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Representative samples of biota collected relative to environmental gradients are important for measuring present distributions and predicting shifts in distribution of taxa in response to climate change or reduced river connectivity. Based on river ecology theory and established measures of species diversity, we present a method to identify suitable river segments for sampling and monitoring changes in taxon diversity. Alpha and beta diversities of selected aquatic macroinvertebrates were assessed in seven South African rivers. Data were drawn from historical and field samples and represented longitudinal species patterns down longitudinal river axes. Representative sampling sites were identified using a logistic regression model to predict the probability of site pairs that were more than 50% similar as a function of up-/downstream distance. Alpha diversities peaked in the upper third of river lengths; beta diversities showed predictable exponential decay rates down river axes up to and excluding the start of estuarine conditions. Application of the model to a 370-km long river indicated that 14 sites should be selected for sampling to capture overall biodiversity patterns. Additional factors, such as confluences tributaries, which influence alpha diversity at sites, are identified and incorporated into site selection. [ABSTRACT FROM AUTHOR]

arabicHierarchical partitioning of diversity is an effective tool in determining at what spatial scales diversity is generated. arabicThis has important implications for managing diversity as we may wish to determine the appropriate scale for conservation activities. arabicWe studied whether ant assemblages are compositionally distinct between different vegetation units and at which hierarchical scale (regional vs local) diversity is being generated. We did this in an attempt to determine at what spatial scales land use management and conservation activities for ants (and therefore invertebrates) should take place. arabicWe sampled ants in 4 vegetation units in North West Province, South Africa, as part of a research expedition for the South African National Survey of Arachnida (SANSA); 92 ant species (Formicidae) were sampled in 25 genera within 6 subfamilies. arabicPartitioning of diversity showed that alpha diversity was high for points (sampling units) and extremely high for sites, but both were not significantly different from the random model. Although small relative to alpha diversity, beta diversity among points contributed significantly more than expected to overall diversity whereas turnover among vegetation units was significantly lower than expected from the null model. arabicThese results indicate that turnover between points within vegetation units is relatively high; turnover at a regional scale was however very low, supported by the few number of species that were site specific. The lack of any spatial structure within sites might suggest that the studies’ grain was too fine or that ant assemblages in a vegetation unit are homogenous in space. arabicThe high turnover observed in the study between points may be exactly that, and if so may well be attributed to habitat quality and ant dispersal mechanisms – supported by other studies. It may, however, simply be an artefact of incomplete sampling. The low beta diversity observed between vegetation types may be attributed to the fact that ants are extremely good dispersers. arabicDifferent colony founding mechanisms could explain why some species contributed more to the turnover between points. arabicOur results indicate that management activities for conservation of ants are sufficient at scales as fine as 400 m×400 m, yet we caution that small conservation areas should be nested within larger reserves in order to maintain landscape connectedness. [ABSTRACT FROM PUBLISHER]

The Baetic ranges are one of the major hot-spots of biodiversity in the Mediterranean basin. The prominent Baetic plant richness is based mostly on the variety of ecological gradients, including the geological substrates such as dolomites. Dolomitic outcrops are not uncommon in the area, and they produce genuine edaphic islands inducing a peculiar flora and vegetation with high endemicity levels. Indeed, the habitats from these outcrops have been included in the Habitats Directive by the EU. This paper deals with the biogeographical relations between the dolomitophilous flora of the Baetic ranges. The presence/absence of those species was recorded in each of the Baetic ranges and the most interesting relations were revealed by means of two complementary strategies: Cluster Analysis and PAE. Using the current biogeographical classification of Rivas-Martinez to describe the results, the ranges of the Rondean Sector appear separated from the rest of the Baetic chorological province, since they comprise the most distinct flora. This division could be explained by the fact that this sector was separated from the Iberian Peninsula during the Messinian age (7.2-5.3 Ma) and, simultaneously, connected to Africa. The rest of the ranges belong to one of the following two groups: (1) the Malacitan-Almijarensean Sector and the western sub-Baetic territories; (2) the eastern territories of the sub-Baetic Sector. The ranges of the Guadician-Bacensean and Alpujarrean-Gadorensean Sectors behave as “satellite” ranges of the two above-mentioned groups. [ABSTRACT FROM AUTHOR]