Summary1. Biogeographical models of species' distributions are essential tools for assessing impacts of changing environmental conditions on natural communities and ecosystems. Practitioners need more reliable predictions to integrate into conservation planning (e.g. reserve design and management). 2. Most models still largely ignore or inappropriately take into account important features of species' distributions, such as spatial autocorrelation, dispersal and migration, biotic and environmental interactions. Whether distributions of natural communities or ecosystems are better modelled by assembling individual species' predictions in a bottom-up approach or modelled as collective entities is another important issue. An international workshop was organized to address these issues. 3. We discuss more specifically six issues in a methodological framework for generalized regression: (i) links with ecological theory; (ii) optimal use of existing data and artificially generated data; (iii) incorporating spatial context; (iv) integrating ecological and environmental interactions; (v) assessing prediction errors and uncertainties; and (vi) predicting distributions of communities or collective properties of biodiversity. 4. Synthesis and applications. Better predictions of the effects of impacts on biological communities and ecosystems can emerge only from more robust species' distribution models and better documentation of the uncertainty associated with these models. An improved understanding of causes of species' distributions, especially at their range limits, as well as of ecological assembly rules and ecosystem functioning, is necessary if further progress is to be made. A better collaborative effort between theoretical and functional ecologists, ecological modellers and statisticians is required to reach these goals.

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The indigenous wildcat, Felis silvestris Schreber, 1775, and the introduced domestic cat, F. catus L., have been sympatric in Britain for more than 2000 years. As a result of interbreeding, any distinction between these two forms has become obscured, although a range of morphological criteria (pelage patterns, body measurements, gut lengths, skull morphometrics) and genetic techniques (immunological distances, electrophoresis, DNA hybridization) have been used previously to distinguish between them.A sample of 333 wild-living cats in Scotland was assessed for coloration and markings of pelage, standard body measurements and weights, and (for carcasses only) limb bone lengths, intestine lengths, and skull measurements. These cats were also classi®ed as wildcat, hybrid, or domestic cat according to traditional pelage criteria.Multivariate analyses on these variables, for adult cats, failed to show any clearly distinct groups. When each of the variables was analysed separately, only the distribution of limb bone and intestine length measurements suggested the possibility that two groups might exist. Group 1 cats had short intestines and long limb bones. Group 2 consisted of cats with long intestines and short limb bones. Although the characteristics de®ning cats in Group 1 were similar to those traditionally associated with wildcats, they exhibited a much broader range of pelage and coloration than traditionally described.The groups exhibited a degree of geographical separation. The distribution of Group 1 cats was found to be related to certain environmental variables, namely mean annual temperature and land with poor potential for forestry and agriculture, suggesting that there may be a biological basis for the separation. The implications of these results on the identi®cation and taxonomy of the wildcat are signi®cant. The concept of the wildcat and the domestic cat as separate species can be challenged. The paper highlights the complexity and dif®culties for conventional taxonomy when used as a means for distinguishing between a wild type and its domesticated form where there is interbreeding.

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