Describing relationships between organisms or groups of organisms that are assumed on the basis of overall similarities and differences. A phenetic classification takes into account as many characteristics as possible and, in contrast to a * phylogenetic classification, does not attach more weight (see weighting ) to characters that are assumed to be the result of evolutionary relationships. (Other characters may be weighted, especially those thought to be 'good' characters.) A phenetic classification does not aim to reflect evolutionary histories but may nevertheless well do so. It is most likely to diverge from a phylogenetic classification in instances of convergent and parallel evolution. Classifications published before or soon after the appearance of Charles Darwin's Origin of Species (1859) were obviously phenetic in nature since taxonomists were not thinking then in evolutionary terms. Most classifications drawn up after about 1880 tend to be phylogenetic. One phenetic system still in common use as a basis of herbarium arrangement is that of George Bentham and Joseph Hooker, published as Genera Plantarum (1862-83). A main difference between this and more modern systems is the placement of the gymnosperms between the dicotyledons and monocotyledons. |
