Evaluating the Taxonomic Status of the Mexican Gray Wolf and the Red Wolf (2019) / Chapter Skim
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2 Guiding Principles for Identifying Species and Subspecies
2 Guiding Principles for Identifying Species and Subspecies
Pages 17-28
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From page 17... ...
The chapter begins with an overview of species and subspecies concepts that are especially relevant to canids in North America. The discussion emphasizes how these concepts can be applied in light of the modern understanding that gene flow between species has played a major role in the evolutionary history of many well-accepted mammalian species, including the canids of North America.
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From page 18... ...
For North American canids, for example, while multiple whole-genome sequences are available from a large set of modern individuals, data from older samples are comparatively sparse. The challenge for modern taxonomy is to use available data of diverse types to assess the taxonomic status of various groups of organisms under modern species concepts.
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From page 19... ...
This can lead to cryptic species that are morphologically similar but so divergent genetically that they are reproductively incompatible and thus have been set on different evolutionary trajectories. The Chronospecies Concept Changes can accumulate across generations of a given lineage, making modern members of a given species highly distinct from their predecessors, despite genetic continuity among generations (Stanley, 1978)
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This concept is relatively easy to apply if gene flow is nonexistent or at least extremely rare among groups of organisms that are considered to belong to distinct species. Increasingly, though, genomic data have revealed that the cross-species exchange of genetic material through hybridization is a core feature of the evolutionary history of many widely accepted species (Arnold, 2006; Grant and Grant, 1992; Mallet, 2005)
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hybrid and a member of the parental species or other hybrids are infertile. Reduced hybrid viability or reduced hybrid fertility imposes a strict barrier to gene flow between the two hybridizing species.
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Perhaps the most extreme example of introgression in mammals involves pigs (Sus scrofa) , which show evidence of gene flow from an extinct species outside the Sus genus that had diverged from pigs an estimated 8.5 million years ago (Ai et al., 2015)
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Each of the outcomes described below is potentially relevant to the evolutionary history of canids in North America. Continued Strict Genetic Separation of Species Species may remain genetically distinct following hybridization.
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Formation of Stable Hybrid Zones It is possible for stable hybrid zones to form when species with ecological adaptations to different environments inhabit neighboring or overlapping ranges or when two formerly geographically separated species meet as a result of a range expansion of one or both of them. In the first case, ecological selection may counteract the effect of hybridization and maintain distinct species.
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ESTABLISHING GUIDELINES FOR DETERMINING TAXONOMIC STATUS The increasing evidence of gene flow among taxonomic groups conflicts with earlier views that strict reproductive isolation is a defining feature of taxonomically valid species. As noted above, all modern species concepts focus on whether a given group of organisms constitutes a distinct, independently evolving lineage that merits recognition as a taxonomically valid species.
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From page 26... ...
These criteria provide a framework for assessing diverse data types useful for evaluating the taxonomic status of the Mexican gray wolf (Chapter 4) and the red wolf (Chapter 5)
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Endangered Species Act. Conservation Biology 20(6)
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From page 28... ...
1996. Policy regarding the recognition of distinct vertebrate population segments under the Endangered Species Act.
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