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Conservation 'in-situ' aims to represent and manage species in conservation-area networks in the long-term. The assumption is that once a species is secured within a conservation network, its overall likelihood of persistence will be increased. Quantitative area selection provides explicit and efficient methods to locate conservation areas, but remain largely unused. In part this is due to a lack of dialogue between theoreticians and practitioners, but current methods also fail to meet important demands of practitioners. In particular, there has been a strong emphasis on efficiency in species representation, but no adequate treatment of persistence. This may lead to a loss of species that could be avoided. An additional problem is that species' distribution data are often far from complete, so that quantitative methods can only use surrogates for species. In this thesis I address both problems. First, I explore the extent to which complementarity areas represent species from the most viable parts of their range. I show that using complementarity biases selection towards marginal populations, which may compromise species' persistence. Second, I propose a framework for integrating explicit criteria for persistence into quantitative area-selection. The framework has three steps: (a) models for current probabilities of occurrence are fitted using available information on habitat suitability and species' potential for dispersal; (b) probabilities of occurrence are then transformed into estimates of persistence using available information on expected threats and species' vulnerabilities; (c) complementarity areas are selected to ensure high persistence for species. An analysis of changes in bird faunas supports the idea that this integrated method can improve probability of persistence. Third, I provide a first test of the idea that maximising environmental variation among conservation areas would maximise species representation. This shows that using environmental surrogates may lead to relatively poor representation of species diversity.