Differences In Range Size Research Articles

Alien spiders in Chile: evaluating Darwin's naturalization hypothesis

Darwin's naturalization hypothesis (DNH) states that the successful establishment of alien species is favored when the phylogenetic relationship between the colonizer and the recipient community is distant. From a population perspective, the establishment involves both the progressive increase in size and spatial distribution of the invasive population. In this study, we focused our attention on the spatial component of establishment, assessing the role of phylogenetic relatedness as a determinant of its extension. Following DNH, it is expected that alien species closely related to the native spiders would show narrower distribution ranges than alien taxa less related to the native species. We found 18 alien spider species in Chile; all of these are synanthropic and most are of African origin. Our results indicate a difference in range size between related and unrelated species but it was not statistically significant. Consequently, the results do not support DNH as an explanation of the distributional component of establishment of alien spider species in Chile. We conclude that ecological constraints do not affect the process of invasion of spiders; therefore, it is only time that determines the spread of alien spiders in this country.

Ecological and evolutionary drivers of range size in Coenagrion damselflies.

Geographic range size is a key ecological and evolutionary characteristic of a species, yet the causal basis of variation in range size among species remains largely unresolved. One major reason for this is that several ecological and evolutionary traits may jointly shape species' differences in range size. We here present an integrated study of the contribution of ecological (dispersal capacity, body size and latitudinal position) and macroevolutionary (species' age) traits in shaping variation in species' range size in Coenagrion damselflies. We reconstructed the phylogenetic tree of this genus to account for evolutionary history when assessing the contribution of the ecological traits and to evaluate the role of the macroevolutionary trait (species' age). The genus invaded the Nearctic twice independently from the Palearctic, yet this was not associated with the evolution of larger range sizes or dispersal capacity. Body size and species' age did not explain variation in range size. There is higher flight ability (as measured by wing aspect ratio) at higher latitudes. Species with a larger wing aspect ratio had a larger range size, also after correcting for phylogeny, suggesting a role for dispersal capacity in shaping the species' ranges. More northern species had a larger species' range, consistent with Rapoport's rule, possibly related to niche width. Our results underscore the importance of integrating macroecology and macroevolution when explaining range size variation among species.

Relative resource allocation to dispersal and competition demonstrates the putative role of hybridity in geographical parthenogenesis

AbstractAimAsexual organisms frequently have larger ranges than their sexual progenitors, a phenomenon referred to as geographical parthenogenesis (GP). In plants, GP is associated not only with asexuality (apomixis), but also with polyploidization and hybridity (allopolyploidy). Dispersal is thought to play a role in range‐size differences in other taxa, but has not been directly related to GP. Here, we compare resource allocation to dispersal‐related traits in sexual diploids, asexual autopolyploids and asexual allopolyploids, and relate these differences to patterns of GP.LocationThe Pacific Northwest, North America.MethodsWe created distribution maps for all cytotypes known in Crataegus series Douglasianae using herbarium records. To quantify dispersal ability, we collected fruit samples from sexual diploids, apomictic allopolyploids and apomictic autopolyploids across their ranges, and used the masses of each fruit component as a proportion of the total fruit mass to gauge relative investment in dispersal and competitive ability.ResultsThe largest ranges belong to apomictic allopolyploids, whereas apomictic autotriploids and sexual diploids have the smallest ranges. Compared to sexual diploids and apomictic autotriploids, the allotetraploids exhibit a more dispersal‐orientated strategy, with proportionally heavier pyrenes and more fruit pulp, but proportionally lighter seeds. Allotriploid taxa, which arose via back‐crosses between sexual diploids and asexual allotetraploids, exhibit an intermediate range size as well as intermediate investment in dispersal.Main conclusionsIn Crataegus series Douglasianae, GP is associated only with allopolyploids, highlighting the potential role of hybridization in range expansion. The data suggest that allopolyploids are associated with increased resource allocation to dispersal‐related traits, whereas sexual diploid C. suksdorfii and asexual autotriploid C. gaylussacia exhibit a more competition‐orientated strategy. These findings are consistent with the hypothesis that hybridization contributes to patterns of GP in asexual allopolyploids, potentially by increasing their dispersal ability.

Biogeography and complex traits: dispersal syndromes, in the sea

news and update ISSN 1948-6596 commentary Biogeography and complex traits: dispersal syndromes, in the sea How dispersal potential manifests as realized mi- gration (sensu Wright 1931) is a core question that links pattern and process in biogeography, ecology and evolution. It is a question that cannot be an- swered by knowing about dispersal alone; the an- swer requires understanding how traits of organ- isms influence dispersal potential, how abiotic and biotic environments filter dispersers, and how in- teractions between organisms and environments determine dispersal routes (e.g., Johnson and Black 1994, Siegel et al. 2003, Shanks 2009). A new paper by Luiz et al. (2013), investigating de- terminants of range size in reef fishes, emphasizes that understanding the relationship between dis- persal potential and migration also may require understanding the traits of non-dispersive phases. Luiz et al. (2013) report that the characteris- tics of generally non-dispersive adult phases cor- relate strongly with differences in range size, which historically have been considered the con- sequence of differences among dispersive larval phases (e.g., Lester et al. 2007). The significance of this initially counter-intuitive finding is that it greatly enriches recent discussion of dispersal that, after decades focusing on the influence of pelagic larval duration (PLD), has, as the authors put it, “yielded mixed results” (Luiz et al. 2013:16498) By analogy, consider how the state of knowledge about dispersal in terrestrial plants might look if we studied fruits alone and not other diverse aspects of dispersal syndromes, such as the animals involved (e.g., Beaudrot et al. 2013). Luiz et al. (2013:16500) find that the indi- vidual and combined effects of adult body size (independent effect [IE] = 36%), nocturnality (IE = 26%), and schooling behavior (IE = 16%) “are more important in determining the size of geographic ranges than larval dispersal potential” (IE = 13%; Table 1). They suggest that these adult character- istics provide key advantages in terms of in- creased establishment success by decreasing pre- dation risk and reducing Allee effects. The result and inference make sense (Figure 1). Population genetic theory has long recognized the bipartite— dispersal and establishment—nature of migration (e.g., Marshall et al. 2010). Similarly, without dis- persal and establishment, there can be no mean- ingful expansion in range size. The same suite of population theory, how- ever, also highlights a weakness in the inference that correlation with adult traits means the domi- nant effects are in “population establishment af- ter propagule arrival” (Luiz et al. 2013:16499); em- phasis added). For example, adult body size tends to correlate with fecundity and with longevity in many fishes (Beverton 1987, Winemiller and Rose 1992, Hixon et al. 2006:306, Juan-Jorda et al. 2013; see also Figure 1a–d). Thus, although the fecundity advantage of large-bodied species may sometimes be counteracted by greater abundance of small-bodied species, complex relationships between body size and abundance (White et al. 2007) mean that larger fish can be both more fe- cund and equally or more abundant than smaller fish (e.g., Munday and Jones 1998). Thus, the ad- vantage of body size may accrue via post-dispersal processes and/or via increased lifetime output of larvae. The total effect size of dispersal poten- tial—considering lifetime larval production, PLD, and Luiz and colleague’s preferred dataset—is therefore greater than 13% and possibly as large as 49% (i.e., 13.3% + 36.0%; Table 1), which could turn their conclusion upside-down. Moreover, if a substantial effect of body size is mediated via lar- val production, their justification for excluding the high-PLD trans-Pacific fishes is limited and the to- tal effect size of dispersal could be as high as 62% (i.e., 24.8% + 37.6%; Table 1), though this would require that other correlated factors, such as young-of-year growth, contribute little. Conse- quently, despite the advances made by Luiz et al. (2013)—a dataset including ~3-5% of marine fishes, an alternative perspective, and application of mixed models—we remain uncertain about the relative importance of factors influencing migra- tion and range size in this dataset and across frontiers of biogeography 6.1, 2014 — © 2014 the authors; journal compilation © 2014 The International Biogeography Society

Does the universality of the species–area relationship apply to smaller scales and across taxonomic groups?

The universality of the shape of the species–area relationship (SAR) is subject to regular debate. Recently, Storch et al. (2012) argued that species–area relationships collapse into a single curve at continental scales after the axes are rescaled adjusting the area‐axis being to the mean range size of species and the species‐axis to the species richness of an area equal to mean range size. It has been claimed that this rescaling generates a universal model, invariant of taxon and continent, and that it is driven by differences in range sizes. Here, we test the universality of the rescaled SAR across scales smaller than the continental level, using presence data for plants, birds and butterflies. We also test an alternative rescaling approach, by using the total extent of the study area and total species richness. At the scales analysed here, we found that the proposed rescaling by Storch et al. adjusts for differences in the extent of the study area and for variation in gamma diversity. Consequently, while the rescaled curves were closely aligned, they did not converge into a single curve. The observed remaining variation is independent of scale and biogeographical region, and is correlated with beta diversity; thus, it reflects the differentiation of species composition in space.

Male Superiority in Spatial Navigation: Adaptation or Side Effect?

In the past few decades, sex differences in spatial cognition have often been attributed to adaptation in response to natural selection. A common explanation is that home range size differences between the sexes created different cognitive demands pertinent to wayfinding in each sex and resulted in the evolution of sex differences in spatial navigational ability in both humans and nonhuman mammals. However, the assumption of adaptation as the appropriate mode of explanation was nearly simultaneous with the discovery and subsequent verification of the male superiority effect, even without any substantive evidence establishing a causal role for adaptation. An alternate possibility that the sex difference in cognition is a genetic or hormonal side effect has not been rigorously tested using the comparative method. The present study directly evaluates how well the range hypothesis fits the available data on species differences in spatial ability by use of a phylogenetically based, cross-species, comparative analysis. We find no support for the hypothesis that species differences in home range size dimorphism are positively associated with parallel differences in spatial navigation abilities. The alternative hypothesis that sex differences in spatial cognition result as a hormonal side effect is better supported by the data.

Habitat characteristics assessmen of the wetlands with breeding Ferruginous Duck Aythya nyroca and Pochard A. ferina in Bulgaria / Ocena habitatnih značilnosti mokrišč z gnezdečimi kostanjevkami Aythya nyroca in sivkami A. ferina v Bolgariji

Abstract The Ferruginous Duck Aythya nyroca and Pochard A. ferina are both regular breeders in Bulgaria. In the 19th and early 20th centuries, the Ferruginous Duck was a widely distributed and abundant breeding species in Bulgaria, while Pochard was first confirmed to breed in the country only in the 1950s. Breeding habitat characteristics of Ferruginous Duck and Pochard were assessed in 2002 during a national census of the former species in 30 and 23 wetlands, respectively, where the species were present. Preferred habitat characteristics were determined based on vegetation cover, water depth, and the presence of mosaic vegetation, bank side vegetation, floating vegetation, shallow or steep banks, shallow mudflats, shallow vegetated areas and woodland along the banks. In 2002, the Ferruginous Duck population in Bulgaria was restricted more to artificial wetlands, like fishponds and micro-reservoirs, while Pochard preferred more natural wetlands, predominantly natural marshes. The altitude of wetlands with Ferruginous Ducks varied markedly, with breeding recorded up to 880 m a.s.l., while Pochard bred at lower altitudes, mostly below 300 m a.s.l. Analysis revealed that Ferruginous Ducks preferred well-vegetated, comparatively shallow wetlands with well-structured mosaic vegetation and a diversity of microhabitats, like shallow mudflats and floating vegetation. The Pochard was found to be more of a generalist in wetland selection, significantly correlated with fewer wetland parameters, and showed preference only for larger, open-water bodies. These results could help explain and give some insight into the reasons for the differences in range size, numbers and distribution of the two species and their respective conservation status in Europe and worldwide. The Pochard, whilst close to the limits of the breeding range in Bulgaria, expands its range in Europe, occupying a variety of wetlands and thus having a favourable status. The Ferruginous Duck is more of a habitat specialist, which limits its distribution and makes it more susceptible to habitat changes. These habitat preferences and the deterioration of the wetland habitats in many parts of its range could probably explain the Ferruginous Duck decreasing population and shrinking breeding range, and thus its current unfavourable conservation status.

Dispersal ability rather than ecological tolerance drives differences in range size between lentic and lotic water beetles (Coleoptera: Hydrophilidae)

AbstractAim In aquatic ecosystems, standing (lentic) and running (lotic) waters differ fundamentally in their stability and persistence, shaping the comparative population genetic structure, geographical range size and speciation rates of lentic versus lotic lineages. While the drivers of this pattern remain incompletely understood, the suite of traits making up the ability of a species to establish new populations is instrumental in determining such differences. Here we explore the degree to which the association between habitat type and geographical range size results from differences in dispersal ability or fundamental niche breadth in the members of theEnochrus bicolorcomplex, an aquatic beetle clade with species across the lentic–lotic divide.Location Western Mediterranean, with a special focus on North Africa, the Iberian Peninsula and Sicily.Methods DNA sequences for four loci were obtained from species of theE. bicolorcomplex and analysed using phylogenetic inference. Dispersal and establishment abilities were assessed in lentic–lotic species pairs of the complex, using flight wing morphometrics and thermal tolerance ranges as surrogates, respectively.Results There were clear differences in range size between the lotic and lentic taxa of the complex, which appears to have had a lotic origin with two transitions to standing waters. Only small differences were observed in temperature tolerance and acclimation ability between the two lotic–lentic sister species studied. By contrast, wing morphometrics revealed clear, consistent differences between lotic and lenticEnochrusspecies pairs, the latter having a higher dispersal capacity.Main conclusions We hypothesize that there have been two habitat shifts from lotic to lentic waters, which have allowed marked expansions in geographical range size in western Mediterranean species of theE. bicolorcomplex. Differences in dispersal rather than in establishment ability appear to underlie differences in geographical range extent, as transitions to lentic waters were associated with changes in wing morphology, but not in thermal tolerance range. In this lineage of water beetles, selection for dispersal in geologically short‐lived lentic systems has driven the evolution of larger range sizes in lentic taxa compared with those of their lotic relatives.

Palaeoclimatic models help to understand current distribution of Caucasian forest species

Spatial and temporal constraints on dispersal explain the absence of species from areas with potentially suitable conditions. Previous studies have shown that post-glacial recolonization has shaped the current ranges of many species, yet it is not completely clear to what extent interspecific differences in range size depend on different dispersal rates. The inferred boundaries of glacial refugia are difficult to validate, and may bias spatial distribution models (SDMs) that consider post-glacial dispersal constraints. We predicted the current distribution of 12 Caucasian forest plants and animals, factoring in the effective geographical distance from inferred glacial refugia as an additional predictor. To infer glacial refugia, we tested the transferability of the current SDMs based on the distribution of climatic variables, and projected the most transferable ones onto two climate scenarios simulated for the Last Glacial Maximum (LGM). We then calculated least-cost distances from the inferred refugia, using elevation as a friction surface, and recalculated the current SDMs incorporating the distances as an additional variable. We compared the predictive powers of the initial with the final SDMs. The palaeoclimatic simulation that best matched the distribution of species was assumed to represent the closest fit to the true palaeoclimate. SDMs incorporating refugial distance performed significantly better for all but one studied species, and the Model for Interdisciplinary Research on Climate (MIROC) climatic simulation provided a more convincing pattern of the LGM climate than the Community Climate System Model (CCSM) simulation. Our results suggest that the projection of suitable habitat models onto past climatic conditions may yield realistic boundaries of glacial refugia, and that the current distribution of forest species in the study region is strongly associated with locations of former refugia. We inferred six major forest refugia throughout western Asia: (1) Colchis; (2) western Anatolia; (3) western Taurus; (4) the upper reaches of the Tigris River; (5) the Levant; and (6) the southern Caspian basin. The boundaries of the modelled refugia were substantially broader than the refugia boundaries inferred solely from pollen records. Thus, our method could be used to: (1) improve models of current species distributions by considering the dispersal histories of the species; and (2) validate alternative reconstructions of palaeoclimate with current distribution data. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 231‐248. ADDITIONAL KEYWORDS: forests ‐ fuzzy envelopes ‐ Mahalanobis distance ‐ post-glacial dispersal ‐ range modelling ‐ reconstruction of palaeoclimate ‐ variable selection ‐ western Asia.

Speciation in little: the role of range and body size in the diversification of Malagasy mantellid frogs

BackgroundThe rate and mode of lineage diversification might be shaped by clade-specific traits. In Madagascar, many groups of organisms are characterized by tiny distribution ranges and small body sizes, and this high degree of microendemism and miniaturization parallels a high species diversity in some of these groups. We here investigate the geographic patterns characterizing the radiation of the frog family Mantellidae that is virtually endemic to Madagascar. We integrate a newly reconstructed near-complete species-level timetree of the Mantellidae with georeferenced distribution records and maximum male body size data to infer the influence of these life-history traits on each other and on mantellid diversification.ResultsWe reconstructed a molecular phylogeny based on nuclear and mitochondrial DNA for 257 species and candidate species of the mantellid frog radiation. Based on this phylogeny we identified 53 well-supported pairs of sister species that we used for phylogenetic comparative analyses, along with whole tree-based phylogenetic comparative methods. Sister species within the Mantellidae diverged at 0.2-14.4 million years ago and more recently diverged sister species had geographical range centroids more proximate to each other, independently of their current sympatric or allopatric occurrence. The largest number of sister species pairs had non-overlapping ranges, but several examples of young microendemic sister species occurring in full sympatry suggest the possibility of non-allopatric speciation. Range sizes of species included in the sister species comparisons increased with evolutionary age, as did range size differences between sister species, which rejects peripatric speciation. For the majority of mantellid sister species and the whole mantellid radiation, range and body sizes were associated with each other and small body sizes were linked to higher mitochondrial nucleotide substitution rates and higher clade diversity. In contrast, small range sizes were unexpectedly associated with a slow-down of mitochondrial substitution rates.ConclusionsBased on these results we define a testable hypothesis under which small body sizes result in limited dispersal capabilities and low physiological tolerances, causing smaller and more strongly fragmented ranges. This can be thought to facilitate reproductive isolation and thus favor speciation. Contrary to the expectation of the faster speciation of such microendemic phenotype species, we only found small body sizes of mantellid frogs to be linked to higher diversification and substitution rates, but not small range sizes. A joint analysis of various species-rich regional anuran radiations might provide enough species with all combinations of range and body sizes for a more conclusive test of this hypothesis.

Range size patterns in European freshwater trematodes

While patterns in geographic range sizes in free‐living species have received much attention, little is known on the corresponding patterns in parasites. For the first time, we report on patterns in geographic range sizes and dimensions of endoparasites, using published species lists of freshwater trematodes in 25 biogeographical regions of Europe. In general, the range sizes of trematodes showed a typical hollow curve frequency distribution, with most species having small ranges. Contrary to expectations, there were no differences in range sizes among trematodes using hosts with high (birds) and limited dispersal capacity (e.g. fish). This suggests that the well known importance of host dispersal capacity for parasite dispersal at small spatial scales is overridden by other factors on larger scales. Regression analyses and Rohde plots showed that the relationship between the latitudinal centre and trematode range size was hump‐shaped in all host groups except for reptiles, for which it was linear. Most of the variation fell within the expectations given by null models, suggesting that the patterns mainly result from the geographic properties of the European continent and the biogeographical regions. Finally, trematode ranges tended to stretch more in east‐west than in north‐south directions, indicating dispersal barrier effects for parasite faunas, probably resulting from the geographical idiosyncrasies of the European continent.

Multiple environmental determinants of regional species richness and effects of geographic range size

Understanding patterns of species richness at broad geographic extents remains one of the most challenging yet necessary scientific goals of our time. Many hypotheses have been proposed to account for spatial variation in species richness; among them, environmental determinants have played a central role. In this study, we use data on regional bat species richness in the New World to study redundancy and complementarity of three environmental hypotheses: energy, heterogeneity and seasonality. We accomplish this by partitioning variation in species richness among components associated with unique and combined effects of variables from each hypotheses, and by partitioning the overall richness gradient into gradients of species with varying breadths of geographic distribution.These three environmental hypotheses explain most variation in the species richness gradient of all bats, but do not account for all positive spatial autocorrelation at short distances. Although environmental predictors are highly redundant, energy and seasonality explain different and complementary fractions of variation in species richness of all bats. On the other hand, heterogeneity variables contribute little to explain this gradient. However, results change dramatically when richness is estimated for groups of species with different sizes of geographic distribution. First, the amount of variation explained by environment decreases with a decrease in range size; this suggests that richness gradients of small‐ranged species can not be explained as easily as those of broadly distributed species, as has been implied by analyses that do not consider differences in range size among species. Second, the relative contribution of environmental predictors to explained variation also changes with change in range size. Seasonality and energy are good predictors of species with broad distributions, but they loose almost all explanatory power for richness of species with small ranges. In contrast, heterogeneity, which is a relatively poor predictor of richness of species with large ranges, becomes the main predictor of richness gradients of species with restricted distributions. This suggests that range size is a different dimension on which heterogeneity and other environmental characteristics are complementary to each other. Our results suggest that determinants of species richness gradients might be complex, or at least more complex than many studies have previously suggested.

Dispersal traits linked to range size through range location, not dispersal ability, in Western Australian angiosperms

ABSTRACTAim We examine the relative importance of seed dispersal mode in determining the range size and range placement in 524 species from six focal plant families (Agavaceae, Euphorbiaceae, Malvacaeae, Sapindaceae, Proteaceae and Fabaceae (Acacia)).Location Western Australia.Methods Taxa were categorized by dispersal mode and life‐form and their distributions modelled using maxent. Geographical range size was compared amongst dispersal mode, life‐form and biome using phylogenetically independent contrasts. Geographical range placement was considered in a similar manner.Results Range size did not vary with dispersal mode (ant versus wind and vertebrate dispersal) or life‐form, and instead varied primarily as a function of the biogeographical region in which a species was found. Range placement, however, did vary among dispersal modes, with the consequence that diversity of wind‐ and ant‐dispersed plants increased with latitude while the diversity of vertebrate‐dispersed plants was more evenly distributed.Main conclusions For the taxa studied, range sizes were a function of the biogeographical region in which species were found. Although differences in range size may exist among species differing in dispersal modes, they are likely to be far smaller than differences among species from different biogeographical regions. The trait most likely to affect species geographical range size, and hence rarity and risks associated with other threats, may simply be the geographical region in which that species has evolved.

Can differences in autonomous selfing ability explain differences in range size among sister‐taxa pairs ofCollinsia(Plantaginaceae)? An extension of Baker's Law

Species with greater selfing ability are predicted to be better adapted for colonizing new habitats (Baker's Law). Here, we tested an expansion of this hypothesis: that species proficient at autonomous selfing have larger range sizes than their less proficient sister taxa. We also tested competing hypotheses regarding seed production and niche breadth on range size. Floral traits affecting the proficiency of autonomous selfing were measured and seed production was calculated for six sister-taxa pairs in the clade Collinsia. We tested for the hypothesized effects of these variables on elevational distribution and range size. We found that species most proficient at selfing had significantly larger range sizes than their sister-taxa that were less proficient at selfing. Species proficient at autonomous selfing occupied a higher mean elevation than their sister taxa, but they did not differ in their total elevational range. Species with greater seed production did not have larger range sizes. Our results extend Baker's Law, suggesting that species proficient at autonomous selfing are better adapted to establish new populations and thus can more readily expand their range. Autonomous selfing ability may play a vital role in explaining variance in range size among other species.

Can minimum convex polygon home ranges be used to draw biologically meaningful conclusions?

AbstractMany conclusions about mammalian ranging behaviour have been drawn based on minimum convex polygon (MCP) estimates of home range size, although several studies have revealed its unpredictable nature compared to that of the kernel density estimator. We investigated to what extent the choice of home range estimator affected the biological interpretation in comparative studies. We found no discrepancy when the question asked covered a wide range of taxa, as real and very large differences in range size were likely to have masked smaller differences due to the choice of home range estimator. However, when the question asked concerned within‐species characteristics, the choice of home range estimator explained as much of the variation in range size as did the ecological variable in question. The implications for macro‐ecological and intraspecific studies are discussed.

Contrasting home-range size and spatial partitioning in cryptic and sympatric pipistrelle bats

The extent of spatial partitioning in insectivorous bats, whose prey is patchily distributed and transient in nature, remains a contentious issue. The recent separation of a common Palaearctic bat, the pipistrelle, into Pipistrellus pipistrellus and Pipistrellus pygmaeus, which are morphologically similar and sympatric, provides an opportunity to examine this question. The present study used radio telemetry to address the spatial distribution and foraging characteristics of P. pipistrellus and P. pygmaeus in northeast Scotland, to test the hypothesis that coexistence between these species is facilitated through spatial segregation. We reveal large and significant differences in the spatial distribution and foraging characteristics of these two cryptic species. Individual P. pipistrellus home ranges were on average three times as large as that of P. pygmaeus, and they foraged for approximately an hour longer each night. Inter-specific spatial overlap was minimal (<5%) and core foraging areas of either species were essentially mutually exclusive despite the proximity of the two roosts. Inter-specific differences in range size were associated with the spatial dispersion of productive foraging sites within individual foraging ranges. P. pipistrellus foraging sites were highly dispersed, necessitating larger ranges. It is predicted that the spatial segregation revealed by the present study is a result of selection favouring the avoidance of competition in these species through differential habitat use.

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

ABSTRACTAim 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.

Vegetation quality and habitat selection by European haresLepus europaeus in a pastural landscape

European haresLepus europaeus Pallas, 1778 have lower population densities and body condition in pastural landscapes than in arable landscapes, but reasons for this are not understood. The aim of this study was to determine whether forage quality is low in pastural landscapes during certain seasons. We carried out chemical analysis of the nutritional quality of 5 habitat types to determine whether hares select high quality habitats, and whether nutritional quality explains seasonal differences in range sizes of hares in pastural landscapes. Hares did not tend to select habitats of high nutritional quality (protein, fat or energy) over those of lower quality. Hares did not increase active range size as the overall energy content of forage at the study site decreased; seasonal differences in active range size were not explained by nutritional quality. Differences may be explained by behavioural changes related to breeding. Pastural habitat is fairly stable in terms of nutritional quality through the year, and results suggest that poor forage quality is unlikely to be responsible for the poor body condition of hares in pastural landscapes. Hares in these landscapes are more likely to be limited by habitat quality in terms of cover than by forage.

Spacing and activity patterns of leopards Panthera pardus in the Royal Bardia National Park, Nepal

Abstract Space use and activity of radio-collared leopards Panthera pardus (two adult males and one adult female) were monitored during 3–25 months in a prey-rich part of the Royal Bardia National Park, Nepal. Annual home ranges of the two males were 47 and 48 km2 and had an overlap of only 7%, whereas the overlap between the female's home range (17 km2) and that of one of the males was 56%. The range sizes were larger than reported from other studies in southeast Asia, but much smaller than some ranges in Africa. When comparing different studies, the sexual difference in range size increased significantly with increasing average range size. Thus, the cost by males of traversing large home ranges is probably not a determinant factor in shaping leopard communities. The female's seasonal home ranges (5.2 and 6.6 km2) were smallest during the seasons when her cubs were less than six months of age. She moved her home range closer to agricultural fields during the season when the abundant and important prey ax...

Macroecology of live‐bearing in fishes: latitudinal and depth range comparisons with egg‐laying relatives

We examine how fishes with contrasting reproductive modes (egg‐laying versus live‐bearing) differ in geographic range size and distribution. One hypothesis based on dispersal suggests that egg‐laying taxa should occupy a wider range of latitudes than live‐bearing, whereas the opposite prediction has been derived from the idea that enhanced maternal input and a ‘safe harbor’ during development will enable live‐bearers to occupy a wider range of latitudes and depths than egg‐layers. Cross‐species analysis supports the first hypothesis for teleosts, with egg‐layers living in a wider range of latitudes than live‐bearers but at lower latitudes, across a narrower depth range and at shallow depth. However, elasmobranchs show the opposite pattern, live‐bearers having wider latitudinal ranges. Phylogenetic paired comparisons of sister egg‐laying and live‐bearing taxa confirm these contrasting patterns between teleosts and elasmobranchs. However, depth range, maximum latitude and depth do not differ with reproductive mode. Latitudinal range size increases with body size among all taxa. However, only teleosts have a positive relationship between body size and maximum latitude, depth and depth range, but this does not differ between reproductive modes. Egg‐laying elasmobranchs have low dispersal, but live‐bearers have not extended their maximum latitude or depth, despite the benefits of sheltered offspring. The differences in range size between egg‐layers and live‐bearers and the distinction between teleosts and elasmobranchs is consequence of contrasting mechanisms of dispersal and benefits of maternally buffered transport of developing offspring.