Phylogenetics

Phylogenetics is a part of systematics that addresses the inference of the evolutionary history and relationships among or groups of organisms (e.g. species, or more inclusive taxa). These relationships are hypothesized by phylogenetic inference methods that evaluate observed heritable traits, such as DNA sequences or morphology, often under a specified model of evolution of these traits. The result of such an analysis is a phylogeny (also known as a phylogenetic tree)—a diagrammatic hypothesis of relationships that reflects the evolutionary history of a group of organisms. The tips of a phylogenetic tree can be living taxa or fossils, and represent the 'end', or the present, in an evolutionary lineage. A phylogenetic diagram can be rooted or unrooted. A rooted tree diagram indicates the hypothetical common ancestor, or ancestral lineage, of the tree. An unrooted tree diagram (a network) makes no assumption about the ancestral line, and does not show the origin or "root" of the taxa in question or the direction of inferred evolutionary transformations. In addition to their proper use for inferring phylogenetic patterns among taxa, phylogenetic analyses are often employed to represent relationships among gene copies or individual organisms. Such uses have become central to understanding biodiversity, evolution, ecology, and genomes.