In biology, phenetics (/fɪˈnɛtɪks/; from Ancient Greek φαίνειν (phainein) 'to appear'), also known as taximetrics, is an attempt to classify organisms based on overall similarity, usually with respect to morphology or other observable traits, regardless of their phylogeny or evolutionary relation.
The method can be traced back to 1763 and Michel Adanson (in his Familles des plantes) because of two shared basic principles – overall similarity and equal weighting – and modern pheneticists are sometimes termed neo-Adansonians.
A common problem with phenetic analysis is that basal evolutionary grades, which retain many plesiomorphies compared to more advanced lineages, seem to be monophyletic.
For a phenetic analysis, the large degree of overall similarity found among the Corvida will make them seem to be monophyletic too, but their shared traits were present in the ancestors of all songbirds already.
One of the most noteworthy applications of phenetics were the DNA–DNA hybridization studies by Charles G. Sibley, Jon E. Ahlquist and Burt L. Monroe Jr., from which resulted the 1990 Sibley-Ahlquist taxonomy for birds.
Indeed, due to the effects of horizontal gene transfer, polyploid complexes and other peculiarities of plant genomics, phenetic techniques of botany – though less informative altogether – may, for these special cases, be less prone to errors compared with cladistic analysis of DNA sequences.
In addition, many of the techniques developed by phenetic taxonomists have been adopted and extended by community ecologists, due to a similar need to deal with large amounts of data.