sister taxa

A phylogenetic tree is a diagram illustrating the evolutionary history of a group of organisms. It shows how species or other taxa are related, with nodes representing common ancestors and branches indicating evolutionary lineages. The more recent the common ancestor, the more closely related the organisms.

Taxonomy is the science of classifying organisms. The fundamental unit is the species, with organisms grouped into nested sets of increasing generality (genus, family, order, etc.), as established by Carolus Linnaeus. This hierarchical system reflects shared ancestry, meaning organisms in the same taxon have similar evolutionary histories. Modern methods like cladistics use shared derived characteristics (synapomorphies) to infer these relationships. Sister taxa are groups that share an immediate common ancestor, making them each other's closest relatives on a phylogenetic tree.