Migration and dispersal of the western leopard toad (amietophrynus pantherinus) in a fragmented agricultural landscape

Includes bibliographical references.Habitat alteration, primarily associated with human expansion and consumption, has been identified as the leading threat to biodiversity worldwide. The net result of an ever increasing human population is the loss of available habitat to species, affecting individual survival, together with the fragmentation of habitat across a landscape, resulting in an increased chance of a genetic bottlenecks and localized extinction. Although many organisms are experiencing the deleterious effects of these processes, amphibians appear to be suffering more than other vertebrate groups. One species that has experienced significant impact through habitat alteration and urbanization is the Western Leopard Toad (Bufonidae: Amietophrynus pantherinus). In the south-western portion of the Western Cape Province, South Africa, the population is large and genetically diverse with numerous potential breeding sites. However, extinctions in the disjunt eastern area, where there are a low number of known breeding sites (currently 7 identified), have raised concern over the conservation of this management unit. In this study radio-telemetry and population genetic data were used to investigate fine scale, short term migration patterns in Western Leopard Toads to specifically assess the role of agricultural land-use and habitat fragmentation on long-term dispersal dynamics

Most soil trophic guilds increase plant growth: a meta-analytical review

Trophic cascades are important drivers of plant and animal abundances in aquatic and aboveground systems, but in soils trophic cascades have been thought to be of limited importance due to omnivory and other factors. Here we use a meta-analysis of 215 studies with 1526 experiments that measured plant growth responses to additions or removals of soil organisms to test how different soil trophic levels affect plant growth. Consistent with the trophic cascade hypothesis, we found that herbivores and plant pathogens (henceforth pests) decreased plant growth and that predators of pests increased plant growth. The magnitude of this trophic cascade was similar to that reported for aboveground systems. In contrast, we did not find evidence for trophic cascades in decomposer- and symbiont-based (henceforth mutualist) food chains. In these food chains, mutualists increased plant growth and predators of mutualists also increased plant growth, presumably by increasing nutrient cycling rates. Therefore, mutualists, predators of mutualists and predators of pests all increased plant growth. Further, experiments that added multiple organisms from different trophic levels also increased plant growth. As a result, across the dataset, soil organisms increased plant growth 29% and non-pest soil organisms increased plant growth 46%. Omnivory has traditionally been thought to confound soil trophic dynamics, but here we suggest that omnivory allows for a simplified perspective of soil food webs – one in which most soil organisms increase plant growth by preying on pests or increasing nutrient cycling rates. An implication of this perspective is that processes that decrease soil organism abundance (e.g. soil tillage) are likely to decrease aboveground productivity. Synthesis Soil foodwebs have resisted generalizations due to their diversity and interconnectedness. Here we use results from a meta-analysis to inform a simplified perspective of soil foodwebs: one in which most soil trophic guilds increase plant growth. Our review also includes the first widespread support for the presence of trophic cascades in soils