Facilitate Range Shifts Research Articles

Can large-scale tree planting in China compensate for the loss of climate connectivity due to deforestation?

Extensive deforestation has been a major reason for the loss of forest connectivity, impeding species range shifts under current climate change. Over the past decades, the Chinese government launched a series of afforestation and reforestation projects to increase forest cover, yet whether the new forests can compensate for the loss of connectivity due to deforestation—and where future tree planting would be most effective—remains largely unknown. Here, we evaluate changes in climate connectivity across China's forests between 2015 and 2019. We find that China's large-scale tree planting alleviated the negative impacts of forest loss on climate connectivity, improving the extent and probability of climate connectivity by 0–0.2 °C and 0–0.03, respectively. The improvements were particularly obvious for species with short dispersal distances (i.e., 3 km and 10 km). Nevertheless, only ~55 % of the trees planted in this period could serve as stepping stones for species movement. This indicates that focusing solely on the quantitative target of forest coverage without considering the connectivity of forests may miss opportunities in tree planting to facilitate climate-induced range shifts. More attention should be paid to the spatial arrangement of tree plantations and their potential as stepping stones. We then identify priority areas for future tree planting to create effective stepping stones. Our study highlights the potential of large-scale tree planting to facilitate range shifts. Future tree-planting efforts should incorporate the need for species range shifts to achieve more biodiversity conservation benefits under climate change.

Future Range Shifts Suggest That the Six-Spined Spruce Bark Beetle Might Pose a Greater Threat to Norway Spruce in Europe than the Eight-Spined Spruce Bark Beetle

Both the eight-spined spruce bark beetle (eight-spined beetle, Ips typographus) and the six-spined spruce bark beetle (six-spined beetle, Pityogenes chalcographus) have major deleterious effects on Norway spruce (i.e., Picea abies, the host tree) in Europe. However, future potential range shifts of the two pests and their range overlap with Norway spruce have not yet been characterized. Through range dynamic models, we characterized their future range expansions, as well as their range overlap with their host tree under current–future change scenarios in 2100. Host availability was the greatest contributor to the range shifts of the two pests, and climatic changes were the main drivers of the range expansion of the host. The potential range, expanded range, and overlapped range were larger for the six-spined beetle than for the eight-spined beetle. The host tree, i.e., Norway spruce, might face increasing threats from the two pests in the future. Future climate change will likely indirectly facilitate range shifts of pests by promoting increases in the area capable of sustaining the host tree. The six-spined beetle might pose a greater threat to Norway spruce than the eight-spined beetle, albeit the latter has previously been considered to have more deleterious effects on Norway spruce.

Decoupling pioneering traits from latitudinal patterns in a north American bird experiencing a southward range shift.

Ecogeographic rules describe spatial patterns in biological trait variation and shed light on the drivers of such variation. In animals, a consensus is emerging that 'pioneering' traits may facilitate range shifts via a set of bold, aggressive and stress-resilient traits. Many of these same traits are associated with more northern latitudes, and most range shifts in the northern hemisphere indicate northward movement. As a consequence, it is unclear whether pioneering traits are simply corollaries of existing latitudinal variation, or whether they override other well-trodden latitudinal patterning as a unique ecogeographic rule of phenotypic variation. The tree swallow Tachycineta bicolor is a songbird undergoing a southward range shift in the eastern United States, in direct opposition of the poleward movement seen in most other native species' range shifts. Because this organic range shift countervails the typical direction of movement, this case study provides for unique ecological insights on organisms and their ability to thrive in our changing world. We sampled female birds across seven populations, quantifying behavioural, physiological and morphological traits. We also used GIS and field data to quantify a core set of ecological factors with strong ties to these traits as well as female performance. Females at more southern expansion sites displayed higher maternal aggression, higher baseline corticosterone and more pronounced elevation of corticosterone following a standardized stressor, contrary to otherwise largely conserved latitudinal patterning in these traits. Microhabitat variation explained some quantitative phenotypic variation, but the expansion and historic ranges did not differ in openness, distance to water or breeding density. This countervailing range shift therefore suggests that pioneering traits are not simply corollaries of existing latitudinal variation, but rather, they may override other well-trodden latitudinal patterning as a unique ecogeographic rule of phenotypic variation.

Variation in intraspecific demography drives localised concordance but species-wide discordance in response to past climatic change

BackgroundUnderstanding how species biology may facilitate resilience to climate change remains a critical factor in detecting and protecting species at risk of extinction. Many studies have focused on the role of particular ecological traits in driving species responses, but less so on demographic history and levels of standing genetic variation. Additionally, spatial variation in the interaction of demographic and adaptive factors may further complicate prediction of species responses to environmental change. We used environmental and genomic datasets to reconstruct the phylogeographic histories of two ecologically similar and largely co-distributed freshwater fishes, the southern (Nannoperca australis) and Yarra (N. obscura) pygmy perches, to assess the degree of concordance in their responses to Plio-Pleistocene climatic changes. We described contemporary genetic diversity, phylogenetic histories, demographic histories, and historical species distributions across both species, and statistically evaluated the degree of concordance in co-occurring populations.ResultsMarked differences in contemporary genetic diversity, historical distribution changes and historical migration were observed across the species, with a distinct lack of genetic diversity and historical range expansion suggested for N. obscura. Although several co-occurring populations within a shared climatic refugium demonstrated concordant demographic histories, idiosyncratic population size changes were found at the range edges of the more spatially restricted species. Discordant responses between species were associated with low standing genetic variation in peripheral populations. This might have hindered adaptive potential, as documented in recent demographic declines and population extinctions for the two species.ConclusionOur results highlight both the role of spatial scale in the degree of concordance in species responses to climate change, and the importance of standing genetic variation in facilitating range shifts. Even when ecological traits are similar between species, long-term genetic diversity and historical population demography may lead to discordant responses to ongoing and future climate change.

Hot and bothered: The role of behaviour and microclimates in buffering species from rising temperatures.

In Focus: Bladon, A. J., Lewis, M., Bladon, E. K., Buckton, S. J., Corbett, S., Ewing, S. R., … Turner, E. C. (2020). How butterflies keep their cool: Physical and ecological traits influence thermoregulatory ability and population trends. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.13319 Threatened with rising average temperatures and the new normal of climate extremes, species that cannot keep pace with climate change must adapt where they are, or face extinction. The ranges of many British butterflies have indeed extended northwards as the climate has warmed, but this option is increasingly restricted by the expansion and intensification of urban and agricultural lands. On a day-to-day basis, butterflies can thermoregulate using behaviours such as adjusting their wing positioning or moving into suitable microclimates. The extent to which these two options buffer individuals from free-air temperature, however, is not well known. Nor is the extent to which the different mechanisms are exploited by different species, and whether that has had any bearing on species' population trends over the time-scale of recent climate change. Using a simple and easily replicated approach, Bladon etal.(2020) were able to quantify intra- and interspecific variation in buffering ability, and species' relative reliance on the two thermoregulatory mechanisms of wing adjustment versus microclimate selection. The authors report marked variation in buffering capacity, correlated with wing size, wing colouration and taxonomic family. Species also differed in their thermoregulatory behaviours, with some - such as the Ringlet Aphantopus hyperantus and Large Skipper Ochlodes sylvanus-achieving impressive buffering through wing positioning. Others, like the Brown Argus Aricia agestis and Small Heath Coenonympha pamphilus, were more reliant on microclimate selection, and these were the species most likely to have shown declining population trends over the past 40years. The study underscores the importance of individual thermoregulatory behaviours for understanding species' vulnerability to climate change. In combination with much improved methods for measuring and modelling climate at biologically relevant scales, the approach of Bladon etal.(2020) can and should be extended to identify the places and species most at risk, and the steps that conservation practitioners can take to maximise resilience to climate change. Much attention has been given to improving habitat connectivity to facilitate range shifts, but we should also consider how microclimate availability can be enhanced to allow species to manage when they cannot move.

Incorporating future climate uncertainty into the identification of climate change refugia for threatened species

Climate change presents a substantial threat to species unable to keep pace via migration or adaptation. In-situ climate refugia, areas currently occupied by a species and that remain suitable in the future, will be vital for species with dispersal limitations. Ex-situ refugia, areas beyond species' current ranges that remain suitable, may facilitate range shifts or provide options for translocation. Assessing both refugia is a conservation priority. Here, we identify refugia for 319 species threatened in New South Wales, using four plausible scenarios describing futures that are Warmer/Wetter, Warmer/Drier, Hotter/Wetter and Hotter/Little Precipitation change, relative to the present. Using Maxent, we identify (a) in-situ refugia for each species under each scenario; (b) regions of consensus – areas projected as in-situ refugia across all scenarios; (c) hotspots of in-situ refugia (regions suitable for >1 species); and (d) regions of consensus for ex-situ refugia. Species were categorised based on the extent of in- and ex-situ refugia. By 2070, refugia will likely be broadest, and narrowest, under the Warmer/Wetter and Hotter/Wetter scenarios, respectively. East coast regions currently suitable for multiple species are unlikely to remain as hotspots. Most species (65%) are projected to have limited regions of consensus for either refugia. Translocation should be explored for species with little-to-no in-situ refugia, but for which ex-situ refugia exist. Management of existing populations will be critical for species with in-situ refugia but limited ex-situ. We highlight how management decisions based on agreement across climate scenarios can be made, irrespective of uncertainty about the magnitude of climate change.

Global loss of climate connectivity in tropical forests

Range shifts are a crucial mechanism enabling species to avoid extinction under climate change1,2. The majority of terrestrial biodiversity is concentrated in the tropics3, including species considered most vulnerable to climate warming4, but extensive and ongoing deforestation of tropical forests is likely to impede range shifts5,6. We conduct a global assessment of the potential for tropical species to reach analogous future climates—‘climate connectivity’—and empirically test how this has changed in response to deforestation between 2000 and 2012. We find that over 62% of tropical forest area (~10 million km2) is already incapable of facilitating range shifts to analogous future climates. In just 12 years, continued deforestation has caused a loss of climate connectivity for over 27% of surviving tropical forest, with accelerating declines in connectivity as forest loss increased. On average, if species’ ranges shift as far down climate gradients as permitted by existing forest connectivity, by 2070 they would still experience 0.77 °C of warming under the least severe climate warming scenario and up to 2.6 °C warming for the most severe scenario. Limiting further forest loss and focusing the global restoration agenda towards creating climate corridors are global priorities for improving resilience of tropical forest biotas under climate change. Physically connected habitats are required for terrestrial species to shift their liveable ranges as the tropics warm. The authors show that over half of tropical forest area is currently unable to provide such climate connectivity, and that loss of connectivity is accelerating with deforestation.

Integrating measures of long-distance dispersal into vertebrate conservation planning: scaling relationships and parentage-based dispersal analysis in the koala

Improved knowledge of dispersal parameters across multiple populations is essential for the effective management of species exposed to ongoing threats from habitat loss, fragmentation and climate change. Currently, management decisions are based on incomplete or insufficient knowledge of key dispersal parameters, especially long-distance dispersal, and its role in maintaining metapopulation connectivity, facilitating range shifts under climate change, or enabling the colonization of new habitats. Using a combination of microsatellite-based population genetic analyses, scaling relationships and parentage-based dispersal analysis we investigated levels and patterns of long-distance dispersal in the koala. Using home range size as a scalar predicted spatial variation in maximum dispersal distance amongst regional populations (range 13.4–43.4 km), while parentage-based dispersal analysis showed that long-distance dispersal (> 11.2 km) accounted for 16.7–18.5% of movements in a focal population. Common movement patterns were discerned, despite varying levels of imprecision and bias, that suggest an important role for long-distance dispersal in maintaining metapopulation connectivity. Our results suggest that implementation of a systematic approach to the estimation of dispersal across multiple populations would benefit koala conservation and management. This will require the use of both empirical and simulation studies to quantify and minimize sources of imprecision and bias that can occur including those related to incomplete sampling, the presence of fine-scale spatial genetic structure and areas of localized inbreeding. As limitations associated with partial sampling are likely to remain an inherent feature of large-scale dispersal studies, a large number of loci should be assayed.

Identifying riparian climate corridors to inform climate adaptation planning.

Riparian habitats have been frequently identified as priority areas for conservation under climate change because they span climatic gradients and have cool, moist microclimates relative to surrounding areas. They are therefore expected to act as dispersal corridors for climate-induced species range shifts and to provide microclimatic refugia from warming. Despite recognition of these values, rigorous methods to identify which riparian areas are most likely to facilitate range shifts and provide refugia are currently lacking. We completed a novel analysis across the Pacific Northwest, USA, that identifies potential riparian corridors featuring characteristics expected to enhance their ability to facilitate range shifts and provide refugia. These features include large temperature gradients, high canopy cover, large relative width, low exposure to solar radiation, and low levels of human modification. These variables were used to calculate a riparian climate-corridor index using a multi-scale approach that incorporates results ranging in scale from local watersheds to the entire Pacific Northwest. Resulting index values for potential riparian corridors in the Pacific Northwest were highest within mountainous areas and lowest within relatively flat, lowland regions. We also calculated index values within ecoregions, to better identify high-value riparian climate corridors within the relatively flat, degraded areas where they may most contribute to climate adaptation. We found that high-value riparian climate-corridors are least protected in flat, lowland areas, suggesting that such corridors should be high priorities for future conservation effort. Our analysis provides critical information on valuable riparian climate-corridors to guide climate adaptation efforts (and riparian management and restoration efforts) in the Pacific Northwest, while offering a novel approach that may be applied to similar efforts in other geographies.

Local adaptation of trees at the range margins impacts range shifts in the face of climate change

AbstractAimThe ability of tree species to track their climatic niche at rates comparable to global warming is of concern, particularly if they are constrained by local adaptation. If a species is locally adapted at its range margin, it could be beneficial for range expansion because it ensures that the genotypes colonizing new areas are the fittest, given that environmental conditions are more similar to the current ones. In trees, local adaptation can slow range expansion when climate change happens much faster than their ability to migrate.LocationQuébec, Canada.Time period2013–2015.Major taxa studiedTrees.MethodsWe investigate experimentally a series of factors thought to constrain the seedling phase at the leading edge of the distribution of a dominant tree species, sugar maple (Acer saccharum Marshall.). We established a seed transplant experiment using six provenances, representing the latitudinal species range, and transplanted them to 12 sites within, at and beyond the current northern species range margin.ResultsAt present, northern provenances provide the best opportunity for establishment beyond the current range, where climatic conditions are more similar than those of the warmer central or southern portions of the species range. Establishment was highest within the species range, but survival rates were comparable to those at the range margin and beyond, regardless of provenance. We also found that the local climate was the most influential factor for early seedling establishment and survival; however, a lack of suitable microsites also significantly constrained recruitment.Main conclusionsOur study highlights the complex interaction between provenance, climate and microsite conditions that is required to ensure successful seedling recruitment. Although sugar maple is currently displaying evidence for local adaptation to facilitate range shifts, it could risk maladaptation in the future if the local climate warms beyond a threshold required to ensure seed germination and a lack of favourable microsite conditions beyond the range.

Distributional responses to marine heat waves: insights from length frequencies across the geographic range of the endemic reef fish Choerodon rubescens

Range shifts as a result of warming oceans call for evaluation of populations at the geographic range level, particularly for highly vulnerable species such as endemics and fisheries targets. We examined the influence of latitudinal temperature gradients and temperature anomalies during a 2011 marine heat wave on range-wide abundance, length frequency and recruitment of Choerodon rubescens, a reef associated fisheries target endemic to Western Australia. Diver-operated stereo-video surveys were conducted at shallow reefs (3–18 m) along 124 sites spanning the entire species’ distribution (21°S–34°S), to obtain abundance, length frequency and habitat data. Models were used to assess the influence of satellite-derived long-term average temperature (2002–2010) and 2011 temperature anomalies, compared to habitat, depth and distance to mainland, on the abundance of adult and juvenile fish and overall population size structure. Long-term temperature had the highest effect on adult C. rubescens abundance, with highest values recorded towards the centre of the temperature gradient investigated (22 °C). In contrast, juveniles were mostly influenced by 2011 temperature anomalies, with highest abundance recorded towards the cooler range edge, where anomalies were lowest. Length-frequency distributions showed recent recruitment towards the cooler range edge coupled with recruitment absence at the warmer edge. Recruitment differences were traced to 2011–2013 when ocean temperatures were up to 3.5 °C higher than average, via back-calculation of juvenile ages. These findings support predictions of a poleward distributional shift in response to ocean warming, and suggest that marine heatwaves can facilitate range shifts by affecting recruitment across latitudinal gradients.

Adaptive evolution to novel predators facilitates the evolution of damselfly species range shifts.

Most species have evolved adaptations to reduce the chances of predation. In many cases, adaptations to coexist with one predator generate tradeoffs in the ability to live with other predators. Consequently, the ability to live with one predator may limit the geographic distributions of species, such that adaptive evolution to coexist with novel predators may facilitate range shifts. In a case study with Enallagma damselflies, we used a comparative phylogenetic approach to test the hypothesis that adaptive evolution to live with a novel predator facilitates range size shifts. Our results suggest that the evolution of Enallagma shifting from living in ancestral lakes with fish as top predators, to living in lakes with dragonflies as predators, may have facilitated an increase in their range sizes. This increased range size likely arose because lakes with dragonflies were widespread, but unavailable as a habitat throughout much of the evolutionary history of Enallagma because they were historically maladapted to coexist with dragonfly predators. Additionally, the traits that have evolved as defenses against dragonflies also likely enhanced damselfly dispersal abilities. While many factors underlie the evolutionary history of species ranges, these results suggest a role for the evolution of predator-prey interactions.

Do group dynamics affect colour morph clines during a range shift?

Species exhibiting colour polymorphism are thought to have an ecological advantage at the landscape scale, because spatial segregation of alternatively adapted ecotypes into diverse habitats can increase the species' niche breadth and thus confer greater geographic range size. However, morph frequencies are also influenced by intrapopulational processes such as frequency- or density-dependent social interactions. To identify how social feedback may affect clinal variation in morph frequencies, we investigated reciprocal interactions between morph-specific thermal tolerance, local climatic conditions and social environments, in the context of a colour-morph frequency cline associated with a recent range expansion in blue-tailed damselflies (Ischnura elegans) in Sweden. Cold tolerances of gynochromes (female-like female morph) were positively correlated with local gynochrome frequencies, suggesting a positive frequency-dependent fitness benefit. In contrast, androchrome (male-mimic female morph) cold tolerances were improved following recent exposure to cold weather, suggesting a beneficial environmental acclimation effect. Thus, according to an environment-matching hypothesis for clinal variation, androchrome frequencies should therefore increase towards the (cooler) range limit. In contrast to this prediction, gynochrome frequencies increased at the expanding range limit, consistent with a positive frequency-dependent social feedback that is beneficial when invading novel climates. Our results suggest that when phenotypes or fitnesses are affected by interactions with conspecifics, beneficial social effects on environmental tolerances may (i) facilitate range shifts, and (ii) reverse or counteract typical patterns of intraspecific interactions and environment-matching clines observed in stable populations observed over broader geographic scales.

Planning for assisted colonization of plants in a warming world.

Assisted colonization is one way of facilitating range shifts for species that are restricted in their ability to move in response to climate change. Here we conceptualize and apply a new decision framework for modelling assisted colonization of plant species prior to in situ realization. Three questions were examined: a) Is species translocation useful in a certain area? b) where, and c) how long will it be successful in the future? Applying our framework to Carex foetida in Italy at the core of its distribution and its southern edge revealed that assisted colonization could be successful in short-term (2010–2039) climate conditions, partially in medium (2040–2069) but not in long-term (2070–2099) scenarios. We show that, for some species, it is likely that assisted colonization would be successful in some portions of the recipient site under current and short-term climate conditions, but over the mid- and long-term, climate changes will make species translocation unsuccessful. The proposed decision framework can help identify species that will need different conservation actions (seed banks and/or botanical gardens) when assisted colonization is unlikely to be successful. Furthermore it has broad applicability, as it can support planning of assisted migration in mountainous areas in the face of climate change.

Range expansion and retraction along a moving contact zone has no effect on the genetic diversity of two passerine birds

Disentangling the factors shaping species distributions remains a central goal in biogeography, ecology and evolutionary biology. The extrinsic pressures that may facilitate range shifts, such as climatic factors or biotic interactions are well known. However, in contrast, the possible intrinsic factors are manifold and hard to generalize across taxa. Recently, several theoretical studies have investigated the consequences of moving range borders on genetic diversity. However, empirical studies that support or refute these theoretical predictions are scarce. Moving contact zones between parapatric sister species are suitable models to test these hypotheses. Changes in genetic diversity can be tested simultaneously along the expanding and receding edges of two species of the contact zone while accounting for intra‐specific effects (e.g. introgression). The two Old World warblersHippolais polyglottaandH. icterinaform a narrow moving contact zone, where interspecific interactions are suspected to be the main factor shaping this zone. We investigated the population genetic structure of both species along a transect ranging from the core range of the expandingH. polyglottaacross the contact zone and far into the range of the recedingH. icterina. The theoretical predictions of changes in genetic diversity at the range edges were tested. No gradual change in genetic diversity was detected for both the expanding and the receding range margin. Furthermore, no genetic structure was found in either species supporting the hypothesis that long distance dispersal (LDD) occurs frequently due to the high mobility of these long‐distance migrants. The results suggest that when dispersal propensity is high and accompanied by frequent LDD events, then neither an enrichment nor a depletion of alleles along moving range edges would be detected. This these species as the probability to retain genetic diversity during exogenous induced range shifts is high in such mobile species.

Signals of climate, conspecific density, and watershed features in patterns of homing and dispersal by Pacific salmon.

It is widely assumed that rates of dispersal in animal populations are plastic in response to intrinsic and extrinsic cues, yet the factors influencing this plasticity are rarely known. This knowledge gap is surprising given the important role of dispersal in facilitating range shifts that may allow populations to persist in a rapidly changing global climate. We used two decades of tagging and recapture data from 19 hatchery populations of Oncorhynchus tshawytscha (Chinook salmon) in the Columbia River, USA, to quantify the effects of regional and local climate conditions, density dependence, watershed features such as area and position on the landscape, and direct anthropogenic influence on dispersal rates by adult salmon during the breeding season. We found that the probability of dispersal, termed "straying" in salmon, is plastic in'response to multiple factors and that populations showed varied responses that were largely idiosyncratic. A regional climate index (Pacific Decadal Oscillation), water temperatures in the mainstem Columbia River that was commonly experience by populations during migration, water temperatures in local subbasins unique to each population during the breeding season, migration distance, and density dependence had the strongest effects on dispersal. Patterns of dispersal plasticity in response to commonly experienced conditions were consistent with gene by environment interactions, though we are tentative about this interpretation given the domesticated history of these populations. Overall, our results warn against attempts to predict future range shifts of migratory species without considering population-specific dispersal plasticity, and also caution against the use of few populations to infer species-level patterns. Ultimately, our results provide evidence that analyses that examine the response of dispersal to single factors may be misleading.

Facilitating climate-change-induced range shifts across continental land-use barriers.

Climate changes impose requirements for many species to shift their ranges to remain within environmentally tolerable areas, but near-continuous regions of intense human land use stretching across continental extents diminish dispersal prospects for many species. We reviewed the impact of habitat loss and fragmentation on species' abilities to track changing climates and existing plans to facilitate species dispersal in response to climate change through regions of intensive land uses, drawing on examples from North America and elsewhere. We identified an emerging analytical framework that accounts for variation in species' dispersal capacities relative to both the pace of climate change and habitat availability. Habitat loss and fragmentation hinder climate change tracking, particularly for specialists, by impeding both propagule dispersal and population growth. This framework can be used to identify prospective modern-era climatic refugia, where the pace of climate change has been slower than surrounding areas, that are defined relative to individual species' needs. The framework also underscores the importance of identifying and managing dispersal pathways or corridors through semi-continental land use barriers that can benefit many species simultaneously. These emerging strategies to facilitate range shifts must account for uncertainties around population adaptation to local environmental conditions. Accounting for uncertainties in climate change and dispersal capabilities among species and expanding biological monitoring programs within an adaptive management paradigm are vital strategies that will improve species' capacities to track rapidly shifting climatic conditions across landscapes dominated by intensive human land use.

The performance of protected areas for biodiversity under climate change

Global environmental changes have been driving large-scale shifts in the distributions of species and in the composition of biological communities. This has thrown the continuing value of Protected Areas (PAs) into question, given that PAs remain static, whereas species move, and they are predicted to continue to move under future climate scenarios. We consider empirical evidence on the observed performance of PAs during the last 40 years of anthropogenic climate change. Despite some losses of populations and species, PAs have continued to accommodate many species, which have shifted to higher elevations, to polewards-facing aspects, and into cooler microhabitats within PAs as the climate has warmed. Even when species have declined in some PAs, they often remain more abundant inside than outside PAs. Furthermore, losses from some PAs are offset by increases in others. As species expand their ranges polewards across fragmented landscapes in response to climate warming, the majority are disproportionately colonizing PAs as they go. Hence, PA networks are acting as stepping-stones of suitable breeding conditions and facilitating range shifts, with many species remaining protected across PA networks as a whole. Finally, there is some evidence that appropriate management of PAs may be able to slow climate-related declines and accelerate expansions. The 40-year track record of species responding to environmental change in PAs suggests that networks of PAs have been essential to biodiversity conservation and are likely to continue to fulfil this role in the future. The challenge for managers will be to consider the balance between retaining current species and encouraging colonization by new species. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, ●●, ●●–●●.

Lattice-work corridors for climate change: a conceptual framework for biodiversity conservation and social-ecological resilience in a tropical elevational gradient

Rapid climate change poses complex challenges for conservation, especially in tropical developing countries where biodiversity is high while financial and technical resources are limited. The complexity is heightened by uncertainty in predicted effects, both for ecological systems and human communities that depend heavily on natural resource extraction and use. Effective conservation plans and measures must be inexpensive, fast-acting, and able to increase the resilience of both the ecosystem and the social-ecological system. We present conservation practitioners with a framework that strategically integrates climate change planning into connectivity measures for tropical mountain ecosystems in Costa Rica. We propose a strategy for doubling the amount of habitat currently protected in riparian corridors using measures that are relatively low cost and fast-acting, and will employ and expand human capital. We argue that habitat connectivity must be enhanced along latitudinal gradients, but also within the same elevational bands, via a lattice-work corridor system. This is needed to facilitate range shifts for mobile species and evolutionary adaptation for less mobile species. We think that conservation measures within the elevational bands must include conservation-friendly land uses that improve current and future human livelihoods under dynamic conditions. Key components include community involvement, habitat priority-setting, forest landscape restoration, and environmental services payments. Our approach is fundamentally adaptive in that the conservation measures employed are informed by on-the-ground successes and failures and modified accordingly, but are relatively low risk and fast-acting. Our proposal, if implemented, would satisfy tenets of climate-smart conservation, improve the resilience of human and ecological communities, and be a model for other locations facing similar challenges.

Upper thermal limits of Drosophila are linked to species distributions and strongly constrained phylogenetically

Upper thermal limits vary less than lower limits among related species of terrestrial ectotherms. This pattern may reflect weak or uniform selection on upper limits, or alternatively tight evolutionary constraints. We investigated this issue in 94 Drosophila species from diverse climates and reared in a common environment to control for plastic effects that may confound species comparisons. We found substantial variation in upper thermal limits among species, negatively correlated with annual precipitation at the central point of their distribution and also with the interaction between precipitation and maximum temperature, showing that heat resistance is an important determinant of Drosophila species distributions. Species from hot and relatively dry regions had higher resistance, whereas resistance was uncorrelated with temperature in wetter regions. Using a suite of analyses we showed that phylogenetic signal in heat resistance reflects phylogenetic inertia rather than common selection pressures. Current species distributions are therefore more likely to reflect environmental sorting of lineages rather than local adaptation. Similar to previous studies, thermal safety margins were small at low latitudes, with safety margins smallest for species occupying both humid and dry tropical environments. Thus, species from a range of environments are likely to be at risk owing to climate change. Together these findings suggest that this group of insects is unlikely to buffer global change effects through marked evolutionary changes, highlighting the importance of facilitating range shifts for maintaining biodiversity.