Phylogenetic diversity is a measure of the evolutionary history and relatedness of a group of organisms. It takes into account not only the number of species present in a community, but also the degree of divergence between those species on the evolutionary tree. This measure is important for understanding the overall biodiversity and evolutionary potential of a community, as well as for identifying and prioritizing conservation efforts. Phylogenetic diversity can be calculated using phylogenetic trees, which show the evolutionary relationships between different species based on their genetic similarities and differences.