Phylogenetic

Phylogenetic is an adjective describing anything related to phylogeny, the evolutionary history and relationships among biological entities such as species, genes, or populations. The term is widely used in biology to describe analyses, methods, and interpretations that aim to reconstruct these relationships.

Phylogenetics uses data from various sources, including comparative morphology, molecular sequences (DNA, RNA, proteins), and fossil evidence. Modern approaches rely on computational methods to infer evolutionary trees. Key methods include cladistics, which groups organisms by shared derived characteristics, and statistical methods such as maximum likelihood and Bayesian inference, which evaluate alternative trees under explicit models of evolution. Trees may be rooted to indicate the direction of evolution or left unrooted when the direction is unknown.

Concepts central to phylogenetics include the idea of clades, which are monophyletic groups consisting of a common ancestor and all its descendants. Other terms include polyphyly and paraphyly, which describe groups that exclude or assemble multiple ancestral lineages. Phylogenetic trees are hypotheses about evolutionary relationships and are continually revised as new data become available. Discrepancies between gene trees and species trees can arise from incomplete lineage sorting, horizontal gene transfer, or convergent evolution.

Applications of phylogenetics span taxonomy and systematics, where relationships help classify organisms; comparative and evolutionary biology; conservation planning; and epidemiology, where pathogen phylogenies illuminate transmission and divergence patterns.

Historically, phylogenetics began with work in morphology and systematics and advanced with Willi Hennig’s cladistics in the mid-20th century. The integration of molecular data and computational methods since the late 20th century has greatly expanded its scope and resolution.