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Abstract: Spiders at 23 Portuguese protected area sites were sampled (pitfall trapped) over 10-month periods. The data allowed for a “biodiversity quality” assessment consisting of the following indices: Species Richness, Biomass, Simpson Index, Species Conservation Value Index and Population Density. These “biodiversity quality” characteristics were reviewed for relative indication of site spider “biodiversity quality”. Spiders are proposed as a group of organisms that could be used to indicate part of the “biodiversity quality” of a site since they can be sampled in a standardised way and yield biodiversity indices for comparison spatially and temporally. The approach adopted in this paper allows a range of “biodiversity quality” indices to be measured for spiders in Portuguese protected areas which, in turn requires decisions from scientists, managers and politicians on what element or characteristic of biodiversity it is intended to be targeted. [Copyright &y& Elsevier]

A considerable number of alternative approaches have been suggested during the last years to predict species richness of a given taxon, while retaining information on the identities of the observed individuals. Such information can be extremely useful for choosing conservation priority areas, either by using raw richness values or, preferentially, by considering the complementarity between potential sites. Among the most popular approaches is the use of indicator taxa. Both one single family and a group of several families are here tested in their ability to predict the number of spider (Araneae) species independently of sampling effort, geographical location and type of habitat. We use data from three Portuguese protected areas as a test case. A two-family indicator group – Gnaphosidae and Theridiidae – is found to be a good surrogate of species richness, even if caution is needed regarding the comparison of sites with considerably different sampling effort or vegetation cover. No single family can be seen as a good surrogate of the totality of spiders. In addition, only a group of the two mentioned families is found to be efficient and reliable either when used to rank sites according to taxa richness or for determining near-minimum sets of sites for conservation. We therefore recommend surrogacy with this indicator group as a promising approach for the prediction of spider species richness or evaluation and ranking of areas according to their conservation importance. The reached conclusions should uphold for Portugal and the entire Mediterranean region. [Copyright &y& Elsevier]

A number of alternative approaches have been suggested during recent years to predict species richness of a given taxa, while retaining information on the identities of the observed individuals. Such information can be extremely useful for choosing conservation priority areas, either by using simple richness values or, preferentially, by considering the complementarity of potential sites. Among the most popular approaches is the use of higher taxa surrogates. Both family and genus richness are here tested in their ability to predict the number of spider (Araneae) species independently of sampling effort, geographical location and type of habitat. We use data from three Portuguese protected areas as a test case. Genus richness is considered a good surrogate of species richness, despite some caution being needed regarding the comparison of sites with considerably different sampling effort, the same not happening with families. Only genera are also found to be reliable either for ranking sites according to taxa richness or for determining near-minimum sets of sites for conservation. We therefore recommend surrogacy at this taxonomic level as a promising approach for the prediction of spider species richness or evaluation and ranking of areas according to their conservation importance. The reached conclusions should uphold for Portugal and the entire Mediterranean region. [Copyright &y& Elsevier]

Spatial variation in biodiversity is one of the key pieces of information for the delimitation and prioritisation of protected areas. This information is especially important when the protected area includes different climatic and habitat conditions and communities, such as those along elevational gradients. Here we test whether the megadiverse communities of spiders along an elevational gradient change according to two diversity models – a monotonic decrease or a hump-shaped pattern in species richness. We also measure compositional variation along and within elevations, and test the role of the preference of microhabitat (vegetation strata) and the functional (guild) structure of species in the changes. We sampled multiple spider communities using standardised and optimised sampling in three forest types, each at a different elevation along a climatic gradient. The elevational transects were at increasing horizontal distances (between 0.1 and 175 km) in the Udzungwa Mountains, Eastern Arc Mountains, Tanzania. The number of species was similar between plots and forest types, and therefore the pattern did not match either diversity model. However, species composition changed significantly with a gradual change along elevations. Although the number of species per microhabitat and guild also remained similar across elevations, the number of individuals varied, e.g. at higher elevations low canopy vegetation was inhabited by more spiders, and the spiders belonging to guilds that typically use this microhabitat were more abundant. Our findings reflex the complex effects of habitat-microhabitat interactions on spider communities at the individual, species and guild levels. If we aim to understand and conserve some of the most diverse communities in the world, researchers and managers may need to place more attention to small scale and microhabitat characteristics upon which communities depend. [ABSTRACT FROM AUTHOR]