Niche dynamics in the European ranges of two African carnivores reflect their dispersal and demographic histories

According to recent phylogeographical evidence, the common genet (Genetta genetta) and the Egyptian mongoose (Herpestes ichneumon) have dissimilar dispersal histories from Maghreb to south‐western Europe. Through comparative ecological niche modelling based on >1100 occurrences, we assessed whether the niche dynamics (i.e. niche shift versus conservatism) of the two species in their European ranges reflected DNA‐based demographic scenarios. Sensitivity analyses and projections of climatic niche models from the species' native ranges (Africa and Middle East) to Europe yielded support for (1) partial climatic niche shift in the northern European range of the common genet and (2) climatic niche conservatism in the Egyptian mongoose. Our results were consistent with demographic scenarios that predicted multiple introductions and demographic expansion in the common genet and long‐term, stable historical demography in the Egyptian mongoose. Our models further predicted a range expansion of the common genet in north‐western France and Italy, and progression of the Egyptian mongoose into Europe from the Near East. Overall, our study suggested a scenario of different niche dynamics in Europe for these two species of African carnivores, supporting the view that historical factors such as dispersal and demographic history may shape niche dynamics and thus distribution potential in colonized ranges. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 737–751.     

Genetic signature of the northward expansion of the Egyptian mongoose Herpestes ichneumon (Herpestidae) in the Iberian Peninsula

In the last three decades, the range of the Egyptian mongoose (Herpestes ichneumon) has increased in the Iberian Peninsula. A panel of microsatellites was used to confront the patterns of genetic diversity of the species with the scenario of its recent northward expansion in its Iberian range. Evidence of substructure and significant genetic differentiation within the studied population were recorded, with a central‐northern subpopulation (CNorth) and a southern subpopulation (S). Northward range expansion was supported by the observed allelic frequencies, diversity parameters, and observed heterozygosity of the studied loci, with S showing a higher allelic diversity and a higher number of private alleles than CNorth. Patterns of isolation‐by‐distance and isolation‐by‐barrier as a result of the Tagus River were demonstrated, suggesting that the river acted as a semi‐permeable barrier, possibly leading to genetic differentiation of the studied population. The observed individuals from CNorth in southern locations and individuals from S in central/northern areas might comprise evidence for long‐range dispersals across the studied range. A bottleneck event after population expansion was supported by a significant heterozygosity deficiency in CNorth, which is in agreement with a scenario of founder events occurring in recently colonized areas after the crossing of the Tagus River.     

Climate change is the primary driver of white‐tailed deer (Odocoileus virginianus) range expansion at the northern extent of its range; land use is secondary

Quantifying the relative influence of multiple mechanisms driving recent range expansion of non‐native species is essential for predicting future changes and for informing adaptation and management plans to protect native species. White‐tailed deer (Odocoileus virginianus) have been expanding their range into the North American boreal forest over the last half of the 20th century. This has already altered predator–prey dynamics in Alberta, Canada, where the distribution likely reaches the northern extent of its continuous range. Although current white‐tailed deer distribution is explained by both climate and human land use, the influence each factor had on the observed range expansion would depend on the spatial and temporal pattern of these changes. Our objective was to quantify the relative importance of land use and climate change as drivers of white‐tailed deer range expansion and to predict decadal changes in white‐tailed deer distribution in northern Alberta for the first half of the 21st century. An existing species distribution model was used to predict past decadal distributions of white‐tailed deer which were validated using independent data. The effects of climate and land use change were isolated by comparing predictions under theoretical “no‐change between decades” scenarios, for each factor, to predictions under observed climate and land use change. Climate changes led to more than 88%, by area, of the increases in probability of white‐tailed deer presence across all decades. The distribution is predicted to extend 100 km further north across the northeastern Alberta boreal forest as climate continues to change over the first half of the 21st century.     

Is the future female for turtles? Climate change and wetland configuration predict sex ratios of a freshwater species

Climate change and land-use change are leading drivers of biodiversity decline, affecting demographic parameters that are important for population persistence. For example, scientists have speculated for decades that climate change may skew adult sex ratios in taxa that express temperature-dependent sex determination (TSD), but limited evidence exists that this phenomenon is occurring in natural settings. For species that are vulnerable to anthropogenic land-use practices, differential mortality among sexes may also skew sex ratios. We sampled the spotted turtle (Clemmys guttata), a freshwater species with TSD, across a large portion of its geographic range (Florida to Maine), to assess the environmental factors influencing adult sex ratios. We present evidence that suggests recent climate change has potentially skewed the adult sex ratio of spotted turtles, with samples following a pattern of increased proportions of females concomitant with warming trends, but only within the warmer areas sampled. At intermediate temperatures, there was no relationship with climate, while in the cooler areas we found the opposite pattern, with samples becoming more male biased with increasing temperatures. These patterns might be explained in part by variation in relative adaptive capacity via phenotypic plasticity in nest site selection. Our findings also suggest that spotted turtles have a context-dependent and multi-scale relationship with land use. We observed a negative relationship between male proportion and the amount of crop cover (within 300 m) when wetlands were less spatially aggregated. However, when wetlands were aggregated, sex ratios remained consistent. This pattern may reflect sex-specific patterns in movement that render males more vulnerable to mortality from agricultural machinery and other threats. Our findings highlight the complexity of species' responses to both climate change and land use, and emphasize the role that landscape structure can play in shaping wildlife population demographics.     

Climate connectivity of the bobcat in the Great Lakes region

The Great Lakes and the St. Lawrence River are imposing barriers for wildlife, and the additive effect of urban and agricultural development that dominates the lower Great Lakes region likely further reduces functional connectivity for many terrestrial species. As the climate warms, species will need to track climate across these barriers. It is important therefore to investigate land cover and bioclimatic hypotheses that may explain the northward expansion of species through the Great Lakes. We investigated the functional connectivity of a vagile generalist, the bobcat, as a representative generalist forest species common to the region. We genotyped tissue samples collected across the region at 14 microsatellite loci and compared different landscape hypotheses that might explain the observed gene flow or functional connectivity. We found that the Great Lakes and the additive influence of forest stands with either low or high canopy cover and deep lake‐effect snow have disrupted gene flow, whereas intermediate forest cover has facilitated gene flow. Functional connectivity in southern Ontario is relatively low and was limited in part by the low amount of forest cover. Pathways across the Great Lakes were through the Niagara region and through the Lower Peninsula of Michigan over the Straits of Mackinac and the St. Marys River. These pathways are important routes for bobcat range expansion north of the Great Lakes and are also likely pathways that many other mobile habitat generalists must navigate to track the changing climate. The extent to which species can navigate these routes will be important for determining the future biodiversity of areas north of the Great Lakes.     

Propagule pressure and land cover changes as main drivers of red and roe deer expansion in mainland Portugal

Aim

The management of the rapid expansion of wild ungulate populations is a challenging task and a societal priority. Using a progressive database of red (Cervus elaphus) and roe (Capreolus capreolus) deer colonization over the last three decades, we estimate the range expansion rates and the underlying mechanisms involved in the expansion patterns of red and roe deer populations at the south‐western edge of its European distribution.

Location

Mainland Portugal.

Methods

We compiled and grouped historical red and roe deer distribution data in three time periods (1981–1990, 1991–2000 and 2001–2010). We used generalized linear mixed models to evaluate how biotic and abiotic drivers determine the expansion patterns of red and roe deer.

Results

We reported a significant expansion of red and roe deer populations during the last three decades. The significant interaction between propagule pressure and land cover suggests that the effects of propagule pressure vary along environmental gradients. We found that the influence of livestock on red and roe deer expansion is idiosyncratic. Contrary to red deer, roe deer expansion was also influenced by climatic conditions. We did not detect any significant effect of human factors on the red and roe deer expansion.

Main conclusions

The synergistic effects between variables should be taken into account when studying the patterns of species expansion. Our study emphasize that policy makers should consider the spatial, temporal, ecological and societal nuances of species expansion in order to prioritize management measures and to allocate management budgets. Although concerted strategies to curtail species spread should mitigate red and roe deer economic and ecological impacts, these effects can be neutralized by a continuous rural exodus and the consequent forest and shrub encroachment.

     

Projected impacts of climate and land-use change on the global diversity of birds

Over the past few decades, land-use and climate change have led to substantial range contractions and species extinctions. Even more dramatic changes to global land cover are projected for this century. We used the Millennium Ecosystem Assessment scenarios to evaluate the exposure of all 8,750 land bird species to projected land-cover changes due to climate and land-use change. For this first baseline assessment, we assumed stationary geographic ranges that may overestimate actual losses in geographic range. Even under environmentally benign scenarios, at least 400 species are projected to suffer >50% range reductions by the year 2050 (over 900 by the year 2100). Although expected climate change effects at high latitudes are significant, species most at risk are predominantly narrow-ranged and endemic to the tropics, where projected range contractions are driven by anthropogenic land conversions. Most of these species are currently not recognized as imperiled. The causes, magnitude and geographic patterns of potential range loss vary across socioeconomic scenarios, but all scenarios (even the most environmentally benign ones) result in large declines of many species. Whereas climate change will severely affect biodiversity, in the near future, land-use change in tropical countries may lead to yet greater species loss. A vastly expanded reserve network in the tropics, coupled with more ambitious goals to reduce climate change, will be needed to minimize global extinctions.     

Novel spatial analysis methods reveal scale‐dependent spread and infer limiting factors of invasion by Sahara mustard

Multiple scale‐dependent ecological processes influence species distributions. Uncovering these drivers of dynamic range boundaries can provide fundamental ecological insights and vital knowledge for species management. We develop a transferable methodology that uses widely available data and tools to determine critical scales in range expansion and to infer dominating scale‐dependent forces that influence spread. We divide a focal geographic region into different sized square cells, representing different spatial scales. We then used herbarium records to determine the species' occupancy of cells at each spatial scale. We calculated the growth in cell occupancy across scales to infer the scale dependent expansion rate. This is the first time such a ‘box‐counting’ method is used to study range expansion. We coupled this multi‐scale analysis with species distribution models to determine the range and spatial scales where suitable climate allows the species to spread, and where other factors may be influencing the expansion. We demonstrate our methodology by assessing the spread of invasive Sahara mustard in North America. We detect critical scales where its spread is limited (100–500 km) or unconstrained (5–50 km) by climatic variables. Using climate‐based models to assess the similarity of climate envelopes in its native and invaded range, we find that the climate in the invaded range generally predicts the native distribution, suggesting that either there has been little local adaptation to climate occurring since introduction or the biological interaction experienced in the invaded range has not driven the species to occupy climatic conditions much different from its native range. Our novel method can be broadly utilized in other studies to generate critical insights into the scale dependency of different ecological drivers that influence the spread and distribution limits, as well as to help parameterizing predictions of future spread, and thus inform management decisions.     

Avian species richness and abundance at Lake Constance: diverging long-term trends in Passerines and Nonpasserines

In Central Europe, massive losses in species richness of breeding birds have been documented in the last decades, but the question arises whether species richness is currently still decreasing or again increasing due to conservation efforts. In this study, we investigated regional and local species richness as well as mean number of breeding pairs and mean biomass per tetrad over a period of some 20 years at Lake Constance. Three quantitative censuses of 303 tetrads (2 × 2 km²) repeated at 10-year intervals (1980–1981, 1990–1992, 2000–2002) revealed an increase in regional species richness (total number of breeding species). At the same time, however, a strong decline in local species richness (number of breeding species per tetrad), number of breeding pairs, and estimated biomass were observed. Changes of species richness differed markedly between Nonpasserine and Passerine birds. Whereas species richness of Nonpasserines remained constant from 1980 to 1990, and even increased between 1990 and 2000, that of Passerines decreased in both periods. This indicates that effects of conservation efforts apparently eclipse more general effects of climate and habitat change in Nonpasserines. The massive abundance and biomass losses observed in formerly common Passerine species are not compensated by gains in populations of Nonpasserine species. The results of the three bird censuses at Lake Constance imply that ongoing habitat degradation and human impacts as well as increasing effects of climate change are the main drivers of the observed population changes.     

Arctic fox versus red fox in the warming Arctic: four decades of den surveys in north Yukon

During the last century, the red fox (Vulpes vulpes) has expanded its distribution into the Arctic, where it competes with the arctic fox (Vulpes lagopus), an ecologically similar tundra predator. The red fox expansion correlates with climate warming, and the ultimate determinant of the outcome of the competition between the two species is hypothesized to be climate. We conducted aerial and ground fox den surveys in the northern Yukon (Herschel Island and the coastal mainland) to investigate the relative abundance of red and arctic foxes over the last four decades. This region has undergone the most intense warming observed in North America, and we hypothesized that this climate change led to increasing dominance of red fox over arctic fox. Results of recent surveys fall within the range of previous ones, indicating little change in the relative abundance of the two species. North Yukon fox dens are mostly occupied by arctic fox, with active red fox dens occurring sympatrically. While vegetation changes have been reported, there is no indication that secondary productivity and food abundance for foxes have increased. Our study shows that in the western Arctic of North America, where climate warming was intense, the competitive balance between red and arctic foxes changed little in 40?years. Our results challenge the hypotheses linking climate to red fox expansion, and we discuss how climate warming’s negative effects on predators may be overriding positive effects of milder temperatures and longer growing seasons.     

Potential impact of climate warming on the distribution of the Golden-striped salamander, Chioglossa lusitanica, on the Iberian Peninsula

The increase in the concentration of greenhouse gases in the atmosphere is expected to impact the world's climate on a time-scale of just decades. We simulated the potential impact of climate warming on the range of the Iberian endemic Golden-striped salamander, Chioglossa lusitanica, by extrapolating present-day GIS-based distribution models. The results indicated a significant decrease in the distribution of the species for 2050 and 2080, with losses ranging from 19 to 35% in Portugal and from 17 to 22% in Spain. The models also predict the fragmentation of the species range, in a pattern mirroring past distributions inferred from the spatial analysis of genetic data.     

Drivers of sett site location by European badgers in Portugal

European badgers (Meles meles) are considered central-place foragers, whose spatial ecology is predominantly determined by sett location. Many studies have assessed the factors determining sett site selection throughout this species’ range, but these have often been geographically limited and have primarily identified locally dependent factors. To infer key factors determining sett location, a broader scale approach is needed. Between June 2014 and January 2017, we surveyed mainland Portugal to detect badger setts in 10?×?10 km cells, corresponding to a total of 657.5 km walked line transects. We detected 54 main setts in 136 surveyed cells. Each sett and non-sett site (i.e. transects without setts) was characterised using bioenvironmental variables (e.g. land cover, presence of human infrastructure, soil). We used generalized linear mixed models to test five hypotheses potentially explaining sett location: land cover composition; anthropogenic disturbance; abiotic environmental drivers; trophic resource availability; and a combined effect of all these factors. Our findings show that the key factors for badger sett site selection in Portugal are: (1) disturbance avoidance (low beehive density; absence of livestock; far from hunting reserves), but with a tendency to be located close to highways and unpaved roads; and (2) ease of excavation (avoidance of sedimentary/metamorphic composite rocks). Although specific factors among these drivers may be more important locally or regionally, these major drivers have also been identified elsewhere in Europe. Our nationwide approach contributes to a broader understanding of general patterns of sett site selection by badgers in southern Europe. Furthermore, it provides the national authorities with novel and broad-scale data to facilitate sustainable species conservation of badgers in the southwestern limit of their range.     

Climate change affects populations of northern birds in boreal protected areas

Human land-use effects on species populations are minimized in protected areas and population changes can thus be more directly linked with changes in climate. In this study, bird population changes in 96 protected areas in Finland were compared using quantitative bird census data, between two time slices, 1981-1999 and 2000-2009, with the mean time span being 14 years. Bird species were categorized by distribution pattern and migratory strategy. Our results showed that northern bird species had declined by 21 per cent and southern species increased by 29 per cent in boreal protected areas during the study period, alongside a clear rise (0.7-0.8 °C) in mean temperatures. Distribution pattern was the main factor, with migratory strategy interacting in explaining population changes in boreal birds. Migration strategy interacted with distribution pattern so that, among northern birds, densities of both migratory and resident species declined, whereas among southern birds they both increased. The observed decline of northern species and increase in southern species are in line with the predictions of range shifts of these species groups under a warming climate, and suggest that the population dynamics of birds are already changing in natural boreal habitats in association with changing climate.     

Differential population responses of native and alien rodents to an invasive predator,habitat alteration and plant masting

Invasive species and anthropogenic habitat alteration are major drivers of biodiversity loss. When multiple invasive species occupy different trophic levels, removing an invasive predator might cause unexpected outcomes owing to complex interactions among native and non-native prey. Moreover, external factors such as habitat alteration and resource availability can affect such dynamics. We hypothesized that native and non-native prey respond differently to an invasive predator, habitat alteration and bottom-up effects. To test the hypothesis, we used Bayesian state-space modelling to analyse 8-year data on the spatio-temporal patterns of two endemic rat species and the non-native black rat in response to the continual removal of the invasive small Indian mongoose on Amami Island, Japan. Despite low reproductive potentials, the endemic rats recovered better after mongoose removal than did the black rat. The endemic species appeared to be vulnerable to predation by mongooses, whose eradication increased the abundances of the endemic rats, but not of the black rat. Habitat alteration increased the black rat''s carrying capacity, but decreased those of the endemic species. We propose that spatio-temporal monitoring data from eradication programmes will clarify the underlying ecological impacts of land-use change and invasive species, and will be useful for future habitat management.     

Life at the edge: Roe deer occurrence at the opposite ends of their geographical distribution,Norway and Portugal

In the face of climate change and habitat fragmentation there is an increasingly urgent need to learn more about factors that influence species distribution patterns and levels of environmental tolerance. Particular insights can be obtained by looking at the edges of a species range, especially from species with wide distributions. The European roe deer was chosen as a model species due to its widespread distribution. By using pellet group counts, we studied summer and winter habitat use of this herbivore at two of the extreme edges of its distribution – southwest of Portugal, and northeast of Norway – in relation to a range of fine-scale environmental factors including forest structure, vegetation characteristics and human disturbance. Our first prediction that roe deer would respond differently to human activity in both counties was supported. While in Norway roe deer are always close to houses, in Portugal they are either far (in summer) or indifferent (winter). However, everywhere and in every season, roe deer are far from roads. Our second prediction that roe deer better tolerate anthropogenic disturbances in the area where the importance of limiting factors is higher (Norway) was validated. However, our third prediction that anthropogenic disturbance would be less tolerated by roe deer outside the limiting seasons in each country was not supported. Our results suggest that roe deer perceive human activities differently in the two countries and that roe deer better tolerate anthropogenic disturbances in Norway.     

Individualistic species limitations of climate‐induced range expansions generated by meso‐scale dispersal barriers

Aim Evidence indicates that species are responding to climate change through distributional range shifts that track suitable climatic conditions. We aim to elucidate the role of meso‐scale dispersal barriers in climate‐tracking responses. Location South coast of England (the English Channel). Methods Historical distributional data of four intertidal invertebrate species were logistically regressed against sea surface temperature (SST) to determine a climate envelope. This envelope was used to estimate the expected climate‐tracking response since 1990 along the coast, which was compared with observed range expansions. A hydrodynamic modelling approach was used to identify dispersal barriers and explore disparities between expected and observed climate tracking. Results Range shifts detected by field survey over the past 20 years were less than those predicted by the changes that have occurred in SST. Hydrodynamic model simulations indicated that physical barriers produced by complex tidal currents have variably restricted dispersal of pelagic larvae amongst the four species. Main conclusions We provide the first evidence that meso‐scale hydrodynamic barriers have limited climate‐induced range shifts and demonstrate that life history traits affect the ability of species to overcome such barriers. This suggests that current forecasts may be flawed, both by overestimating range shifts and by underestimating climatic tolerances of species. This has implications for our understanding of climate change impacts on global biodiversity.     

Expanding northward: influence of climate change,forest connectivity,and population processes on a threatened species' range shift

Species' ranges are dynamic, shifting in response to a large number of interrelated ecological and anthropogenic processes. Climate change is thought to be one of the most influential drivers of range shifts, but the effects of other confounded ecological processes are often ignored even though these processes may modify expected range responses to climate change. To determine the relative effects of climate, forest availability, connectivity, and biotic processes such as immigration and establishment, we examine range changes occurring in a species of bird, the Hooded Warbler (Wilsonia citrina). We focus predominantly on the periphery of the species' northern range in Canada but we also examine data from the entire species' range. Nesting records in southern Ontario were obtained from two breeding bird Atlases of Ontario separated by a period of 20 years (1981–1985 and 2001–2005), and the rate of range expansion was estimated by comparing the number of occupied areas in each Atlas. Twelve hypotheses of the relationship between the rate of range expansion and factors known to influence range change were examined using model‐selection techniques and a mixed modeling approach (zero‐inflated Poisson's regression). Cooler temperatures were positively related to a lack of range expansion indicating that climate constrained the species' distribution. Establishment probability (based on the number of occupied, neighboring Atlas squares) and immigration from populations to the south (estimated using independent data from the North American Breeding Bird Survey) were also important predictors of range expansion. These biotic process variables can mask the effects of forest availability and connectivity on range expansion. Expansion due to climate change may be slower in fragmented systems, but the rate of expansion will be influenced largely by biotic processes such as proximity to neighboring populations.     

Disentangling the relative importance of changes in climate and land-use intensity in driving recent bird population trends

Threats to biodiversity resulting from habitat destruction and deterioration have been documented for many species, whilst climate change is regarded as increasingly impacting upon species' distribution and abundance. However, few studies have disentangled the relative importance of these two drivers in causing recent population declines. We quantify the relative importance of both processes by modelling annual variation in population growth of 18 farmland bird species in the UK as a function of measures of land-use intensity and weather. Modelled together, both had similar explanatory power in accounting for annual fluctuations in population growth. When these models were used to retrodict population trends for each species as a function of annual variation in land-use intensity and weather combined, and separately, retrodictions incorporating land-use intensity were more closely linked to observed population trends than retrodictions based only on weather, and closely matched the UK farmland bird index from 1970 onwards. Despite more stable land-use intensity in recent years, climate change (inferred from weather trends) has not overtaken land-use intensity as the dominant driver of bird populations.     

Linking habitat use to range expansion rates in fragmented landscapes: a metapopulation approach

Temperature increases because of climate change are expected to cause expansions at the high latitude margins of species distributions, but, in practice, fragmented landscapes act as barriers to colonization for most species. Understanding how species distributions will shift in response to climate change therefore requires techniques that incorporate the combined effects of climate and landscape‐scale habitat availability on colonization rates. We use a metapopulation model (Incidence Function Model, IFM) to test effects of fine‐scale habitat use on patterns and rates of range expansion by the butterfly Hesperia comma. At its northern range margin in Britain, this species has increased its breadth of microhabitat use because of climate warming, leading to increased colonization rates. We validated the IFM by reconstructing expansions in five habitat networks between 1982 and 2000, before using it to predict metapopulation dynamics over 100 yr, for three scenarios based on observed changes to habitat use. We define the scenarios as “cold‐world” (only hot, south‐facing 150–250° hillsides are deemed warm enough), “warm‐world” in which 100–300° hillsides can be populated, and “hot‐world”, where the background climate is warm enough to enable use of all aspects (as increasingly observed). In the simulations, increased habitat availability in the hot‐world scenario led to faster range expansion rates, and to long‐term differences in distribution size and pattern. Thus, fine‐scale changes in the distribution of suitable microclimates led to landscape‐scale changes in population size and colonization rate, resulting in coarse‐scale changes to the species distribution. Despite use of a wider range of habitats associated with climate change, H. comma is still expected to occupy a small fraction of available habitat in 100 yr. The research shows that metapopulation models represent a potential framework to identify barriers to range expansion, and to predict the effects of environmental change or conservation interventions on species distributions and persistence.     

Specialization in plant-hummingbird networks is associated with species richness, contemporary precipitation and quaternary climate-change velocity

Large-scale geographical patterns of biotic specialization and the underlying drivers are poorly understood, but it is widely believed that climate plays an important role in determining specialization. As climate-driven range dynamics should diminish local adaptations and favor generalization, one hypothesis is that contemporary biotic specialization is determined by the degree of past climatic instability, primarily Quaternary climate-change velocity. Other prominent hypotheses predict that either contemporary climate or species richness affect biotic specialization. To gain insight into geographical patterns of contemporary biotic specialization and its drivers, we use network analysis to determine the degree of specialization in plant-hummingbird mutualistic networks sampled at 31 localities, spanning a wide range of climate regimes across the Americas. We found greater biotic specialization at lower latitudes, with latitude explaining 20-22% of the spatial variation in plant-hummingbird specialization. Potential drivers of specialization--contemporary climate, Quaternary climate-change velocity, and species richness--had superior explanatory power, together explaining 53-64% of the variation in specialization. Notably, our data provides empirical evidence for the hypothesized roles of species richness, contemporary precipitation and Quaternary climate-change velocity as key predictors of biotic specialization, whereas contemporary temperature and seasonality seem unimportant in determining specialization. These results suggest that both ecological and evolutionary processes at Quaternary time scales can be important in driving large-scale geographical patterns of contemporary biotic specialization, at least for co-evolved systems such as plant-hummingbird networks.