Is the Rapoport effect widespread? Null models revisited

Aim  To test the Rapoport effect using null models and data sets taken from the literature. We propose an improvement on an existing method, testing the Rapoport effect in elevational and latitudinal distributions when distributions are restricted by sampling.
Location  Global.
Methods  First, we hypothesized that real range size distributions are similar to those expected by null assumptions (expected by only imposing boundaries to species distributions). When these distributions were different from those expected under the null assumptions, we tested the hypothesis that these distributions correspond to those expected when a Rapoport effect occurs. We used two simulation methods, random and pseudo-random, which differed only in that the latter one assumes fixed species mid-points, coinciding with real mid-points. Observed correlations between range size and mid-point were compared with the frequency distribution of 1000 simulations, using both simulation methods. We compared the correlation curves generated by 1000 simulations with those of the observed distributions, testing whether correlations indicated a Rapoport effect.
Results  Several significant patterns of correlations between range size and mid-point were observed in the data sets when compared with random and pseudo-random simulations. However, few of these correlations were consistent with a Rapoport effect.
Main conclusions  Although some recent studies are consistent with a Rapoport effect, our results suggest that the Rapoport effect is not a widespread pattern in global ecology.     

Are there latitudinal and altidudinal Rapoport effects in the geographic ranges of Andean passerine birds?

We analysed the range-sizes of 835 Andean passerine species (including 414 endemics and 421 non-endemics) to test for latitudinal and altitudinal Rapoport effects (LRE and ARE). We tested for positive range-size: latitude/altitude correlations using three different methods: (i) Rohde's mid-point method, (ii) species sorted out by altitude, and (iii) a phylogenetic comparative method (CAIC). Using Rohde's mid-point method, the mean latitudinal extent of species does not follow a Rapoport pattern, but the mean latitudinal occupancy of all passerines and non-endemics do increase with latitude. The latitudinal ranges of endemics sorted out by altitude follow a reverse Rapoport effect, but non-endemics support the pattern. CAIC confirms the latitudinal increase in the occupancy of non-endemics, but regressions have low coefficients of determination. The ARE is supported by the mean altitudinal extent of species, but the trend vanishes when controlling for geometric effects. Low-altitude species occupy about the same proportion of the available altitudinal space as do high-altitude ones. Our analyses suggest that latitude and altitude have low explanatory power for understanding the spatial variation in range-sizes at a continental scale. We show how different patterns can emerge from applying different criteria to the analysis of data.     

Geographical and ecological patterns of range size in North American trees

We analysed the degree to which spatial, ecological and phylogenetic factors influenced geographic gradients in range size for all trees native to North America. We compared observed range sizes, measured in either one (latitudinal or longitudinal extent) or two dimensions (range area), with three null models that respected constraints imposed by the geometry of the continent; we tested whether climatic gradients could account for increasing range size with latitude – a Rapoport effect – in North American trees; and whether variation in range size was associated with phylogeny or ecological characteristics of species. We documented an excess of species with small ranges and a lack of widely distributed species compared with null expectations both with and without environmental constraints. We found evidence for a Rapoport effect in North American trees, at different taxonomic levels and for different groups defined by ecological characteristics. This pattern is not an outcome constrained by continental shape and does not depend on the metric for range size, but it is consistent with the climatic variability hypothesis proposed to explain the Rapoport pattern. Finally we showed that trees east of the Rocky Mountains have larger ranges on average than trees to the west or in Mexico and that the proportion of deciduous compared to evergreen species increases with range size. Variation in range size among North American trees is not spatially random, and has a phylogenetic and ecological signal. Consistent with the climatic variability hypothesis, range size of North American trees increases with increasing variability in annual temperature range at higher latitudes.     

Diversity and distribution of small mammals in the South American Dry Andes

The Andean mountain range has played an important role in the evolution of South American biota. However, there is little understanding of the patterns of species diversity across latitudinal and altitudinal gradients. In this paper, we examine the diversity of small mammals along the South Central Dry Andes (SCDA) within the framework of two contrasting hypotheses: (a) species richness decreases with increasing elevation and latitude; and (b) species richness peaks at altitudinal midpoints (mid‐domain). We explore the composition of the species pool, the impact of species–area relationships and the Rapoport effect (i.e. size of geographic ranges) along latitudinal and elevational gradients. First, we constructed a database of SCDA small mammals. Then, species richness patterns were analysed through generalized models, and species–area relationships were assessed by log–log regressions; the curvilinear method (c = S/Az) was use to compute richness corrected by area size. Lastly, the Rapoport effect was evaluated using the midpoint method. Our results show: (1) a richness of 67 small mammals along the SCDA, of which 36 are endemic; (2) a hump‐shaped pattern in species richness along elevation and latitudinal gradients; (3) a species–area relationship for both gradients; (4) endemic species corrected by area present a strong and positive relationship with elevation; (5) a Rapoport effect for the latitudinal ranges, but no effect across the elevational gradient; and (6) a major species turnover between 28° and 30° south latitude. This is the first study quantifying the diversity of small mammals encompassing the central Andean region. Overall, our macrogeographic analysis supports the previously postulated role of the Andes in the diversification of small mammals (i.e. in situ cladogenesis) and highlights some basic attributes (i.e. anatomy of geographic ranges; species–area relationships) when considering the consequences of climate change on biodiversity conservation of mountain ecosystems.     

Measuring range sizes of South-East Asian hawkmoths (Lepidoptera: Sphingidae): effects of scale, resolution and phylogeny

Aim  The effects of resolution and spatial extent on range measures were explored in estimates of the geographic distribution of tropical hawkmoths. Furthermore, data were tested for phylogenetic autocorrelation.
Location  South-East Asia.
Methods  Various range measures, such as geographic information system (GIS)-supported range estimates, minimum convex polygons, latitudinal and longitudinal extents, and their products, were derived from original distribution records and compared to each other. A taxonomic classification of the species was used to analyse phylogenetic effects on range sizes.
Results  Range size measures exhibit a strongly right-skewed frequency distribution with many geographically restricted species and few widespread taxa. Rankings from GIS-supported, comprehensive range size estimates do not deviate greatly from more crude measurements of lower resolution. Comprehensive ranges and ranges within South-East Asia are correlated strongly, but already at this rather large scale the ranking of species changes considerably. Other measures of occupancy with an increasingly more localized consideration of 'range' show decreasing strengths of correlation. We found a weak, but significant, autocorrelation in range area data: related groups of species have ranges of similar size.
Main conclusions  Spatial resolution did not affect range ranking greatly in our data. However, macroecological studies based only on parts of species' ranges must be viewed critically, particularly if their extent is small compared to comprehensive ranges. Phylogenetic non-independence of range size data must be considered in comparative analyses.     

What determines conformity to Bergmann's rule?

Aim  Bergmann's rule, the tendency of body size within species in bird and mammal populations to be positively correlated with latitude, is among the best known biogeographical generalizations. The factors behind such clines, however, are not well understood. Here we use a large data base of 79 mammalian carnivore species to examine the factors affecting latitudinal size clines.
Location  Worldwide.
Methods  We measured the skulls and teeth of carnivores in natural history museums, and calculated the amount of variation in size explained by latitude, supplementing our measurements with published data. We examined the effects of a number of variables on the tendency to show latitudinal clines.
Results  We found that geographical range and latitudinal extent are strongly related to size clines. Minimum temperatures across the range, net primary productivity and habitat diversity also have some, albeit much less, influence.
Main conclusions  We suggest that species with large geographical ranges are likely to encounter significant heterogeneity in those factors that influence body size, and are thus likely to exhibit size clines. However, the key factors that determine body size may not always operate along a latitudinal (or other geographical) cline, but be spatially linked to patches in the species range. One such important factor is likely to be food availability, which we show is a strong predictor of size in the brown bear ( Ursus arctos ) but is not associated with a latitudinal cline. We argue that the spatial distribution of key resources within the species range constitutes a significant predictor of carnivore body size.     

When does diversity fit null model predictions? Scale and range size mediate the mid‐domain effect

Aim  Recently, a flurry of studies have focused on the extent to which geographical patterns of diversity fit mid-domain effect (MDE) null models. While some studies find strong support for MDE null models, others find little. We test two hypotheses that might explain this variation among studies: small-ranged groups of species are less likely than large-ranged species to show mid-domain peaks in species richness, and mid-domain null model predictions are less robust for smaller spatial extents than for larger spatial extents.
Location  We analyse data sets from elevational, riverine, continental and other domains from around the world.
Methods  We use a combination of Spearman rank correlations and binomial tests to examine whether differences within and among studies and domains in the predictive power of MDE null models vary with spatial scale and range size.
Results  Small-ranged groups of species are less likely to fit mid-domain predictions than large-ranged groups of species. At large spatial extents, diversity patterns of taxonomic groups with large mean range sizes fit MDE null model predictions better than did diversity patterns of groups with small mean range sizes. MDE predictions were more explanatory at larger spatial extents than at smaller extents. Diversity patterns at smaller spatial extents fit MDE predictions poorly across all range sizes. Thus, MDE predictions should be expected to explain patterns of species richness when ranges and the scale of analysis are both large.
Main conclusions  Taken together, the support for these hypotheses offers a more sophisticated model of when MDE predictions should be expected to explain patterns of species richness, namely when ranges and the scale of analysis are both large. Thus the circumstances in which the MDE is important are finite and apparently predictable.     

Latitudinal variation in global range-size of aquatic macrophyte species shows evidence for a Rapoport effect

1. To test hypotheses concerning the applicability of the Rapoport effect (RE: “species that occur at higher latitudes tend to have greater geographical range-size than species which have ranges limited to latitudes closer to the equator”) to aquatic macrophytes at global scale, we analysed the world latitudinal distribution and range-size of 1,083 vascular aquatic macrophyte species, from 91 genera in 11 families. We targeted macrophyte families strongly associated with inland aquatic habitats (i.e. with a zero, or only very low, proportion of constituent species which occur also in non-aquatic habitats), and which are distributed across a substantial latitudinal gradient, a necessary condition to test our hypotheses.
2. The macrophyte species present in these families include plants from all the normally accepted life form-defined functional groups of macrophytes, namely submerged, free-floating, floating-leaf rooted and emergent species, and represent the three major vascular taxonomic groups occurring as aquatic macrophytes (ferns/fern allies, monocots, and dicots). For the analysis, we used both latitude-only and areal measures of macrophyte species geographic range-size, within a 10 × 10° (latitude × longitude) grid of 238 grid cells, covering the six world ecozones (Palaearctic, Orient, Australasia, Nearctic, Neotropics, Afrotropics) that primarily contain inland freshwater and brackish macrophyte habitats.
3. The results provide new insight into the relationships between global range-size of macrophytes, latitude, and other potential spatio-environmental and anthropogenic drivers acting upon these plants at world scale. In particular, the outcomes indicated that: (1) the range-size versus latitude distribution of macrophytes shows evidence of a strong RE influence, with significantly greater species range-size at higher latitudes; and (2) the β-diversity pattern of species distribution along this latitudinal gradient is poorly explained by nestedness organisation, and species turnover is a more likely explanation of the observed changes in species distribution with latitude.
4. Spatio-environmental and anthropogenic variables other than latitude may also influence the observed global geographical pattern of macrophyte range-size, although their importance as predictors varies between individual families. Extent of agricultural land use, altitude, and historic (post-Quaternary) climate change velocity were all significant predictor variables for some families. However, interestingly, neither the area of land nor the area of waterbody present per grid cell were major influences on macrophyte range-size distribution.
5. Our finding of evidence for an RE, acting at global scale in aquatic macrophytes, contributes to increasing the generality of conclusions so far reached about the large-scale factors that drive patterns of species range-size at global scale. The study also provides a baseline for future macroecological work on aquatic plants, and potentially other freshwater organisms, particularly in the context of predicting how the world ranges of freshwater biota will respond to ongoing global environmental change.

     

Further perspectives on the breeding distribution of migratory birds: South American austral migrant flycatchers

1. Patterns of distribution of breeding austral migrant tyrant-flycatchers in temperate South America were quantified and analysed in conjunction with a variety of ecological, biogeographical and climatic variables.
2. The pattern of proportion of migratory to total breeding tyrannids was most strongly associated with latitude and two temperature variables, mean temperature of the coldest month and relative annual range of temperature.
3. The strong associations of latitude and temperature with percentage of migrants are consistent with the results of most similar investigations of the breeding distributions of migratory birds, both for migrants breeding in North America and in Europe, but contradict the hypothesis that habitat complexity plays a major role in structuring the proportion of migrants in communities of breeding birds.
4. The consistency of results among studies of migrants on different continents suggests that temperature and latitude, presumably a surrogate for one or more climatic variables, are globally significant factors in the breeding distributions of migratory birds.
5. The results for austral migrant flycatchers are consistent with the hypothesis that the prevalence of migration at any particular locality is ultimately dependent on the abundance of resources in the breeding season and the severity of the winter season, or on the difference in resource levels between summer and winter.     

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.     

Beyond Rapoport's rule: evaluating range size patterns of New World birds in a two-dimensional framework

Aim To evaluate Rapoport's rule for New World birds in two‐dimensional geographical space. We specifically test for a topography × climate interaction that predicts little difference in range sizes between lowlands and mountains in cold climates, whereas in the tropics, montane species have narrow ranges and lowland species have broad ranges. Location The western hemisphere. Methods We used digitized range maps of breeding birds to generate mean range sizes in grids of 27.5 × 27.5 km and 110 × 110 km across North and South America. We examined the geographical pattern with respect to range in elevation, mean temperature in the coldest month, their interaction, biome size and continental width, using model II analysis of variance, multiple regression and simple correlation. Results In northern latitudes species have broad ranges in both mountainous and flat areas. However, range sizes in the mountains and lowlands diverge southwards, with the most extreme differences in the tropics. Further, there are minimal differences in range sizes across latitudes in lowlands. The smallest mean ranges occur in the tropical Andes. Mean range sizes in north‐central Canada, Central America and Argentina/Chile are also small, reflecting the narrowing of the continents in these areas. The best regression model explained 51% of the variation in mean range size. Main conclusions The two‐dimensional range size pattern indicates that neither winter temperature nor annual variability in temperature strongly influences the distribution of range sizes directly; rather, climate influences bird range sizes indirectly via effects on habitat size. Also, macroclimate interacts with topographic relief across latitudes, generating sharp mesoscale habitat gradients in tropical mountains but not in high latitude mountains or in lowlands at any latitude. Birds respond to these habitat gradients, resulting in ‘latitudinal’ range size gradients in topographically complex landscapes but not in simple landscapes.     

An inverse latitudinal gradient of diversity of peracarid crustaceans along the Pacific Coast of South America: out of the deep south

Aim To understand the ecological and historical/evolutionary processes underlying an inverse latitudinal gradient of richness (LGR) using crustacean peracarid species as a model group. Location The Pacific coast of South America, along the Chilean coast between 18° S and 56° S. Methods The LGR was evaluated using a dataset including 320 marine peracarid species reported for the coasts of Chile. Five ecological hypotheses invoking a relationship between species richness and present‐day conditions were tested: species–energy, species–area, Rapoport rescue effect, mid‐domain geometric constraint and niche breadth. Historical/evolutionary hypotheses (i.e. biogeographic conservatism, and diversification rates) were indirectly tested by analysing the latitudinal variation in the taxonomic distinctness, the taxonomic conservatism of the midpoint of the latitudinal range and the degree of nestedness at different taxonomic levels. Results Richness increased poleward, varying approximately eightfold, following an inverse LGR coupled with an increase in bathymetric distribution. Overall this inverse LGR seems robust to uncertainties in the completeness of the species inventory. We found support for only two of the five ecological hypotheses tested: species–area and Rapoport rescue effect. Historical/evolutionary hypotheses seemed important in structuring the richness pattern, as indicated by the higher taxonomic distinctness in the southern region, the strong taxonomic inertia in the mean range size and the high degree of nestedness of assemblages at different taxonomic levels. Conclusions When combined, these results underscore the importance of long‐term processes and historical/evolutionary explanations for the inverse LGR, conceptualized in what we term the ‘out of the deep south’ hypothesis that involves the effects of both biogeographic niche conservatism and evolutionary rates. We propose that the southern region may be a source of evolutionary novelties and/or exhibit higher diversification rates (i.e. higher speciation/lower extinction rates). Furthermore, phylogenetic conservatism of latitudinal range may limit the geographic expansion of these new taxa towards the depauperated northern region.     

Patterns of turtle species'geographic range size and a test of Rapoport's rule

There has been a recent resurgence of interest in documenting and explaining patterns of species' range sizes with the goal of determining if general patterns exist. Much recent debate has centered on whether Rapoport's rule, the tendency for range size to increase with increasing latitude, is a general rule or a local effect. I calculated the sizes of turtle species ranges from distribution maps and used published natural history data to examine how range size varies with latitude, and to determine if differences in range size exist among continents, and if correlations with body size, available land area, habitat and diet breadth exist. The distribution of turtle range sizes extended over six orders of magnitude and formed a lognormal distribution with many species having moderate or small ranges and few species having large ranges. Range size was positively correlated with available land area, habitat breadth, diet breadth, and body size. Multiple regression accounted for only 39% of the variance in range size indicating that other important factors remain unknown. At both global and continental scales, range size is largest near the equator and decreases with increasing latitude, the apposite of Rapoport's rule. However, range size did increase latitudinally above 25-30°N in both the Neararctic and Palearctic suggesting that the pattern would be more accurately considered a local effect than a general rule. Larger range sizes at low latitudes may occur because more land area in the tropics provides much suitable habitat for ectotherms and there are few large scale physical barriers to dispersal. Rapoport patterns result from the occurrence of a small number of wide-ranging cold tolerant species that have reinvaded northern latitudes after Pleistocene glaciation. Patterns of the longitudinal and latitudinal extents of species ranges and their positions illustrate the importance of climate, mountain ranges, deserts, and coastlines, as barriers potentially affecting range size.     

Latitudinal extent and natural history characteristics of birds in Nicaragua

This paper assesses the latitudinal extent of terrestrial breeding birds in Nicaragua. In particular, associations among latitudinal midpoint, body mass, and latitudinal extent are examined; significant differences between natural history characteristics (trophic guild, forest dependence, number of forest types) and latitudinal extent are identified; and a test is undertaken of Rapoport's rule for birds at the edge of their northern or southern range in Nicaragua. Birds in Nicaragua were classified into four categories based on latitudinal extent: birds generally restricted to Central America (20%); birds near the edge of their range within Nicaragua (34%); Neotropical birds (42%); and Pan‐American birds (4%). Latitudinal midpoint had a significant negative correlation with latitudinal extent over different taxonomic scales. Natural history characteristics of trophic guild, forest dependence and number of forest types can account for significant differences in species latitudinal extent. Carnivores had greater latitudinal extents than most other trophic guilds, non‐forest birds had greater latitudinal extents than birds that require patchy forest, and birds that occur in four or more forest types had greater latitudinal extents than birds restricted to one or two forest types. Contrary to Rapoport's rule, birds with a northern affinity or latitudinal midpoint north of Nicaragua had significantly smaller latitudinal extents than birds with a southern affinity or latitudinal midpoint south of Nicaragua. A comparison of natural history characteristics of birds with northern and southern affinities found no difference between trophic guild or forest dependence but a significant difference among the number of forest types used by forest birds. Birds with a southern affinity were restricted to fewer forest types than birds with a northern affinity.     

Latitudinal patterns of range size and species richness of New World woody plants

Aim  Relationships between range size and species richness are contentious, yet they are key to testing the various hypotheses that attempt to explain latitudinal diversity gradients. Our goal is to utilize the largest data set yet compiled for New World woody plant biogeography to describe and assess these relationships between species richness and range size.
Location  North and South America.
Methods  We estimated the latitudinal extent of 12,980 species of woody plants (trees, shrubs, lianas). From these estimates we quantified latitudinal patterns of species richness and range size. We compared our observations with expectations derived from two null models.
Results   Peak richness and the smallest- and largest-ranged species are generally found close to the equator. In contrast to prominent diversity hypotheses: (1) mean latitudinal extent of tropical species is greater than expected; (2) latitudinal extent appears to be decoupled from species richness across New World latitudes, with abrupt transitions across subtropical latitudes; and (3) mean latitudinal extents show equatorial and north temperate peaks and subtropical minima. Our results suggest that patterns of range size and richness appear to be influenced by three broadly overlapping biotic domains (biotic provinces) for New World woody plants.
Main conclusions  Hypotheses that assume a direct relationship between range size and species richness may explain richness patterns within these domains, but cannot explain gradients in richness across the New World.     

Latitudinal patterns of mammalian species richness in the New World: the effects of sampling method and faunal group

Abstract. Although the latitudinal gradient of species richness for mammals in North America is well documented, few investigators have quantified the relationship in South America. We examined the pattern in North and South America, at two spatial scales (2.5° and 5°) for each of two sampling methods (quadrats and latitudinal bands). A scale effect was evident for quadrats but not for bands. Significant linear relationships between species richness and latitude were found for three faunal groups: all mammals, nonvolant species, and bats. Effects of area confound the latitudinal relationship. By statistically removing such effects, we found that the latitudinal gradient is not an artifact of the species-area relationship, and that the latitudinal gradients for North and South America were statistically indistinguishable. Our data suggest that both faunal subgroups, nonvolant species and bats, contributed substantially to the overall mammalian pattern. Further, multiple regression analyses showed that only latitude is a necessary variable to explain bat richness; for nonvolant species, in addition to latitude, area and longitude may be important.     

Biogeographical patterns and Rapoport's rule in southeastern Pacific benthic polychaetes of the Chilean coast

Recently three biogeographical units were identified along the Chilean coast (the Magellanic Province, an Intermediate Area, and the Peruvian Province), however few studies have focused on the factors and dynamic processes that formed these spatial units (e.g. Rapoport's rule and its causal mechanisms). In this study we used benthic polychaetes of the Chilean coast to evaluate patterns of latitudinal distribution and species richness, and the existence of the three main biogeographical provinces described for the Chilean coast. Additionally, we evaluated the latitudinal Rapoport effects and geometric constraint as a null hypothesis explaining the species richness distribution.
We found that benthic polychaete diversity increased towards southern latitudes. The cluster and ordination (non-metric MultiDimensional Scaling, nMDS) analyses of the distribution data, presented only two statistically significant (bootstrapping techniques) biogeographic provinces along the Chilean coast, with a break occurring between 41° and 42°S. While, our results did not support a latitudinal Rapoport effect, they did support the view that latitudinal Rapoport effects are a local phenomenon, occurring only for the Northeastern Pacific marine taxa. The relationship between latitudinal range extent and mean latitude indicated the existence of two hard boundaries at either extreme of the Chilean coast, limiting the geographical ranges of the species. However, geometric constraints tested using a Monte Carlo simulation approach showed a weak level of mid-domain effect on species richness. Finally, we propose that geometric constraint together with the geomorphology and historical characteristics of the Chilean coast explain the biogeographical patterns of benthic polychaete taxa in Chile.     

Latitudinal and altitudinal diversity patterns and Rapoport effects in north-west European land snails and their causes

The latitudinal and altitudinal range sizes of north-west European land-snail species increase with increasing latitude/altitude. These Rapoport effects are not caused by northern/high-altitude species with wider latitudinal/altitudinal ranges and southern/low-altitude species with narrower latitudinal/altitudinal ranges, as predicted by the climatic variability hypothesis. They are instead caused mainly by different northern/upper borders of species occurring in the south part of the study area or at low and intermediate altitudes, respectively. This pattern indicates that the observed Rapoport effects are the result mainly of differential northward/upward expansion of species that were restricted to southern/low or intermediate altitude refugia during the glacials. Although all species occurring in a refugium experienced the same climatic conditions, there is stochastic variation in their climatic tolerance. Species with broader climatic tolerance were able to expand farer northwards/upwards postglacial. The altitudinal distribution of species richness in the analysed alpine faunas cannot be explained by the Rapoport-rescue hypothesis, because species richness peaks at intermediate altitudes and because there is no negative correlation between the number of range borders and altitude. The Rapoport-rescue hypothesis alone is probably also insufficient to explain the decrease in species richness with increasing latitude.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 309–323.     

Temperature change effects on marine fish range shifts: A meta-analysis of ecological and methodological predictors

The current effects of global warming on marine ecosystems are predicted to increase, with species responding by changing their spatial distributions. Marine ectotherms such as fish experience elevated distribution shifts, as temperature plays a key role in physiological functions and delineating population ranges through thermal constraints. Distributional response predictions necessary for population management have been complicated by high heterogeneity in magnitude and direction of movements, which may be explained by both biological as well as methodological study differences. To date, however, there has been no comprehensive synthesis of the interacting ecological factors influencing fish distributions in response to climate change and the confounding methodological factors that can affect their estimation. In this study we analyzed published studies meeting criteria of reporting range shift responses to global warming in 115 taxa spanning all major oceanic regions, totaling 595 three-dimensional population responses (latitudinal, longitudinal, and depth), with temperature identified as a significant driver. We found that latitudinal shifts were the fastest in non-exploited, tropical populations, and inversely correlated with depth shifts which, in turn, dominated at the trailing edges of population ranges. While poleward responses increased with rate of temperature change and latitude, niche was a key factor in predicting both depth (18% of variation) and latitudinal responses (13%), with methodological predictors explaining between 10% and 28% of the observed variance in marine fish responses to temperature change. Finally, we found strong geographical publication bias and limited taxonomical scope, highlighting the need for more representative and standardized research in order to address heterogeneity in distribution responses and improve predictions in face of changing climate.     

Broad-scale patterns of body size in squamate reptiles of Europe and North America

Aim  To document geographical interspecific patterns of body size of European and North American squamate reptile assemblages and explore the relationship between body size patterns and environmental gradients.
Location  North America and western Europe.
Methods  We processed distribution maps for native species of squamate reptiles to document interspecific spatial variation of body size at a grain size of 110 × 110 km. We also examined seven environmental variables linked to four hypotheses possibly influencing body size gradients. We used simple and multiple regression, evaluated using information theory, to identify the set of models best supported by the data.
Results  Europe is characterized by clear latitudinal trends in body size, whereas geographical variation in body size in North America is complex. There is a consistent association of mean body size with measures of ambient energy in both regions, although lizards increase in size northwards whereas snakes show the opposite pattern. Our best models accounted for almost 60% of the variation in body size of lizards and snakes within Europe, but the proportions of variance explained in North America were less than 20%.
Main conclusions  Although body size influences the energy balance of thermoregulating ectotherms, inconsistent biogeographical patterns and contrasting associations with energy in lizards and snakes suggest that no single mechanism can explain variation of reptile body size in the northern temperate zone.