS coefficients and R2 values of richness models, indicating that when richness is well explained by the environment, the relative importance of environmental drivers is similar in the richness OLS and its corresponding set of GLMs. Main conclusions, The deconstruction of species richness based on macroecological traits revealed that, at least for range size and phylogenetic level, the causes underlying patterns in viperid richness differ for the various sets of species. On the other hand, our analyses of extreme deconstruction using GLM for species geographical range support the idea that, if environmental drivers determine the geographical distribution of species by establishing niche boundaries, it is expected, at least in theory, that the overlap among ranges (i.e. richness) will reveal similar effects of these environmental drivers. Richness patterns may be indeed viewed as macroecological consequences of population-level processes acting on species geographical ranges. [source]