Search

Studying biodiversity in light of increased fragmentation in agroecosystems requires the understanding of scale-dependent and multi-scale determinants of various community measures. In a heterogeneous agro-landscape, we aimed to understand whether: (1) Reptile communities are affected by a certain variable that belongs to a particular scale, or, by a combination of variables at different scales, and (2) Reptile community measures are affected differentially by variables related to different scales. We sampled reptiles in three 12.6 km2 land units by using 100 × 50 m plots within 27 natural habitat patches. We collected spatial information of different scale-oriented physical and biotic variables and analyzed changes in community measures at four scales—landscape, land unit, patch and plot—by using the model selection approach based on the AICc. Multiple-scale, rather than single-scale models, best explained all three community measures, indicating that the reptile community structure is highly affected by ecological processes operating at different scales, from the local up to the entire landscape scale. However, abundance, species richness and diversity were affected dissimilarly by different combined determinants and at different scales. Reptile biodiversity at our heterogenous agro-landscape is highly influenced by determinants of multiple scales, where each scale has its contribution to the overall obtained pattern. Number of individuals and species richness respond differently to various processes, depending on the scale at which these processes operate. Agro-landscapes retain the complexity of ecological systems and can serve to maintain natural communities through land sharing practices.

To test the effects of connectivity on fish diversity in isolated reef patches we deployed pairs of artificial reefs (AR) at constant distances (12 and 25 m) from a large continuous reef and added series of small ARs to half of them. These small reefs served as stepping-stones to increase fish movement between the large ARs and the continuous reef. Species gain and loss curves were compared to obtain deeper understanding of the underlying mechanisms in relation to the theory of island biogeography. We found that AR without stepping-stones maintained up to 57-fold more individuals than ARs with stepping-stones during mass recruitment events that were dominated by the family Apogonidae. However, in-between these mass recruitment events the overall impact of the stepping-stones on richness and abundance was small. By contrast, increasing distance from the continuous reef from 12 to 25 m increased fish richness, although this was confounded with time since AR deployment. Increase in richness with distance was predominantly caused by elevated species gain. Our results suggest that fish assemblages respond in distinct ways to two types of isolation: (1) Increased richness with distance from a continuous reef, and (2) increased fluctuation in abundance with decreased connectivity. The latter may be the outcome of accumulation and then abrupt emigrations of fishes from isolated reefs. This study confirms that the spatial setting of reef patches in relation to larger or continuous reefs alters fish assemblages, which may be important for planning AR deployments that maximizes diversity.

Understanding species-diversity patterns in heterogeneous landscapes invites comprehensive research on how scale-dependent processes interact across scales. We used two common beetle families (Tenebrionidae, detrivores; Carabidae, predators) to conduct such a study in the heterogeneous semi-arid landscape of the Southern Judean Lowland (SJL) of Israel, currently undergoing intensive fragmentation. Beetles were censused in 25 different-sized patches (500–40,000 m2). We used Fisher’s α and non-parametric extrapolators to estimate species diversity from 11,125 individuals belonging to 56 species. Patch characteristics (plant species diversity and cover, soil cover and degree of stoniness) were measured by field transects. Spatial variables (patch size, shape, physiognomy and connectivity) and landscape characteristics were analyzed by GIS and remote-sensing applications. Both patch-scale and landscape-scale variables affected beetle species diversity. Path-analysis models showed that landscape-scale variables had the strongest effect on carabid diversity in all patches. The tenebrionids responded differently: both patch-scale and landscape-scale variables affected species diversity in small patches, while mainly patch-scale variables affected species diversity in large patches. Most of the paths affected species diversity both directly and indirectly, combining the effects of both patch-scale and landscape-scale variables. These results match the biology of the two beetle families: Tenebrionidae, the less mobile and more site-attached family, responded to the environment in a fine-grained manner, while the highly dispersed Carabidae responded to the environment in a coarse-grained manner. We suggest that understanding abiotic and biotic variable interactions across scales has important consequences for our knowledge of community structure and species diversity patterns at large spatial scales.