Habitat Isolation Research Articles

Pollinator distribution in patches of suitable habitat depends more on patch isolation than on floral abundance

Intrinsic complexity of real-world systems makes particularly difficult to decipher which factors influence the dispersal of pollinators in the landscape matrix and their distribution amongst patches of suitable habitat. Saltmarshes are an ideal and naturally simplified landscape to study the ability of different groups of pollinators to disperse across a landscape matrix, as they consist of a matrix of flooded areas surrounding patches of suitable habitat with different degrees of isolation from the mainland and different levels of floral abundance. We hypothesise that pollinator distribution to flowering plants depends more on patch isolation than on floral abundance, with pollinator richness and visitation rates to flowering plants decreasing with increasing distance from the mainland. To this end, we established 60 permanent plots at varying distances from the mainland and monitored pollinator visitation to entomophilous plants. We also quantified the reproductive success of entomophilous species in the surveyed plots by calculating fruit set. We found that the pollinator community of saltmarshes consisted only of flying pollinators with good dispersal abilities, while we recorded no flightless pollinator species. Both pollinator richness and visitation rate decreased with increasing distance of patches of suitable habitat from the mainland, affecting reproductive success of a non-autogamous entomophilous species. Interestingly, floral abundance did not affect pollinator richness and visitation rate to flowering plants, nor did it affect reproductive success of target plant species. In saltmarshes, the pollinator distribution depends more on patch distance from the mainland than on floral abundance. Our results suggest that the presence of patches of suitable habitat in a landscape matrix does not necessarily ensure the maintenance of pollinators. Rather, our results suggest that suitable habitat isolation is the critical factor in pollinator dispersal and distribution that should be considered to improve landscape matrix permeability to pollinators.

Phenotypic and environmental correlates of natal dispersal movements in fragmented landscapes

ContextNatal dispersal critically influences eco-evolutionary dynamics and the persistence of spatially structured populations. As both short- and long-distance movements contribute to population persistence in fragmented landscapes, understanding dispersal requires assessing phenotypic and environmental effects on a wide range of distances.ObjectivesTo assess phenotypic and environmental correlates of dispersal movements in fragmented landscapes.MethodsWe radio-tracked juvenile middle spotted woodpeckers in fragmented landscapes to assess phenotypic and environmental effects on emigration age, transfer duration (in days), and transfer distances.ResultsLarge fledglings and those in good condition emigrated earlier than smaller individuals and those in worse condition. Birds in better condition also reduced transfer duration. Overall, females dispersed earlier, remained shorter at transfer and moved further than males. However, while females increased transfer distances with increasing connectivity, males increased distances with decreasing connectivity. Emigration age increased with decreasing patch size and increasing patch quality, and with decreasing population density in patches with soft edges. Both transfer duration and distance increased with decreasing population density.ConclusionsThe correlations between phenotypic traits of fledglings and their posterior movements suggest that early-life conditions influenced dispersal through carry-over effects. Early emigration from low-quality and high-populated patches can be a behavioural mechanism to quickly escape adverse natal conditions, but population density effects were modulated by edge hardness. Finally, because reductions in connectivity led to similar transfer distances between sexes through a reduction in female distances, a lack of sex-biased dispersal can be a previously overlooked effect of habitat isolation that may alter eco-evolutionary dynamics.

Exploring the influences of different processes of habitat fragmentation on ecosystem services

Exploring the factors influencing ecosystem services (ESs) is crucial for protecting them. Habitat fragmentation is a critical factor that has been proved to have positive or negative effects on various ESs. However, the detailed effects of different habitat fragmentation processes have not been thoroughly explored. This study aimed to explore the complicated influences of different habitat fragmentation processes on the variations in ESs, and identify the most significant influencing processes. The Yangtze River Delta region of China was selected as the study area. Three basic habitat fragmentation processes were quantified: a decrease in habitat area, an increase in habitat isolation, and an increase in habitat edge. Generalized additive models and a geographical detector were adopted to explore the influences of different fragmentation processes on the variations in the four ESs. The results suggested that different habitat fragmentation processes had linear/nonlinear/combined effects on different ESs, and the decrease in habitat area was the most significant fragmentation process. Carbon storage and habitat quality were affected significantly by habitat fragmentation. However, habitat fragmentation contributed less to the variations in water yield and soil retention, because they were more closely associated with climate factors. The influences of these fragmentation processes exhibited a positive and nonlinear interaction. These findings suggest that integrating the nonlinear effects of fragmentation in practical ESs management and landscape planning might be essential. Moreover, our study provides a fundamental reference for related research.

Genetic Variation in Gaultheria nummularioides (Ericaceae: Gaultherieae) from the Sky Islands of the Himalaya-Hengduan Mountains

Species diversity is high in the Himalaya-Hengduan Mountains, particularly at the edges characterized by deep ravines and “sky islands”. Studies focused on sky-island species are sparse and the patterns observed in response to both geographic and climatic factors are inconsistent. Here phylogeographic and phylogenetic analyses of Gaultheria nummularioides, a species originating in the late Pliocene with its main distribution in the Himalaya-Hengduan Mountains, were conducted to reveal the pattern of genetic dynamics in response to physical geography, glacial fluctuations, and monsoons. We found that in this species genetic variation is higher among populations than within populations, with a significant phylogeographic boundary between the central Himalaya and the eastern Himalaya and the Hengduan Mountains. We also found a high incidence of private alleles, possibly associated with strong habitat isolation. The phylogeographic pattern recovered is consistent with populations in glacial refugia that have experienced expansion after glaciation. The divergence times of most haplotypes coincide with the time of the weakening of the Asian monsoon in these regions. Models of geographic range size showed a significant decrease from the Last Interglacial through the Last Glacial Maximum to the Current, and a predicted increase from the Current to the year 2070. Our study provides insights for understanding speciation among sky islands in this region.

Cascading effects of habitat loss on ectoparasite-associated bacterial microbiomes

Suitable habitat fragment size, isolation, and distance from a source are important variables influencing community composition of plants and animals, but the role of these environmental factors in determining composition and variation of host-associated microbial communities is poorly known. In parasite-associated microbial communities, it is hypothesized that evolution and ecology of an arthropod parasite will influence its microbiome more than broader environmental factors, but this hypothesis has not been extensively tested. To examine the influence of the broader environment on the parasite microbiome, we applied high-throughput sequencing of the V4 region of 16S rRNA to characterize the microbiome of 222 obligate ectoparasitic bat flies (Streblidae and Nycteribiidae) collected from 155 bats (representing six species) from ten habitat fragments in the Atlantic Forest of Brazil. Parasite species identity is the strongest driver of microbiome composition. To a lesser extent, reduction in habitat fragment area, but not isolation, is associated with an increase in connectance and betweenness centrality of bacterial association networks driven by changes in the diversity of the parasite community. Controlling for the parasite community, bacterial network topology covaries with habitat patch area and exhibits parasite-species specific responses to environmental change. Taken together, habitat loss may have cascading consequences for communities of interacting macro- and microorgansims.

Flexible drought deciduousness in a neotropical understory herb.

PremiseAdaptive divergence across environmental gradients is a key driver of speciation. Precipitation seasonality gradients are common in the tropics, yet drought adaptation is nearly unexplored in neotropical understory herbs. Here, we examined two recently diverged neotropical spiral gingers, one adapted to seasonal drought and one reliant on perennial water, to uncover the basis of drought adaptation.MethodsWe combined ecophysiological trait measurements in the field and greenhouse with experimental and observational assessments of real‐time drought response to determine how Costus villosissimus (Costaceae) differs from C. allenii to achieve drought adaptation.ResultsWe found that drought‐adapted C. villosissimus has several characteristics indicating flexible dehydration avoidance via semi‐drought‐deciduousness and a fast economic strategy. Although the two species do not differ in water‐use efficiency, C. villosissimus has a more rapid growth rate, lower leaf mass per area, lower stem density, higher leaf nitrogen, and a strong trend of greater light‐saturated photosynthetic rates. These fast economic strategy traits align with both field‐based observations and experimental dry‐down results. During drought, C. villosissimus displays facultative drought‐deciduousness, losing lower leaves during the dry season and rapidly growing new leaves in the wet season.ConclusionsWe revealed a drought adaptation strategy that has not, to our knowledge, previously been documented in tropical herbs. This divergent drought adaptation evolved recently and is an important component of reproductive isolation between C. villosissimus and C. allenii, indicating that adaptive shifts to survive seasonal drought may be an underappreciated axis of neotropical understory plant diversification.

Quantification of the effect of host patch configuration on the abundance of Bemisia tabaci in central Argentina: a multimodel inference approach.

Bemisia tabaci is a complex of species, which is considered the most common and important pest of a wide range of crops belonging to many different botanical families. In Argentina, this species is recognized as a vector of geminiviruses, and Middle East-Asia Minor 1, Mediterranean, New World and New World 2 have been found to coexist in the same area. Landscape elements, like habitat patch area and isolation, define the habitat configuration and have a direct effect on insect populations between and within host patches. In this paper, we analyse the effect of potato patch configuration on the distribution and abundance of B. tabaci. Potato patches were identified using Landsat TM5 and TM7 images, and a supervised classification was performed to quantify the spatial distribution of the patches in the whole study area. Potato patch metrics were estimated using Fragstats 4.4. Generalized linear mixed models were employed to analyse the relationship between whiteflies and landscape configuration, through a multimodel inference approach, finding that B. tabaci abundance and landscape metrics were very variable. After a multimodel selection process, we found that perimeter-to-area ratio and Euclidean distance between patches were the variables that best explained whitefly abundance in potato patches. Implications of these findings are discussed.

European blue and green infrastructure network strategy vs. the common agricultural policy. Insights from an integrated case study (Couesnon, Brittany)

Urbanization and agricultural intensification are the main drivers of biodiversity losses through multiple stressors, especially habitat fragmentation, isolation and loss. Designing Blue and Green Infrastructure Networks (BGIN) has been recommended as a potential tool for land-use planning to increase ecosystem services while preserving biodiversity. All municipalities in France are required to perform BGIN planning. This article focuses on the Couesnon watershed (Brittany, France) and the participatory process used to define and analyze five possible pathways of future land-use and land-cover changes that included implementation of BGINs. Impacts on biodiversity were estimated by quantifying the change in landscape connectivity of woodlands, grasslands and wetlands. The effectiveness of BGIN policies was assessed by comparing current landscape connectivity (2018) to those in possible futures. Landscape connectivity referred to functional connectivity for three indicator species (Abax parallelepipedus, Maniola jurtina and Arvicola sapidus) across three landscape features: woodlands, grasslands and wetlands, respectively. Results allowed impacts of urban and agricultural land-use changes to be identified in terms of extent and quality. If BGIN policies were applied effectively to control the expansion of gray infrastructure, they would help increase the area and the quality of grassland and woodland connectivity by no more than 2%. Agricultural land-use and land-cover changes could have more impact on the extent of grassland (−82% to +38%) and wetland (−49% to +47%) connectivity. Current and future trends for hedgerows implied a decrease in woodland connectivity of 9.8–33.8%. Impacts on the quality of landscape connectivity is not proportional with the extent, as a decrease of the latter can have relatively more negative impacts on the former, and inversely. The study highlights that the BGIN strategy can preserve landscape connectivity effectively in urban ecosystems, where human density is higher, but can be threatened by agricultural intensification.

Trophic niche partitioning of five sympatric shark species in the tropical eastern Pacific Ocean revealed by multi-tissue fatty acid analysis

Fatty acid (FA) analysis of consumer tissues has recently shown utility in drawing further inferences about trophic niche dynamics of marine predators such as sharks. In this study, we examined liver, plasma, and muscle FAs in five coexisting pelagic sharks (blue (Prionace glauca), silky (Carcharhinus falciformis), bigeye thresher (Alopias superciliosus), pelagic thresher (Alopias pelagicus), and smooth hammerhead (Sphyrna zygaena)) inhabiting the tropical eastern Pacific Ocean. Results showed complex inter- and intra-individual and tissue variation among the five shark species. Based on multivariate analysis of the muscle FAs, P. glauca and C. falciformis have the largest FA niche widths, indicating diverse feeding habits or habitat isolation, whereas A. pelagicus and S. zygaena occupied a narrower niche width, reflecting increased trophic specialization. High percentages of muscle FA niche overlap indicated strong resource competition between S.zygaena and C. falciformis and a degree of dietary isolation by P. glauca. Interpretations of feeding ecology differed based on the analysis of plasma FAs, which could be attributed to higher dietary FA turnover rates. The liver was deemed unsuitable to examine FA niche metrics based on high and unexplained intra-specific variance in liver FAs as well as the unique lipid metabolism in chondrichthyans. Overall, our multi-tissue approach revealed the magnitude of potential competitive interactions among coexisting tropical shark species. It also expanded our understanding of inter-tissue variability and best practices when using FA analysis to estimate trophic niche metrics of sharks.

Avian species richness and tropical urbanization gradients: Effects of woodland retention and human disturbance.

Urbanization is a major driver of tropical biodiversity loss. In temperate regions avian species richness–urbanization intensity relationships typically exhibit unimodal patterns, with peak richness at intermediate urbanization levels. In tropical regions, the form of such relationships and the extent to which they are moderated by patches of seminatural habitat are unclear. We address these questions in Bangkok, Thailand (one of the largest and most rapidly expanding tropical mega‐cities) and generate conservation recommendations for tropical biodiversity in urban locations. We use repeated point count surveys at a random location, and the largest available woodland patch, in 150 1 km × 1 km grid cells selected along the urbanization gradient. Woodland patches support higher species richness compared with randomized locations (except for non‐natives), and avian species richness declines linearly with increasing urbanization. The contrast with unimodal patterns in temperate regions is probably driven by divergent patterns of habitat heterogeneity along tropical and temperate urbanization gradients. Moreover, we provide novel evidence that retaining patches of urban woodland moderates adverse impacts of urbanization on avian species richness. For most species groups, the benefits of woodland increase as urbanization intensifies, despite such woodland patches being very small (mean of 0.38 ha). Avian species richness in woodland patches is maximized, and community composition less similar to that in randomized locations, when woodland patches are larger and visited by fewer people. Assemblages of forest‐dependent species (which provide additional ecological functions) have higher richness, and are less similar to those in randomized locations, in patches of woodland with higher tree species richness and biomass. Finally, species richness in randomized sites is greatest when they are closer to woodland patches, and such assemblages more closely resemble those of woodland sites. Our work highlights four strategies for tropical urban bird conservation: (1) conserving woodland patches across the urbanization gradient regardless of patch size, (2) improving the quality of existing woodland by increasing tree biomass and diversity, (3) creating additional woodland that is well distributed throughout the urban area to minimize effects of habitat isolation and (4) reducing human disturbance, especially in areas of the highest habitat quality, while ensuring that the benefits of connecting people to nature are realized in other locations.

Rapid linear transport infrastructure development in the Carpathians: A major threat to the integrity of ecological connectivity for large carnivores

The development of sustainable transport is a key challenge in societies where there is an accelerated need for socio-economic development. This is the case for seven countries from central and south-eastern Europe that share the Carpathian Mountains. The challenge of developing sustainable transport requires transdisciplinary, or at least cross-sectoral cooperation, between the transport development and nature conservation sectors. Such cooperation is not in the culture of the Carpathian countries, which together host some of the most remarkable biodiversity values in Europe, including the largest populations of brown bear, grey wolf and Eurasian lynx. The overall length of motorways in these countries more than quintupled in the last 30 years and the rapid expansion of Linear Transport Infrastructure (LTI) continues at exacerbating rates. The rich biodiversity habitats are being fragmented and the concept of ecological connectivity is poorly understood and implemented by the national authorities. Ecological networks for large carnivores are not defined nor officially recognised in the Carpathian countries, with little exceptions. The legislation is not consistent across the strands of ecological connectivity and is not harmonised between the countries to effectively support transnational conservation efforts. Thus, the critical intersections between planned or even existing LTI and ecological corridors for large carnivores cannot be identified, in most cases leading to increasing habitat fragmentation and isolation of wildlife populations in the region. We summarised all this key context-related information for the Carpathians in relation to LTI development and ecological connectivity. To counteract this trend in the Carpathian ecoregion, we propose a set of recommendations to: improve and harmonise the legislation; develop and endorse methodologies for designating ecological corridors; address the cumulative impact on ecological connectivity; define other threats on landscape permeability; improve stakeholder engagement, cooperation and communication; develop comprehensive and transparent biodiversity and transport databases; monitor wildlife and transport for implementing most appropriate mitigation measures and strategies; build capacity to address the issue of sustainable transportation; and foster transnational cooperation and dialogue. Bringing these elements together will support the design of ecological networks in a way that considers the needs and location of both current and future habitats and contribute to efforts to address the climate crisis. These specific recommendations are relevant also for other areas of the world facing similar problems as the Carpathians.

Oreocharis hainanensis (Gesneriaceae), a new species from karst regions in Hainan Island, South China

Oreocharis hainanensis, a new species of Gesneriaceae is described and illustrated from low-altitudual karst areas in Hainan Island, South China. The new species is easily distinguished from its closely-related O. jasminina by campanulate floral tube, zygomorphic corolla and exserted stamens. It also shows different habitats from the four currently-recognized Oreocharis taxa on the island. Molecular phylogeny analysis based on plastid trnL-trnF and nuclear ITS1/2 sequences supported the delimitation of the new species, which forms a monophyletic clade with all the other Oreocharis taxa from Hainan Island. The roles of habitat and floral isolation in the evolution of the new species and its affinities are discussed. The species was assessed as Vulnerable (VU C1 and D2) according to IUCN Red List Categories and Criteria.

Integrating ecological and molecular data to investigate species maintenance and interspecific hybridization between the redbreast sunfish (Lepomis auritus) and the pumpkinseed sunfish (Lepomis gibbosus)

True sunfishes (genus Lepomis Rafinesque, 1819) of North America are renowned for hybridization, although hybrids often comprise only a fraction of the sunfish population in natural systems. Species boundaries may be maintained through premating mechanisms (e.g., ethological and habitat isolation), which may be facilitated by the promiscuous sunfish mating system; primarily, singular males guard nests that multiple females visit. Natural hybridization occurs between redbreast ( Lepomis auritus (Linnaeus, 1758)) and pumpkinseed ( Lepomis gibbosus (Linnaeus, 1758)) sunfishes, but there is no published research on its extent and causes. In this study, we assessed the relationship between ecological variables and the prevalence of hybridization in a sunfish population in a freshwater lake. Nests of both species were evaluated for differences in substrate, date, water depth, temperature, and dissolved oxygen. Sequencing of one fragment of nuclear DNA (calmodulin intron 4) and one fragment of mitochondrial DNA (12S) was employed on adult males and eight offspring from each nest to determine genetic identity and hybridization direction. Nonparametric tests found a significant difference in substrate between species’ nests ( p < 0.01), warranting further investigation into nest substrate as a mechanism for species maintenance. Furthermore, we observed asymmetrical hybridization with the less abundant species (redbreast sunfish) disproportionately affected.

Future simulated landscape predicts habitat loss for the Golden Langur (Trachypithecus geei): A range level analysis for an endangered primate

Trachypithecus geei Khajuria, 1956 or Golden langur are an endangered colobine primate species that are distributed in the transboundary region of Bhutan and India. The species is severely threatened because of increasing habitat fragmentation and isolation across its entire range, especially the populations in Assam, India. The distribution range of the species has not been updated for the last two decades, nor is there any proper evaluation of the habitat requirements for the species. Therefore, we mapped the habitat suitability for the species across its entire distribution and projected its habitat suitability on the simulated landscape for the future (2031). The results indicate that out of the total range extent (66,320 km2), only 12,265 km2 (18.49%) is suitable for the species at present, which will further be reduced to 8884 km2 by the year 2031, indicating major range contraction. These suitable habitats are largely scattered and fragmented in southern range of the species. Among the predictors used, the distance to evergreen and deciduous broadleaf forest was the strongest predictor out of the 35 used for model building. Moreover, land use and land cover were found to be more informative than the climatic variables. Much of the suitable habitats of the species are located outside the protected area network in the landscape. Therefore, we identified landscape configurations and suitable habitat areas for the future conservation and monitoring of Golden Langur in the protected areas of its range.

Habitat isolation reduces intra- and interspecific biodiversity and stability.

Fragmentation is predicted to reduce biodiversity and stability by increasing habitat isolation and impeding dispersal among patches. These effects may manifest at both the interspecific and intraspecific levels, yet few studies have simultaneously explored dispersal effects across levels of organization. We used field mesocosm experiments to examine how habitat isolation (in the form of dispersal rate) alters inter- and intraspecific stability and diversity in local zooplankton communities. We observed effects of increasing dispersal rate at both the intra- and interspecific levels. Increasing dispersal increased local species diversity and reduced mean temporal variability of populations. At the intraspecific level, Daphnia pulex clonal diversity was enhanced by dispersal and mean temporal variability of clone abundances through time was reduced.

Performance Trade-Offs and Resource Availability Drive Variation in Reproductive Isolation between Sympatrically Diverging Crossbills.

AbstractTheoretical models indicate that speciation, especially when the scope for gene flow is great (e.g., sympatric speciation), is most likely when strong performance trade-offs coincide with reproduction. We tested this classic hypothesis using measures of the strength of three prezygotic reproductive isolating barriers (habitat isolation, reduced immigrant fecundity, and behavioral isolation) between two young (~2,000 years) and sympatric red crossbill (Loxia curvirostra) ecotypes. All three isolating barriers increased with increases in performance trade-offs, with total reproductive isolation varying between 0.72 and 1 (0 represents random mating, and 1 represents complete reproductive isolation). Strong trade-offs led to strong habitat isolation, an inability to breed in the "wrong" habitat, and more assortative flocks, with the latter leading to stronger behavioral isolation. Reproductive isolation decreased as resource availability increased relative to the demands of breeding, with higher resource availabilities eliminating the positive relationship between reproductive isolation and performance trade-offs. This latter result is consistent with previous work suggesting that increasing resource abundance dampens the effect of strong performance trade-offs on evolutionary divergence. Because many organisms, with the notable exception of host-specific phytophagous insects, rely on abundant food resources with weak performance trade-offs while breeding, our results may explain why sympatric speciation is uncommon.

Habitat requirements of Boreal Owl (Aegolius funereus) and Pygmy Owl (Glaucidium passerinum) in rear edge montane populations on the Balkan Peninsula

Rear-edge populations of montane species are known to be vulnerable to environmental change, which could affect them by habitat reduction and isolation. Habitat requirements of two cold-adapted boreo-alpine owl species — Boreal Owl (Aegolius funereus) and Pygmy Owl (Glaucidium passerinum) — have been studied in refugial montane populations in the western Rhodopes, South Bulgaria. Data on owl presence and forest stand attributes recorded in situ have been used to identify significant predictors for owl occurrence. The results revealed Boreal Owl's preference for comparatively dense forests (high canopy closure values), big trees (diameter at breast height ≥50 ​cm) and large amount of fallen dead wood in penultimate stage of decay. For Pygmy Owl the only significant explanatory variable was the total amount of fallen dead wood. Results suggest preference of both owl species for forests with structural elements typical of old-growth forests (i.e., veteran trees, deadwood), the Pygmy Owl being less prone to inhabit managed forests. Being at the rear edge of their Palearctic breeding range in Europe both Boreal and Pygmy Owls are of high conservation value on the Balkan Peninsula. Hence, additional efforts are needed for their conservation in the light of climate change and resulting alteration of forest structural parameters. Current findings can be used for adjusting forest management practices in order to ensure both, sustainable profit from timber and continuous species survival.

Comparative biogeography of volant and nonvolant mammals in a temperate island archipelago

AbstractIsland biogeography theory is a foundational ecological concept that describes how island or habitat patch size and isolation predict biodiversity, but few have studied how the effects of island biogeography vary with life history characteristics of temperate mammal communities. From 2014 to 2020, we surveyed volant and nonvolant mammals within the Apostle Islands archipelago (Wisconsin, USA) using camera trapping, live trapping, and acoustic monitoring. We used linear regression and information‐theoretic model selection to evaluate the effects of island size and isolation on indices of biodiversity. We also examined the effects of life history characteristics (i.e., body mass, winter inactivity) on the relative abundance and distribution of each species on the islands and the mainland. For volant mammals, island size and isolation were not associated with any metrics of diversity. We found island size was positively associated with nonvolant mammal species richness and diversity, but not species evenness. Island isolation was not a significant predictor for small nonvolant mammal diversity, although both size and isolation appeared to influence island biogeography of medium‐large nonvolant mammals. We also found that the interaction between winter inactivity and body mass influenced the vagility of nonvolant mammals in the archipelago. Our results suggest that life history characteristics are important in mediating species responses to biogeography, supporting the dispersal‐limitation nonequilibrium view of island biogeography theory, particularly for nonvolant mammals.

Reforestation enhanced landscape connectivity for thermal buffering in China

Deforestation-induced landscape fragmentation causes habitat loss and isolation, modifies local climate, and therefore threatens biodiversity. While, on the contrary, how large-scale reforestation may improve the connectivity and thermal buffers of habitats is not well understood. We show that decades long large-scale reforestation in China has effectively increased the size and connectivity of forest patches by gradually filling gaps among isolated patches and creating more core forests. The core forests have a stronger capacity to cool the land surface, leading to a daily mean cooling effect of −0.42 ± 0.23 °C relative to nearby marginal forests. Moreover, the core forests reduce diurnal range and seasonal variation of land surface temperature by 1.41 ± 0.23 °C and 0.42 ± 0.55 °C, respectively, relative to nearby marginal forests. The thermal buffering capacity of large size core forest (>100 km2) is more than twice that of small size (⩽10 km2). Despite their relatively low thermal buffering capacity, the marginal forests contribute about 73% to the increase of forest area in China during the last two decades and create buffer zones for the core forests to resist external disturbances, maintaining the internal stability of the forest ecosystem. We highlight that improving the integrity and connectivity of the forests with ecological restoration and succession can further enhance potential of forests to buffer local thermal environment under the current reforestation efforts, and thereby providing better connected thermal habitats for species to survive under climate change.

Intra‐Alpine Islands: Population genomic inference reveals high degree of isolation between freshwater spring habitats

AbstractAimAlpine spring ecosystems have long been considered as highly isolated, island‐like habitats. This presumption, however, is insufficiently supported empirically and conclusions about spring isolation have been based on indirect evidence. Therefore, we investigated the population genomic structure of Partnunia steinmanni Walter, 1906, a strictly spring‐dwelling water mite (Hydrachnidia) species, to shed light on the degree of interconnection among freshwater spring habitats.LocationProtected areas across the Alps, Central Europe.MethodsPartnunia steinmanni populations were sampled by hand‐net from 12 springs. Population genomic structure was inferred with 2263 polymorphic restriction site‐associated DNA (RADseq) loci of 256 individuals. We assessed genomic admixture, the phylogenetic relationship, isolation by distance, contemporary migration, effective population sizes, and genetic diversity among individuals from different springs.ResultsWe observed strong genetic differentiation between individuals from different springs. Water mites from each spring qualified as well‐delimited distinct populations with only little intra‐spring migration, even when these were located in close geographic proximity. Furthermore, we found subtle shared genetic structure among springs within the same area, and a southwestern genotype associated with the Rhône catchment that extended into eastern populations. Effective population size estimates and standing genetic variation within springs were generally low.Main conclusionsOur findings indicate strong insularity of freshwater springs and headwater areas, likely caused by intra‐alpine Pleistocene isolation and limited dispersal abilities of strictly spring‐bound species like P. steinmanni. Our results support the concept of spring habitat isolation and highlight the importance of alpine protected areas to conserve springs as substantial components of freshwater biodiversity.