Impact Of Habitat Fragmentation Research Articles

Impacts of Habitat Fragmentation on Terrestrial Biodiversity in Tropical Forests in Democratic Republic of Congo

Purpose: The aim of the study was to examine impacts of habitat fragmentation on terrestrial biodiversity in tropical forests in Democratic Republic of Congo Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study found that habitat fragmentation poses a significant threat to terrestrial biodiversity in tropical forests, particularly in the Democratic Republic of Congo (DRC). The fragmentation of forest habitats due to human activities such as logging, agriculture, and infrastructure development leads to the isolation of species populations, loss of genetic diversity, and disruption of ecological processes. As a result, endemic species in the DRC, including primates, birds, and large mammals, face heightened risks of population decline and extinction. Moreover, habitat fragmentation exacerbates other environmental challenges, such as climate change and invasive species encroachment, further compromising biodiversity conservation efforts in the region. Unique Contribution to Theory, Practice and Policy: Metapopulation Theory, Landscape Ecology Theory & Island Biogeography Theory may be used to anchor future studies on impacts of habitat fragmentation on terrestrial biodiversity in tropical forests in Democratic Republic of Congo. Implement habitat corridors that physically link fragmented habitats, facilitating the movement of species and genetic exchange. These corridors should be strategically placed based on ecological modeling to maximize effectiveness. Develop and enforce integrated land-use policies that consider both conservation and development needs. Policies should promote land-use planning that minimizes habitat fragmentation and incorporates ecological networks.

No impact of habitat fragmentation on condition and dispersal ability in the highly mobile butterfly Pieris rapae

AbstractThe loss and fragmentation of natural habitats due to agricultural intensification have a strong negative impact on farmland biodiversity. The concomitant isolation of essential resources may exert selection pressures toward increased dispersal performance in flying insects, possibly resulting in differences in flight morphology and dispersal propensity across landscapes. Here, we compared condition, flight morphology, dispersal capacity, and propensity of the common butterfly Pieris rapae among four pairs of highly fragmented “modern” and less fragmented “traditional” agricultural landscapes. We did not find differences between landscape types, but between locations and sexes. These results are not entirely unexpected, as P. rapae is a highly mobile generalist species, able to exploit temporarily available resources such as rapeseed in modern agricultural landscapes. In addition, our negative results may suggest a lack of time for evolutionary change such that differences may appear in the future. However, more specialized species with low dispersal ability may show clearer patterns and may well suffer from habitat fragmentation, and investigating such interrelation is an important task for future research.

Impact of habitat fragmentation on genetic structure of Capparis spinosa populations revealed by ISSR markers

The results from empirical studies on the impact of habitat fragmentation on genetic variation of populations are controversial, ranging from negative to positive effects. This contradiction has been attributed to either species characteristics (e.g. plant life history) or environmental components (e.g. the scale of habitat fragmentation). To examine the role of DNA marker types on these effects, we carried out a comparative study of seven populations of Capparis spinosa L. (caper, Capparaceae) using ISSR markers and compared these results with those obtained previously using RAPD markers. Although both ISSR and RAPD markers showed high consistency and indicated that genetic variation in populations was not correlated with either geographical distance (P ≥ 0.47, P ≥ 0.83; for ISSR and RAPD, respectively) or altitude (P ≥ 0.535, P ≥ 0.419; for ISSR and RAPD respectively), the levels of variation were related to population size. ISSR analysis showed that genetic variation did not significantly differ between small and large populations (P ≥ 0.4149), while RAPD analysis indicated significant effect of population size on this variation (P ≤ 0.002). This may suggest that, in addition to species and environmental components, types of DNA markers used for assessing population genetic variations affect results on the impact of fragmentation on genetic variation.

Impact of Habitat Fragmentation on the Diversity of Flora and Fauna of Bangladesh

Impact of Habitat Fragmentation on the Diversity of Flora and Fauna of Bangladesh

No Evidence of Low Genetic Diversity Despite High Levels of Inbreeding and Poor Genetic Connectivity AmongTetrastigma loheri(Vitaceae) Populations in Remaining Forest Areas in Cebu, Philippines

Abstract—Little is known about the effects of habitat fragmentation on the patterns of genetic diversity and genetic connectivity of species in the remaining tropical forests of Southeast Asia. This is particularly evident in Cebu, a Philippine island that has a long history of deforestation and has lost nearly all of its forest cover. To begin filling this gap, data from 13 microsatellite loci developed forTetrastigma loheri(Vitaceae), a common vine species in Philippine forests, were used to study patterns of genetic diversity and genetic connectivity for the four largest of the remaining forest areas in Cebu. Evidence of relatively high levels of inbreeding was found in all four areas, despite no evidence of low genetic diversity. The four areas are genetically differentiated, suggesting low genetic connectivity. The presence of inbreeding and low genetic connectivity in a commonly encountered species such asT. loheriin Cebu suggests that the impact of habitat fragmentation is likely greater on rare plant species with more restricted distributions in Cebu. Conservation recommendations for the remaining forest areas in Cebu include the establishment of steppingstone corridors between nearby areas to improve the movement of pollinators and seed dispersers among them.

Effects of Open and Forest Habitats on Distribution and Diversity of Bumblebees (Bombus) in the Małopolska Upland (Southern Poland): Case Study.

Simple SummarySouthern Poland represents one of the most diverse habitats for bumblebees (Bombus sp.); however, little is known about the abundance and distribution of many insect species in this region. Bumblebees are important for crop and wildflower pollination in different temperate latitudes because many plant species are only pollinated by them. Studies were conducted in natural and semi-natural habitats in southern Poland during the years 2003–2006 and compared with material collected from 2017–2020. During this eight-year-long study, more than 6214 bumblebee specimens of 25 species were found in the Małopolska Upland. The most frequently observed bumblebee species were: Bombus pascuorum, B. lapidarius, B. pratorum, and B. lucorum. The low-numbered bumblebees were: Bombus humilis, B. pomorum, B. veteranus, B. muscorum, and B. semenoviellus. There were also four rarely found species: Bombus confuses, B. ruderatus, B. soroeensis, and B. jonellus.Bumblebees are an important insect group occurring in different land ecosystems, but the number of these species has declined dramatically across Poland as well as in Europe in recent years. The fragmentation of bumblebee habitats influences the abundance and richness in community composition and trophic and competitive interactions. During the years 2003–2006 and 2017–2020, we studied the diversity and distribution of bumblebee species in two natural (boron-mixed Vaccinio-Piceetea and riparian forest Querco-Fagetea) and two semi-natural (segetal-ruderal Stellarietea mediae ruderal Artemisietea vulgaris) habitats in southern Poland. For that, we evaluated how habitats as well as local flowering communities influenced bumblebees’ abundance, richness, and community composition in 16 sites (which are located in four parks). Bumblebee communities responded to environmental factors in different ways according to the type of habitat. Vegetation factors were the most important drivers of bumblebee community structures. Forests showed the lowest bumblebee abundance, richness, and diversity, and the highest dominance levels of these parameters were found in the open ruderal-segetal habitats. The meadows from the Molinio arrhenatheretea class were characterized by bumblebee communities with a more complex structure. Species diversity was positively correlated with open ruderal-segetal habitats, and negatively with mixed forest cover, while abundance was positively correlated with forest cover. Studies like this are necessary to anticipate the impact of habitat fragmentation on bumblebee decline.

Understanding and modelling wildfire regimes: an ecological perspective

Recent extreme wildfire seasons in several regions have been associated with exceptionally hot, dry conditions, made more probable by climate change. Much research has focused on extreme fire weather and its drivers, but natural wildfire regimes—and their interactions with human activities—are far from being comprehensively understood. There is a lack of clarity about the ‘causes’ of wildfire, and about how ecosystems could be managed for the co-existence of wildfire and people. We present evidence supporting an ecosystem-centred framework for improved understanding and modelling of wildfire. Wildfire has a long geological history and is a pervasive natural process in contemporary plant communities. In some biomes, wildfire would be more frequent without human settlement; in others they would be unchanged or less frequent. A world without fire would have greater forest cover, especially in present-day savannas. Many species would be missing, because fire regimes have co-evolved with plant traits that resist, adapt to or promote wildfire. Certain plant traits are favoured by different fire frequencies, and may be missing in ecosystems that are normally fire-free. For example, post-fire resprouting is more common among woody plants in high-frequency fire regimes than where fire is infrequent. The impact of habitat fragmentation on wildfire crucially depends on whether the ecosystem is fire-adapted. In normally fire-free ecosystems, fragmentation facilitates wildfire starts and is detrimental to biodiversity. In fire-adapted ecosystems, fragmentation inhibits fires from spreading and fire suppression is detrimental to biodiversity. This interpretation explains observed, counterintuitive patterns of spatial correlation between wildfire and potential ignition sources. Lightning correlates positively with burnt area only in open ecosystems with frequent fire. Human population correlates positively with burnt area only in densely forested regions. Models for vegetation-fire interactions must be informed by insights from fire ecology to make credible future projections in a changing climate.

Joint Impacts of Drought and Habitat Fragmentation on Native Bee Assemblages in a California Biodiversity Hotspot.

Simple SummaryGlobal climate change is causing more frequent and severe droughts, which can have serious impacts on our environment. To examine how a severe drought in 2014 impacted wild bees in scrub habitats of San Diego, California, we compared bee samples collected before and after the drought. We also investigated whether habitat loss and fragmentation worsened the impacts of drought on wild bees by comparing samples collected from large natural reserves to those from small fragments of scrub habitat embedded in urban areas. Samples collected after the drought contained fewer bee species and fewer individual bees of most species, indicating that bee populations suffered losses during the drought. However, after-drought samples contained large numbers of Dialictus sweat bees, indicating that some bee species benefitted from environmental conditions present during the drought. The impact of drought on the composition of bee samples was three fold higher than the impact of habitat fragmentation, and habitat fragmentation did not appear to have exacerbated the impacts of drought. Our findings highlight the importance of studying how impacts of climate change compare with impacts of habitat loss and other threats to biodiversity conservation.Global climate change is causing more frequent and severe droughts, which could have serious repercussions for the maintenance of biodiversity. Here, we compare native bee assemblages collected via bowl traps before and after a severe drought event in 2014 in San Diego, California, and examine the relative magnitude of impacts from drought in fragmented habitat patches versus unfragmented natural reserves. Bee richness and diversity were higher in assemblages surveyed before the drought compared to those surveyed after the drought. However, bees belonging to the Lasioglossum subgenus Dialictus increased in abundance after the drought, driving increased representation by small-bodied, primitively eusocial, and generalist bees in post-drought assemblages. Conversely, among non-Dialictus bees, post-drought years were associated with decreased abundance and reduced representation by eusocial species. Drought effects were consistently greater in reserves, which supported more bee species, than in fragments, suggesting that fragmentation either had redundant impacts with drought, or ameliorated effects of drought by enhancing bees’ access to floral resources in irrigated urban environments. Shifts in assemblage composition associated with drought were three times greater compared to those associated with habitat fragmentation, highlighting the importance of understanding the impacts of large-scale climatic events relative to those associated with land use change.

Comprehensive analysis of population genetics of Phoxinus phoxinus ujmonensis in the Irtysh River: Abiotic and biotic factors.

As a widely distributed species along the Irtysh River, Phoxinus phoxinus ujmonensis (Kaschtschenko, 1899) was used as a model to investigate genetic diversity and population structure as well as the influence of environmental factors on population genetics. In this study, we specifically developed 12 polymorphic microsatellite loci. The analysis of microsatellite and mtDNA markers revealed a high and a moderate genetic diversity across seven populations, respectively. Moderate differentiation was also detected among several populations, indicating the impact of habitat fragmentation and divergence. The absence of isolation by distance implied an extensive gene flow, while the presence of isolation by adaptation implied that these populations might be in the process of adapting to divergent habitats. Correlation analysis showed that abiotic factors like dissolved oxygen, pH, total dissolved solids, and conductivity in water as well as biotic factors like plankton diversity and fish species diversity had impact on genetic diversity and divergence in P. phoxinus ujmonensis populations. The results of this study will provide an insight into the effect of environmental factors on genetic diversity and contribute to the study of population genetics of sympatric species.

The negative effects of habitat fragmentation operate at the scale of dispersal.

Habitat loss is often considered the greatest near-term threat to biodiversity. Yet the impact of habitat fragmentation, or the change in habitat configuration for a given amount of habitat loss, has been intensely debated. We isolated effects of habitat loss from fragmentation on the demography, movement, and abundance of wild populations of a specialist herbivore, Chelinidea vittiger, by removing 2,088 patches across 15 landscapes. We compared fragmentation resulting from random loss, which is often considered in theory, to aggregated loss, which is often observed in the real world. When quantifying fragmentation caused by random vs. aggregated loss, aggregated loss led to less fragmented landscapes than random loss based on patch isolation, but more fragmented landscapes when based on isolation at a larger mesoscale scale defined by dispersal distances of C.vittiger. Overall, habitat loss decreased population size and demographic parameters, with thresholds occurring at approximately 70-80% patch loss. Synergistic effects also occurred, where an aggregated pattern of loss had negative effects at low, but not high, amounts of habitat loss. Effects on population size of C.vittiger were driven by reductions in movement and subsequent reproduction. The direction of habitat fragmentation effects from random and aggregated loss treatments, for a given habitat amount, was conflictingly positive or negative depending on the scale at which fragmentation was quantified. Fragmentation quantified at the scale of dispersal for this species best explained population size and highlighted that fragmentation had negative effects at a mesoscale. Our results emphasize the importance of quantifying habitat fragmentation at biologically appropriate scales.

Economics of Habitat Fragmentation: A Review and Critique of the Literature

Understanding the signficance of habitat fragmentation for ecological function has been a focus in the natural sciences for decades. More recently, the field of economics has begun to assess the drivers and impact of habitat fragmentation, as well as potential policy and market-based mechanisms to address fragmentation. We present a review of the existing economics literature that addresses habitat pattern/fragmentation and we define themes, issues, and next steps for this literature. First, this paper reviews economic modeling and empirical approaches to identifying drivers and patterns of fragmentation. The next section summarizes the literature on analysis of optimal land use patterns and the tradeoffs of managing for ecological and economic objectives. The last literature section contains description of policy and mechanisms for addressing habitat fragmentation in the context of single and multiple landowners who do not manage land for habitat benefits explicitly. We conclude with a discussion of unanswered questions and next steps for research and data analysis on habitat fragmentation.

Islands within an island: Population genetic structure of the endemic Sardinian newt, Euproctus platycephalus.

The identification of historic and contemporary barriers to dispersal is central to the conservation of endangered amphibians, but may be hindered by their complex life history and elusive nature. The complementary information generated by mitochondrial (mtDNA) and microsatellite markers generates a valuable tool in elucidating population structure and the impact of habitat fragmentation. We applied this approach to the study of an endangered montane newt, Euproctus platycephalus. Endemic to the Mediterranean island of Sardinia, it is threatened by anthropogenic activity, disease, and climate change. We have demonstrated a clear hierarchy of structure across genetically divergent and spatially distinct subpopulations. Divergence between three main mountain regions dominated genetic partitioning with both markers. Mitochondrial phylogeography revealed a deep division dating to ca. 1 million years ago (Mya), isolating the northern region, and further differentiation between the central and southern regions ca. 0.5 Mya, suggesting an association with Pleistocene severe glacial oscillations. Our findings are consistent with a model of southward range expansion during glacial periods, with postglacial range retraction to montane habitat and subsequent genetic isolation. Microsatellite markers revealed further strong population structure, demonstrating significant divergence within the central region, and partial differentiation within the south. The northern population showed reduced genetic diversity. Discordance between mitochondrial and microsatellite markers at this scale indicated a further complexity of population structure, in keeping with male‐biased dispersal and female philopatry. Our study underscores the need to elucidate cryptic population structure in the ecology and conservation strategies for endangered island‐restricted amphibians, especially in the context of disease and climate change.

Using Microsatellite DNA to Understand Bobwhite Behavior and Population Structure (Post Abstract)

Northern bobwhite (Colinus virginianus) have a flexible mating system with varying degrees of parental investment in offspring. Questions of relatedness of mates and the dynamics of covey membership have not been answered. It is not known how different patterns of mating systems impact productivity of bobwhite populations. In addition to behaviors, the genetic structure of bobwhite populations likely varies across landscapes, and may depend on the distribution and abundance of habitat types. These issues have critical conservation and management implications, such as the impact of habitat fragmentation on gene flow. Recent advances in molecular techniques provide an opportunity to investigate these questions through examination of small, repetitive, highly variable regions of DNA known as microsatellites. Microsatellites provide the fine-scale resolution needed to objectively understand certain population structures and reproductive strategies. Microsatellite analysis techniques have been used successfully to research relatedness and extra-pair paternity of a number of species. Therefore, we have begun to investigate the genetic basis for many northern bobwhite behaviors related to reproduction. Our primary objectives are to determine: (1) relatedness of individuals within coveys and groups over time, (2) relatedness between reproductive pairs relative to random pairings, (3) relatedness of chicks in broods, (4) rates of extrapair fertilization, (5) rates of intra-specific nest parasitism, and (6) the relatedness of incubating birds to their eggs. To do so, we have developed a series of microsatellite markers for northern bobwhites. We radiomarked approximately 75% of bobwhites on our study area at Tall Timbers Research Station. We collected body feathers from adults and 1.5 mm patagial micro-biopsies from each chick (4 days old) found brooding with radiomarked adults for microsatellite analysis. We are determining relatedness and parentage, based on these microsatellite data, using programs RELATEDNESS and CERVUS. Additionally, we are testing our tissue collection techniques on a pen-reared population of bobwhites to determine the efficiency of DNA amplification via the polymerase chain reaction for 4 tissue collection techniques: patagial micro-biopsy, down and feather shaft, egg tooth, and egg membrane. Additionally, we are pairing pen-reared adult hens and males for different periods of time to determine the presence of sperm storage and test for evidence of sperm competition. Further, we are crossing individuals of known relatedness over several generations to test the accuracy of paternity inferences calculated by CERVUS with respect to bobwhite microsatellite data. Finally, by collecting feathers from hunterkilled bobwhites throughout the Red Hills and the southeast, we will compare the genetic structure of the bobwhite population(s) of the Red Hills, likely the last panmictic population in the southeast, to more isolated, declining populations. In our poster we present a detailed description of this research along with first year results.

Impacts of Habitat Fragmentation on Northern Bobwhites in the Gulf Coast Prairie Landscape Conservation Cooperative

The northern bobwhite (Colinus virginianus) has experienced range wide declines over the last several decades, primarily due to loss and fragmentation of habitat. As populations decline, there is a need for understanding factors that impact bobwhite population persistence at local and regional spatial scales. Our goal was to assess changes in land use and their relationship to bobwhite declines at 3 different spatial scales (region, county, and home range) in Texas, Oklahoma, and Louisiana. We used North American Breeding Bird Survey (BBS) data from 1974-2014 to create abundance maps and trends. At the regional scale, we compared bobwhite abundance with road density (2000, 2010), human population (1970-2010), and land use (1974-2012). We then used the BBS data to identify counties with stable and declining bobwhite abundance, and then compared bobwhite abundance to land use at metapopulation (800-9600 ha) and home range scales (15 ha). Bobwhite populations decreased from 45.93 ± 1.01 birds/count in 1970 to 11.55 ± 0.64 birds/count in 2012. as road density and human population increased. Pasture and other land increased, woodland was relatively stable, and cropland decreased in 2012. At the metapopulation level, declining populations had higher road density, more edge and patch area for pasture, and larger patches of cropland compared to stable populations. At the home range scale, declining populations had significantly fewer, and smaller, woody patches, more herbaceous habitat, and less bare ground. This study demonstrates that while on a small scale managers can provide woody cover and reduce cropland effects to support stable populations, the large-scale drivers of bobwhite decline, namely human population growth and the resulting loss of habitat, will be critical to quail management in the future.

Habitat fragmentation differentially affects trophic levels and alters behavior in a multi-trophic marine system.

Seagrass, an important subtidal marine ecosystem, is being lost at a rate of 110km2year-1, leading to fragmented seagrass seascapes. Habitat fragmentation is predicted to affect trophic levels differently, with higher trophic levels being more sensitive, stressing the importance of a multi-trophic perspective. Utilizing the trophic relationship between the blue crab (Callinectes sapidus) and hard clam (Mercenaria mercenaria), where adult blue crabs prey on juvenile blue crabs, and juvenile blue crabs prey on small hard clams, we examined whether predation rates, abundance, and behavior of predators and prey differed between continuous and fragmented seagrass in a multi-trophic context at two sites in Barnegat Bay, NJ. We tested the hypothesis that fragmented habitats would differentially affect trophic levels within a tri-trophic system, and our results supported this hypothesis. Densities of adult blue crabs were higher in fragmented than continuous habitats. Densities of juvenile blue crabs, the primary predator of hard clams, were lower in fragmented habitats than continuous, potentially due to increased predation by adult blue crabs. Clams experienced lower predation and burrowed to a shallower depth in fragmented habitats than in continuous habitat, likely due in part to the low densities of juvenile blue crabs, their primary predator. Our results suggest that while trophic levels are differentially affected, the impact of habitat fragmentation may be stronger on intermediate rather than top trophic levels in some marine systems.

Resilience to agricultural habitat fragmentation in an arboreal marsupial

The impact of habitat fragmentation on arboreal mammals is poorly understood and potentially greater than for ground-dwelling mammals. We investigated the influence of landscape fragmentation on a generalist arboreal marsupial, the koomal (Trichosurus vulpecula hypoleucus), a geographically isolated subspecies of the common brushtail possum endemic to south-western Australia. Since European settlement this taxon has undergone a significant reduction in range and population. We describe a year-long trapping study, incorporating radio-tracking, of a koomal population in a fragmented agricultural landscape to determine how agriculture and habitat fragmentation affect populations. In all, 61 free-ranging individuals were captured. Mark–recapture modelling estimated the population of 28.8 per trapping event with a total population size of 69 individuals having been present in the test landscape during the course of the study. Population demographics were comparable with populations found in relatively continuous landscapes. Mean home-range size was 8.8 ha of remnant vegetation for males and 7.9 ha for females. Home ranges usually incorporated several patches. Utilisation of shrublands, wetlands, and areas infested with Phytophthora dieback was not observed. Individuals required access to a selection of suitable denning trees and distances between patches <100 m did not appear to impair movement, with gaps <400 m regularly crossed.

Genetic Diversity and Structure among Isolated Populations of the Endangered Gees Golden Langur in Assam, India.

Gee’s golden langur (Trachypithecus geei) is an endangered colobine primate, endemic to the semi-evergreen and mixed-deciduous forests of Indo-Bhutan border. During the last few decades, extensive fragmentation has caused severe population decline and local extinction of golden langur from several fragments. However, no studies are available on the impact of habitat fragmentation and the genetic diversity of golden langur in the fragmented habitats. The present study aimed to estimate the genetic diversity in the Indian population of golden langur. We sequenced and analyzed around 500 bases of the mitochondrial DNA (mtDNA) hypervariable region-I from 59 fecal samples of wild langur collected from nine forest fragments. Overall, genetic diversity was high (h = 0.934, π = 0.0244) and comparable with other colobines. Populations in smaller fragments showed lower nucleotide diversity compared to the larger forest fragments. The median-joining network of haplotypes revealed a genetic structure that corresponded with the geographical distribution. The Aie and Champabati Rivers were found to be a barrier to gene flow between golden langur populations. In addition, it also established that T. geei is monophyletic but revealed possible hybridization with capped langur, T. pileatus, in the wild. It is hoped that these findings would result in a more scientific approach towards managing the fragmented populations of this enigmatic species.

Foliar diseases in a seasonal tropical dry forest: Impacts of habitat fragmentation

The effects of forest fragmentation on fungal pathogens causing leaf damage to the shrub and tree community were investigated in a seasonal tropical dry forest. The study was carried out in 4 forest fragments, and 2 continuous forest sites located in the Chamela-Cuixmala Biosphere Reserve and surrounding areas (Jalisco, Mexico), along three years. Results showed that fungi were the pathogenic agents causing foliar damage in plants from both, fragments and continuous forest. Disease incidence was higher in 2004 due to a relatively high annual precipitation. The occurrence of leaf fungal pathogens was lower in fragments, than in continuous forest. Plant species diversity was significantly lower in fragments than in continuous forest, and was positively correlated to the number of diseased plant species, and to the proportion of diseased leaves and the leaf area damaged per plant. In addition, disease occurrence was negatively correlated with canopy openness. In conclusion, our results highlight the consequences of environmental changes associated to fragmentation on foliar fungal plant pathogens, a particular group of organisms that until recently has been mostly overlooked in tropical natural systems.

Intraspecific body size increases with habitat fragmentation in wild bee pollinators

In modern agricultural landscapes, fragmentation of partial habitats is a significant filter for multi-habitat users, reducing local taxonomic and functional diversity. There is compelling evidence that small species are more susceptible than large species. The impact of habitat fragmentation on intraspecific body-size distribution, however, is yet unexplored. We tested habitat fragmentation, a major driver of pollinator loss, for its impact on intraspecific body-size distributions of solitary wild-bee species. Subsequently, we tested individual body size for its impact on pollination services. We sampled 1272 individuals of the four most common Andrena wild bee species in 22 newly established flowering fields (0.21–0.41 ha) in Hessen, Central Germany, over two consecutive years. Study sites were located in a ca. 80 ha landscape context of increasing habitat fragmentation. We analysed the pollen loads of the most abundant species. Body size within local populations of the two medium-sized bees increased with fragmentation, suggesting intraspecific selection for higher dispersal capacity. Pollen analysis carried out for the most common species revealed that larger individuals visited a significantly smaller plant spectrum. Habitat fragmentation may thus alter pollination services without necessarily affecting species richness or composition. Systematic body-size variation at the population level thus explains the considerable variability between simple community measures and ecosystem functioning. Filtering processes at the individual level require increased understanding for targeting pollination services under current and future land-use change.

Swimming through sand: connectivity of aquatic fauna in deserts.

Freshwater ecosystems in arid regions range from highly fragmented to highly connected, and connectivity has been assumed to be a major factor in the persistence of aquatic biota in arid environments. This review sought to synthesize existing research on genetic estimation of population connectivity in desert freshwaters, identify knowledge gaps, and set priorities for future studies of connectivity in these environments. From an extensive literature search, we synthesized the approaches applied, systems studied, and conclusions about connectivity reached in population genetic research concerning desert freshwater connectivity globally. We restrict our scope to obligate aquatic fauna that disperse largely via freshwaters and exclude those with active aerial dispersal abilities. We examined 92 papers, comprising 133 studies, published from 1987 to 2014. Most described studies of fishes and invertebrates in the deserts of Australia and North America. Connectivity declined with increasing scale, but did not differ significantly among arid regions or taxonomic classes. There were significant differences in connectivity patterns between species with different dispersal abilities, and between spring and riverine habitats at local scales. Population connectivity in desert freshwaters is typically most influenced by the ecology of the species concerned and hydrological connectivity. Most studies did not assess predefined models of connectivity, but described gene flow and/or genetic structure. Climate change and anthropogenic impacts worldwide are likely to increase the incidence and impact of habitat fragmentation in already threatened desert freshwaters. To reduce this risk, biodiversity conservation and environmental management must address connectivity, but often the required information does not exist. Researchers can provide this by explicitly considering the effects of hydrology and species’ ecology on connectivity, and incorporating these into connectivity models, which are vital for understanding connectivity in desert freshwaters.