Biology 1001A Lecture Notes - Lecture 19: Species Complex, Phenotypic Plasticity, Reproductive Isolation
20 Jan 2020
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Species a distinct cluster in phenotypic space, no overlap with other such clusters several problems: ex species exhibiting sexual dimorphism, phenotypic plasticity one genotype can yield several different phenotypes. Biological species concept: reproductive isolation & shared gene pool. Species smallest group of populations that are all more closely related to each other than to anything else (smallest monophyletic unit) species that look exactly the same, but do not ever interbreed. Lumping versus splitting often depends on the species concept being used. Or, the two populations may have become partly or completely reproductively isolated prezygotic isolation (hybrids not formed) postzygotic isolation (hybrids are unfit) Reinforcement: selection favours evolution of prezygotic isolation if populations come back into secondary contact, and if postzygotic isolation has already occurred, individuals who avoid hybridizing have a selective advantage.
