Aphyly: A Systematic Designation for a Taxonomic Problem

Abstract

A taxon is aphyletic when it is deemed to be non-monophyletic or unresolved, therefore aphyletic taxa are a taxonomic problem rather than an evolutionary anomaly. A problem arises in systematics when taxonomic names assigned to aphyletic taxa are treated as if they were natural groups. In the absence of a taxonomic and systematic revision, anomalous taxa should be labelled as aphyletic without recourse to phylogenetic inference (i.e., interpretation). Doing so avoids the validation of aphyletic names and the creation of dubious results in fields that rely on systematic and taxonomic data.

The dichotomy of the modern bioregionalization revival

“…Biogeographical areas may be natural (monophyletic) or artificial (aphyletic; Ebach & Williams, 2010). Artificial areas human constructsmay not be distinguished from natural biotic areas if the regions are defined but not tested (sensu Michaux, 2010).…”

Aphyly: identifying the flotsam and jetsam of systematics

“…That is, many named taxa in use today are yet to be characterized by synapomorphies and hence are of unknown status relative to their “‐phyly”. In an earlier paper we suggested that such groups might be referred to as aphyletic , simply “meaning that they require taxonomic revision” (Ebach and Williams, , p. 124; see also Wilkins and Ebach, ; p. 144), and that those groups obviously have no status with respect to any phylogenetic interpretation. In our view, application of this terminology would avoid the oft made assumption that when a monophyletic group is discovered (i.e.…”

“…By identifying the flotsam and jetsam in systematics, we avoid making faux pas in regards to our phylogenetic interpretations. Ebach and Williams (), however, did not sufficiently emphasize the taxonomic nature of the term aphyly.…”

“…While these developments are of some significance in the evolution of Hennig's thoughts on kinds of taxonomic groups, his trajectory from “Restkörper” to paraphyly, it is the first term, “Restkörper”, we are interested in, as it is more general and of greater utility for practising taxonomists and seems related to, if not identical to, our aphyly (Ebach and Williams, ).…”

“…Bernardi utilized ancestry as a criterion of demarcation between kinds of groups (poly‐ and paraphyletic groups), in the same fashion as Archibald did later when describing his metataxa concepts (metaspecies, mixotaxa and ambitaxa) (Archibald, ). We utilized characters (synapomorphies) rather than ancestry, but the intent is the same: to recognize groups that “require taxonomic revision” (Ebach and Williams, , p. 124).…”