Effects Of Habitat Fragmentation Research Articles

Synergistic effects of climate change and habitat fragmentation on species range shifts and metapopulation persistence

The effects of climate and landscape change on biodiversity are relatively well described. However, there is limited understanding of the interactions between these processes, which generally operate at differing spatial scales. My objective was to evaluate the synergistic effects of climate and landscape changes on persistence and range shift dynamics. The model species was the Cabrera vole, Microtus cabrerae, a habitat specialist with limited dispersal ability. The present study demonstrated that, as a result of the combined effects of climate and landscape change, this species’ future potential distribution will be considerably reduced. The combined effect of climate change and landscape connectivity was assessed using the software MetaLandSim, a newly developed package, with a good balance between data requirements and output quality, allowing researchers to account for connectivity and dispersal in range forecasting. With this R package, the species’ metapopulational dynamics could be simulated at the landscape scale, and range expansion for different connectivity scenarios could be computed.

A methodology to assess habitat fragmentation effects through regional indexes: Illustration with forest biodiversity hotspots

The fragmentation of natural environments is a critical issue involving major challenges for biodiversity conservation and ecosystem management. Large-scale information on areas sensitive to fragmentation is needed to improve the effectiveness of planning efforts. One promising metric combining the landscape spatial configuration with species characteristics is the metapopulation capacity λ, which can be used to rank different fragmented landscapes in terms of their capacity to support viable metapopulations. A methodology to globally derive a fragmentation metric based on metapopulation capacity, at appropriate and meaningful spatial scales for fragmentation mechanisms, was developed. To illustrate the applicability and interest of the methodology, worldwide regionalised fragmentation indexes, calculated with a dispersal distance of 1 km valid for a broad range of species, were provided for all forest ecoregions included in the biodiversity hotspots. Ecoregions were divided by a virtual grid and a statistical analysis of metapopulation capacity values calculated at the grid square scale was performed to obtain a Forest Fragmentation Potential FFP at three levels of spatial aggregation within the ecoregion (highly converted forest, entire forest, and the whole ecoregion). The results highlighted significant intra- and inter-ecoregions differences, showing great potential to extend the use of these indexes to land use planning and areas prioritisation for both ecological protection and restoration. The influence of the different parameters used in the proposed approach is discussed as well as the limitations of the main assumptions. One important result is that the derived methodology can be easily adapted to a large number of species, scales, or regions to improve the coverage of fragmentation indexes.

Edge effects of oil palm plantations on tropical anuran communities in Borneo

The expansion of industrial agriculture (oil palm) has significantly reduced lowland tropical diversity through direct loss or alteration of habitat, leading to habitat fragmentation and edge effects. Edge effects can have serious impacts on species diversity and community dynamics. To assess the effect of oil palm plantation edges on anuran communities in Sabah, Malaysian Borneo, we surveyed anuran species and measured structural habitat and landscape parameters at 74 sites spread across forest and plantation habitats along the Kinabatangan River. We then evaluated how anuran species richness and assemblage composition varied in relation to these environmental parameters. Relative species richness was higher at forest sites, compared to oil palm plantation sites. Plantation sites were dominated by wide-ranging terrestrial species, and assemblage composition varied mostly in relation to standing surface water. Forest habitats supported both more endemic and arboreal species. Variability on anuran assemblage composition in forest habitats was greatest in relation to distance to forest edge followed by canopy density, which was also partially correlated with forest edge distance. Moreover, anuran species richness in forest habitats declined as proximity to the forest-plantation interface increased, and as canopy density decreased. Our study provides further evidence that oil palm plantations provide little conservation benefit to anurans. Furthermore, oil palm plantations appear to have adverse pervasive impacts on amphibian diversity considerable distances into adjacent forest areas. These findings suggest that in order for small patches or narrow corridors of retained forest in landscapes managed for oil palm to maintain biodiversity values in the long term, their sizes and widths need to adequately account for the considerable influence of edge effects.

Synergistic effects of climate change and habitat fragmentation on species range shifts and metapopulation persistence

Synergistic effects of climate change and habitat fragmentation on species range shifts and metapopulation persistence

The effect of isolation, fragmentation, and population bottlenecks on song structure of a Hawaiian honeycreeper.

Little is known about how important social behaviors such as song vary within and among populations for any of the endemic Hawaiian honeycreepers. Habitat loss and non‐native diseases (e.g., avian malaria) have resulted in isolation and fragmentation of Hawaiian honeycreepers within primarily high elevation forests. In this study, we examined how isolation of Hawai'i ‘amakihi (Chlorodrepanis virens) populations within a fragmented landscape influences acoustic variability in song. In the last decade, small, isolated populations of disease tolerant ‘amakihi have been found within low elevation forests, allowing us to record ‘amakihi songs across a large elevational gradient (10–1800 m) that parallels disease susceptibility on Hawai'i island. To understand underlying differences among populations, we examined the role of geographic distance, elevation, and habitat structure on acoustic characteristics of ‘amakihi songs. We found that the acoustic characteristics of ‘amakihi songs and song‐type repertoires varied most strongly across an elevational gradient. Differences in ‘amakihi song types were primarily driven by less complex songs (e.g., fewer frequency changes, shorter songs) of individuals recorded at low elevation sites compared to mid and high elevation populations. The reduced complexity of ‘amakihi songs at low elevation sites is most likely shaped by the effects of habitat fragmentation and a disease‐driven population bottleneck associated with avian malaria, and maintained through isolation, localized song learning and sharing, and cultural drift. These results highlight how a non‐native disease through its influence on population demographics may have also indirectly played a role in shaping the acoustic characteristics of a species.

Genetic Diversity of Dominant Plant Species in Tropical Land-Use Systems in Sumatra, Indonesia

Biodiversity hotspots like tropical lowland rainforests in Sumatra are threatened by the agricultural expansion, which increases the deforestation rate in Indonesia, which is highest worldwide. Main land-use change drivers in Indonesia include the production of rubber and palm oil, both of which lead to a high forest conversion rate. In the remaining and degraded forest patches, species diversity has declined and species composition has been altered. Effects of habitat fragmentation and land-use change on genetic structure were frequently investigated at the species level and compared across plant species, but not for plant communities. In addition, the effect of land-use change on the genetic structure of plants has not yet been investigated. Using Amplified Fragment Length Polymorphism marker, the genetic diversity of 112 dominant plant species was assessed in four different land-use systems in Sumatra: old growth tropical lowland rainforest, jungle rubber, rubber plantation, and oil palm plantation. The four systems were investigated in two regions with four replicates, respectively. Because of different species compositions, characterized by different life history traits, forest and jungle rubber plots showed the highest diversity level, while oil palm and rubber plantations showed the lower diversity levels. The two intensively managed plantation systems showed similar genetic diversity levels as the tree dominated systems but are dominated by mainly alien species. This indicates that oil palm and rubber plantations could not be identified as habitats of conservational value. The newly introduced collection and analysis approach presents a universally applicable method to investigate different ecosystems in their plant genetic diversity to support the identification of habitats with high conservational value.

生境片段化对千岛湖马尾松林内土壤种子库的影响

生境片段化对千岛湖马尾松林内土壤种子库的影响

Can fishways mitigate fragmentation effects on Great Plains fish communities?

Fishways are a common tool for mitigating the effects of habitat fragmentation on fish, but their utility in low-gradient, sand-bed rivers of the Great Plains is not well studied. The Lincoln Street Fishway on the Arkansas River became operational in 2015 and was built specifically to pass small-bodied threatened fishes. We compared current and historical surveys up- and downstream of the barrier to test the effect of the fishway on community structure and conducted tagging experiments to test the ability of fishes to move into and through the fishway. Differences in community structure and species richness between communities up- and downstream of the dam were reduced following construction of the fishway. Surveys within the fishway revealed that 74% of species from the sampled community were using the fishway. Fishes marked with visible implant elastomer downstream of the dam were recaptured in the fishway, qualitatively showing that small-bodied fishes could move into and upstream within the fishway. We further quantified upstream movement for three species of small-bodied minnow tagged with passive integrated transponder tags during manipulations of flows through the fishway. Our results illustrate the potential for fishways to mitigate the effects of habitat fragmentation on fishes in sand-bed rivers.

Detecting the response of bird communities and biodiversity to habitat loss and fragmentation due to urbanization

Birds are considered a good model for indicators of biodiversity response to habitat variations, as they are very sensitive to environmental change. However, continuous observations of habitat alterations from undisturbed landscapes to human-dominated ones, as well as the associated effects on bird biodiversity, are lacking. In this study, New Jiangwan Town in Shanghai, China was selected to illustrate the response of bird species, and thus biodiversity, to habitat loss and fragmentation. Land use/land cover (LULC) data and bird records from 2002 to 2013 were collected and analyzed. The results suggested that, due to urban sprawl, the area of wetland and shrub land had dropped by 82.4% and 87.3% by the end of 2013. Four different urbanization stages were identified in terms of the spatio-temporal variations in the landscape. To measure bird biodiversity, species richness and relative abundance were calculated, and they could account for the overall trend in biodiversity but might mask the process of species replacement. As an indicator of biodiversity accounting, the mean species abundance (MSA) of the original species would not include exotic or invasive species in its calculation, and its value decreased from 100% to 76.8% to 52.2% to 24.5% in the four corresponding stages. Finally, suggested by redundant analysis, the effects of habitat loss and fragmentation on bird biodiversity differed in various bird communities, and the area and connectivity of wetlands were the most significant variables. Our findings could provide important information to inform bird biodiversity protection and habitat restoration.

Aspectos da criação de tayassuídeos no Brasil

As espécies Tayassu tajacu e o Tayassu pecari conhecidos popularmente como cateto equeixada, respectivamente, ou também denominados porcos-do-mato, pertencem à famíliaTayassuidae. A criação em cativeiro destas espécies tem-se difundido em vários países nasúltimas décadas, em razão da demanda de carnes exóticas, principalmente em restaurantesespecializados. Devido ao crescente consumo deste tipo de carne, há a necessidade deimplantação de programas de manejo, reprodutivos e de saúde, visando à criação em cativeirode modo sustentável, economicamente viável e com níveis adequados de biosseguridade. Acriação em cativeiro dos catetos e queixadas pode gerar produtos de grande valor comercial erepresentam uma alternativa proteica ao consumo humano, bem como pode minimizar osefeitos da caça predatória, fragmentação de habitat, tráfico e extinção das espécies, quepoderiam resultar em desequilíbrios ecológicos. Os Tayassuídeos de vida livre ou de cativeirosão susceptíveis a maioria dos agentes infecciosos que acometem os suínos domésticos,incluindo micro-organismos de potencial zoonótico, apesar de certa variação geográfica naprevalência das doenças. O presente estudo revisou os principais aspectos da criação deTayassuídeos no Brasil, com ênfase as principais doenças de origem bacteriana, viral eparasitárias que acometem essas espécies.

Population genetics of traditional landraces of Cucurbita pepo L., 1753 in the cloud forest in Baja Verapaz, Guatemala

Little is known regarding the effect of fragmentation and human agricultural management on the genetic variation and gene flow of Cucurbita pepo L., 1753 in moderate fragmented areas in central Guatemala. We hypothesize that the genetic variation of C. pepo is affected by forest fragmentation and by traditional agricultural management. Therefore, we aim to determine: (1) the genetic diversity and genetic structure of C. pepo in the Cloud Forest Corridor (CFC) (2) the extent of genetic admixture between commercial variety (CV) and traditional landraces (TL) of C. pepo, (3) the effect of habitat fragmentation in the population genetics of C. pepo with a landscape approach, and (4) the potential relationship between traditional management practices and genetic diversity of C. pepo in the CFC. We detected the existence of high level of genetic diversity (AR = 3.43; He = 0.50), inbreeding (Fis = 0.25) and moderate population structure of C. pepo in the CFC (Fst = 0.16). No correlation between landscape and genetics was found. Also, we found high genetic admixture between CV and TL. It seems that human practices, mainly related with seed exchange patterns, could affect genetic diversity of C. pepo in the CFC. C. pepo populations in the CFC are structured, with inbreeding, and show admixture with the CV, an aspect that could affect its genetic diversity. The agricultural management influenced the population genetics of C. pepo in the CFC, but the landscape did not. We suggest that special efforts should be made to preserve the diversity of this important indigenous food source for Guatemalan people as well as their management practices.

The effects of habitat fragmentation on hummingbird mediated pollen flow

The effects of habitat fragmentation on hummingbird mediated pollen flow

Phylogeography and genetic effects of habitat fragmentation on endemic Urophysa (Ranunculaceae) in Yungui Plateau and adjacent regions.

Urophysa is a Chinese endemic genus with only two species (U. rockii and U. henryi) distributed in Yungui Plateau (Guizhou Province) and adjacent regions (i.e., Provinces of Hunan, Hubei, Chongqing and Sichuan). The aim of this study was to determine the genetic diversity and population differentiation within Urophysa and investigate the effect of the Yungui Plateau uplift and climate oscillations on evolution of Urophysa. In this study, micro-morphological characteristics, nine microsatellite loci (SSR), two nuclear loci (ITS and ETS) and two chloroplast fragments (psbA-trnH and trnL-trnF) were used to analyze the phylogenetic relationships and assess genetic and phylogeographical structure of Urophysa. Isolation by distance (IBD) was performed to research the effects of geographical isolation. We detected high genetic diversity at the species level but low genetic diversity within populations. Striking genetic differentiation (AMOVA) among populations and a significant phylogeographical structure (NST > GST, p < 0.01) were detected among U. henryi populations, along with significant effects of isolation by distance (IBD). Molecular clock estimation using calibration strategy and cpDNA substitution rate indicated that the divergence of U. henryi occurred during late Miocene to early Quaternary, when the orogeny of Yungui Plateau was violent. U. rockii originated at the early Quaternary and further differentiated at early Pleistocene. Our results suggested that habitat fragmentation played an important role in the genetic diversity and population differentiation of U. rockii and U. henryi. Heterogenous geomorphological configuration and complicated environment resulted from rapid uplift of the Yungui Plateau were inferred as important incentives for the modern phylogeograhpical pattern and species divergence of Urophysa. The geographical isolation, limited gene flow, specialized morphologies and the Pleistocene climatic oscillation greatly contributed to the allopatric divergence of U. rockii. Significant genetic drift and inbreeding were detected in these two species, in situ measures should be implemented to protect them.

Genetic evidence of fragmented populations and inbreeding in the Colombian endemic Dahl’s toad-headed turtle (Mesoclemmys dahli)

Population fragmentation is one of the most concerning consequences of habitat fragmentation, as small and isolated populations suffer increased genetic drift and inbreeding. However, the extent to which habitat fragmentation leads to population fragmentation depends not only on the landscape structure, but also on the response of organisms to it. This behavioral component makes it difficult to detect population fragmentation even if the habitat is fragmented, unless appropriate tools are used. In this study, we used a molecular approach to evaluate if Dahl’s toad-headed turtle (Mesoclemmys dahli) population was fragmented, given that it occurs in a very restricted area within the most degraded biome of Colombia, the tropical dry forest. We developed a panel of 15 microsatellite loci in order to perform the first genetic assessment of M. dahli across its complete geographic range. We found that M. dahli has significant genetic structure with at least four subpopulations, with surprisingly moderate to high levels of genetic diversity. Despite high levels of genetic diversity, subpopulations are very small (effective population sizes < 50) and isolated, with little to no contemporary gene flow among them. As a consequence, mating among related individuals has been occurring, and all four populations are showing high degrees of inbreeding. To counteract this threat, we recommend an urgent genetic rescue strategy accompanied by habitat restoration, and advocate for a new conservation status assessment, not based on geographic range, but on adult population size and level of fragmentation.

Multi-species genetic connectivity in a terrestrial habitat network

BackgroundHabitat fragmentation reduces genetic connectivity for multiple species, yet conservation efforts tend to rely heavily on single-species connectivity estimates to inform land-use planning. Such conservation activities may benefit from multi-species connectivity estimates, which provide a simple and practical means to mitigate the effects of habitat fragmentation for a larger number of species. To test the validity of a multi-species connectivity model, we used neutral microsatellite genetic datasets of Canada lynx (Lynx canadensis), American marten (Martes americana), fisher (Pekania pennanti), and southern flying squirrel (Glaucomys volans) to evaluate multi-species genetic connectivity across Ontario, Canada.ResultsWe used linear models to compare node-based estimates of genetic connectivity for each species to point-based estimates of landscape connectivity (current density) derived from circuit theory. To our knowledge, we are the first to evaluate current density as a measure of genetic connectivity. Our results depended on landscape context: habitat amount was more important than current density in explaining multi-species genetic connectivity in the northern part of our study area, where habitat was abundant and fragmentation was low. In the south however, where fragmentation was prevalent, genetic connectivity was correlated with current density. Contrary to our expectations however, locations with a high probability of movement as reflected by high current density were negatively associated with gene flow. Subsequent analyses of circuit theory outputs showed that high current density was also associated with high effective resistance, underscoring that the presence of pinch points is not necessarily indicative of gene flow.ConclusionsOverall, our study appears to provide support for the hypothesis that landscape pattern is important when habitat amount is low. We also conclude that while current density is proportional to the probability of movement per unit area, this does not imply increased gene flow, since high current density tends to be a result of neighbouring pixels with high cost of movement (e.g., low habitat amount). In other words, pinch points with high current density appear to constrict gene flow.

Habitat fragmentation leads to reduced pollinator visitation, fruit production and recruitment in urban mangrove forests.

Mangrove forests worldwide undergo anthropogenic fragmentation that may threaten their existence, and yet there have been few tests of the effects of fragmentation on demographic processes critical for mangrove regeneration. Predicting the effects of habitat fragmentation on mangroves is problematic as pollinators may move more freely across water than terrestrial habitat, and propagules can be widely dispersed by water. Here, within each of two estuaries, we compared pollinator diversity and activity, reproductive effort and output, and rates of recruitment for sets of three large (>1500 trees), medium (300-500) and small (<50) stands. As predicted, most measures of reproductive activity and success were inversely related to stand size with large stands typically producing significantly more and larger fruit, and significantly more seedlings. Most strikingly, we found the effect of fragmentation on the abundance of pollinators (honeybees), the production and quality of fruit and the survival rate of seedlings to be similar, showing significant reduction of recruitment in small stands. This study provides the first rigorous evidence that recruitment of mangroves, like for many terrestrial plants, is negatively impacted by habitat fragmentation. From a management perspective, we argue that in the short term our data imply the importance of conserving the largest possible stands. However, additional work is needed to determine (1) the proportion of recruits within small stands that originate within large stands, (2) how seedling performance varies with fruit size and genotype, and (3) how seedling size and performance vary with the abundance and diversity of pollen.

Habitat fragmentation and the prevalence of parasites (Diptera, Streblidae) on three Phyllostomid bat species

AbstractEctoparasitism in bats seems to be influenced strongly by the type of roost preferred by the hosts, and group size; however, the effect of habitat loss and fragmentation on the prevalence of ectoparasites in bats has scarcely been studied. In northeastern Yucatan, Mexico, we estimated the prevalence of infestation by Streblidae flies in three phyllostomid bat species with different roost preferences (caves, trees, or both) in two types of landscape matrices (tropical semi‐deciduous forest and man‐made pastures) that differed in area of forest cover and the number of forest fragments. Habitat fragmentation and the presence of a contrasting matrix may limit the availability of roosts (trees) and the movement of bats across the landscape. Accordingly, we hypothesized higher prevalence of Streblidae infestation in the pasture matrix and in the group of bats that roost in trees. Bat abundance was higher in the pasture matrix; however, the prevalence of infestation was significantly higher in the continuous forest matrix and in bats that roosted in caves. The prevalence of some species of Streblidae was affected by habitat fragmentation in species that roost in caves, such as Desmodus rotundus, as well as those using foliage and caves, such as Artibeus jamaicensis. Our results provide evidence that some species of Streblidae may respond differently to habitat fragmentation than their hosts, generating changes to bat‐ectoparasite interactions in fragmented areas. Environmental variations involving roosts, not evaluated in this study, may influence our results, since these factors affect ectoparasite abundance and reproduction.

More cool than tool: Equivoques, conceptual traps and weaknesses of ecological networks in environmental planning and conservation

The paper critically examines the equivoques, conceptual traps and weaknesses of the recent ‘ecological network’ paradigm, invocated as a cool environmental planning tool to the aim to mitigate the effect of habitat fragmentation on biodiversity. We highlight as: (i) there is a semantic ambiguity deriving from the languages used in this interdisciplinary arena; (ii) these plans will be considered a true tool for biodiversity conservation when they will adopt a logic of problem solving and the standards requested in project cycle management (clear objectives, decision-making approach, appropriate monitoring and indicators, adaptive management); (iii) planners should follow a costs/benefits analysis comparing different scenarios and verifying that the ‘connectivity’ option effectively work better; (iv) each ecological network should be considered as a context-specific strategy where connectivity is only a simplified and schematic key of interpretation; (v) planners should carried out a local selection of fragmentation-sensitive targets that may not correspond with the species of conservation concern included in global or national red lists.

Quantification of habitat fragmentation reveals extinction risk in terrestrial mammals

Although habitat fragmentation is often assumed to be a primary driver of extinction, global patterns of fragmentation and its relationship to extinction risk have not been consistently quantified for any major animal taxon. We developed high-resolution habitat fragmentation models and used phylogenetic comparative methods to quantify the effects of habitat fragmentation on the world's terrestrial mammals, including 4,018 species across 26 taxonomic Orders. Results demonstrate that species with more fragmentation are at greater risk of extinction, even after accounting for the effects of key macroecological predictors, such as body size and geographic range size. Species with higher fragmentation had smaller ranges and a lower proportion of high-suitability habitat within their range, and most high-suitability habitat occurred outside of protected areas, further elevating extinction risk. Our models provide a quantitative evaluation of extinction risk assessments for species, allow for identification of emerging threats in species not classified as threatened, and provide maps of global hotspots of fragmentation for the world's terrestrial mammals. Quantification of habitat fragmentation will help guide threat assessment and strategic priorities for global mammal conservation.

Does the seed bank contribute to the build-up of a genetic extinction debt in the grassland perennial Campanula rotundifolia?

Habitat fragmentation threatens global biodiversity. Many plant species persist in habitat fragments via persistent life cycle stages such as seed banks, generating a species extinction debt. Here, seed banks are hypothesized to cause a temporal delay in the expected loss of genetic variation, which can be referred to as a genetic extinction debt, as a possible mechanism behind species extinction debts. Fragmented grassland populations of Campanula rotundifolia were examined for evidence of a genetic extinction debt, investigating if the seed bank contributed to the extinction debt build-up. The genetic make-up of 15 above- and below-ground populations was analysed in relation to historical and current levels of habitat fragmentation, both separately and combined. Genetic diversity was highest in above-ground populations, though below-ground populations contained 8 % of unique alleles that were absent above-ground. Above-ground genetic diversity and composition were related to historical patch size and connectivity, but not current patch characteristics, suggesting the presence of a genetic extinction debt in the above-ground populations. No such relationships were found for the below-ground populations. Genetic diversity measures still showed a response to historical but not present landscape characteristics when combining genetic diversity of the above- and below-ground populations. The fragmented C. rotundifolia populations exhibited a genetic extinction debt. However, the role of the seed banks in the build-up of this extinction debt is probably small, since the limited, unique genetic diversity of the seed bank alone seems unable to counter the detrimental effects of habitat fragmentation on the population genetic structure of C. rotundifolia.