Fragmentation Of Suitable Habitat Research Articles

Habitat Selection Differences of Two Sympatric Large Carnivores in the Southwestern Mountains of China

Large terrestrial carnivores play a crucial role in the top–down control of terrestrial ecosystems by maintaining ecosystem stability and biodiversity. However, intense interspecific competition typically occurs among large sympatric carnivores, leading to population reduction or extinction. Spatial partitioning through divergent habitat selection mitigates such competition. In this study, we analyzed the main environmental factors influencing the habitat selection and fragmentation of suitable habitats in Xinlong County, Sichuan Province, using 410 infrared cameras from 2015 to 2023. By employing generalized linear and maximum entropy models, we developed an ensemble model to predict the suitable habitat distribution of leopards (Panthera pardus) and wolves (Canis lupus). The results revealed significant disparities in suitable habitat distributions of leopards and wolves as coexisting large carnivores. Leopards prefer understory, whereas wolves prefer high-altitude meadows. Wolves spatially avoid leopards, who secure relatively superior resources and relegate wolves to inferior habitats. Although suitable habitat patches for both species cluster intensely, habitat connectivity remains low owing to pronounced anthropogenic disturbances, which is especially evident in the higher fragmentation of wolf habitats. These results suggest that sympatric large carnivores can reduce spatial competition intensity and promote spatial partitioning by selecting divergently suitable habitats, thereby facilitating species coexistence.

Land-use change is associated with multi-century loss of elephant ecosystems in Asia

Understanding historic patterns of land use and land cover change across large temporal and spatial scales is critical for developing effective biodiversity conservation management and policy. We quantify the extent and fragmentation of suitable habitat across the continental range of Asian elephants (Elephas maximus) based on present-day occurrence data and land-use variables between 850 and 2015 A.D. We found that following centuries of relative stability, over 64% (3.36 million km2) of suitable elephant habitat across Asia was lost since the year 1700, coincident with colonial-era land-use practices in South Asia and subsequent agricultural intensification in Southeast Asia. Average patch size dropped 83% from approximately 99,000–16,000 km2 and the area occupied by the largest patch decreased 83% from ~ 4 million km2 (45% of area) to 54,000 km2 (~ 7.5% of area). Whereas 100% of the area within 100 km of the current elephant range could have been considered suitable habitat in the year 1700, over half was unsuitable by 2015, driving potential conflict with people. These losses reflect long-term decline of non-forested ecosystems, exceeding estimates of deforestation within this century. Societies must consider ecological histories in addition to proximate threats to develop more just and sustainable land-use and conservation strategies.

Move and you're dead: commercial trawl fisheries select for fish that don't move far

Abstract Recent research on harvest-induced evolution of behaviour in (especially aquatic) animals has focused on the shy-bold axis, but foraging and dispersal behaviour have received little attention. Here, we consider the selective effect of systematically localised trawl harvesting from a wild population of mobile animals that vary phenotypically in their range of movement (resulting in a continuum between wide-ranging and sedentary behaviours). We use a spatially explicit individual-based model of an empirically-based demersal fish population and trawl fishing in a realistic seascape. We test whether a sustained spatially concentrated pattern of fishing can select for or against wide-ranging vs. more sedentary behaviour as the fish perform biased random foraging in a seascape of spatially varying resource quality, leading to an approximation of the ideal free distribution. The simulation predicted a strong micro-evolutionary shift towards more sedentary behaviour as wide-ranging animals flow into a population sink caused by concentrated fishing. The shift towards short-rangers increased with fishing intensity and spatial precision with which fishing activity matches fish abundance; it decreased with habitat spatial complexity (fragmentation of suitable habitat). Most cases led to the effective extinction of the trait values at the upper end of the ranging continuum, indicating important implications for the management of exploited fish stocks.

The impacts of climate change on the habitat distribution of the vulnerable Patagonian-Fueguian species Ctenomys magellanicus (Rodentia, Ctenomyidae)

The ongoing climate change could intensify endangerment of species with a restricted distribution and small population size, such as rare or endemic species. Magellanic tuco-tuco (Ctenomys magellanicus) is the southernmost Patagonian-Fueguian fossorial caviomorph rodent with a small distribution. This species has been categorized as vulnerable due to a strong population decline caused by over-exploitation and habitat loss and degradation produced by sheep grazing. This study aims to estimate suitable habitat distribution for C. magellanicus and predict suitable habitat distribution and potential range shifts under near-future climate change. For these, we used the method of maximum entropy distribution modeling, using 116 occurrence records from literature and, most importantly, direct species surveys. Seven climatic variables, associated with the water regime and with various aspects of the temperature variation between seasons of Patagonia, were the most important for the species’ distribution. Under the major part of future climate change scenarios, the suitable habitat for C. magellanicus will likely be severely and negatively affected. Specifically, it would decrease mainly in its continental present distribution, with a drastic loss and fragmentation of suitable habitats. Our results can be useful for design evidence-based conservation and management policies.

Effect of Antipredator Training on Spatial Behaviour of Male and Female Greater RheasRhea americanaReintroduced Into the Wild

The Greater Rhea Rhea americana is a South-American flightless bird whose populations have decreased due to poaching and fragmentation of suitable habitats, and there has been an urgent need to carry out management practices to prevent local or regional extinctions. Several studies revealed that reintroduction might be an appropriate action for increasing the viability of wild populations of this species. Nevertheless, although this is a popular and useful conservation strategy, the animals to be released should be prepared against risks like predation and dispersion that could influence the post-release success. We evaluated the effect of an antipredator training applied to captive-bred Greater Rheas before they were released into the wild, on their dispersal and home range size and overlap, supposing that the trained animals would avoid dispersing into places with predators and, consequently, they would reduce their home range. We also studied the habitat use by the released rheas. Eleven trained and nine control (untrained) animals were marked and monitored two to four times per day during the first week, and from 4 to 19 consecutive days per month during four months, throughout the breeding and post-breeding seasons. The antipredator training affected the home range in different ways according to sex. Trained females exhibited smaller home ranges (mean ± S.E.: 0.54 ± 0.58 km2) than the rest of the individuals (control females 5.8 ± 0.75 km2, control and trained males: 2.11 ± 0.65 km2 and 2.96 ± 0.65 km2, respectively), whereas their overlap was greater (63.83 ± 16.95%) than that of the untrained females (24.04 ± 21.88%). Males of both experimental groups showed similar distances travelled (3.21 ± 0.29 km), which were also greater than those of females (2.21 ± 0.32 km). The home ranges of males were not influenced by the training and they showed a high degree of overlapping (among control males 29.96 ± 18.95%, and among trained males: 35.81 ± 18.95%). Both groups similarly used crops and in lesser extent open areas and grassland. Only the trained females reduced their movements and wandering as a result of the previous conditioning. They moved to crop or open areas, avoiding tall vegetation such as that present in grasslands, which may make difficult to detect predators. On the other hand, in the males, the influence of the reproductive season and the complex mating system exhibited by this species prevailed over the possible effects of training. Our work shows new and useful data about the spatial behaviour and reintroduction for conservation of the Greater Rhea.

A zoogeographical boundary between the Palaearctic and Sino-Japanese realms documented by consistent north/south phylogeographical divergences in three woodland birds in eastern China

Aim The location of zoogeographical boundaries in eastern China has long been the subject of debate. To identify any north/south genetic divergence between the Palaearctic and Sino-Japanese realms proposed by previous studies, we conducted a comparative phylogeographical study involving three passerine species with wide latitudinal distributions in eastern China. Location Eastern China. Methods Two mitochondrial genes and three nuclear introns were amplified and sequenced. Population structures were analysed using intra-specific phylogeny, tcs networks, AMOVA and structure inferences. We tested for evidence of genetic barriers based on pairwise differences. Lineage divergences, demographic dynamics and gene flow between lineages were estimated using Bayesian methods. Results A congruent north/south phylogeographical divergence was identified for three species. A geographical barrier was inferred at c. 40° N in eastern China. The population sizes of the northern and southern lineages have both been stable through the late Pleistocene, while multiple divergences were inferred during the early and middle Pleistocene. Main conclusions Our results suggest a general phylogeographical break in north-eastern China, coinciding with the Palaearctic/Sino-Japanese boundary. Physical blocking of the Yan Mountains and fragmentation of suitable habitat during glacial stages between the north and south probably acted together to provide long-lasting barrier effects. Our comparative phylogeographical approach demonstrates that the Palaearctic/Sino-Japanese boundary may represent a gene-flow barrier even within widespread species.

Neotropical forest expansion during the last glacial period challenges refuge hypothesis

The forest refuge hypothesis (FRH) has long been a paradigm for explaining the extreme biological diversity of tropical forests. According to this hypothesis, forest retraction and fragmentation during glacial periods would have promoted reproductive isolation and consequently speciation in forest patches (ecological refuges) surrounded by open habitats. The recent use of paleoclimatic models of species and habitat distributions revitalized the FRH, not by considering refuges as the main drivers of allopatric speciation, but instead by suggesting that high contemporary diversity is associated with historically stable forest areas. However, the role of the emerged continental shelf on the Atlantic Forest biodiversity hotspot of eastern South America during glacial periods has been ignored in the literature. Here, we combined results of species distribution models with coalescent simulations based on DNA sequences to explore the congruence between scenarios of forest dynamics through time and the genetic structure of mammal species cooccurring in the central region of the Atlantic Forest. Contrary to the FRH predictions, we found more fragmentation of suitable habitats during the last interglacial (LIG) and the present than in the last glacial maximum (LGM), probably due to topography. We also detected expansion of suitable climatic conditions onto the emerged continental shelf during the LGM, which would have allowed forests and forest-adapted species to expand. The interplay of sea level and land distribution must have been crucial in the biogeographic history of the Atlantic Forest, and forest refuges played only a minor role, if any, in this biodiversity hotspot during glacial periods.

Distribution of the common lizard (Zootoca vivipara) and landscape favourability for the species in Northern Ireland

AbstractThe common lizard (Zootoca vivipara) is Ireland's only native reptile, forming a key part of the island's biodiversity. However, there is a general paucity of distributional and abundance data for the species. In this study, we collated incidental records for common lizard sightings to define the distribution of the species in Northern Ireland. Maximum entropy modelling was employed to describe species-habitat associations. The resulting predicted landscape favourability was used to evaluate the current status of the species based on the distribution of its maximum potential range in relation to the degree of fragmentation of remaining suitable habitat. In common with previous studies in the Republic of Ireland, sightings were highly clustered indicating under-recording, observer bias, and fragmentation of suitable habitat. A total of 98 records were collated from 1905 to 2009. The species was recorded in 63 (ca. 34%) of 186 × 10 km Northern Irish grid squares. Lizard occurrence was strongly and positively associated with landscapes dominated by heathland, bog and coastal habitats. The single best approximating model correctly classified the presence of lizards in 84.2% of cases. Upland heath, lowland raised bog and sand dune systems are all subject to Habitat Action Plans in Northern Ireland and are threatened by conversion to agriculture, afforestation, invasive species encroachment and infrastructural development. Consequently, remaining common lizard populations are likely to be small, isolated and highly fragmented. Establishment of an ecological network to preserve connectivity of remaining heath and bog will not only benefit remaining common lizard populations but biodiversity in general.

Threatened fishes of the world: Poecilia latipunctata Meek, 1904 (Poeciliidae)

Common names: Tamesi molly (US), Topote del Tamesi (MX). Conservation status: Listed as ‘critically endangered’ by the IUCN based on population declines, fragmentation of populations, and decline of habitat quality. The species is federally protected by the Mexican government (SEDESOL 1994). Identification: Poecilia latipunctata is a typical molly characterized by a longitudinal stripe of discontinuous black spots midside of body. The maximum size is ~50 mm. Illustration by Debby Kaspari. Distribution: Confined to the headwaters of the Rio Tamesi (Rios Guayalejo and Mante), Tamaulipas, Mexico. It was introduced into La Media Luna, San Luis Potosi (Miller et al. 2005). Ecology: This species prefers gravelly to muddy habitats with clear, flowing water and aquatic vegetation. It also occurs in irrigation ditches with lower flow and overhanging vegetation. Poecilia latipunctata predominantly feeds on detritus and algae (Darnell 1962). It occurs sympatrically with two other molly species, P. mexicana and P. formosa, and has been documented to serve as sperm donor for gynogenetic P. formosa females (Niemeitz et al. 2002). Although phenotypically a short-fin molly, the species is closely related to the long fin clade within the mollies (Ptacek et al. 2005). Threats: The species is threatened predominantly through fragmentation of suitable habitats as well as habitat deterioration by intense agriculture and invasive species. Conservation recommendations: The species is protected by Mexican law, but no specific conservation actions have been taken to date. The current distribution and abundance of P. latipunctata should be Environ Biol Fish (2009) 85:31–32 DOI 10.1007/s10641-009-9451-1

La foresta come habitat del Gallo cedrone: ricerca applicata e nuove esperienze di gestione

Capercaillie (Tetrao urogallus L.) is considered as an indicator species for naturally open coniferous forests, with high proportions of old and open stands. At present, Capercaillie conservation status is threatened in all its central European distribution range: the species has narrow habitat preferences and large spatial requirements and it is particularly susceptible to changes in landscape and habitat use. Forestry practices are commonly considered as the major factor influencing Capercaillie’s population dynamics, though direct human disturbance is another threat of considerable impact. Increasing loss and fragmentation of suitable habitats have resulted in small populations with different levels of connectivity, up to complete isolation. Preservation, restoration and improvement of the habitat are the most important conservation measures to ensure the long-term survival of Capercaillie populations. Integrating silvicultural practices with specific environmental requirements of this forest grouse is therefore of crucial importance. Some results of recent research and conservation efforts carried out in central-eastern Alpine Arc of Switzerland and Italy are presented here, based on different research approaches. Preliminary experiences of management guidelines applied to conservation strategy of such a symbolic species are also commented. A conservation strategy recently developed by Regione Lombardia is discussed. Secondly, two studies developed in the frame of a research project concerning “A metapopulation model of Capercaillie in the Swiss Alps” are presented, referring to different spatial scale (forest stand and landscape). A specific Action Plan at Swiss national level will be developed based on the main results of this project. Finally implementation of Special Forest Reserves is described, as a possible long-term tool for protecting and conserving Capercaillie populations.

Genetic diversity and fitness in peripheral and central populations of the European tree frog Hyla arborea.

Genetic diversity is expected to decrease in small and isolated populations as a consequence of founder effects, bottlenecks, inbreeding and genetic drift. In this study we analyse temporal and spatial effects on genetic variation and progeny viability of the European tree frog (Hyla arborea) at two scales. First, the Swedish distribution has been isolated from the continental distribution for more than 8000 thousand years, and secondly, within Sweden, recent habitat alterations that have taken place during this century have increased isolation between local populations. Genetic variation and progeny survival in relation to isolation was studied within the entire Swedish distribution of the tree frog. Allozyme electrophoresis analysis of froglets, sampled across the Swedish distribution, revealed a low overall genetic variation (1.06 alleles/locus) at the protein level in comparison with continental populations (1.54-1.68 alleles/locus). However, egg hatchability (97%) and early larval survival (95%) were not lower than in other parts of the tree frog distribution or in other anuran species. Within the Swedish distribution, early larval survival was lower in isolated breeding ponds than in more central ones. However, no differences in genetic variation were found in relation to isolation. Polymorphism was detected only at a single locus, and was restricted geographically to the eastern part of the Swedish distribution. Bottlenecks due to climatic changes and fragmentation of suitable habitat (primarily natural pastures with ponds) are suggested as possible causes of the low genetic diversity of the Swedish tree frog population.

Spatial prediction of rufous bristlebird habitat in a coastal heathland: a GIS‐based approach

Summary To develop a conservation management plan for a species, knowledge of its distribution and spatial arrangement of preferred habitat is essential. This is a difficult task, especially when the species of concern is in low abundance. In south‐western Victoria, Australia, populations of the rare rufous bristlebird Dasyornis broadbenti are threatened by fragmentation of suitable habitat. In order to improve the conservation status of this species, critical habitat requirements must be identified and a system of corridors must be established to link known populations. A predictive spatial model of rufous bristlebird habitat was developed in order to identify critical areas requiring preservation, such as corridors for dispersal. Habitat models generated using generalized linear modelling techniques can assist in delineating the specific habitat requirements of a species. Coupled with geographic information system (GIS) technology, these models can be extrapolated to produce maps displaying the spatial configuration of suitable habitat. Models were generated using logistic regression, with bristlebird presence or absence as the dependent variable and landscape variables, extracted from both GIS data layers and multispectral digital imagery, as the predictors. A multimodel inference approach based on Akaike's information criterion was used and the resulting model was applied in a GIS to extrapolate predicted likelihood of occurrence across the entire area of concern. The predictive performance of the selected model was evaluated using the receiver operating characteristic (ROC) technique. A hierarchical partitioning protocol was used to identify the predictor variables most likely to influence variation in the dependent variable. Probability of species presence was used as an index of habitat suitability. Negative associations between rufous bristlebird presence and increasing elevation, ‘distance to creek’, ‘distance to coast’ and sun index were evident, suggesting a preference for areas relatively low in altitude, in close proximity to the coastal fringe and drainage lines, and receiving less direct sunlight. A positive association with increasing habitat complexity also suggested that this species prefers areas containing high vertical density of vegetation. The predictive performance of the selected model was shown to be high (area under the curve 0·97), indicating a good fit of the model to the data. Hierarchical partitioning analysis showed that all the variables considered had significant independent contributions towards explaining the variation in the dependent variable. The proportion of the total study area that was predicted as suitable habitat for the rufous bristlebird (using probability of occurrence at a ≥ 0·5 level) was 16%. Synthesis and applications. The spatial model clearly delineated areas predicted as highly suitable rufous bristlebird habitat, with evidence of potential corridors linking coastal and inland populations via gullies. Conservation of this species will depend on management actions that protect the critical habitats identified in the model. A multiscale approach to the modelling process is recommended whereby a spatially explicit model is first generated using landscape variables extracted from a GIS, and a second model at site level is developed using fine‐scale habitat variables measured on the ground. Where there are constraints on the time and cost involved in measuring finer scale variables, the first step alone can be used for conservation planning.

Distribution and status of Rana latastei in Italy (Amphibia, Ranidae)

Data regarding distribution, demographic parameters, ecological preferences and conservation status of Rana latastei in Italy are reported. By comparing bibliographic information and original field data, the authors wish to provide a first estimate concerning the possible risk of rarefaction of this species throughout the national territory. Observations were carried out in an area corresponding lo a large portion of the distribution range in Italy; in particular, the following regions were considered: Piedmont, Lombardy, Venetia and Friuli-Venezia Giulia. The populations of Rana latastei seem to have undergone a constant decline in recent decades; the species is threatened mainly from the limited extension and fragmentation of suitable habitats and should probably be considered in the category “vulnerable”.

Modelling habitat suitability of the swamp antechinus ( Antechinus minimus maritimus) in the coastal heathlands of southern Victoria, Australia

In recent years, predictive habitat distribution models, derived by combining multivariate statistical analyses with Geographic Information System (GIS) technology, have been recognised for their utility in conservation planning. The size and spatial arrangement of suitable habitat can influence the long-term persistence of some faunal species. In southwestern Victoria, Australia, populations of the rare swamp antechinus ( Antechinus minimus maritimus) are threatened by further fragmentation of suitable habitat. In the current study, a spatially explicit habitat suitability model was developed for A. minimus that incorporated a measure of vegetation structure. Models were generated using logistic regression with species presence or absence as the dependent variable and landscape variables, extracted from both GIS data layers and multi-spectral digital imagery, as the predictors. The most parsimonious model, based on the Akaike Information Criterion, was spatially extrapolated in the GIS. Probability of species presence was used as an index of habitat suitability. A negative association between A. minimus presence and both elevation and habitat complexity was evidenced, suggesting a preference for relatively low altitudes and a vegetation structure of low vertical complexity. The predictive performance of the selected model was shown to be high (91%), indicating a good fit of the model to the data. The proportion of the study area predicted as suitable habitat for A. minimus ( Probability of occurrence ⩾0.5) was 11.7%. Habitat suitability maps not only provide baseline information about the spatial arrangement of potentially suitable habitat for a species, but they also help to refine the search for other populations, making them an important conservation tool.

What makes a narrow-range taxon? Insights from Australian freshwater snails.

A combination of intrinsic and extrinsic factors, such as dispersal capabilities or opportunities, habitat preferences, life history attributes, physiological attributes, habitat availability, biotic and abiotic interactions and historical factors, determine not only the geographic distribution of a taxon, but its propensity for population differentiation and speciation. Freshwater hydrobiid snails have little intrinsic ability to disperse outside their immediate habitat and opportunities for accidental dispersal are limited. Long-term permanency of habitat is critical and the existence of many taxa is highly dependent on local hydrological conditions and/or rainfall, water chemistry, geology and the structure of the non-aquatic environment. Dispersal success is apparently related to habitat, including factors such as size and riparian vegetation and canopy, as well as proximity to other populations and the intrinsic behaviour of the snails. Speciation patterns for complex clusters of narrow-range taxa are generally not well understood. Allozyme data for four genetically distinct taxa were analysed to determine the patterns of differentiation of populations at Wilsons Promontory, Victoria. Two of these taxa showed high levels of local differentiation largely concordant with geographic location, suggesting long in situ evolution. The other two taxa showed much less divergence between populations, suggesting relatively recent dispersal. Narrow-range hydrobiid diversity is concentrated in parts of south-eastern Australia, including Tasmania, and in artesian springs associated with the Great Artesian Basin. These areas of high diversity unfortunately largely coincide with some of the least protected areas. Human-induced changes to habitat will undoubtedly threaten the viability of highly localised taxa or populations. The loss or fragmentation of suitable habitat may have caused the extinction of some taxa or may be contributing to the accelerated differentiation of some populations.

Behaviour of specialist species in habitat corridors: arboreal dormice avoid corridor gaps

Linear habitat elements (corridors) may be important for species survival if they promote dispersal between fragments of suitable habitat, although there is little understanding of the behavioural basis for their use. I conducted experiments to determine how the movement of an arboreal habitat specialist species (the dormouse,Muscardinus avellanarius) was affected by gaps in corridors (hedgerows) and the presence of food resources. Movements in noncorridor habitat were also assessed. Translocated dormice were clearly averse to crossing even narrow gaps in hedgerows and remained in hedgerows, rather than move into surrounding noncorridor habitat. Gaps are thus likely to constrain movement along habitat corridors. Dormice travelled further in a hedgerow lacking food resources, implying that lack of food may (within an animal’s fasting endurance) actually promote movement. Although strongly arboreal, dormice were able to locomote rapidly through noncorridor habitat (a grass field). Noncorridor habitat thus does not represent a complete barrier to movements of at least 100m. The results imply that appropriately managed hedgerows (without gaps) may play an important role as corridors in the dispersal of dormice between woodlands.