Figure 56.2 Subsets of Species in Communities Ecologists often use subsets of species to define communities. (A) All the amphibian species in a community could be grouped together by taxonomic affinity. (B) All the species that use pollen as a resource form a guild. (C) All the legumes (e.g., vetch, clover, and peas) that have nitrogen-fixing bacteria could be placed in the same functional group. Species within functional groups may or may not use the same resources.