Basal (phylogenetics)
In phylogenetics, basal refers to the direction of the base (or root) of a rooted phylogenetic tree.
The term is commonly used in scientific literature to refer to the sister group of a particular clade of interest. Despite the ubiquity of this usage, many systematists believe it is unnecessary and misleading[1]. This is because a pair of sister branches of a phylogenetic tree are equally ranked and can be freely rotated about their last common node. The term tends to be applied only when one branch (the one deemed "basal") is less diverse than another branch. This raises an equivocal usage for this term in that it also refers to the direction of the root of the tree. As the root represents a hypothetical ancestor, this consequently carries misleading connotations that the sister group of a more species-rich clade is primitive[2].
References
- ^ Krell, Frank T (2004). "Which side of the tree is more basal?". Systematic Entomology. 29: 279–281.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Jenner, Ronald A (2006). "Unburdening evo-devo: ancestral attractions, model organisms, and basal baloney". Development Genes and Evolution. 216: 385–394.