Land use and soil characteristics affect soil organisms differently from above-ground assemblages.

BACKGROUND: Land-use is a major driver of changes in biodiversity worldwide, but studies have overwhelmingly focused on above-ground taxa: the effects on soil biodiversity are less well known, despite the importance of soil organisms in ecosystem functioning. We modelled data from a global biodiversity database to compare how the abundance of soil-dwelling and above-ground organisms responded to land use and soil properties. RESULTS: We found that land use affects overall abundance differently in soil and above-ground assemblages. The abundance of soil organisms was markedly lower in cropland and plantation habitats than in primary vegetation and pasture. Soil properties influenced the abundance of soil biota in ways that differed among land uses, suggesting they shape both abundance and its response to land use. CONCLUSIONS: Our results caution against assuming models or indicators derived from above-ground data can apply to soil assemblages and highlight the potential value of incorporating soil properties into biodiversity models.

Evidence of positive selection on six spider developmental genes.

Spiders constitute more than 49,000 described species distributed all over the world, and all ecological environments. Their order, Araneae, is defined by a set of characteristics with no parallel among their arachnid counterparts (e.g., spinnerets, silk glands, chelicerae that inoculate venom, among others). Changes in developmental pathways often underlie the evolution of morphological synapomorphies, and as such spiders are a promising model to study the role of developmental genes in the origin of evolutionary novelties. With that in mind, we investigated changes in the evolutionary regime of a set of six developmental genes, using spiders as our model. The genes were mainly chosen for their roles in spinneret ontogeny, yet they are pleiotropic, and it is likely that the origins of other unique morphological phenotypes are also linked to changes in their sequences. Our results indicate no great differences in the selective pressures on those genes when comparing spiders to other arachnids, but a few site-specific positive selection evidence were found in the Araneae lineage. These findings lead us to new insights on spider evolution that are to be further tested.

A revision of the Neotropical genus Austrohahnia Mello-Leitão (Araneae, Hahniidae).

The Neotropical genus Austrohahnia Mello-Leitão, 1942 is revised, comprising four species from Argentina. The genus is here transferred to the subfamily Hahniinae Bertkau, 1878 from Cybaeolinae Lehtinen, 1967. Austrohahnia is diagnosed by a single synapomorphy, short setae ventrally on the abdomen, in immature as well as adult stages. The type species A. praestans Mello-Leitão, 1942 is redescribed. Austrohahnia catleyi new species is described and illustrated based both sexes from the alder forests of northwestern Argentina. Austrohahnia melloleitaoi (Schiapelli & Gerschman, 1942) new combination was transferred from Hahnia C.L. Koch, 1841, the male is described and illustrated for the first time, and the female is redescribed. Austrohahnia isophthalma (Mello-Leitão, 1941) new combination is also transferred from Hahnia and considered a nomen dubium. New geographic records of studied species are provided.

A new Amazonian species of Cryptocellus (Arachnida, Ricinulei), with descriptions of its integumental structures and all free-living life stages.

A new species of Cryptocellus Westwood, 1874 is described, based on males, females and all free-living immature stages. Cryptocellus muiraquitan sp. nov. from Juruti, Pará, Brazil, is a member of the foedus group of species and probably closely related to Cryptocellus icamiabas Tourinho & Azevedo, 2007, C. abaporu Bonaldo & Pinto-da-Rocha, 2003 and C. simonis Hansen & Sørensen, 1904. The new species is illustrated using stereomicroscopy and scanning electron microscopy. The large diversity of integumental structures of the new species is described and compared to that of previously studied species of Cryptocellus and Pseudocellus Platnick, 1980.

The cost-effectiveness of biodiversity surveys in tropical forests.

The identification of high-performance indicator taxa that combine practical feasibility and ecological value requires an understanding of the costs and benefits of surveying different taxa. We present a generic and novel framework for identifying such taxa, and illustrate our approach using a large-scale assessment of 14 different higher taxa across three forest types in the Brazilian Amazon, estimating both the standardized survey cost and the ecological and biodiversity indicator value for each taxon. Survey costs varied by three orders of magnitude, and dung beetles and birds were identified as especially suitable for evaluating and monitoring the ecological consequences of habitat change in our study region. However, an exclusive focus on such taxa occurs at the expense of understanding patterns of diversity in other groups. To improve the cost-effectiveness of biodiversity research we encourage a combination of clearer research goals and the use of an objective evidence-based approach to selecting study taxa.