Phylogenetic diversity and conservation: examples at different scales and a population level proposal for Agave victoriae-reginae in the Mexican Chihuahuan desert

methods outlined by Vane-Wright et al. (1991), May( 1990), and Faith (1997) , whose foundations are similar, an briefly reviewed and their use is exemp lified. These methods, bused on phylogenetic diversity, can accomodate in t heir analyses data of different quality and at different hierarchical level s, both taxonomically and spatially. Their application can be used as a gui de for selecting, for conservation purposes, areas with a high phylogenetic diversity, species or higher level taxa that deserve particular conservati on efforts, or populations for ex situ and in situ conservation measures. T he method of critical fauna analysis seeks to find the minimum set of areas which encompass the highest proportion of total phylogenetic diversity of a particular taxon. However, it is recommended to use this concept carefull y since species are composed of numerous populations with different life hi stories, levels of local adaptation, etc., and not only phylogenetic divers ity must be accounted for. Pielou's (1969) partitioning of the Shannon dive rsity index is reviewed and its application in the characterization of the diversity of three North American forests is shown. Finally, an analysis of phylogenetic diversity is developed for the ten known populations of Agave victoriae-reginae, an endemic and endangered species from the Chihuahuan d esert, in Mexico. Data from population genetics (genetic diversity, number of alleles, etc.) and population size, together with the genealogy of popul ations derived from a cluster analysis using Nei's genetic distances, were used to reveal the populations that merit particular conservation efforts f rom the phylogenetic diversity point of view.