Showing papers in "Journal of Biogeography in 2015"

Habitat fragmentation and species richness

Abstract: In a recent article in this journal, Fahrig (2013, Journal of Biogeography, 40, 1649–1663) concludes that variation in species richness among sampling sites can be explained by the amount of habitat in the ‘local landscape’ around the sites, while the spatial configuration of habitat within the landscape makes little difference. This conclusion may be valid for small spatial scales and when the total amount of habitat is large, but modelling and empirical studies demonstrate adverse demographic consequences of fragmentation when there is little habitat across large areas. Fragmentation effects are best tested with studies on individual species rather than on communities, as the latter typically consist of species with dissimilar habitat requirements. The total amount of habitat and the degree of fragmentation tend to be correlated, which poses another challenge for empirical studies. I conclude that fragmentation poses an extra threat to biodiversity, in addition to the threat posed by loss of habitat area.

Biodiversity in the Mexican highlands and the interaction of geology, geography and climate within the Trans-Mexican Volcanic Belt

Abstract: Aim (1) To synthesize data on the physical and phylogeographical history of the Mexican highlands, with a focus on the Trans-Mexican Volcanic Belt (TMVB), and (2) to propose approaches and analyses needed for examining the interaction of climate and volcanism. Location Mexico. Methods We performed a literature and data survey of the climatic, geological and phylogeographical history of the Mexican highlands. We then assessed how the expected effects of topographic isolation, co-occurring palaeoclimatic fluctuations and volcanism can be tested against the distribution of genetic diversity of high-elevation taxa. Results The Mexican highlands present a complex biogeographical, climatic and geological history. Montane taxa have been exposed to a sky-island dynamic through climate fluctuations, allowing for long-term in situ population persistence, while also promoting recent divergence and speciation events. Volcanic activity transformed part of the Mexican highlands during the Pleistocene, mainly in the TMVB, leading to co-occurring climate and topographical changes. The TMVB highlands provide a suitable template to examine how low-latitude mountains can facilitate both the long-term persistence of biodiversity as well as allopatric and parapatric speciation driven by climatic and geological events. Main conclusions Climate fluctuations, together with recent volcanism, have driven the diversification and local persistence of biodiversity within the Mexican highlands. The climate–volcanism interaction is challenging to study; however, this can be overcome by coupling genomic data with landscape analyses that integrate the geological and climatic history of the region.

Shifting seas: the impacts of Pleistocene sea‐level fluctuations on the evolution of tropical marine taxa

Abstract: Aim Pleistocene glacial cycles reduced global sea level by up to 130 m below present levels. These changes had profound impacts on coastal marine life, including a reduction of habitable area, changes in ocean currents, and shifts in water column thermal dynamics. We provide a comprehensive review of the impact of glacial sea-level changes during the Pleistocene on tropical coastal marine life and a set of maps showing how coastlines worldwide changed during periods of low sea levels. Location We focused on coastal marine taxa within tropical latitudes, with deeper coverage of the world’s major coral reef biogeographical provinces. Methods We examined recent and historical literature that alluded to the effects of Pleistocene sea-level fluctuations in a variety of common marine clades. Data for shelf habitat area and map construction were obtained from the NOAA ETOPO1 database, with final manipulations carried out in Adobe Illustrator CS6.

A continental‐scale analysis of feral cat diet in Australia

Abstract: Aim Reducing the impacts of feral cats (Felis catus) is a priority for conservation managers across the globe, and success in achieving this aim requires a detailed understanding of the species’ ecology across a broad spectrum of climatic and environmental conditions. We reviewed the diet of the feral cat across Australia and on Australian territorial islands, seeking to identify biogeographical patterns in dietary composition and diversity, and use the results to consider how feral cats may best be managed. Location Australia and its territorial islands. Methods Using 49 published and unpublished data sets, we modelled trophic diversity and the consumption of eight food groups against latitude, longitude, mean temperature, precipitation, environmental productivity and climate-habitat regions. Results We recorded 400 vertebrate species that feral cats feed on or kill in Australia, including 28 IUCN Red List species. We found evidence of continental-scale prey-switching from rabbits to small mammals, previously recorded only at the local scale. The consumption of arthropods, reptiles, rabbits, rodents and medium-sized native mammals varied with different combinations of latitude, longitude, mean annual precipitation, temperature and environmental productivity. The frequency of rodents and dasyurids in cats’ diets increased as rabbit consumption decreased. Main conclusions The feral cat is an opportunistic, generalist carnivore that consumes a diverse suite of vertebrate prey across Australia. It uses a facultative feeding strategy, feeding mainly on rabbits when they are available, but switching to other food groups when they are not. Control programmes aimed at culling rabbits could potentially decrease the availability of a preferred food source for cats and then lead to greater predation pressure on native mammals. The interplay between cat diet and prey species diversity at a continental scale is complex, and thus cat management is likely to be necessary and most effective at the local landscape level.

Dispersal strength determines meta‐community structure in a dendritic riverine network

Abstract: Aim Meta-community structure is a function of both local (site-specific) and regional (landscape-level) ecological factors, and the relative importance of each may be mediated by the dispersal ability of organisms. Here, we used aquatic invertebrate communities to investigate the relationship between local and regional factors in explaining distance decay relationships (DDRs) in fragmented dendritic stream networks. Location Dryland streams distributed within a 400-km 2 section of the San Pedro River basin, south-eastern Arizona, USA. Methods We combined fine-scale local information (flow and habitat characteristics) with regional-scale information to explain DDR patterns in community composition of aquatic invertebrate species with a wide range of dispersal abilities. We used a novel application of a landscape resistance modelling approach (originally developed for landscape genetic studies) that simultaneously assessed the importance of local and regional ecological factors as well as dispersal ability of organisms. Results We found evidence that both local and regional factors influenced aquatic invertebrate DDRs in dryland stream networks, and the importance of each factor depended on the dispersal capacities of the organisms. Local and weak dispersers were more affected by site-specific factors, intermediate dispersers by landscape-level factors, and strong dispersers showed no discernable pattern. This resulted in a strongly hump-shaped relationship between dispersal ability and landscape-level factors, where only moderate dispersers showed evidence of DDRs. Unlike most other studies of dendritic networks, our results suggest that overland pathways, using perennial refugia as stepping-stones, might be the main dispersal route in fragmented stream networks. Main conclusions We suggest that using a combination of landscape and local distance measures can help to unravel meta-community patterns in dendritic systems. Our findings have important conservation implications, such as the need to manage river systems for organisms that span a wide variety of dispersal abilities and local ecological requirements. Our results also highlight the need to preserve perennial refugia in fragmented networks, as they may ensure the viability of aquatic meta-communities by facilitating dispersal.

Distinct effects of climate warming on populations of silver fir (Abies alba) across Europe

Abstract: Most of this dataset was obtained through funding from the following research projects: CGL2011-26654 (Spanish Commission of Science and Technology and Fondos Europeos de Desarrollo Rural – FEDER), 387/2011−1012S (Organismo Autonomo de Parques Nacionales – OAPN, Spain), and FORMAT (European Union funded ENV4-CT97-0641 project). J.J.C. also acknowledges the support of Fundacion Agencia Aragonesa para la Investigacion y el Desarrollo (ARAID). We would also like to thank the Spanish Meteorological State Agency (AEMET) and the Climatic Research Unit (CRU) for providing the climatic databases used in this study. We thank the FPS COST Action FP1106 STReESS for facilitating collaborative work.

Variation in plant diversity in mediterranean-climate ecosystems: The role of climatic and topographical stability

Abstract: Aim Although all five of the major mediterranean-climate ecosystems (MCEs) of the world are recognized as loci of high plant species diversity and endemism, they show considerable variation in regional-scale richness. Here, we assess the role of stable Pleistocene climate and Cenozoic topography in explaining variation in regional richness of the globe's MCEs. We hypothesize that older, more climatically stable MCEs would support more species, because they have had more time for species to accumulate than MCEs that were historically subject to greater topographic upheavals and fluctuating climates. Location South-western Africa (Cape), south-western Australia, California, central Chile and the eastern (Greece) and western (Spain) Mediterranean Basin. Methods We estimated plant diversity for each MCE as the intercepts of species–area curves that are homogeneous in slope across all regions. We used two down-scaled global circulation models of the Last Glacial Maximum (LGM) to quantify climate stability by comparing the change in the location of MCEs between the LGM and present. We quantified the Cenozoic topographic stability of each MCE by comparing contemporary topographic profiles with those present in the late Oligocene and the early Pliocene. Results The most diverse MCEs – Cape and Australia – had the highest Cenozoic environmental stability, and the least diverse – Chile and California – had the lowest stability. Main conclusions Variation in plant diversity in MCEs is likely to be a consequence not of differences in diversification rates, but rather the persistence of numerous pre-Pliocene clades in the more stable MCEs. The extraordinary plant diversity of the Cape is a consequence of the combined effects of both mature and recent radiations, the latter associated with increased habitat heterogeneity produced by mild tectonic uplift in the Neogene.

Contrasting species and functional beta diversity in montane ant assemblages.

Abstract: Aim Beta diversity describes the variation in species composition between sites and can be used to infer why different species occupy different parts of the globe. It can be viewed in a number of ways. First, it can be partitioned into two distinct patterns: turnover and nestedness. Second, it can be investigated from either a species identity or a functional-trait point of view. We aim to document for the first time how these two aspects of beta diversity vary in response to a large environmental gradient. Location Maloti-Drakensberg Mountains, southern Africa. Methods We sampled ant assemblages along an extensive elevational gradient (900–3000 m a.s.l.) twice yearly for 7 years, and collected functional-trait information related to the species’ dietary and habitat-structure preferences. We used recently developed methods to partition species and functional beta diversity into their turnover and nestedness components. A series of null models were used to test whether the observed beta diversity patterns differed from random expectations. Results Species beta diversity was driven by turnover, but functional beta diversity was composed of both turnover and nestedness patterns at different parts of the gradient. Null models revealed that deterministic processes were likely to be responsible for the species patterns but that the functional changes were indistinguishable from stochasticity. Main conclusions Different ant species are found with increasing elevation, but they tend to represent an increasingly nested subset of the available functional strategies. This finding is unique and narrows down the list of possible factors that control ant existence across elevation. We conclude that diet and habitat preferences have little role in structuring ant assemblages in montane environments and that some other factor must be driving the non-random patterns of species turnover. This finding also highlights the importance of distinguishing between different kinds of beta diversity.

Convergence in drought stress, but a divergence of climatic drivers across a latitudinal gradient in a temperate broadleaf forest

Abstract: Aim Information about climate stressors on tree growth is needed in order to assess the impacts of global change on forest ecosystems. Broad-scale patterns of climatic limitations on tree growth remain poorly described across eastern North American deciduous forests. We examined the response of broadleaf tree species to climate in relation to their taxonomy, functional traits and geographical location. Location Eastern North America (32–45° N; 70–88° W). Methods We used a network of 86 tree-ring width chronologies from eight species that cover a wide range of ecological and climatic conditions. Species were analysed individually or combined according to taxa and wood anatomical functional traits. We identified climate stressors through correlations between growth and climate (from 1916 to 1996). We also explored patterns in the climate responses of these species with two clustering techniques.

Using species richness and functional traits predictions to constrain assemblage predictions from stacked species distribution models

Abstract: Aim Modelling species distributions at the community level is required to make effective forecasts of global change impacts on diversity and ecosystem functioning. Community predictions may be achieved using macroecological properties of communities (macroecological models, MEM), or by stacking of individual species distribution models (stacked species distribution models, S-SDMs). To obtain more realistic predictions of species assemblages, the SESAM (spatially explicit species assemblage modelling) framework suggests applying successive filters to the initial species source pool, by combining different modelling approaches and rules. Here we provide a first test of this framework in mountain grassland communities. Location The western Swiss Alps. Methods Two implementations of the SESAM framework were tested: a ‘probability ranking’ rule based on species richness predictions and rough probabilities from SDMs, and a ‘trait range’ rule that uses the predicted upper and lower bound of community-level distribution of three different functional traits (vegetative height, specific leaf area, and seed mass) to constrain a pool of species from binary SDMs predictions. Results We showed that all independent constraints contributed to reduce species richness overprediction. Only the ‘probability ranking’ rule allowed slight but significant improvements in the predictions of community composition. Main conclusions We tested various implementations of the SESAM framework by integrating macroecological constraints into S-SDM predictions, and report one that is able to improve compositional predictions. We discuss possible improvements, such as further understanding the causality and precision of environmental predictors, using other assembly rules and testing other types of ecological or functional constraints.

Geographical variability in the controls of giant kelp biomass dynamics

Abstract: Aim Coastal marine environments experience a wide range of biotic and abiotic forces that can limit and punctuate the geographical range and abundance of species through time. Determining the relative strengths and nonlinear effects of these processes is vital to understanding the biogeographical structures of species. There has been an ongoing discussion concerning the relative importance of these processes in controlling the dynamics of giant kelp, Macrocystis pyrifera, an important structure-forming species on shallow reefs in the eastern Pacific. We used novel spatial time-series that span nearly three decades to determine the dominant drivers of giant kelp canopy biomass and the temporal and spatial scales over which they operate across the dominant range of the giant kelp in North America. Location Near-shore areas from Ano Nuevo, California, to the USA/Mexico border. Methods We employed empirical orthogonal functions to elucidate the primary drivers of giant kelp canopy biomass across space and time and then fit generalized additive and linear models to determine the nonlinear effect and relative importance of each of these potential drivers along the c. 1500-km study region over a 25-year period. Results Wave disturbance, nitrate availability and the state of the North Pacific Gyre Oscillation were the most important environmental predictors of giant kelp canopy biomass, explaining 24.5%, 12.7% and 6.1% of the variance, respectively. Environmental drivers of canopy biomass exhibited profound spatial differences in relative effect sizes. Nonlinear effect shapes of each potential biomass driver were determined, which explained these spatial differences. Main conclusions These large-scale analyses help to reconcile the local-scale conclusions of canopy biomass dynamics across the California coastline and show that these dynamics differ predictably in space and time in accordance with local and regional differences in environmental drivers. By characterizing the nonlinear effects of these drivers, we identified spatio-temporal patterns of processes that cannot be detected by remote sensing.

The Sahul–Sunda floristic exchange: dated molecular phylogenies document Cenozoic intercontinental dispersal dynamics

Abstract: Aim The aim was to characterize the temporal dynamics of the Sahul–Sunda floristic exchange using published dated molecular phylogenies. Location The Sahul and Sunda shelves in Australasia and Southeast Asia. Methods Dated molecular phylogenies were compiled from the literature for plant clades that contained at least one node representing a biogeographical disjunction between the Sahul and Sunda shelves. For these nodes the age, ancestral geographical area and propagule type were determined. Results We analysed 49 clades from 21 published phylogenies representing a diverse set of angiosperm lineages. The inferred age of the disjunctions ranged from c. 33 Ma to c. 1 Ma; the earliest age marked the onset of the Sahul–Sunda floristic exchange. Disjunctions (resulting from dispersal/migration events) occurred at the rate of 0.41 per 2 Myr between 34 and 12 Ma. Thereafter the rate sharply increased, coincident with the shelves effectively merging. For nearly two-thirds (63%) of the nodes Sunda was the ancestral area, and for 90% the ancestral species possessed zoochorous propagules. Main conclusions There is strong support for a dynamic model of floristic exchange between Sahul and Sunda. Fewer (18%) disjunctions occurred prior to Sahul and Sunda merging around 12 Ma, which we attribute to a combination of the effect of overwater dispersal barriers and relatively stable, saturated species assemblages resistant to the establishment of newly arrived lineages. The exchange, once underway, was strongly asymmetrical; eastwards migration into Sahul predominated over the reverse by a factor of c. 2.4. As zoochorous lineages were overrepresented among the successful dispersers, we infer a strong role for localized animal dispersal across narrow water barriers.

Climate change, genetic markers and species distribution modelling

Abstract: Ecologists and biogeographers are currently expending great effort forecasting shifts in species geographical ranges that may result from climate change. However, these efforts are problematic because they have mostly relied on presence‐only data that ignore within‐species genetic diversity. Technological advances in high‐throughput sequencing have now made it cost‐effective to survey the genetic structure of populations sampled throughout the range of a species. These data can be used to delineate two or more genetic clusters within the species range, and to identify admixtures of individuals within genetic clusters that reflect different patterns of ancestry. Species distribution models (SDMs) applied to the presence and absence of genetic clusters should provide more realistic forecasts of geographical range shifts that take account of genetic variability. High‐throughput sequencing and spatially explicit models may be used to further refine these projections.

Anthropogenic influence on Amazonian forests in pre-history: An ecological perspective

Abstract: An important debate has been re-invigorated by new data concerning the size and environmental impacts of human populations in the Amazon Basin during pre-history. Here, we review the history of debates concerning pre-historic human occupation of the Amazon Basin along with the presentation of empirical data from archaeological and palaeoecological research. The combined evidence suggests that human occupation and resulting influence on Amazonian ecosystems were heterogeneous on both regional and local scales. Pre-historic occupation sites are more likely to have been located in forests with a pronounced dry season or in forests that are within 15 km of a river floodplain, rather than in ever-wet forests or in interfluvial regions far removed from large rivers. Forest enrichment of preferred species and game depletion through hunting are most probable within 15 km of an occupation site. Given the spatial and temporal patterning of these data, views of significant Amazonian-wide cultural impacts on riverine and interfluvial forest are not supported at this time.

Origin of the forest steppe and exceptional grassland diversity in Transylvania (central-eastern Europe)

Abstract: Aim The forest steppe of the Transylvanian Plain is a landscape of exceptionally diverse steppe-like and semi-natural grasslands. Is this vegetation a remnant of a once continuous temperate forest extensively cleared by humans, or has the area, since the last glacial, always been a forest steppe? Understanding the processes that drive temperate grassland formation is important because effective management of this biome is critical to the conservation of the European cultural landscape. Location Lake Stiucii, north-western Romania, central-eastern Europe. Methods We analysed multi-proxy variables(pollen, coprophilous fungi,plant macroremains, macrocharcoal) from a 55,000 year discontinuous sequence (c. 55,000–35,000; 13,000–0 cal. yr bp), integrating models of pollenbased vegetation cover, biome reconstruction, global atmospheric simulations and archaeological records. Results Needleleaf woodland occurred during glacial Marine Isotope Stage (MIS) 3, but contracted at the end of this period. Forest coverage of c. 55% (early Holocene) and 65% (mid-Holocene) prevailed through the Holocene, but Bronze Age humans extensively cleared forests after 3700 cal. yr bp. Forest coverage was most widespread between 8600 and 3700 cal. yr bp, whereas grasses, steppe and xerothermic forbs were most extensive between 11,700 and 8600 cal. yr bp and during the last 3700 cal. yr bp. Cerealia pollen indicate the presence of arable agriculture by c. 7000 cal. yr bp. Main conclusions We have provided the first unequivocal evidence for needleleaf woodland during glacial MIS 3 in this region. Extensive forests prevailed prior to 3700 cal. yr bp, challenging the hypothesis that the Transylvanian lowlands were never wooded following the last glaciation. However, these forests were never fully closed either, reflecting dry growing season conditions, recurrent fires and anthropogenic impacts, which have favoured grassland persistence throughout the Holocene. The longevity of natural and semi-natural grasslands in the region may explain their current exceptional biodiversity. This longer-term perspective implies that future climatic warming and associated fire will maintain these grasslands.

Environmental and historical controls of floristic composition across the South American Dry Diagonal

Abstract: Aim The aim of this study was to test the role of environmental factors and spatially autocorrelated processes, such as historical fragmentation and dispersal limitation, in driving floristic variation across seasonally dry tropical forests (SDTFs) in eastern South America. Location SDTFs extending from the Caatinga phytogeographical domain of north-eastern Brazil to the Chaco phytogeographical domain of northern Argentina, an area referred to as the Dry Diagonal. Methods We compiled a database of 282 inventories of woody vegetation in SDTFs from across the Dry Diagonal and combined this with data for 14 environmental variables. We assessed the relative contribution of spatially autocorrelated processes and environmental factors to the floristic turnover among SDTFs across the Dry Diagonal using variation partitioning methods. In addition, we used multivariate analyses to determine which environmental factors were most important in explaining the turnover. Results We found that the environmental factors measured (temperature, precipitation and edaphic conditions) explained 21.3% of the variation in species composition, with 14.1% of this occurring independently of spatial autocorrelation. A spatially structured fraction of 4.2% could not be accounted for by the environmental factors measured. The main axis of compositional variation was significantly correlated with a north–south gradient in temperature regime. At the extreme south of the Dry Diagonal, a cold temperature regime, in which frost occurred, appeared to underlie floristic similarities between chaco woodlands and southern SDTFs. Main conclusions Environmental variables, particularly those related to temperature regime, seem to be the most significant factors affecting variation in species composition of SDTFs. Thus historical fragmentation and isolation alone cannot explain the turnover in species composition within SDTFs, as is often assumed. Compositional and environmental heterogeneity needs to be taken into account both to understand the past distribution of SDTFs and to manage and conserve this key tropical biome.

Fighting their last stand? A global analysis of the distribution and conservation status of gymnosperms

Abstract: Aim Gymnosperms are often described as a marginal and threatened group, members of which tend to be out-competed by angiosperms and which therefore preferentially persist at higher latitudes and elevations The aim of our synthesis was to test these statements by investigating the global latitudinal and elevational distribution of gymnosperms, as well as their conservation status, using all extant gymnosperm groups (cycads, gnetophytes, ginkgophytes and conifers) Location Worldwide Methods We developed a database of 1014 species of gymnosperms containing latitudinal and elevational distribution data, as well as their global conservation status, as described in the literature The 1014 species comprised 305 cycads, 101 gnetophytes, the only living representative of ginkgophytes, and 607 conifers Generalized additive models, frequency histograms, kernel density estimations and distribution maps based on Takhtajan's floristic regions were used Results Although the diversity of gymnosperms decreases at equatorial latitudes, approximately 50% of the extant species occur primarily between the tropics More than 43% of gymnosperms can occur at very low elevations (≤ 200 m asl) Gymnosperms, considering all species together as well as their main taxonomic groups separately, do not exhibit a latitudinal diversity gradient as commonly observed for many other taxa Gymnosperms, and especially conifers, are on average less threatened at higher and equatorial latitudes Main conclusions Gymnosperms display an unusual latitudinal diversity gradient, which we suggest cannot fully be accounted for by angiosperm dominance and competitive superiority We hypothesize that other factors explain their present distribution, such as the development of centres of endemism in several regions and the adaptation of certain taxa to cold and arid climates

Attributing forest responses to global-change drivers: Limited evidence of a CO2-fertilization effect in Iberian pine growth

Abstract: We thank the referees for improving a previous version of the manuscript. We are particularly indebted to all the support provided by the people from the “Laboratorio de Sanidad Forestal” (Mora de Rubielos, Aragon Government), particularly Rodolfo Hernandez, Juan Manuel Gil, Miguel Ros, Victor Perez Fortea and Araceli Ortiz. We also thank Melissa Hoffer and Justin Waito for their help with laboratory work. Antonio Gazol is supported by a Postdoctoral grant from MINECO (Contrato Formacion Postdoctoral MINECO – FPDI 2013–16600). This study was supported by projects CGL2011–26654 (Spanish Ministry of Economy and Competitiveness), 387/2011 and 1032S/2013 (Spanish Ministry of Agriculture and Environment, OAPN, Spain). The research was also partly funded by the Canada Research Chair Program and a NSERC discovery grant to J.C. Tardif. We are also indebted to all people who helped us sampling in the field. We thank AEMET, CRU and ESRL-NOAA for providing climatic and CO2 data.

Stacked species distribution models and macroecological models provide congruent projections of avian species richness under climate change

Abstract: Aim Using survey data for North American birds, we assess how well historical patterns of species richness are explained by stacked species distribution models and macroecological models. We then describe the degree to which projections of future species richness differ, employing both modelling approaches across multiple emissions scenarios. Location USA and Canada.

Epiphytic lichen diversity along elevational gradients: biological traits reveal a complex response to water and energy

Abstract: Aim Patterns of epiphytic lichen diversity along elevational gradients covering the range of Norway spruce forests were analysed. The roles of water and energy variables in shaping the observed species–elevation relationship were tested, as well as how growth form and photobiont type distribution varied along the gradient. Location South Tyrol, northern Italy. Methods Eight sites were selected spanning the elevational range of spruce forests (900–1900 m a.s.l.) and the regional rainfall gradient. At each site, a pair of forest stands (one mature even-aged and one multilayered) was selected at three elevation steps. Epiphytic lichens were surveyed according to European guidelines for lichen diversity monitoring. Explanatory variables indicative of both forest structure and climate were included in the models. Results A positive relationship was found between number of species and elevation. This reflected the physiological response of epiphytic lichens to the main climatic factors, trait selection being the mechanism that determined the response at community level. Nonlinear species–temperature and trait–temperature relationships predicted that major changes may be expected in the intermediate part of the gradient. Lichens with a Trentepohlia algal partner were more frequent at lower elevations and proved to be sensitive to environmental factors indicative of forest structure. Lichen growth forms had contrasting patterns related to temperature, crustose species richness being enhanced by increasing values, and alectorioid and foliose lichens by decreasing values. Alectorioid lichens were also negatively influenced by rainfall. Main conclusions In a climate change scenario, lichen diversity in alpine regions will probably not benefit from an increase in air temperature in the same way as flowering plants. Monitoring variations in the proportions of growth form and photobiont type may represent a tool for detecting the effects of climate change on lichen species.

Dispersal traits drive the phylogenetic distance decay of similarity in Neotropical stream metacommunities

Abstract: Aim The drivers of phylogenetic beta diversity include both local processes (e.g. environmental filtering) and regional processes (e.g. dispersal limitation). The role of environmental filtering can be investigated more directly by analysing community–environment associations, but dispersal limitation is one of the most challenging processes to examine. We investigated the role of traits related to dispersal – flight capacity, body size and voltinism – as drivers of phylogenetic distance decay relationships in Neotropical stream insect communities. Location Headwater streams spread over 600 km in south-eastern Brazil. Methods We compiled a data set of aquatic insect communities inhabiting streams across the State of Sao Paulo (Brazil). Then, we investigated environmental and spatial signals on phylobetadiversity patterns of aquatic insects using Mantel tests, multiple regressions on distance matrices and variation partitioning. We employed null models to investigate whether phylogenetic distance decay differed from pure compositional distance decay. We deconstructed the data set based on dispersal-related traits; we then ran distance decay analyses for these subsets separately. Results Geographical distance, rather than environmental distance, better explained the patterns of phylobetadiversity. We found that the phylogenetic decay relationship differed from the relationship expected for the null models only for univoltine, large-bodied genera with a high-flight capacity. Main conclusions Dispersal limitation, rather than species sorting, was the main driver for phylogenetic beta diversity in the metacommunity that we studied. We suggest that life-history strategies and mainly voltinism drive the distance decay of similarity in the insect communities examined. We additionally discuss the role of dispersal events over time to explain differences in distance decay patterns among tropical and other regions.

Testing the effect of palaeodrainages versus habitat stability on genetic divergence in riverine systems: study of a Neotropical fish of the Brazilian coastal Atlantic Forest

Abstract: Aim Patterns of genetic variation within freshwater fish populations may reflect the historical impact of climate change on either sea-level or environmental conditions. Past sea-level changes enlarged palaeodrainages and so connected currently isolated rivers, whereas changes in environmental conditions reduced forest cover and may have constrained the movement of fish specialized to this habitat. We assayed genetic variation in Hollandichthys multifasciatus, a freshwater fish endemic to the Atlantic Forest of coastal Brazil, to test the relative importance of these factors in shaping current patterns of genetic divergence. Location River drainages along the south-eastern Brazilian coast. Methods A GIS was used to reconstruct palaeodrainages during the Last Glacial Maximum (LGM). Niche modelling was used to infer areas of stability for the southern Atlantic Forest sensu stricto (present and LGM). The contribution of river connections inside or outside areas of stability was evaluated using a calibrated phylogeny, analyses of molecular variance, and Bayesian skyline plots from two mtDNA loci. Results Analyses of 182 individuals from 26 populations and 12 palaeodrainages indicated that structure associated with palaeodrainages explains 75% of the genetic variation among populations, with estimated divergence times occurring within the Pleistocene. The variation explained by palaeodrainages and estimated population sizes was unrelated to the ecological stability of the region. Main conclusions This study demonstrates the importance of Pleistocene palaeodrainages in structuring genetic divergence patterns. The analyses suggest that past connections due to sea-level retreat played a significant role in the diversification of the ichthyofauna along the Brazilian coastal drainages. Moreover, the lack of a signature of habitat stability in structuring genetic variation suggests that refugia may be less important in structuring genetic diversity for freshwater species than for terrestrial species. In addition, our work highlights the utility of a GIS-based approach to recover past connections among coastal basins. Understanding these connections is crucial for studying diversification of riverine organisms and for identifying areas of conservation priority.

Revisiting the past to foretell the future: summer temperature and habitat area predict pika extirpations in California

Abstract: Aim The American pika (Ochotona princeps) appears to have experienced climate mediated upslope range contraction in the Great Basin of North America, but this result has not yet been extended to other portions of the pika’s range. Our goals were: first, to determine the environmental parameters that most influence current pika distribution within California; second, to infer whether these constraints explain extirpations that have occurred in California; third, to predict future extirpations; and fourth, to advance methods for assessing the degree to which pikas and other climate-sensitive mammals are threatened by climate change. Location Historical pika record locations in California, USA, spanning four degrees of latitude and longitude, from Mount Shasta to the southern Sierra Nevada. Methods We identified 67 precise historical pika record locations and surveyed them exhaustively, over multiple years, to determine whether pika populations persist at those sites. We used an information theoretic approach and logistic regression to model current pika occupancy as a function of 16 environmental variables, tested our best-performing model as a predictor of historical occupancy, and then used our model to predict future pika occupancy given anticipated climate change. Results Pikas no longer occurred at 10 of 67 (15%) historical sites in California. The best predictors of occupancy were average summer temperature and talus habitat area within a 1-km radius. A logistic model fitted to this relationship correctly predicted current occupancy at 94% of sites and correctly hindcasted past occupancy at 93% of sites, suggesting that the model has strong temporal transferability. Depending on the future climate scenario, our model projects that by 2070 pikas will be extirpated from 39% to 88% of these historical sites in California. Main conclusions Our simple species distribution model for pikas performs remarkably well for both current and historical periods. Pika distribution appears to be governed primarily by behavioural restrictions mediated by summer temperature and by the configuration of talus habitat available to pikas locally. Pikas, and other montane species in the western USA, may be subjected to above-average exposure to climate change because summer temperature is projected to rise more than annual temperature.

Cold tolerance of tree species is related to the climate of their native ranges

Abstract: Aim Species ranges are confined by environmental parameters such as minimum temperatures. Beyond correlations of ranges and climatic parameters, however, physiological tolerances (here: cold tolerance) have rarely been linked to the climate of species' ranges. We hypothesize that natural range shifts due to climate warming and proactive-assisted colonization may each be constrained by limits to the tolerance of species to rare frost events. Location Bayreuth, Germany, and the Northern Hemisphere. Methods We quantified cold tolerance (LT50 obtained by relative electrolyte leakage method) of 27 native and exotic (Northern Hemisphere) tree species in the autumn, mid-winter and spring of 2011–12 at the Ecological Botanical Garden of the University of Bayreuth, Germany, and linked observed cold tolerances as well as changes in cold tolerance between sampling dates to the climate of the native ranges of the species. Results Observed cold tolerance was strongly related to the climate of the native ranges of the species (cross-validated correlations between climate and expressed cold tolerance determined by boosted regression trees were 0.50 in autumn, 0.49 in mid-winter, and 0.65 in spring). Cold tolerance was generally greater for species that experienced colder temperatures and lower levels of precipitation in their native ranges. Changes in cold tolerance between the three sampling dates over the winter, however, were not linked to the climate of the native ranges. Main conclusions Our results demonstrate the evolutionary importance of cold tolerance, which should be acknowledged in assisted colonization trials and projections of range shifts by considering absolute minimum temperature as an important ecological factor.

Integration of global fossil and modern biodiversity data reveals dynamism and stasis in ant macroecological patterns

Abstract: Results The analyses of generic composition and community structure were congruent, supporting a strong affinity between the Western Palaearctic ant fauna and modern Indomalayan and Australasian assemblages, and of a widespread Holarctic ant palaeofauna, and affinity between fossil Caribbean and modern Neotropical faunas. In addition, neither generic composition nor community structure of fossil assemblages showed evidence of taphonomic bias towards arboreal taxa.

The climate space of fire regimes in north-western North America

Abstract: Aim Studies of fire activity along environmental gradients have been undertaken, but the results of such studies have yet to be integrated with fire-regime analysis. We characterize fire-regime components along climate gradients and a gradient of human influence. Location We focus on a climatically diverse region of north-western North America extending from northern British Columbia, Canada, to northern Utah and Colorado, USA. Methods We used a multivariate framework to collapse 12 climatic variables into two major climate gradients and binned them into 73 discrete climate domains. We examined variation in fire-regime components (frequency, size, severity, seasonality and cause) across climate domains. Fire-regime attributes were compiled from existing databases and Landsat imagery for 1897 large fires. Relationships among the fire-regime components, climate gradients and human influence were examined through bivariate regressions. The unique contribution of human influence was also assessed. Results A primary climate gradient of temperature and summer precipitation and a secondary gradient of continentality and winter precipitation in the study area were identified. Fire occupied a distinct central region of such climate space, within which fire-regime components varied considerably. We identified significant interrelations between fire-regime components of fire size, frequency, burn severity and cause. The influence of humans was apparent in patterns of burn severity and ignition cause. Main conclusions Wildfire activity is highest where thermal and moisture gradients converge to promote fuel production, flammability and ignitions. Having linked fire-regime components to large-scale climate gradients, we show that fire regimes – like the climate that controls them – are a part of a continuum, expanding on models of varying constraints on fire activity. The observed relationships between fire-regime components, together with the distinct role of climatic and human influences, generate variation in biotic communities. Thus, future changes to climate may lead to ecological changes through altered fire regimes.

When biogeographical provinces collide: Hybridization of reef fishes at the crossroads of marine biogeographical provinces in the Arabian Sea

Abstract: Aim: Suture zones are areas where closely related species from different biogeographical regions come into contact and interbreed. This concept originated from the study of terrestrial ecosystems but it remains unclear whether a similar phenomenon occurs in the marine environment. Here we investigate a potential suture zone from a previously unknown hybrid hotspot at the Socotra Archipelago (Yemen), located in the Arabian Sea, where fauna from the Red Sea, Gulf of Aden, Arabian Sea, western Indian Ocean and greater Indo-Polynesian Province intersect. Location: Red Sea, Gulf of Aden, Arabian Sea and Indian Ocean. Methods: Putative hybrid reef fish were identified based on intermediate coloration and morphology. Underwater observations and collections were conducted to determine: (1) whether parent species form heterospecific social groups or breeding pairs; (2) the sex and reproductive status of morphologically intermediate individuals; and (3) whether parent species were forming mixed species associations owing to a dearth of conspecific partners. To support hybrid status, morphologically intermediate and parental individuals were genotyped using mitochondrial DNA cytochrome c oxidase subunit I (COI), nuclear recombination-activating gene 2 (RAG2) and the nuclear TMO-4C4 (TMO) gene. Results: We observed putative hybrids involving 14 species from four reef fish families at Socotra. Most cases involved a parental species with a restricted distribution (e.g. Red Sea or Arabian Sea) and a broadly distributed Indo-Pacific species. In most cases, at least one of the parent species was rare at Socotra. Hybrid gene flow was largely unidirectional, and although introgression was rare, we found evidence that some butterflyfish and surgeonfish hybrids were fertile and formed breeding groups with parental species. Main conclusions: The rate of hybrid discovery at Socotra is much greater than that recorded elsewhere in the marine environment and involved both allopatric and sympatric species. This study highlights the importance of biogeographical location, reef habitat, environmental conditions and abundance disparities at Socotra in potentially facilitating hybridization among reef fishes at the edge of their distribution.

Palaeotropical origins, boreotropical distribution and increased rates of diversification in a clade of edible ectomycorrhizal mushrooms (Amanita section Caesareae)

Abstract: Aim The geographical distributions of most fungal species are still poorly known; consequently, their origins and historical distributions remain largely understudied. High levels of cryptic diversity, scarce fossil records and poorly sampled regions can explain some of these shortcomings. We extensively sampled an iconic group of edible ectomycorrhizal (EM) fungi, Amanita caesarea and its allies, in order to infer evolutionary patterns on a global scale. Location Worldwide. Methods DNA sequences from three nuclear genes were derived for 120 collections. Divergence times were estimated using fossil calibrations within the Agaricomycetes, followed by more inclusive (A. sect. Caesareae + outgroup) root-recalibrated estimations. Ultrametric trees from beast were used in ancestral-area reconstructions and to infer geodispersal models. They were further used in diversification-rate analyses using maximum-likelihood and Bayesian methods. Results Molecular dating and ancestral-area reconstruction indicated a Palaeotropical origin of A. sect. Caesareae between the Palaeocene and Eocene. Dispersal events to temperate regions in Mediterranean Europe, eastern Australia and North and Central America, occurred mostly during the late Miocene and Pliocene. A boreotropical model was supported as the most likely mode of geodispersal. Diversification rates were significantly higher in the New World than in the Old World. Main conclusions We present evidence that this group of edible EM mushrooms was ancestrally Palaeotropical from around the Eocene to the late Miocene, reaching temperate insular and continental areas during the late Miocene and Pliocene. The mode of dispersal is largely consistent with Wolfe's boreotropical hypothesis. We also found that the overall diversification rate has been rather constant, but has increased relatively recently in the New World, possibly as a result of the well-documented Plio-Pleistocene climatic fluctuations.

Latitudinal shift in thermal niche breadth results from thermal release during a climate‐mediated range expansion

Abstract: AimClimate change is currently altering the geographical distribution of species, but how this process contributes to biogeographical variation in ecological traits is unknown. Range-shifting species are predicted to encounter and respond to new selective regimes during their expansion phase, but also carry historical adaptations to their ancestral range. We sought to identify how historical and novel components of the environment interact to shape latitudinal trends in thermal tolerance, thermal tolerance breadth and phenotypic plasticity of a range-shifting species. LocationSouthern and central Sweden. MethodsTo evaluate phenotypic responses to changes in the thermal selective environment, we experimentally determined the upper and lower thermal tolerances of >2000 wild-caught damselflies (Ischnura elegans) from populations distributed across core and expanding range-edge regions. We then identified changing correlations between thermal tolerance, climate and recent weather events across the range expansion. Niche modelling was employed to evaluate the relative contributions of varying climatic selective regimes to overall habitat suitability for the species in core versus range-edge regions. ResultsUpper thermal tolerance exhibited local adaptation to climate in the core region, but showed evidence of having been released from thermal selection during the current range expansion. In contrast, chill coma recovery exhibited local adaptation across the core region and range expansion, corresponding to increased climatic variability at higher latitudes. Adaptive plasticity of lower thermal tolerances (acclimation ability) increased towards the northern, expanding range edge. Main conclusionsOur results suggest micro-evolutionary mechanisms for several large-scale and general biogeographical patterns, including spatially and latitudinally invariant heat tolerances (Brett's rule) and increased thermal acclimation rates and niche breadths at higher latitudes. Population-level processes unique to climate-mediated range expansions may commonly underpin many broader, macro-physiological trends.