Systematics and the Origin of Species On Ernst Mayr's 100th Anniversary (2005) / Chapter Skim
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13 Ernst Mayr and the Modern Concept of Species--KEVIN DE QUEIROZ
13 Ernst Mayr and the Modern Concept of Species--KEVIN DE QUEIROZ
Pages 243-264
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From page 243... ...
Although the general metapopulation lineage species concept and Mayr's popular species definition are commonly confused under the name ``the biological species concept,'' they are more or less clearly distinguished in Mayr's early writings on the subject. Virtu ally all modern concepts and definitions of the species category, not only those that require intrinsic reproductive isolation, are to be considered biological according to the criterion proposed by Mayr.
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From page 244... ...
book, the importance of species is also attested to by the fact that one of the most important and enduring influences of this book, along with subsequent repetitions and elaborations (Mayr, 1963, 1970, 1982) , concerns its discussion of species concepts, including a proposed definition of the species category that became a text
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From page 245... ...
The incompatibility results from treating certain properties acquired by diverging population lineages as necessary properties of species, including potential interbreeding and its counterpart, intrinsic reproductive isolation, in the case of Mayr's definition. Reinterpreting these properties as neither necessary nor sufficient for the definition of the species category eliminates the incompatibilities among alternative concepts of species, resulting in a unified species concept that brings taxonomic practice in line with common claims about the theoretical significance of species, and that is highly consistent with the general concept of species for which Ernst Mayr was arguably the most articulate and prolific advocate.
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From page 246... ...
and at least partially incompatible, definitions of the species category, hereafter referred to as the ``species problem,'' creates difficulties given that species are used as basic units of comparison in diverse types of studies. On the one hand, species taxa recognized according to different species concepts often will not be comparable to one another with regard to the biological properties they possess.
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From page 247... ...
It is certainly the case that all are based on important biological properties. THE METAPOPULATION LINEAGE CONCEPT OF SPECIES The reconciliation of alternative and incompatible species concepts derives from the recognition of a more general concept of species that is shared by all contemporary species concepts and definitions (de Queiroz, 1998, 1999, 2005)
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From page 248... ...
metapopulation lineages (de Queiroz, 1998, 1999, 2005)
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From page 249... ...
lineage terminology simply reflects a different temporal perspective on entities of the same basic kind, I will hereafter use the term ``metapopulation lineage'' to encompass both views. Virtually all contemporary species definitions (by which I mean those advocated by some contemporary group of biologists)
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From page 250... ...
Because the metapopulation lineage concept of species is general in the sense that it is shared by all modern concepts and definitions of species, it has previously been referred to as the ``general lineage concept of species'' (de Queiroz, 1998, 1999, 2005) , although it might be more accurately termed the ``general metapopulation lineage concept of species.'' THE SPECIES AS A FUNDAMENTAL CATEGORY OF BIOLOGICAL ORGANIZATION An important corollary of the metapopulation lineage concept of the species is that the species is a fundamental category of biological organization.
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From page 251... ...
Despite the relatively wide acceptance of the idea that the species represents a fundamental category of biological organization, some of the ways in which biologists continue to treat species taxonomically are inconsistent with that proposition. The practices in question appear to be holdovers from the earlier interpretation of the species category as a rank in the hierarchy of taxonomic categories (i.e., as opposed to its later interpretation as a fundamental category of biological organization)
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From page 252... ...
Under most current species definitions, the species is not the most general category at its particular level of organization. The reason is that those definitions commonly require separately evolving metapopulation lineages to possess some additional property before they are considered species.
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From page 253... ...
Thus, even if the species category is being treated as fundamentally different from the genus, the family, and the other higher taxonomic categories, it is still effectively being treated as a different rank rather than a different kind relative to the lower ones, in particular, relative to the subspecies category. In other cases, metapopulation lineages that have not yet acquired the stipulated property are not granted any formal taxonomic recognition whatsoever (i.e., as opposed to being ranked as subspecies)
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From page 254... ...
Because different authors adopt species definitions that treat different contingent properties of metapopulation lineages as necessary properties of species (e.g., intrinsic reproductive isolation, diagnosability, or exclusive coalescence of alleles) , those authors commonly disagree about which metapopulation lineages deserve to be ranked as species (de Queiroz, 1998, 1999, 2005)
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From page 255... ...
Those disagreements result from authors adopting different contingent properties (species criteria) as the basis for their species definitions.
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From page 256... ...
First, it retains the element common to all contemporary concepts and definitions of species by adopting the general concept of species as separately evolving metapopulation lineages. Second, it eliminates the conflicts among rival concepts by treating this property, existence as a separately evolving metapopulation lineage, as the only necessary property of species.
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From page 257... ...
Under a general and unified concept of species, the various contingent properties, although no longer treated as necessary properties of species, remain important in two ways. First, they continue to serve as important lines of evidence relevant to assessing the separation of metapopulation lineages.
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From page 258... ...
ERNST MAYR AND THE MODERN CONCEPT OF SPECIES The proposed resolution of the conflicts among alternative definitions of the species category described above is at odds with the common interpretation of Ernst Mayr's popular species definition, which treats intrinsic reproductive isolation as a necessary property of species. Nevertheless, the proposal is highly compatible with, and might even be considered the culmination of, the general metapopulation lineage concept of species for which Ernst Mayr was arguably the most important spokesman.
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From page 259... ...
Equation of the term ``biological species concept'' with the general concept of species as metapopulation lineages rather than the specific criterion of intrinsic reproductive isolation is supported by Mayr's own writings, in particular, by the properties he identified as being important for distinguishing the concept of species in its newer and uniquely biological sense from older conceptualizations of the species category. According to Mayr (1963, 1970)
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From page 260... ...
concept of species and Mayr's species definition became further obscured by common reference to both ideas as the biological species concept. In sum, there is an important distinction between the general concept of species as metapopulations or metapopulation lineages (the true biological species concept)
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From page 261... ...
In any case, the concise definition with its treatment of intrinsic reproductive isolation as a necessary property of species is an important part of the species problem (the existence of alternative and partially incompatible definitions of the species category) , whereas the general theoretical concept of species as metapopulation lineages forms the basis of a solution to this problem that results in a unified concept of species.
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From page 262... ...
(1999) The general lineage concept of species and the defining properties of the species category.
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From page 263... ...
(1997) A hierarchy of species concepts: The denouement in the saga of the species problem.
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