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Speciation

Speciation. “It is really laughable to see what different ideas are prominent in various naturalists’ minds, when they speak of ‘species’. It all comes, I believe, from trying to define the indefinable”. Charles Darwin. What is a species?. Using the BSC.

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Speciation

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  1. Speciation

  2. “It is really laughable to see what different ideas are prominent in various naturalists’ minds, when they speak of ‘species’. It all comes, I believe, from trying to define the indefinable”. • Charles Darwin

  3. What is a species?

  4. Using the BSC • "a species is an array of populations which are actually or potentially interbreeding, and which are reproductively isolated from other such arrays under natural conditions." (Ernst Mayr) • Reproductive isolation is the failure of populations to interbreed or to form viable or fertile hybrids • Speciation = generation of a reproductive isolating mechanism

  5. Fig. 24-4 Prezygotic barriers Postzygotic barriers Habitat Isolation Behavioral Isolation Temporal Isolation Mechanical Isolation Gametic Isolation Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown Individuals of different species Viable, fertile offspring Mating attempt Fertilization (c) (e) (f) (a) (g) (h) (l) (i) (d) (j) (b) (k)

  6. Fig. 24-4a Prezygotic barriers Mechanical Isolation Habitat Isolation Temporal Isolation Behavioral Isolation Individuals of different species Mating attempt (e) (f) (a) (c) (d) (b)

  7. Fig. 24-4i Prezygotic barriers Postzygotic barriers Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown Gametic Isolation Viable, fertile offspring Fertilization (h) (g) (l) (i) (j) (k)

  8. Speciation is often gradual, so we expect to see some “gray areas”(are they different species or not?)

  9. Speciation is often gradual, so we expect to see some “gray areas”(are they different species or not?) Canislatrans Canislycaon Canis lupus

  10. Speciation is often gradual, so we expect to see some “gray areas”(are they different species or not?) Canislatrans Canislycaon Canis lupus CanisSoup

  11. The BSC can only apply to a small portion of life

  12. The PSC • the smallest set of organisms that share a common ancestor and can be distinguished from other such sets. • Or • the smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent (Cracraft 1983) • Speciation = cladogenesis

  13. Eastern and Western Northern Flickers • Morphological differences evolved in allopatry • Differences don’t function as premating RIM’s (they hybridize in the Great Plains) • Don’t seem to be any postmating RIM’s (hybrids fit and reproduce)

  14. Moore et al., 1991, Mol. Biol. Evol. 8(3):327-344

  15. Types of speciation • Anagenesis—draw it

  16. Types of speciation • Anagenesis—draw it • Cladogenesis—draw it

  17. Types of speciation • Anagenesis—draw it • Cladogenesis—draw it • Reticulate speciation—draw it

  18. Bold = species thought to have formed as hybrids Red arrows = mtDNA source Koblmülleret al.BMC Evolutionary Biology 2007 7:7   doi:10.1186/1471-2148-7-7

  19. 3 hybrid species of sunflower that thrive where the parental species cannot

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