Reviews in Fish Biology and Fisheries 9: 353–373, 1999.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
Species concepts and phylogenetics
ario C.C. de Pinna
Department of Zoology, Universidade de São Paulo, Caixa Postal 11461, São Paulo – SP 05422-970, Brazil
(E-mail: email@example.com); Current address: Setor de Ictiologia, Museu de Zoologia da Universidade de São
Paulo, Caixa Postal 42694, São Paulo – SP 04299-970, Brazil
Accepted 22 September 1999
Abstract page 353
Historical and ahistorical concepts of species 355
Historical concepts of species 355
Hennigian species concept
Evolutionary species concept
Genealogical species concept
Monophyletic species concept
Phylogenetic species concept
Neophylogenetic species concept
Individual organism species concept
Elements of the problem 358
Species and monophyly
Tokogeny and phylogeny
Taxa and the unit of evolution
Pattern and process
Species as individual organisms and exemplars 366
Species as conjectures 367
Concepts of species proposed within the phylogenetic paradigm are critically reviewed. Most so called ‘phylo-
genetic species concepts’ rely heavily on factors immaterial to phylogenetic hypotheses. Thus, they have limited
empirical content and offer weak bases on which to make decisions about real problems related to species.
Any workable notion of species relies on an explicit character analysis, rather than on abstract properties of
lineages, narrative predications and speculations on tokogenetic relationships. Species only exist conjecturally,
as the smallest meaningful units for phylogenetic analysis, as based on character evidence. Such an idea considers
species to be conjectures based on similarity, that are subsequently subject to testing by the results of analysis.
Species, thus, are units of phylogenetic analysis in the same way as hypotheses of homology are units of com-
parable similarities, i.e. conjectures to be tested by congruence. Although monophyly need not be demonstrated
for species-level taxa, hypotheses of relationships are the only basis to refute species limits and guide necessary
rearrangements. The factor that leads to recognition of species is similarity in observed traits. The concept of life
cycle is introduced as an important element in the discussion of species, as an efﬁcient way to convey subsidiary
notions of sexual dimorphism, polymorphism, polytypy and clusters of diagnosable semaphoronts. The notion of
exemplars is used to expand the concept of species-as-individual-organisms into a more generally usable concept.
Species are therefore proposed for a diagnosable sample of (observed or inferred) life cycles represented by
exemplars all of which are hypothesized to attach to the same node in a cladogram, and which are not structured