Species In Fragmented Landscapes Research Articles

Intraspecific trait variability facilitates tree species persistence along riparian forest edges in Southern Amazonia

Tropical forest fragmentation from agricultural expansion alters the microclimatic conditions of the remaining forests, with effects on vegetation structure and function. However, little is known about how the functional trait variability within and among tree species in fragmented landscapes influence and facilitate species’ persistence in these new environmental conditions. Here, we assessed potential changes in tree species’ functional traits in riparian forests within six riparian forests in cropland catchments (Cropland) and four riparian forests in forested catchments (Forest) in southern Amazonia. We sampled 12 common functional traits of 123 species across all sites: 64 common to both croplands and forests, 33 restricted to croplands, and 26 restricted to forests. We found that forest-restricted species had leaves that were thinner, larger, and with higher phosphorus (P) content, compared to cropland-restricted ones. Tree species common to both environments showed higher intraspecific variability in functional traits, with leaf thickness and leaf P concentration varying the most. Species turnover contributed more to differences between forest and cropland environments only for the stem-specific density trait. We conclude that the intraspecific variability of functional traits (leaf thickness, leaf P, and specific leaf area) facilitates species persistence in riparian forests occurring within catchments cleared for agricultural expansion in Amazonia.

Inferring population connectivity in eastern massasauga rattlesnakes (Sistrurus catenatus) using landscape genetics.

Assessing the environmental factors that influence the ability of a threatened species to move through a landscape can be used to identify conservation actions that connect isolated populations. However, direct observations of species' movement are often limited, making the development of alternate approaches necessary. Here we use landscape genetic analyses to assess the impact of landscape features on the movement of individuals between local populations of a threatened snake, the eastern massasauga rattlesnake (Sistrurus catenatus). We linked connectivity data with habitat information from two landscapes of similar size: a large region of unfragmented habitat and a previously studied fragmented landscape consisting of isolated patches of habitat. We used this analysis to identify features of the landscape where modification or acquisition would enhance population connectivity in the fragmented region. We found evidence that current connectivity was impacted by both contemporary land-cover features, especially roads, and inherent landscape features such as elevation. Next, we derived estimates of expected movement ability using a recently developed pedigree-based approach and least-cost paths through the unfragmented landscape. We then used our pedigree and resistance map to estimate resistance polygons of the potential extent for S. catenatus movement in the fragmented landscape. These polygons identify possible sites for future corridors connecting currently isolated populations in this landscape by linking the impact of future habitat modification or land acquisition to dispersal ability in this species. Overall, our study shows how modeling landscape resistance across differently fragmented landscapes can identify habitat features that affect contemporary movement in threatened species in fragmented landscapes and how this information can be used to guide mitigation actions whose goal is to connect isolated populations.

Random placement models explain species richness and dissimilarity of frog assemblages within Atlantic Forest fragments.

Understanding the effects of random versus niche-based processes on biodiversity patterns is a central theme in ecology, and an important tool for predicting effects of habitat loss and fragmentation on biodiversity. We investigated the predictive power of random processes to explain species richness and species dissimilarity of amphibian assemblages in a fragmented tropical landscape of the Atlantic Forest of South America. We analyzed a large database of amphibian abundance and occupancy, sampled in 21 forest fragments ranging in size from 1.9 to 619ha. We compared observed species richness and species dissimilarity with the outcomes of two null (random placement) models: 1- the traditional Coleman's area-based model and 2- an abundance-based model (based on the number of individuals observed in each fragment). We applied these models for all species combined, and separately for forest-dependent and habitat-generalist species. The abundance-based model fitted the observed species richness data better than the area-based model for all species, forest-dependent species, and generalist species. The area-based and the abundance-based models were also able to significantly explain species dissimilarity for all species and for generalists, but not for forest dependent species. The traditional area-based model assigned too many individuals to large fragments, thus failing to accurately explain species richness within patches across the landscape. Although niche-based processes may be important to structuring the regional pool of species in fragmented landscapes, our results suggest that part of the variation in species richness and species dissimilarity can be successfully explained by random placement models, especially for generalist species. Evaluating which factors cause variation in the number of individuals among patches should be a focus in future studies aiming to understand biodiversity patterns in fragmented landscapes.

Can matrix structure affect animal navigation between fragments? A dispersal experiment using release platforms

AbstractThe persistence of species in fragmented landscapes relies on landscape connectivity and individuals’ ability in dispersing among habitat patches. Accordingly, matrix structure can affect the orientation of dispersing individuals across the landscape. In this study, we measured the impact of matrix structure on the dispersal performance of the white‐eared opossum (Didelphis albiventris). We released individuals in three types of matrix: bare field, corn crops, and soybean crops, with distances of 30, 50, and 100 m to the nearest habitat patch. To test if the release height would affect the individuals’ dispersal performance, we released animals from the ground and from 2‐m‐high platforms. We released and tracked 14 individuals in bare field on the ground; 30 in corn crops, 22 on the ground, and 8 on platforms; 17 on soybeans crop, 12 on the ground, and 5 on platforms. The type of matrix influenced the perceptual range. Perceptual range was 100 m in bare field, 50 m in corn field, and <30 m in soybean field. The platforms only increased the perceptual range of individuals in the corn field from 50 to 100 m. Visual and olfactory cues would cause this effect. We conclude that matrix structure affects dispersal performance, and that vertical elements of the matrix, such as scattered trees, may increase orientation in crop fields during inter‐patch dispersal.

Assessment of drivers of spatial genetic variation of a ground-dwelling bird species and its implications for conservation.

In modern wildlife ecology, spatial population genetic methods are becoming increasingly applied. Especially for animal species in fragmented landscapes, preservation of gene flow becomes a high priority target in order to restore genetic diversity and prevent local extinction. Within Central Europe, the Alps represent the core distribution area of the black grouse, Lyrurus tetrix. At its easternmost Alpine range, events of subpopulation extinction have already been documented in the past decades. Molecular data combined with spatial analyses can help to assess landscape effects on genetic variation and therefore can be informative for conservation management. Here, we addressed whether the genetic pattern of the easternmost Alpine black grouse metapopulation system is driven by isolation by distance or isolation by resistance. Correlative ecological niche modeling was used to assess geographic distances and landscape resistances. We then applied regression‐based approaches combined with population genetic analyses based on microsatellite data to disentangle effects of isolation by distance and isolation by resistance among individuals and subpopulations. Although population genetic analyses revealed overall low levels of genetic differentiation, the ecological niche modeling showed subpopulations to be clearly delimited by habitat structures. Spatial genetic variation could be attributed to effects of isolation by distance among individuals and isolation by resistance among subpopulations, yet unknown effects might factor in. The easternmost subpopulation was the most differentiated, and at the same time, immigration was not detected; hence, its long‐term survival might be threatened. Our study provides valuable insights into the spatial genetic variation of this small‐scale metapopulation system of Alpine black grouse.

Using experimental reintroductions to resolve the roles of habitat quality and metapopulation dynamics on patch occupancy in fragmented landscapes.

Declines of species in fragmented landscapes can potentially be reversed either by restoring connectivity or restoring local habitat quality. Models fitted to snapshot occupancy data can be used to predict the effectiveness of these actions. However, such inferences can be misleading if the reliability of the habitat and landscape metrics used is unknown. The only way to unambiguously resolve the roles of habitat quality and metapopulation dynamics is to conduct experimental reintroductions to unoccupied patches so that habitat quality can be measured directly from data on vital rates. We, therefore, conducted a 15-year study that involved reintroducing a threatened New Zealand bird to unoccupied forest fragments to obtain reliable data on their habitat quality and reassess initial inferences made by modeling occupancy against habitat and landscape metrics. Although reproductive rates were similar among fragments, subtle differences in adult survival rates resulted in λ (finite rate of increase) estimations of <0.9 for 9 of the 12 fragments that were previously unoccupied. This was the case for only 1 of 14 naturally occupied fragments. This variation in λ largely explained the original occupancy pattern, reversing our original conclusion from occupancy modeling that this occupancy pattern was isolation driven and suggesting that it would be detrimental to increase connectivity without improving local habitat quality. These results illustrate that inferences from snapshot occupancy should be treated with caution and subjected to testing through experimental reintroductions in selected model systems.

Movement of forest‐dependent dung beetles through riparian buffers in Bornean oil palm plantations

AbstractFragmentation of tropical forests is increasing globally, with negative impacts for biodiversity. In Southeast Asia, expansion of oil palm agriculture has caused widespread deforestation, forest degradation and fragmentation.Persistence of forest‐dependent species within these fragmented landscapes is likely to depend on the capacity of individuals to move between forest patches. In oil palm landscapes, riparian buffers along streams and rivers are potential movement corridors, but their use by moving animals is poorly studied.We examined how six dung beetle species traversed riparian buffers connected to a continuous forest reserve area within an oil palm plantation in Sabah, Malaysian Borneo. We used a mark–release–recapture study and a new Bayesian Joint Species Movement Modelling (JSMM) approach, extended to a continuous capture process model.Dung beetle species were fairly generalist in their habitat use, but two species showed a statistically supported preference for riparian buffer forest over oil palm, and one species showed a strong preference for forest reserve over riparian buffer, indicating the importance of forested areas within oil palm landscapes for some species.A land‐use change simulation indicated that the loss of riparian buffers in oil palm will result in reduced movement by forest‐dependent species.Synthesis and applications. Our results provide evidence for the use of riparian buffers in oil palm plantations for forest‐dependent dung beetle species, strengthening the case for their retention, restoration and re‐establishment. Furthermore, our study demonstrates the wider applicability of the Joint Species Movement Modelling (JSMM) framework to assess movement behaviour of species in fragmented landscapes, a vital tool for future forest and landscape management and conservation prioritisation exercises.

Invasive spread in meta‐food‐webs depends on landscape structure, fertilization and species characteristics

Land use change and biological invasions collectively threaten biodiversity. Yet, few studies have addressed how altering the landscape structure and nutrient supply can promote biological invasions and particularly invasive spread (the spread of an invader from the place of introduction), or asked whether and how these factors interact with biotic interactions and invader properties. We here bridge this knowledge gap by providing a holistic network‐based approach. Our approach combines a trophic network model with a spatial network model allowing us to test which combinations of abiotic and biotic factors can facilitate invasions and in particular invasive spread in food webs. We numerically simulated 6300 single‐species invasions in clustered and random landscapes at different levels of nutrient supply. In total, our simulation experiment yielded 69% successful invasions – 71% in clustered landscapes and 66% in random landscapes, with the proportion of successful invasions increasing with nutrient supply. However, invasive spread was generally higher in random than in clustered landscapes. The latter can facilitate invasive spread within a habitat cluster, but prevent invasive spread between clusters. Low nutrient levels generally prevented the establishment of invasive species and their subsequent spread. However, successful invaders could have more severe impacts as they contribute more to total biomass density and species richness under such conditions. Good dispersal abilities drive the broad‐scale spread of invasive species in fragmented landscapes. Our approach makes an important contribution towards a better understanding of what combination of landscape and invader properties can facilitate or prevent invasive spread in natural ecosystems. This should allow ecologists to more effectively predict and manage biological invasions.

Pedigree-based assessment of recent population connectivity in a threatened rattlesnake.

Managing endangered species in fragmented landscapes requires estimating dispersal rates between populations over contemporary timescales. Here, we developed a new method for quantifying recent dispersal using genetic pedigree data for close and distant kin. Specifically, we describe an approach that infers missing shared ancestors between pairs of kin in habitat patches across a fragmented landscape. We then applied a stepping-stone model to assign unsampled individuals in the pedigree to probable locations based on minimizing the number of movements required to produce the observed locations in sampled kin pairs. Finally, we used all pairs of reconstructed parent-offspring sets to estimate dispersal rates between habitat patches under a Bayesian model. Our approach measures connectivity over the timescale represented by the small number of generations contained within the pedigree and so is appropriate for estimating the impacts of recent habitat changes due to human activity. We used our method to estimate recent movement between newly discovered populations of threatened Eastern Massasauga rattlesnakes (Sistrurus catenatus) using data from 2996 RAD-based genetic loci. Our pedigree analyses found no evidence for contemporary connectivity between five genetic groups, but, as validation of our approach, showed high dispersal rates between sample sites within a single genetic cluster. We conclude that these five genetic clusters of Eastern Massasauga rattlesnakes have small numbers of resident snakes and are demographically isolated conservation units. More broadly, our methodology can be widely applied to determine contemporary connectivity rates, independent of bias from shared genetic similarity due to ancestry that impacts other approaches.

Synergistic impacts of aggressive species on small birds in a fragmented landscape

Abstract Attempts to conserve threatened species in fragmented landscapes are often challenging because factors such as habitat loss, habitat degradation and dominant species interact to reduce threatened species’ capacity to survive and reproduce. Understanding how threatening and mitigating processes interact is critical if conservation measures are to be effective. We used data from long‐term monitoring of bird populations and multivariate latent variable models to quantify how Australian woodland birds respond to the presence of the Noisy Miner, a despotic species known to exclude other bird species. We then investigated the extent to which the presence of other aggressive species exacerbates the impacts of the Noisy Miner, and to what extent these impacts can be mitigated by dense midstorey plantings. We found strong synergies between the Noisy Miner and two other aggressive species (Grey Butcherbird and Pied Butcherbird), despite weak effects of butcherbirds in isolation. The impacts of aggressive birds are most pronounced for small‐bodied species, but these impacts are lessened in the presence of high midstorey cover. Synthesis and applications. Accounting for interactions reveals that revegetation may be capable of improving conservation outcomes even when the proximate cause of species declines (i.e. exclusion or predation by aggressive bird species) cannot be managed directly.

Enter the Matrix: Use of Secondary Matrix by Mouse Lemurs

Madagascar is home to many threatened and endemic primate species, yet this island has seen dramatic declines in lemur habitat due to forest loss. This forest loss has resulted in an increasingly fragmented forest landscape, with fragments isolated from each other by grasslands (i.e., matrix). The grassland matrix is not entirely homogeneous containing matrix elements such as isolated trees and shrubs and linear features such as drainage lines. Because most lemurs are predominantly arboreal, they may preferentially use matrix elements to facilitate dispersal between fragments for access to mates or reduce feeding competition, allowing gene flow between fragments of habitat. Therefore, it is important to understand to what degree they use the matrix. We investigated matrix use in two mouse lemurs, the grey mouse lemur (Microcebus murinus) and the golden-brown mouse lemur (Microcebus ravelobensis) in a fragmented landscape in northwest Madagascar. We tested the predictions that: (1) lemurs use matrix less often than forest fragments, (2) if they use the matrix, then they will preferentially use matrix elements compared to grassland, and (3) M. murinus will disperse into the matrix further than M. ravelobensis. In 2011, we visually surveyed line transects in four areas containing matrix elements and four adjacent forest fragments during nocturnal walks. In 2017, we set up traplines in four areas of the matrix containing matrix elements, three areas that were grassland, and six traplines in adjacent fragments. We compared the relative abundance of mouse lemurs in matrix transects to fragmented forest transects, and the relative abundance of captured lemurs in matrix elements, grassland, and fragment traplines. We found that encounter rates of mouse lemurs did not significantly differ between the matrix and fragmented forest transects or traplines. Our sample size was too low to determine if the mean distance from the forest was greater for either Microcebus spp. Our study highlights that mouse lemurs do use matrix elements and there may be interspecific differences in use. Further research is needed to confirm species-specific matrix use, why mouse lemurs use matrix, and how much matrix elements facilitate movement for each species in fragmented landscapes.

Forested riparian belts as reservoirs of plant species in fragmented landscapes of tropical mountain cloud forest

Background: Cloud forest in central Veracruz is highly fragmented. However, different arboreal elements are still present within the agricultural matrix, including small patches of secondary forest, isolated trees and forested riparian belts. These elements could be important for cloud forest species conservation.&#x0D; Questions: What is the structure and composition of forested riparian belts within current anthropic landscapes, and what is their potential contribution as reservoirs of mountain cloud forest native plant species?&#x0D; Studied species: Vegetation community of forested riparian belts of cloud forest.&#x0D; Study site and dates: Eastern Mexico (central Veracruz), January to November 2018&#x0D; Methods: Along 14 segments of riparian belts (?400 m long), distributed across different tributary streams, six 50 × 2 m transects were placed (three per riverside) per segment. Every plant rooted within a transect and ? 1.5 m in height was identified and measured (height and DBH).&#x0D; Results: A total of 2,062 plants from 161 species, 102 genera and 55 families were recorded in the 14 sites (8,400 m² sampled). Structural attributes and floristic composition varied widely amongst sites. Elevation and the amount of forest cover (i.e., area) within 500 m of each sampling site were the most important factors underlying the spatial variation in species composition.&#x0D; Conclusions: Riparian belts were remarkably heterogeneous harboring a notable richness of tree and shrub species many of them native of the original cloud forest. This diversity reveals that these arboreal elements are keystone structures for biodiversity conservation and also have a high potential as propagule sources for cloud forest restoration in anthropic landscapes.

Anthropogenic thermal gradient in managed landscapes determines physiological performance and explains the edge-biased distribution of ectothermic arthropods

The intensive management of tree plantations has replaced and fragmented native forests worldwide. A direct consequence of this activity is the creation of new edges, which generate changes in microclimatic conditions in the adjacent forest as well as in the neighboring clearcut stands left over after harvesting by clearcut logging. Thus, newly created anthropogenic thermal gradients could influence ectothermic responses regarding abundance and physiology of native species in fragmented landscapes. Interestingly, the consequences of these changes have not been studied in insects. To test the effects of the anthropogenic thermal gradient on the abundance and physiology of ectothermic species, we chose the fragmented Maulino forest and the ground-dwelling beetle Ceroglossus chilensis (Coleoptera: Carabidae) as our biological model, working with seven fragments of native forest surrounded by active and clearcut pine plantation stands. We measured temperature variables and beetle abundance in different months using transects perpendicular to the edge and used general linear modelling to explain abundance with temperature. In addition, we assessed the preferential body temperatures (Tb) and Rollover Speed (RoS) of C. chilensis at five different temperatures in controlled conditions to explain field abundance. We found that mean ambient temperatures were up to 42% higher in clearcut stands than in native forest fragments during summer. However, ambient temperatures in autumn were similar between native forest fragments and clearcut stands. The abundance of C. chilensis, is concentrated near the edge in the native forest (between 2 and 10 m to interior of native forest), regardless of month sampled. The abundance of C. chilensis was higher at the edge than inside native forest interiors or clearcut stands, regardless of the month. Ambient temperature surpasses preferential body temperature (14–15.99 °C) and physiological performance of C. chilensis (15 °C), particularly during summer. Ceroglossus chilensis abundance at the edge of clearcut stands could be favored by understory structural complexity in understory vegetation, creating suitable microclimatic conditions and increasing abundance of prey resource. In essence, we found that the higher temperatures found near the edge inside forest interiors might enable individuals of C. chilensis to display thermoregulatory behavior by concentrating activity at these particular regions, resulting in increased abundances and more concentrated occurrences, helping to explain the edge-biased distribution. Thus, we offer evidence that physiological performance might be a key functional trait to explain abundance of ectothermic species in fragmented forest landscapes. We submit to decision makers linked to the forestry industry, that managing the understory of young tree plantations and increasing the structural complexity at remnant forest edges to cushion high temperatures in clearcut stands would enable more effective conservation planning of thermosensitive ectotherms in disturbed forest landscapes.

Habitat amount and quality, not patch size, determine persistence of a woodland-dependent mammal in an agricultural landscape

The classical theory of island biogeography explains loss of species in fragmented landscapes as an effect of remnant patch size and isolation. Recently this has been challenged by the habitat amount and habitat continuum hypotheses, according to which persistence in modified landscapes is related to total habitat amount rather than habitat configuration or the ability of species to use all habitats to varying degrees. Distinguishing between these theories is essential for effective conservation planning in modified landscapes. Identify which factors of habitat type, amount and configuration predict the persistence of a keystone woodland specialist, the eastern bettong Bettongia gaimardi, in a fragmented landscape. In the Midlands region of Tasmania we carried out camera surveys at 62 sites in summer and winter. We included habitat and landscape features to model whether habitat amount or patch size and isolation influenced the presence of the eastern bettong, and to measure effects of habitat quality. Habitat amount within a 1 km buffer was a better predictor of occupancy than patch size and isolation. Occupancy was also affected by habitat quality, indicated by density of regenerating stems. Our results support the habitat amount hypothesis as a better predictor of presence. For a species that is able to cross the matrix between remnant patches and utilise multiple patches, the island biogeography concept does not explain habitat use in fragmented landscapes. Our results emphasize the value of small remnant patches for conservation of the eastern bettong, provided those patches are in good condition.

Habitat fragmentation affects individual condition: evidence from small mammals of the Brazilian Atlantic Forest

Habitat loss and fragmentation are likely to affect individual condition as they usually alter the quality of habitat. However, responses of individuals of different species to these processes may be subtle and difficult to detect, despite that such responses may reveal interesting and diverse strategies of persistence of species in fragmented landscapes. Here, we used model selection to 1) compare the body condition (Scaled Mass Index) of 2 Neotropical marsupials (Didelphis aurita and Philander frenatus) from 6 continuous forest sites and 25 forest fragments, and 2) determine whether local habitat structure and landscape and temporal factors affect body condition in forest fragments. Body condition of both species was lower in forest fragments compared to continuous forest sites, but only in the super-humid season for D. aurita and in the humid season for P. frenatus. When only forest fragments were compared, body condition of D. aurita was higher in the humid season, in sites with fewer Cecropia trees and water courses, lower percent forest cover, and surrounded by a mixed matrix (plantation and cattle ranching), or located in small rural properties. Body condition of P. frenatus was slightly higher in the super-humid season, in sites surrounded by a mixed matrix, with fewer Cecropia trees and water courses, more lianas, and greater percent forest cover. Our results revealed negative effects of habitat loss and fragmentation on both species, but also different responses of each species to local extrinsic environmental factors. We suggest that body condition should not be used as a direct indicator of animal fitness or habitat quality. Nonetheless, body condition may still reveal subtle and previously undetected responses of species to habitat disturbance and fragmentation.

Increased nest predation near protected capercaillie leks: a caveat against small reserves

Protecting animal aggregation sites is intuitively an efficient conservation approach, particularly for threatened species in fragmented landscapes. However, the appropriate scale of protection depends on accompanying threats, such as predator attraction to the same aggregation sites, to which the target species may need to respond by moving to alternative habitat patches. We performed experiments using artificial ground nests around protected capercaillie leks in commercially managed forest landscape in Estonia. We considered two scales: the landscape up to 3 km from the lek centre, and among 10–30-ha forest compartments, which differed in predator abundance. We found that nest predation significantly declined with distance from the lek. Nests were depredated by multiple mammalian and avian predator species and total predator abundance explained most of the between-forest variation in predation rate. Our results indicate that, in this hemiboreal area, (i) ground nest predation is largely determined by landscape-scale distribution of predators and (ii) predators can aggregate at capercaillie leks. The implication is that lek-centred habitat protection used for the capercaillie and other grouse may be ineffective unless the peripheral habitat quality and predator abundance are specifically addressed. More generally, predation pressure can be a serious problem in small set-asides within hostile landscapes for threatened ground-nesting birds.

Defaunation as a trigger for the additional loss of plant species in fragmented landscapes: considerations on the state of Espírito Santo, southeastern Brazil

Abstract Here we present a brief review on how the loss of fauna can cause a concomitant loss in plant diversity in the state of Espírito Santo, focusing on the context of current habitat loss and fragmentation and the importance of the mutualistic interactions between animals and plants. We discuss the main groups of fauna that are involved in pollination and seed dispersal, especially those that are found in the state of Espírito Santo. These ecological processes were selected due to their relevance for population dynamics and population genetics of plants. In Atlantic Forest, important pollinators include a variety of insects (especially bees), along with many species of birds and bats. Seed dispersers also include many taxonomic groups, from ants to large mammals. Each of these groups contribute in their own unique and complementary, rather than redundant, way. Habitat fragmentation causes a variety of problems for habitat integrity and the reduction of species diversity, and smaller fragments tend to support fewer species and smaller populations. As a consequence, pollinators and seed dispersers are lost or their activity is reduced, thereby reducing even further the reproductive success of the plants, leading to a vicious cycle of reduction of species diversity.

Spatial mismatch analysis among hotspots of alien plant species, road and railway networks in Germany and Austria.

Road and railway networks are pervasive elements of all environments, which have expanded intensively over the last century in all European countries. These transportation infrastructures have major impacts on the surrounding landscape, representing a threat to biodiversity. Roadsides and railways may function as corridors for dispersal of alien species in fragmented landscapes. However, only few studies have explored the spread of invasive species in relationship to transport network at large spatial scales. We performed a spatial mismatch analysis, based on a spatially explicit correlation test, to investigate whether alien plant species hotspots in Germany and Austria correspond to areas of high density of roads and railways. We tested this independently of the effects of dominant environments in each spatial unit, in order to focus just on the correlation between occurrence of alien species and density of linear transportation infrastructures. We found a significant spatial association between alien plant species hotspots distribution and roads and railways density in both countries. As expected, anthropogenic landscapes, such as urban areas, harbored more alien plant species, followed by water bodies. However, our findings suggested that the distribution of neobiota is strongest correlated to road/railways density than to land use composition. This study provides new evidence, from a transnational scale, that alien plants can use roadsides and rail networks as colonization corridors. Furthermore, our approach contributes to the understanding on alien plant species distribution at large spatial scale by the combination with spatial modeling procedures.

The mid‐distance dispersal optimum, evidence from a mixed‐model climate vulnerability analysis of an edaphic endemic shrub

AbstractAimPredicting accurate species responses to climate change in fragmented landscapes is challenging in conservation biogeography. We assessed the role of dispersal, including long‐distance dispersal (LDD), for the long‐term persistence of a rare plant species (Vella pseudocytisus subsp. paui) under current climate conditions and four future climate scenarios; and analysed the effect of competition for its regional survival.LocationEster Iberian system, Aragón, Spain.MethodsWe used BioMove, a linked modelling platform that integrates demographic, dispersal and competition features with biogeographic predictions of range dynamics, and whose results can inform risk assessments and conservation planning. We linked Vella's population dynamics and habitat suitability models with its well‐documented life history traits and ecological characteristics to enhance our understanding of its inherent vulnerability to dispersal, competitive interactions and climate change.ResultsWe found thresholds in the effect of long dispersal distances on population persistence, suggesting a mid‐distance optimum, which reduces mortality risk associated with the increasing proportion of LDD seeds. Moreover, increasing the proportion of LDD propagules reduces Vella's ability to compete in currently occupied and nearby unoccupied habitats by reducing the number of local recruitments.Main conclusionsWhereas LDD ability is generally assumed to be beneficial for the long‐term persistence of plant species in fragmented landscapes, our results suggest that moderate to high distances between new colonization increase the species’ dispersal‐related mortality. Higher numbers of LDD events reduce the number of local propagules in established populations, reducing regional survival for Vella. Moreover, associated range shifts of potentially better climate‐adapted competitors could prevent Vella individuals from colonizing new climatically suitable habitats. These findings can support development of more efficient conservation management strategies for establishing new population patches to mitigate population losses due to climate change. Our findings may also apply as a framework for other narrowly distributed endemic shrub species, particularly edaphic endemics.

Differential matrix use by Neotropical birds based on species traits and landscape condition.

There is considerable uncertainty about the role of human-modified habitats in supporting species in fragmented landscapes. This is because few studies sample outside of native habitats in the "matrix." Those that do, often fail to sample landscapes in a way that accounts for the confounding effects of native habitat pattern and species detection biases that can obscure species responses. We employed multi-species hierarchical occupancy models to determine the use of human-modified habitats by Neotropical birds in landscapes that were similar in forest amount and configuration but surrounded by a matrix of agriculture (predominately pasture), bauxite mining (surface mining for aluminum), or suburban development in central Jamaica. We found that the vast majority of bird species used the matrix: with the highest mean occurrences for open-associated, followed by generalist, and last forest-associated species. Migrant species had higher mean occurrences in all matrix types relative to resident species. Contrary to our expectation, mean occurrence for the entire species community, and for forest-associated and migrant species, were highest in bauxite, intermediate in suburban, and lowest in agriculture. Open-associated species had higher occurrences in both bauxite and agricultural matrices, whereas generalist species had higher occurrences in suburban matrices. Additional behavioral observations indicated that Neotropical birds used matrix areas, particularly scattered trees, to acquire food, and secondarily, as movement conduits. Matrix use patterns reflected the differential availability of potential resources and structural connectivity across the three landscape types, but only for those species adapted to open/edge environments and with generalized habitat requirements. Patterns of matrix use by forest specialists reflected the differential levels of degradation of the native forest; thus, we propose that higher matrix use for forest-dependent species may be induced by diminished within-forest resources. These results underscore that effective management of human-modified matrices requires in-depth understanding of the trade-offs between the benefits available in the matrix and the impacts on the disturbance of native habitats.