Effects of landscape structure and patch characteristics on the density of central populations of the eastern green lizard Lacerta viridis

A better understanding of the impact of habitat loss on population density can be achieved by evaluating effects of both parameters within remnant habitat patches and parameters of the landscape surrounding those patches. The integration of predictors at the patch and landscape level is scarce in animal ecological studies, especially for reptiles. In this study, a patch-landscape approach was applied to evaluate the combined effects of within-patch habitat quality, patch geometry and landscape configuration and composition on the density of remnant populations of the eastern green lizard, Lacerta viridis, in a highly modified landscape in Bulgaria. Landscape composition variables (proportion of different land covers) were measured at different spatial scales surrounding patches. Single-scale models were built to evaluate combined effects of all predictors on density, when including all landscape composition variables at a specific spatial scale. Multi-scale models were applied to analyze combined effects when including landscape composition variables at the scale of their strongest effect (scale of effect, SoE). Results showed that the SoE of proportion of cropland and urban areas was small (50 m), while for proportion of habitat was large (1.5 km). The overall effect of habitat loss was better explained by the multi-scale model. Population density increased with patch area and decreased with patch shape irregularity and with the proportion of three land cover types surrounding patches-cropland, urban areas, and habitat. Combining patch and landscape parameters is important to identify ecological processes that occur simultaneously at different spatial levels and landscape scales, which would imply the application of multi-scale approaches for the protection of wild animal populations. Results are contrasted with what is known about occupancy patterns of the species in the same region and approaches to integrate both occupancy and density, in the field design of animal ecological studies are suggested.

Functional diversity of snakes is explained by the landscape composition at multiple areas of influence

Roadkill and landscape composition affect snakes at different spatial scales, depending on the functional trait value of the species, which is reflected in the functional diversity indices at the assemblage level. This study evaluated the effect of roads and landscape composition on snakes' functional diversity at different areas of influence (250, 500, 1000, and 2000 m buffer areas). We compared roadkill snake species with those assemblages inhabiting the adjacent vegetation in the Orinoco region, Colombia. We surveyed snakes using transects on the road and adjacent areas on 13 landscapes along the road. We evaluated the effect of 16 landscape metrics at six land cover classes on the snake's functional diversity at four different areas of influence (from 250 to 2000 m around the sampled sites). The functional redundancy index was higher for roadkill species, suggesting that roads eliminate species that play similar roles in the assemblage and ecosystem processes. Likewise, the low values of functional redundancy in the adjacent vegetation call attention to the fact that each species surviving in this transformed landscape has a crucial active role in ecosystem processes in snake assemblages. For roadkill snakes, forest metrics explained changes in functional richness and functional evenness at a 250 m area of influence. In comparison, transient crop and pasture metrics explained changes in functional evenness and divergence at 2000 m. For snakes inhabiting the adjacent vegetation, the cohesion of pasture explained changes in functional richness at 250 m, and forest metrics explained changes in functional redundancy and evenness at 2000 m. Anthropogenic landscape transformation may have a greater effect on snake functional diversity at local scales than roadkill. In savanna ecosystems, the presence of native forest at 2000 m radius around roads promotes the conservation of snake assemblages. However, within a 250 m radius, the risk of snake roadkill increases when the road borders native forest. Therefore, it is necessary to implement wildlife crossing in these sections of the road.

Support for an area-heterogeneity tradeoff for biodiversity in croplands

Rapid expansion of the human population poses a challenge for wildlife conservation in agricultural landscapes. One proposal for addressing this challenge is to increase biodiversity in such landscapes by increasing crop diversity. However, studies report both positive and negative effects of crop diversity on biodiversity. One possible explanation, derived from the "area-heterogeneity tradeoff hypothesis," is that the effect of crop diversity on biodiversity depends on a tradeoff between increasing the number of crop types in a landscape and decreasing the amount of each single crop type. This should cause positive effects of increasing crop diversity at low to intermediate crop diversity and negative effects at intermediate to high crop diversity. We also propose two factors that could change the point at which the effect of increasing crop diversity shifts from positive to negative. First, we predicted that this shift would occur at a lower crop diversity when the surrounding landscape contains less semi-natural habitat and at a higher crop diversity when the landscape contains more semi-natural habitat. This should increase the likelihood of detecting negative effects of crop diversity when semi-natural cover is low and positive effects when it is high. Second, we predicted that the shift from a positive to negative effect would occur at a lower crop diversity when it is measured locally than when it is measured at greater distances from the site, making detection of negative crop diversity effects more likely when measurements are at local extents. We tested these predictions using data on the biodiversity of herbaceous plants, butterflies, syrphid flies, woody plants, bees, carabid beetles, spiders, and birds at 221 crop field edges in Eastern Ontario, Canada. We found support for an area-crop diversity tradeoff. Semi-natural cover and measurement extent influenced the biodiversity-crop diversity relationship, with positive effects when semi-natural cover was high and negative effects when semi-natural cover was low and when crop diversity was measured at local extents. The results suggest that policies/guidelines designed to increase crop diversity will not benefit biodiversity in the landscapes where conservation action is most urgently needed, that is, in landscapes with high agricultural use and low semi-natural cover.

Landscape-level heterogeneity of agri-environment measures improves habitat suitability for farmland birds

Agri-environment schemes (AESs), ecological focus areas (EFAs), and organic farming are the main tools of the common agricultural policy (CAP) to counteract the dramatic decline of farmland biodiversity in Europe. However, their effectiveness is repeatedly doubted because it seems to vary when measured at the field-versus-landscape level and to depend on the regional environmental and land-use context. Understanding the heterogeneity of their effectiveness is thus crucial to developing management recommendations that maximize their efficacy. Using ensemble species distribution models and spatially explicit field-level information on crops grown, farming practice (organic/conventional), and applied AES/EFA from the Integrated Administration and Control System, we investigated the contributions of five groups of measures (buffer areas, cover crops, extensive grassland management, fallow land, and organic farming) to habitat suitability for 15 farmland bird species in the Mulde River Basin, Germany. We used a multiscale approach to identify the scale of effect of the selected measures. Using simulated land-use scenarios, we further examined how breeding habitat suitability would change if the measures were completely removed and if their adoption by farmers increased to meet conservation-informed targets. Buffer areas, fallow land, and extensive grassland were beneficial measures for most species, but cover crops and organic farming had contrasting effects across species. While different measures acted at different spatial scales, our results highlight the importance of land-use management at the landscape level-at which most measures had the strongest effect. We found that the current level of adoption of the measures delivers only modest gains in breeding habitat suitability. However, habitat suitability improved for the majority of species when the implementation of the measures was increased, suggesting that they could be effective conservation tools if higher adoption levels were reached. The heterogeneity of responses across species and spatial scales indicated that a mix of different measures, applied widely across the agricultural landscape, would likely maximize the benefits for biodiversity. This can only be achieved if the measures in the future CAP will be cooperatively designed in a regionally targeted way to improve their attractiveness for farmers and widen their uptake.

Homogenization of terrestrial mammals in fragmented rainforests: the loss of species turnover and its landscape drivers

Understanding the factors and mechanisms shaping differences in species composition across space and time (β-diversity) in human-modified landscapes has key ecological and applied implications. This topic is, however, challenging because landscape disturbance can promote either decreases (biotic homogenization) or increases (biotic differentiation) in β-diversity. We assessed temporal differences in intersite β-diversity of medium-bodied and large-bodied mammals in the fragmented Lacandona rainforest, Mexico. We hypothesized that, given the relatively short history of land-use changes in the region, and the gain and loss of some species caused by landscape spatial changes, β-diversity would increase through time, especially its nestedness component. We estimated β-diversity between 24 forest sites (22 forest patches and two continuous forest sites) in 2011 and 2017 to assess whether β-diversity is decreasing or increasing in the region, and calculated its turnover and nestedness components to understand the mechanisms responsible for changes in β-diversity, separately assessing mammal groups with different body mass, feeding guild, and habitat specialization. We then related such temporal changes in β-diversity to temporal changes in five landscape variables (forest cover, matrix openness, number of patches, edge density and interpatch distance) to identify the landscape drivers of β-diversity. In contrast with our expectations, β-diversity decreased over time, suggesting an ongoing biotic homogenization process. This pattern was mostly driven by a decrease in species turnover in all mammal groups, especially in landscapes with decreasing forest cover and increasing forested matrices. Although the nestedness component showed a three-fold increase through time, species turnover was 22 and six times higher than nestedness in 2011 and 2017, respectively. The decreased turnover appears to be driven by an increase in dispersal (i.e., spillover) of native species among patches. The prevalence of species turnover over nestedness indicates that different forest sites have a fairly distinct subset of species (i.e., high complementarity in species composition). Therefore, conserving all remaining forest patches and increasing forest cover is of utmost importance to effectively maintain β-diversity and conserve the total diversity (γ) of mammal assemblages in this Mesoamerican biodiversity hotspot.

Scale-Dependent Waylaying Effect of Pollinators and Pollination of Mass-Flowering Plants

Pollinators foraging for food resources can be waylaid by mass-flowering plants located in their foraging pathway in landscapes. The waylaying effect of pollinators is often studied at a single spatial scale; to date, little is known about the best spatial extent at which waylaying effect of pollinators can be measured. In this study, we selected a landscape with mass-flowering tufted vetches to determine the spatial scale of waylaying effect of honey bees as well as the consequence of waylaying effect on vetch pollination service. The spatial scale of waylaying effect was determined by the strongest association between honey bee density and distance, selected from a gradient of nested circular buffers centering on apiaries in three different locations. Linear models were used to predict the influence of flower visitor densities on pollination service. For our landscape, honey bee densities were best associated with distances at spatial scales of 500 m, 1150 m, and 1400 m respectively for the three locations of apiaries. Honey bee was the only pollinator whose density displayed a positive relationship with pollination service. At the scales of effect, honey bee density and pollination service declined along the distance. Our findings suggest that the waylaying effect of pollinators needs to be examined at a specific spatial scale and farmers who use honey bees to pollinate their mass-flowering crops need to consider the spatial scale of waylaying effect of pollinators in order to maximize pollination service within agricultural ecosystems.

Do spatial scale and life history affect fish-habitat relationships?

Understanding how animals interact with their environment is a fundamental ecological question with important implications for conservation and management. The relationships between animals and their habitat, however, can be scale-dependent. If ecologists work at suboptimal spatial scales, they will gain an incomplete picture of how animals respond to the landscape. Identifying the scale at which animal-landscape relationships are strongest (the "scale of effect") will improve our ability to better plan management and conservation activities. Several recent studies have greatly enhanced our knowledge about the scale of effect, and the potential drivers of interspecific variability, in particular life-history traits. However, while many marine systems are inherently multiscalar, research into the scale of effect has been mainly focussed on terrestrial taxa. As the scales of observation in fish-habitat association studies are often selected based on convention rather than biological reasoning, they may provide an incomplete picture of the scales where these associations are strongest. We examined fish-habitat associations across four nested spatial scales in a temperate reef system to ask: (a) at what scale are fish-habitat associations the strongest, (b) are habitat elements consistently important across scales, and (c) do scale-dependent fish-habitat associations vary in relation to either body size, geographic range size or trophic level? We found that: (a) the strongest fish-habitat associations were observed when these relationships were examined at considerably larger spatial scales than usually investigated; (b) the importance of environmental predictors varied across spatial scales, indicating that conclusions about the importance of habitat elements will depend on the scales at which studies are undertaken; and (c) scale-dependent fish-habitat associations were consistent across all life-history traits. Our results highlight the importance of considering how animals relate to their environment and suggest the small scales often chosen to examine fish-habitat associations are likely to be suboptimal. Developing a more mechanistic understanding of animal-habitat associations will greatly aid in predicting and managing responses to future anthropogenic disturbances.