Species concepts

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Species concepts

• New species are produced by speciation

C
B
B
time
time
A
A
Phenotypic change
Population divergence
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Species defined by a species concept Species
diagnosed by unique differences
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Species level lineages
Biparental organisms Organisms are united to form
species-level lineages by the process of
reproduction
Uniparental organisms Constant divergence because
lineages are not linked together by reproduction
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• The Biological Species Concept
• Species are groups of actually or potentially
  interbreeding natural populations that are
  reproductively isolated from other such groups.
• Species criterion absence of interbreeding.
• The species concept
• Used in field of anthropology
• Used to make decisions re the Endangered Species
  Act

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• Criterion of reproductive isolation presents
  problems
• 1. Populations that are geographically separated.
• 2. Asexual and parthenogenetic populations.
• 3. Morphological differences and similarities may
  not be effective in distinguishing species under
  this concept.
• A. Individual variation (e.g., ontological
  variation)
• B. Geographic variation
• C. How much hybridization is permitted?
• D. Cryptic species

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Problem 1 Ontological variation
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Problem 2 Geographic variation
South-central AZ
Southwest AZ
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Problem 3 How much hybridization is permitted?
Discordant hybridization
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Is there presently such a thing as a Red wolf?
Readily hybridizes How much should be allocated
to its survival?
The red wolf problem
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3. One species or two?
Fertile hybrids
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The hybridization zone SW New Mexico
Sites 22, 26, 28, 30
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Three concordant step-clines
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uniparens
velox
Aspidoscelis velox (3n, parthenogenetic) 1. A.
gularis stictogramma ? x A. inornata ? 2. F1
diploid parthenogenetric ? x A. inornata ?
Problem 4 Cryptic species
Aspidoscelis uniparens (3n, parthenogenetic) 1.
A. inornata ? x A. gularis stictogramma ? 2. F1
diploid parthenogenetic ? x A. inornata ?
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• Barriers to interspecific hybridization
• Reproductive isolating mechanisms
• A. Prereproductive (favored by natural selection)
• 1. Ecological
• Temporal (phenological)
• Habitat segregation
• 2. Behavioral
• 3. Mechanical
• B. Postreproductive
• Gametic wastage
• Other species concepts

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• The Evolutionary Species Concept
• A species is an entity composed of organisms
• maintaining its identity from other such entities
  through time and space
• and having its own independent evolutionary fate
  and historical tendencies.
• Operationalism absent
• Use fixed diagnostic differences