Please cite this article as: Boenigk, J., et al., Concepts in protistology: Species definitions and boundaries.
European J. Protistol. 48 (2012): 96102 doi:10.1016/j.ejop.2011.11.004
EJOP-25234; No. of Pages 7
Available online at www.sciencedirect.com
European Journal of Protistology 48 (2012): 96102
Concepts in protistology: Species definitions and boundaries
Jens Boenigk
a,*
, Marc Ereshefsky
b
, Kerstin Hoef-Emden
c
, James Mallet
d
, David Bass
e
a
General Botany, University Duisburg-Essen, Universitätsstr, 5, 45117 Essen, Germany
b
Department of Philosophy, University of Calgary, 618 Campus Place N.W., Calgary, Canada
c
Botanical Institute, Cologne Biocenter, University of Cologne, Zülpicher Str. 47b, 50674 Cologne, Germany
d
Galton Laboratory, Department of Genetics, Evolution and Environment (GEE), University College London, Gower Street, London WC1E
6BT, United Kingdom
e
Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, United Kingdom
Received 24 August 2011; received in revised form 28 November 2011; accepted 28 November 2011
Abstract
This paper summarises the Symposium ‘Concepts in Protistology’, during the VI European Congress of Protistology, Berlin,
25–29 July 2011. There is an increasing focus on cataloguing the number of species on earth, species barcoding initiatives,
and the increasing need to reconcile molecular with morphological data in protists within a taxonomic framework. We identify
several obstructions to defining species in protists, including the high incidence of asexuality, high levels of both morphological
conservation and evolutionary convergence, high levels of genetic diversity that cannot so far be correlated with phenotypic
characters, conflicting signals between both genetic and phenotypic taxonomic markers, and different requirements and chal-
lenges of species definition in different protist groups. We assert that there is no species ‘category’ for protists, and recommend
that a working definition of species is clarified on a case-by-case basis. Thus, a consensus approach may emerge within protist
groups, but any one approach is unlikely to encompass a wide phylogenetic range. However, as long as clarity of intent and
method is maintained, the utility of the term ‘species’ in protists will also be maintained as a reproducible and convenient (if
artificial) way of referring to particular lineages within a tightly defined context.
© 2011 Published by Elsevier GmbH.
Keywords: Species concept; Protist; SSU rDNA; ITS rDNA; COI; OTU
Introduction
Although the high-level taxonomy of protists is a well-
grounded (although not resolved) area of research, the
opposite end of the taxonomic spectrum, alpha-taxonomy,
and what constitutes protist species are issues fraught with
uncertainty and disagreement. The fact that there is no gener-
ally accepted basis for delimiting species in protists has many
unfortunate consequences, prime among them being (1) a
*
Corresponding author.
E-mail address: jens.boenigk@uni-due.de (J. Boenigk).
lack of basic communicability about fundamental biological
units (with obvious negative implications for barcoding), (2)
lack of clarity regarding their evolutionary and ecological sig-
nificance, and (3) a drastic underestimation of protist diversity
and importance in more general biodiversity papers. A good
example of the latter is shown by Mora et al. (2011), in which
(by no fault of theirs) estimates of species numbers of protists
(in particular) are unrealistically depressed, in part because
of the problem with defining ‘species’ and also because of the
rapidly changing and relatively unstructured nature of protist
taxonomy overall.
The ECOP workshop did not set out to ‘decide’ on the
‘best’ species concept to apply to protists, but rather to assess
0932-4739/$ – see front matter © 2011 Published by Elsevier GmbH.
doi:10.1016/j.ejop.2011.11.004