Historical biogeography, diversity and conservation of Australia's tropical rainforest herpetofauna

[Extract] Faced with a combination of increasing degradation of habitats and sparse knowledge of species and their distributions, biologists are struggling to find ways of predicting spatial patterns of diversity and then to devise effective strategies for conservation. Area-based conservation planning typically applies complementarity algorithms to identify one or more combinations of areas that effectively represent the known pattern of species diversity (Margules & Pressey 2000). Usually, high-quality distribution data are available for only a limited number of taxonomic groups (e.g. trees, birds, butterflies), so geographic patterns of diversity in these groups must act as a 'surrogate' for those of other taxa. Even this level of knowledge may be lacking for some areas, or at finer spatial scales, leading to the use of environmental (e.g. climate, soil, etc) data in addition to, or in place of, species' occurrence information (Ferrier 2002; see also Faith et al. 2001). The efficiency of such surrogates appears to vary, especially at the finer spatial scales relevant to most conservation planning efforts (see, for example, van Jaarsveld et al. 1998; Moritz et al. 2001; Lund & Rahbeck 2002). \ud Even where the geographic pattern of species diversity is known or can be predicted from other taxa, species-based conservation plans may be ineffective at capturing genetic diversity within and across species (Crozier 1997; Moritz 2002). In this context, attention has been given to using evolutionary trees to estimate the phylogenetic diversity (PD) (Faith 1992) represented by a given set of species or areas. Both simulations (Nee & May 1997; Chapter 5, this volume) and evidence (Polanski et al. 2001; Rodrigues & Gaston 2002) suggest that conservation priorities established though complementarity (dissimilarity) analysis of species are often effective at capturing phylogenetic diversity. However, Rodrigues et al.(Chapter 5, this volume) found that species-based approaches can under represent PD where some areas have few, but phylogenetically divergent, endemic species and suggested that this situation could arise on small, long isolated islands.\ud Much of the work on developing methods for conservation planning has focused on analysis of biodiversity pattern, with less attention to the underlying process, in particular the biogeographic and evolutionary processes that have shaped current patterns of diversity. Recent theory (Rosenzweig 1995; Hubbe1l 2001) demonstrates how spatial processes of speciation and extinction can affect the distribution of species diversity at varying geographic scales determined by a combination of environmental heterogeneity and intrinsic dispersal limitation. We suggest that phylogenetic analyses, both within and across species, can contribute directly to conservation planning by illuminating these processes, by identifying spatial surrogates for representing them in a conservation plan and by using this information to improve predictions of biodiversity pattern. Phylogenetic analyses also provide a richer perspective on diversity above and below the species level than do 'flat-field' lists of species (Avise 2000; Brooks & McLennan 2002).\u