Species

369

Appendix B: A Summary List of Species Definitions

Groups and categories are distinctly different and there is no real connection

between them. The tradition in codes of nomenclature artificially forces the

use of taxonomic categories in a hierarchy for groups. A biological classifica-

tion is a contrived system of categories used for the storage and retrieval of

information about biological diversity, taxa, or groups. The concept ‘category’

is a class and has no separate existence from its use in organizing objects or

thoughts; categories have no reality. Unlike groups, categories have no attri-

butes; things or objects are not members of categories, but are parts of groups;

and organisms are not members of any taxonomic category.

R. L. Mayden^1

Warren Herb Wagner’s Syncretic and Eclectic Species Definition

A convenient taxonomic category that defines a unit of organismic diversity

with one or more ancestors in [a] given time frame and composed of individual

organisms that resemble one another in all or most of their structural and func-

tional characters, that reproduce true by any means, sexual or asexual, and

constitute a distinct phylogenetic line that differs consistently and persistently

from populations of other species in character state combinations including

geographical, ecological, physiological, morphological, anatomical, cytologi-

cal, chemical, and genetic, the character states of number and kind ordinarily

used for species discrimination in the same and related genera and if partially

or wholly sympatric and co-existent with related species in the same habitats,

unable to cross or, if able to cross, able to maintain the species distinctness.

Circular sheet, dated 19 November 1998^2

There are numerous species “concepts” at the research and practical levels in the sci-
entific literature. Mayden’s (1997) list of 22 distinct species concepts along with syn-
onyms is a useful starting point for a review. I have added authors where I can locate
them in addition to Mayden’s references, and I have tried to give the concepts names,
such as biospecies for “biological species,” and so on, following George 1956, except
where nothing natural suggests itself. I have used Mayden’s abbreviations, except as
noted, and added new ones for novel conceptions. A closely similar annotated list is
found in Zachos 2016. In some cases I have adopted his terminology.
There have also been several additional concepts since Mayden’s review, so I
have added the views of Pleijel 1999 and Wu 2001a, b, and several newer revisions

(^1) Mayden 1997, 386.
(^2) Pers. comm.