This chapter discusses the use of phylogenetic distances to infer mechanisms of ecological assembly. Mechanisms influencing patterns of community assembly act on the ecological similarities and differences of organisms, and not on the number of species. Phylogenetic patterns of relatedness have provided an especially useful and popular approach to quantifying expected species ecological differences for examining community assembly. Over the past decade, phylogenetic information has been widely used in community assembly studies to test a basic set of hypotheses about the relatedness of co-occurring species. This chapter considers two kinds of metrics employing phylogenetic information: those that examine patterns of relatedness by measuring phylogenetic distances among species, and those that provide an index of phylodiversity within an assemblage by accounting for the distribution of or evenness in edge lengths.