Different climatic envelopes among invasive populations may lead to underestimations of current and future biological invasions

Aim We explore the impact of calibrating ecological niche models (ENMs) using (1) native range (NR) data versus (2) entire range (ER) data (native and invasive) on projections of current and future distributions of three Hieracium species. Location H. aurantiacum, H. murorum and H. pilosella are native to Europe and invasive in Australia, New Zealand and North America. Methods Differences among the native and invasive realized climatic niches of each species were quantified. Eight ENMs in BIOMOD were calibrated with (1) NR and (2) ER data. Current European, North American and Australian distributions were projected. Future Australian distributions were modelled using four climate change scenarios for 2030. Results The invasive climatic niche of H. murorum is primarily a subset of that expressed in its native range. Invasive populations of H. aurantiacum and H. pilosella occupy different climatic niches to those realized in their native ranges. Furthermore, geographically separate invasive populations of these two species have distinct climatic niches. ENMs calibrated on the realized niche of native regions projected smaller distributions than models incorporating data from species’ entire ranges, and failed to correctly predict many known invasive populations. Under future climate scenarios, projected distributions decreased by similar percentages, regardless of the data used to calibrate ENMs; however, the overall sizes of projected distributions varied substantially. Main conclusions This study provides quantitative evidence that invasive populations of Hieracium species can occur in areas with different climatic conditions than experienced in their native ranges. For these, and similar species, calibration of ENMs based on NR data only will misrepresent their potential invasive distribution. These errors will propagate when estimating climate change impacts. Thus, incorporating data from species’ entire distributions may result in a more thorough assessment of current and future ranges, and provides a closer approximation of the elusive fundamental niche.     

Niche Conservatism and Future Changes in the Potential Area Coverage of Arundina graminifolia,an Invasive Orchid Species from Southeast Asia

The Asian orchid, Arundina graminifolia, has been introduced to many locations over the last 50 yr, predominantly in South and Central America. A list of localities of A. graminifolia was compiled and used to model potential climatic niches based on the maximum entropy method. The differences are presented between niches occupied by native and invasive populations of A. graminifolia, and possible changes in the potential range of the species are discussed on the basis of various climate change scenarios. The coverage of habitats suitable for A. graminifolia will be reduced under future climate changes scenarios. The created niche distribution models indicated a more significant reduction in the potential ecological niches of the studied species in its invasive range. Nevertheless, areas with potentially suitable bioclimatic conditions for A. graminifolia should be monitored to prevent future uncontrolled invasion of the orchid into new habitats and to study its impact on the local ecosystems, as vast areas of its potential niche in the Americas are still unoccupied.     

The naturalization status of African Spotted Orchid (Oeceoclades maculata) in Neotropics

Naturalization status of the African orchid introduced in the Neotropics, Oeceoclades maculata, was studied. Ecological niche modeling was applied to estimate the present distribution of the suitable habitats for the African Spotted Orchid. The similarity of the niches occupied by natural and invasive populations of the studied species was calculated. Moreover, future distribution of its suitable habitats was estimated on the basis of three different climatic change scenarios, and the potential further expansion scale was calculated based on range overlap test. Although currently O. maculata seems to have reached its potential limits of invasion in South America and as for now it should not spread to the new habitats, the species still has a potential of invasiveness in North America. The future climate changes will probably result in shifts in the distribution of African Spotted Orchid suitable niches thereby causing its expansion to the new areas.     

Thresholds of sea‐level rise rate and sea‐level rise acceleration rate in a vulnerable coastal wetland

Feedbacks among inundation, sediment trapping, and vegetation productivity help maintain coastal wetlands facing sea‐level rise (SLR ). However, when the SLR rate exceeds a threshold, coastal wetlands can collapse. Understanding the threshold helps address key challenges in ecology—nonlinear response of ecosystems to environmental change, promotes communication between ecologists and resource managers, and facilitates decision‐making in climate change policies. We studied the threshold of SLR rate and developed a new threshold of SLR acceleration rate on sustainability of coastal wetlands as SLR is likely to accelerate due to enhanced anthropogenic forces. Deriving these two thresholds depends on the temporal scale, the interaction of SLR with other environmental factors, and landscape metrics, which have not been fully accounted for before this study. We chose a representative marine‐dominated estuary in the northern Gulf of Mexico, Grand Bay in Mississippi, to test the concept of SLR thresholds. We developed a mechanistic model to simulate wetland change and then derived the SLR thresholds for Grand Bay. The model results show that the threshold of SLR rate in Grand Bay is 11.9 mm/year for 2050, and it drops to 8.4 mm/year for 2100 using total wetland area as a landscape metric. The corresponding SLR acceleration rate thresholds are 3.02 × 10^?4 m/year² and 9.62 × 10^?5 m/year² for 2050 and 2100, respectively. The newly developed SLR acceleration rate threshold can help quantify the temporal lag before the rapid decline in wetland area becomes evident after the SLR rate threshold is exceeded, and cumulative SLR a wetland can adapt to under the SLR acceleration scenarios. Based on the thresholds, SLR that will adversely impact the coastal wetlands in Grand Bay by 2100 will fall within the likely range of SLR under a high warming scenario (RCP 8.5), highlighting the need to avoid RCP 8.5 to preserve these marshes.     

Phylogeography and climatic niche evolution in live oaks (Quercus series Virentes) from the tropics to the temperate zone

Aim We investigated the phylogeography, geographical variation in leaf morphology, freezing tolerance and climatic niches of two widespread evergreen sister oak species (Quercus) in the series Virentes. Location South‐eastern USA, Mexico and Central America. Methods Nuclear microsatellites and non‐recombining nuclear and chloroplast DNA sequences were obtained from trees throughout the range of two sister lineages of live oaks, represented by Quercus virginiana in the temperate zone and Q. oleoides in the tropics. Divergence times were estimated for the two major geographical and genetic breaks. Differentiation in leaf morphology, analysed from field specimens, was compared with the molecular data. Freezing sensitivities of Q. virginiana and Q. oleoides populations were assessed in common garden experiments. Results The geographical break between Q. virginiana and Q. oleoides was associated with strong genetic differentiation of possible early Pleistocene origin and with differentiation in freezing sensitivity, climatic envelopes and leaf morphology. A second important geographical and genetic break within Q. oleoides between Costa Rica and the rest of Central America showed a mid‐Pleistocene divergence time and no differentiation in leaf morphology. Population genetic differentiation was greater but genetic diversity was lower within the temperate Q. virginiana than within the tropical Q. oleoides, and genetic breaks largely corresponded to breaks in leaf morphology. Main conclusions Two major breaks, one between Mexico and the USA at the boundary of the two species, and a more recent one within Q. oleoides between Honduras and Costa Rica, implicate climatic changes as potential causes. The latter break may be associated with the formation of the Cordillera de Guanacaste, which was followed by seasonal changes in precipitation. In the former case, an ‘out of the tropics’ scenario is hypothesized, in which the acquisition of freezing tolerance in Q. virginiana permitted colonization of and expansion in the temperate zone, while differences in climatic tolerances between the species limited secondary contact. More pronounced Pleistocene changes in climate and sea level in the south‐eastern USA relative to coastal Mexico and Central America may explain the greater population differentiation within temperate Q. virginiana and greater genetic diversity in tropical Q. oleoides. These patterns are predicted to hold for other taxa that span temperate and tropical zones of North and Central America.     

Exploring the effects of warming seas by using the optimal and pejus temperatures of the embryo of three Octopoda species in the Gulf of Mexico

Using data related to thermal optimal and pejus of the embryos of Octopus americanus from Brazil and O. insularis and O. maya from Mexico, this study aimed to project the potential distribution areas in the Gulf of Mexico and predict distribution shifts under different Representative Concentration Pathway scenarios (RCP 6 and 8.5) for the years 2050 and 2100. The different thermal tolerances elicited different responses to current and future scenarios. In this sense, O. insularis and O. maya thermal niches stretch from the Caribbean to Florida. Nevertheless, O. insularis may inhabit warmer areas than O. maya. Surprisingly, no area was considered thermally habitable for O. americanus, which could have been associated with the use of data of populations thermally adapted to temperate conditions south of Brazil. According to models, a warming scenario would cause a restriction of the available thermal niche of O. maya, while O. insularis could expand under RCP 6 scenarios. This restriction was more substantial in the RCP 8.5 scenario. Nevertheless, under the RCP 8.5 scenario, the temperature in 2100 may negatively affect even O. insularis, the species most thermal tolerant. If our results are accurate, the fishing yield of O. insularis will increase in the future, replacing the heavily exploited O. maya in the coasts of the southern Gulf of Mexico. Regarding O. americanus, no inference might be made until thermal tolerances of locally adapted populations can be studied.     

Effects of soil water temperature on root hydraulic resistance of six species of Iberian pines

Abstract

The Iberian Peninsula hosts six native pine species, which are distributed according to an altitudinal gradient from coastal to mountain areas, close to 1000 m a.s.l. Root hydraulic responses are the key factors of spatial segregation of trees in response to environmental factors such as temperature and water availability, and they will be a determinant of future population and species spatial dynamics in a changing climate scenario. Root hydraulic responses to soil water temperatures ranging from 30°C to 0°C were compared for young plants of these six aforementioned species. Hydraulic resistance (Rh) increased for all species in response to temperature decrease. Mountain pines showed higher Rh values than coastal pines at all temperatures, and showed a more prompt and marked hydraulic response when temperatures dropped down. Data point out that mountain pines display a clear mechanism to avoid cold embolism and secondary water stress, while coastal species have a limited responsiveness to temperature changes due to scarce hydraulic regulation. These differences in hydraulic behaviour support the spatial segregation between mountain and coastal pines in the Iberian Peninsula, and will be one of the factors at the basis of the future shifts of species and populations that will be associated to climate change.     

Predicting the distributions of Pouteria adolfi-friederici and Prunus africana tree species under current and future climate change scenarios in Ethiopia

Distributions of potential ranges of plant species are not yet fully known in Ethiopia where high climatic variability and vegetation types are found. This study was undertaken to predict distributions of suitable habitats of Pouteria adolfi-friederici and Prunus africana under current and two future climate scenarios (RCP 4.5 and RCP 8.5 in 2050 and 2070) in Ethiopia. Eleven environmental variables with less correlation coefficients (r < 0.7) were used to make the prediction. Shifting in extents of habitat suitability and effects of elevation, solar radiation and topographic position in relation to the current and future climatic scenarios were statistically analysed using independent t-test and linear model. We found decreasing area of highly suitable habitat from 0.51% to 0.46%, 0.36% and 0.33%, 0.24% for Prunus africana and 1.13% to 1.02%, 0.77% and 0.76%, 0.60% for Pouteria adolfi-friederici, under RCP 4.5 and RCP 8.5 by 2050 and 2070 respectively. Moist and dry afromontane forests are identified as the most suitable habitat for both species. Overall, our results suggest that climate change can promote dynamic suitable habitat niches under different future climate scenarios. Therefore, biodiversity conservation strategies should take into account habitat suitability dynamics issues and identify where to conserve species before implementing conservation practices.     

Niche shifting in response to warming climate after the last glacial maximum: inference from genetic data and niche assessments in the chisel‐toothed kangaroo rat (Dipodomys microps)

During Pleistocene glacial‐interglacial cycles, the geographic range is often assumed to have shifted as a species tracks its climatic niche. Alternatively, the geographic range would not necessarily shift if a species can adapt in situ to a changing environment. The potential for a species to persist in place might increase with the diversity of habitat types that a species exploits. We evaluate evidence for either range shift or range stability between the last glacial maximum (LGM) and present time in the chisel‐toothed kangaroo rat (Dipodomys microps), an endemic of the Great Basin and Mojave deserts. We modeled how the species’ range would have changed if the climatic niche of the species remained conserved between the LGM and present time. The climatic models imply that if D. microps inhabited the same climatic niche during the LGM as it does today, the species would have persisted primarily within the warm Mojave Desert and expanded northwards into the cold Great Basin only after the LGM. Contrary to the climatic models, the mitochondrial DNA assessment revealed signals of population persistence within the current distribution of the species throughout at least the latest glacial‐interglacial cycle. We concluded that D. microps did not track its climatic niche during late Pleistocene oscillations, but rather met the challenge of a changing environment by shifting its niche and retaining large portions of its distribution. We speculate that this kind of response to fluctuating climate was possible because of ‘niche drifting’, an alteration of the species’ realized niche due to plasticity in various biological characters. Our study provides an example of an approach to reconstruct species’ responses to past climatic changes that can be used to evaluate whether and to what extent taxa have capacity to shift their niches in response to the changing environment – information becoming increasingly important to predicting biotic responses to future environmental changes.     

Managing for change: wetland transitions under sea‐level rise and outcomes for threatened species

Aim Global sea‐level rise (SLR) could be as much as 1.8 metres by 2100, which will impact coastal wetland communities and threatened species. We evaluated the likely outcomes of SLR for wetland communities using a process‐based simulation model and coupled this with a metapopulation model for a threatened native rodent (Xeromys myoides). Furthermore, we tested the amplified impacts of SLR, urban growth and introduced predators on X. myoides persistence. Location South‐east Queensland, Australia. Methods We adapted the Sea Level Affects Marshes Model to subtropical Australia. We used LiDAR elevation data, field data to parameterize surface accretion and shallow subsidence, and local knowledge to configure wetland transitions. SLR was simulated based on the IPCC B1 and A1FI scenarios, as well as the maximal limit of 1.8 m by 2100. Further, we coupled our demographic model to projected shifts in wetland habitat, and estimates of future wetland loss to urban expansion and feral cat (Felis catus) predation. Results Our models project a general decline in wetland communities under SLR, with a noted exception of mangroves. Under the A1FI scenario, SLR allows mangroves to migrate inland, with urban development acting as an obstruction in some areas. Mangrove expansion provides an unexpected benefit for dependent X. myoides populations, although the inclusion of predation and habitat loss due to urban development still suggests extirpation in c. 50 years. Main conclusions Through this case study, we illustrate the usefulness of process‐based SLR models in understanding outcomes for wetland communities and dependent species. Our models will underscore decision‐making in a dynamic system, with global applications for urban planning, conservation prioritization and wildlife management.     

Current and future habitat availability for Thick‐billed and Maroon‐fronted parrots in northern Mexican forests

Thick‐billed Parrots (Rhynchopsitta pachyrhyncha) and Maroon‐fronted Parrots (Rhynchopsitta terrisi) are the only parrots in Mexico found in high‐elevation coniferous forests. Both species are critically endangered due to logging, and climate change is expected to further reduce their available habitat. Our objectives were to assess the present and future availability of a suitable habitat for these parrots using ecological niche models. Future climatic scenarios were estimated by overlaying the present distributions of these parrots on maps of projected biome distributions generated using a North American vegetation model. Our climatic scenarios revealed that the distribution of key habitats for both parrots will likely be affected as the climate becomes more suitable for xeric biomes. The climate associated with coniferous forests in the current range of Maroon‐fronted Parrots is predicted to disappear by 2090, and the climate associated with the key coniferous habitats of Thick‐billed Parrots may contract. However, our results also indicate that suitable climatic conditions will prevail for the high‐elevation coniferous biomes where Thick‐billed Parrots nest. The degree to which both species of parrots will be able to adapt to the new scenarios is uncertain. Some of their life history traits may allow them to respond with a combination of adaptive and spatial responses to climatic change and, in addition, suitable climatic conditions will prevail in some portions of their ranges. Actions needed to ensure the conservation of these parrots include strict control of logging and integration of rapid response teams for fire management within the potential foraging ranges of nesting pairs. A landscape with a greater proportion of restored forests would also aid in the recovery of current populations of Thick‐billed and Maroon‐fronted parrots and facilitate their responses to climate change.     

Future Scenarios as a Research Tool: Investigating Climate Change Impacts, Adaptation Options and Outcomes for the Great Barrier Reef, Australia

Climate change is a significant future driver of change in coastal social-ecological systems. Our knowledge of impacts, adaptation options, and possible outcomes for marine environments and coastal industries is expanding, but remains limited and uncertain. Alternative scenarios are a way to explore potential futures under a range of conditions. We developed four alternative future scenarios for the Great Barrier Reef and its fishing and tourism industries positing moderate and more extreme (2–3 °C above pre-industrial temperatures) warming for 2050 and contrasting ‘limited’ and ‘ideal’ ecological and social adaptation. We presented these scenarios to representatives of key stakeholder groups to assess the perceived viability of different social adaptation options to deliver desirable outcomes under varied contexts.     

Back to the future: using historical climate variation to project near‐term shifts in habitat suitable for coast redwood

Studies that model the effect of climate change on terrestrial ecosystems often use climate projections from downscaled global climate models (GCMs). These simulations are generally too coarse to capture patterns of fine‐scale climate variation, such as the sharp coastal energy and moisture gradients associated with wind‐driven upwelling of cold water. Coastal upwelling may limit future increases in coastal temperatures, compromising GCMs’ ability to provide realistic scenarios of future climate in these coastal ecosystems. Taking advantage of naturally occurring variability in the high‐resolution historic climatic record, we developed multiple fine‐scale scenarios of California climate that maintain coherent relationships between regional climate and coastal upwelling. We compared these scenarios against coarse resolution GCM projections at a regional scale to evaluate their temporal equivalency. We used these historically based scenarios to estimate potential suitable habitat for coast redwood (Sequoia sempervirens D. Don) under ‘normal’ combinations of temperature and precipitation, and under anomalous combinations representative of potential future climates. We found that a scenario of warmer temperature with historically normal precipitation is equivalent to climate projected by GCMs for California by 2020–2030 and that under these conditions, climatically suitable habitat for coast redwood significantly contracts at the southern end of its current range. Our results suggest that historical climate data provide a high‐resolution alternative to downscaled GCM outputs for near‐term ecological forecasts. This method may be particularly useful in other regions where local climate is strongly influenced by ocean–atmosphere dynamics that are not represented by coarse‐scale GCMs.     

基于MaxEnt模型预测中国兰属植物的分布格局及主导气候因子(附表)

兰属(Cymbidium)中，除了兔耳兰C.lancifolium以外的所有种均被列为国家重点保护野生植物。为探究其在未来气候条件下的潜在分布格局，该研究基于兰属植物已知的分布点和19个气候因子，利用最大熵(MaxEnt)模型和地理信息系统(ArcGIS)模拟兰属以及其中20种兰属植物在9种不同气候情景(当代以及未来2030s、2050s、2070s和2090s 4个时间段各两种温室气体排放情景)下的潜在分布格局。结果表明：(1)最干旱季降水量(Bio17)、年降水量(Bio12)和温度季节性变化(Bio4)是影响兰属植物地理分布格局的主导气候因子。(2)不同兰属植物在未来情景下的适生区表现出不同的变化趋势，并且影响其分布的主导气候因子也有所不同。其中，冬凤兰(C.dayanum)等8个物种的适生区面积整体呈扩张趋势，而西藏虎头兰(C.tracyanum)等12个物种的适生区面积整体则呈缩减趋势。该研究结果为兰属植物就地保护与迁地保护提供了重要参考，对兰属等濒危野生植物的保护具有积极意义。     

Climate change effects on turtles of the genus Kinosternon (Testudines: Kinosternidae): an assessment of habitat suitability and climate niche conservatism

The Chelonian lineage has been exposed to several climate change events along its evolutionary history, but the rapid contemporary change in climate patterns has the potential to erode turtle populations. This study focuses on (1) evaluating the climatically suitable area available for 15 species of mud turtles of the genus Kinosternon, and on (2) assessing whether or not these species retain their ancestral climate niche. Occurrence data was collected for these species and, using the Maxent algorithm and WorldClim bioclimatic variables, suitable present and future climatic niche areas were modeled. In addition, we also carried out climatic niche similarity analyses between pairs of species to evaluate whether these conserve their climatic niche. Our models suggest that most species of Kinosternon will lose a high proportion of their suitable habitat in the future. Most mud turtle species seem to conserve their climatic niche, suggesting the prevalence of niche conservatism in the group. Our results indicate that several mud turtle species could be at severe risk of disappearing over the next few decades due to the loss of climatically suitable areas and of the conservation of their climatic niches.

     

Habitat distribution models for intertidal seaweeds: responses to climatic and non‐climatic drivers

Aim Because intertidal organisms often live close to their physiological tolerance limits, they are potentially sensitive indicators of climate‐driven changes in the environment. The goals of this study were to assess the effect of climatic and non‐climatic factors on the geographical distribution of intertidal macroalgae, and to predict future distributions under different climate‐warming scenarios. Location North‐western Iberian Peninsula, southern Europe. Methods We developed distribution models for six ecologically important intertidal seaweed species. Occurrence and microhabitat data were sampled at 1‐km² resolution and analysed with climate variables measured at larger spatial scales. We used generalized linear models and applied the deviance and Bayesian information criterion to model the relationship between environmental variables and the distribution of each target species. We also used hierarchical partitioning (HP) to identify predictor variables with higher independent explanatory power. Results The distributions of Himanthalia elongata and Bifurcaria bifurcata were correlated with measures of terrestrial and marine climate, although in opposite directions. Model projections under two warming scenarios indicated the extinction of the former at a faster rate in the Cantabrian Sea (northern Spain) than in the Atlantic (west). In contrast, these models predicted an increase in the occurrence of B. bifurcata in both areas. The occurrences of Ascophyllum nodosum and Pelvetia canaliculata, species showing rather static historical distributions, were related to specific non‐climatic environmental conditions and locations, such as the location of sheltered sites. At the southernmost distributional limit, these habitats may present favourable microclimatic conditions or provide refuges from competitors or natural enemies. Model performances for Fucus vesiculosus and F. serratus were similar and poor, but several climatic variables influenced the occurrence of the latter in the HP analyses. Main conclusions The correlation between species distributions and climate was evident for two species, whereas the distributions of the others were associated with non‐climatic predictors. We hypothesize that the distribution of F. serratus responds to diverse combinations of factors in different sections of the north‐west Iberian Peninsula. Our study shows how the response of species distributions to climatic and non‐climatic variables may be complex and vary geographically. Our analyses also highlight the difficulty of making predictions based solely on variation in climatic factors measured at coarse spatial scales.     

Potential impacts of climatic change on the breeding and non-breeding ranges and migration distance of European Sylvia warblers

Aim  To explore the potential impacts of climatic change on species with different migratory strategies using Sylvia warblers breeding in Europe as a ‘model’ species group. Location  Europe and Africa. Methods  Climate response surfaces and generalized additive models (GAMs) were used to model relationships between species recorded breeding and non‐breeding ranges and recent climate. Species potential future breeding and non‐breeding ranges were simulated for three scenarios of late 21st‐century climate. The simulated potential future and present ranges were compared in terms of their relative extent and overlap, as well as their location. The impact of any shifts in potential range location on migration distance were quantified. Results  Potential breeding ranges consistently showed a shift northwards, whereas potential non‐breeding ranges showed no consistent directional shift, even when trans‐Saharan migrants were considered separately from resident/short‐distance or partial migrants. Future potential range extent relative to simulated recent range extent varied considerably among species, although on average range extent increased. Overlap between future and recent simulated range was generally low, averaging < 36% for both breeding and non‐breeding ranges. Overlap was consistently less for range‐restricted than for widespread species. Migration distance increased generally, by about twice as much in the case of trans‐Saharan migrant species than for short‐distance migrants. In many cases potential future non‐breeding areas were simulated in regions far from the species present non‐breeding area, suggesting that new migration strategies and routes may need to be developed in response to climatic change. Main conclusions  Migratory species can be expected to suffer greater negative impacts from climatic change than species that are resident or undertake only short‐distance or partial migrations. Trans‐Saharan migrants face the greatest potential increases in migration distances, whereas range‐restricted species are expected to experience major population reductions because of the limited, or in some cases lack of, overlap between their present and potential future ranges.     

Structure and environmental relationships of insectivorous bat assemblages in tropical Australian savannas

Abstract Patterns in the composition of assemblages of microbat species sampled during the late dry season (the ‘build‐up’) in north Australian savannas were assessed against a range of environmental factors as well as four a priori defined habitat types (riparian, escarpments, coastal and woodlands). Distinct species assemblages were most strongly associated with topographic and climatic variables. There were also limited associations with vegetation structure, fire and local roost potential but no associations with insects or water availability. Total species diversity at sample sites was associated with distance to rivers and rainfall. In general, species assemblages were not clearly defined and the number of significant environmental associations was relatively few. We compare these associations with those reported for bat assemblages elsewhere in Australia.     

Sea‐level rise,habitat loss,and potential extirpation of a salt marsh specialist bird in urbanized landscapes

Sea‐level rise (SLR) impacts on intertidal habitat depend on coastal topology, accretion, and constraints from surrounding development. Such habitat changes might affect species like Belding's savannah sparrows (Passerculus sandwichensis beldingi; BSSP), which live in high‐elevation salt marsh in the Southern California Bight. To predict how BSSP habitat might change under various SLR scenarios, we first constructed a suitability model by matching bird observations with elevation. We then mapped current BSSP breeding and foraging habitat at six estuarine sites by applying the elevation‐suitability model to digital elevation models. To estimate changes in digital elevation models under different SLR scenarios, we used a site‐specific, one‐dimensional elevation model (wetland accretion rate model of ecosystem resilience). We then applied our elevation‐suitability model to the projected digital elevation models. The resulting maps suggest that suitable breeding and foraging habitat could decline as increased inundation converts middle‐ and high‐elevation suitable habitat to mudflat and subtidal zones. As a result, the highest SLR scenario predicted that no suitable breeding or foraging habitat would remain at any site by 2100 and 2110. Removing development constraints to facilitate landward migration of high salt marsh, or redistributing dredge spoils to replace submerged habitat, might create future high salt marsh habitat, thereby reducing extirpation risk for BSSP in southern California.     

Topographic,latitudinal and climatic distribution of Pinus coulteri: geographic range limits are not at the edge of the climate envelope

With changing climate, many species are projected to move poleward or to higher elevations to track suitable climates. The prediction that species will move poleward assumes that geographically marginal populations are at the edge of the species' climatic range. We studied Pinus coulteri from the center to the northern (poleward) edge of its range, and examined three scenarios regarding the relationship between the geographic and climatic margins of a species' range. We used herbarium and iNaturalist.org records to identify P. coulteri sites, generated a species distribution model based on temperature, precipitation, climatic water deficit, and actual evapotranspiration, and projected suitability under future climate scenarios. In fourteen populations from the central to northern portions of the range, we conducted field studies and recorded elevation, slope and aspect (to estimate solar insolation) to examine relationships between local and regional distributions. We found that northern populations of P. coulteri do not occupy the cold or wet edge of the species' climatic range; mid‐latitude, high elevation populations occupy the cold margin. Aspect and insolation of P. coulteri populations changed significantly across latitudes and elevations. Unexpectedly, northern, low‐elevation stands occupy north‐facing aspects and receive low insolation, while central, high‐elevation stands grow on more south‐facing aspects that receive higher insolation. Modeled future climate suitability is projected to be highest in the central, high elevation portion of the species range, and in low‐lying coastal regions under some scenarios, with declining suitability in northern areas under most future scenarios. For P. coulteri, the lack of high elevation habitat combined with a major dispersal barrier may limit northward movement in response to a warming climate. Our analyses demonstrate the importance of distinguishing geographically vs. climatically marginal populations, and the importance of quantitative analysis of the realized climate space to understand species range limits.