Species concepts • Problem with fossil material – How many species are represented? • Coexisting populations – How many species were represented? – Homo sapiens – Homo neanderthalensis – or Homo sapiens sapiens and – Homo sapiens neanderthalensis? • What is a species?
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Species concepts Problem with fossil material – How many species are represented? Coexisting populations – How many species were represented? – Homo sapiens.
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Species concepts
• Problem with fossil material– How many species are represented?
• Coexisting populations– How many species were represented?– Homo sapiens– Homo neanderthalensis– or Homo sapiens sapiens and– Homo sapiens neanderthalensis?
• What is a species?
Species defined by a species concept
Most individuals use anon-dimensional species concept
Backyard bird feederSpecies identified by uniquedifferences.
Species levellineages
Biparental organismsOrganisms are unitedto form species-levellineages by the process of reproduction
• 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
• Biological species concept = no interbreeding • Barriers to interspecific hybridization• Reproductive isolating mechanisms• A. Pre-reproductive (favored by natural selection)
– 1. Ecological• Timing of reproduction• Habitat segregation
– 2. Behavioral (courtship, etc.)– 3. Mechanical
• B. Post-reproductive (not favored by natural selection)– Waste of gametes in doomed fertilizations
• Other species concepts
• 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
How many species? Problem 1: Ontological variation
Problem 2:Geographicvariation
Southwest AZ South-centralAZ
Problem 3: How much hybridization is permitted?
Discordant hybridization
The red wolf problem
Is there presently such a thing as a Red wolf?
Readily hybridizesHow much $ should be allocated to its survival?
3. One species or two?
Fertilehybrids
The hybridization zone: SW New Mexico
Sites 22, 26, 28, 30
Three concordantstep-clines
• 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
Aspidoscelis velox (3n, parthenogenetic)
1. A. stictogramma x A. inornata 2. F1 diploid parthenogenetic x A. inornata
Aspidoscelis uniparens (3n, parthenogenetic)
1. A. inornata x A. stictogramma 2. F1 diploid parthenogenetic x A. inornata