SPECIATION IN MAMMALS AND THE GENETIC SPECIES CONCEPT

We define a genetic species as a group of genetically compatible interbreeding natural populations that is genetically isolated from other such groups. This focus on genetic isolation rather than reproductive isolation distinguishes the Genetic Species Concept from the Biological Species Concept. Re...

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Bibliographic Details
Published in:	Journal of mammalogy 2006-08, Vol.87 (4), p.643-662
Main Authors:	Baker, Robert J., Bradley, Robert D.
Format:	Article
Language:	eng
Subjects:	Allopatric species Animal genetics Bateson–Dobzhansky–Muller model Biological and medical sciences Biological taxonomies cryptic species cytochrome b Definitions Evolutionary genetics FEATURE ARTICLES Fundamental and applied biological sciences. Psychology genetic isolation Genetic Species Concept Genetics hybrid zones Hybridity Hybridization J.A. Allen Memorial Article Mammalia Mammalogy Mammals Molecular biology phylogroups Population genetics reproductive isolation Scanning electron microscopy Speciation speciation in mammals Species Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution Zoology
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Summary:	We define a genetic species as a group of genetically compatible interbreeding natural populations that is genetically isolated from other such groups. This focus on genetic isolation rather than reproductive isolation distinguishes the Genetic Species Concept from the Biological Species Concept. Recognition of species that are genetically isolated (but not reproductively isolated) results in an enhanced understanding of biodiversity and the nature of speciation as well as speciation-based issues and evolution of mammals. We review criteria and methods for recognizing species of mammals and explore a theoretical scenario, the Bateson–Dobzhansky–Muller (BDM) model, for understanding and predicting genetic diversity and speciation in mammals. If the BDM model is operating in mammals, then genetically defined phylogroups would be predicted to occur within species defined by morphology, and phylogroups experiencing stabilizing selection will evolve genetic isolation without concomitant morphological diversification. Such species will be undetectable using classical skin and skull morphology (Morphological Species Concept). Using cytochrome-b data from sister species of mammals recognized by classical morphological studies, we estimated the number of phylogroups that exist within mammalian species and hypothesize that there will be >2,000 currently unrecognized species of mammals. Such an underestimation significantly affects conclusions on the nature of speciation in mammals, barriers associated with evolution of genetic isolation, estimates of biodiversity, design of conservation initiatives, zoonoses, and so on. A paradigm shift relative to this and other speciation-based issues will be needed. Data that will be effective in detecting these “morphologically cryptic genetic species” are genetic, especially DNA-sequence data. Application of the Genetic Species Concept uses genetic data from mitochondrial and nuclear genomes to identify species and species boundaries, the extent to which the integrity of the gene pool is protected, nature of hybridization (if present), and introgression. Genetic data are unique in understanding species because the use of genetic data 1) can quantify genetic divergence from different aspects of the genome (mitochondrial and nuclear genes, protein coding genes, regulatory genes, mobile DNA, microsatellites, chromosomal rearrangements, heterochromatin, etc.); 2) can provide divergence values that increase with time, providing an e
ISSN:	0022-2372 1545-1542