BIOC51H3 Lecture 19: BGYB51H3 Lecture 19 Notes Nov 12
11 Aug 2010
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BGYB51H3 Lecture 18/19 Notes
-host race is a subgroup that specializes on a particular host or have habitat requirements
-the specialization evolved due to selection
-variation in emergence time in hawthorn flies, which can lead to speciation
-disruptive selection occurs in apple and hawthorn flies in which hawthorns that emerge
between both peak periods do less well than other hawthorns
-flies show strong preference for one fruit type
-incipient species are populations that have diverged but are not isolated, which indicates
there is some gene flow
-a difference in colour can be caused by a single nucleotide substitution in a gene regulating
melanin
-if one population occupies a niche, selection leads to adaptation to that niche and new
environment, causing divergence
-sexual selection concentrates on the phenotypic variation among individuals in their ability
to obtain mates
-sexual selection affects mating success and gene flow and can result in divergence of species
-reproductive isolation can lead to divergent traits that
x prevent interbreeding
x interbreeding leads to poor hybrids
-female choice or incompatible genitalia can prevent interbreeding
-hybrid fitness determines if speciation is maintained
-poor hybrid fitness maintains speciation, equal hybrid fitness renews gene flow and
homogenization, higher hybrid fitness causes gene flow and potential loss of parent species
-reinforcement may cause pre-zygotic isolating mechanisms such as
x mate choice
x incompatible genitalia
x timing of mating
-speciation requires that there is a loss of gene flow initially
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Document Summary
Host race is a subgroup that specializes on a particular host or have habitat requirements. Variation in emergence time in hawthorn flies, which can lead to speciation. Disruptive selection occurs in apple and hawthorn flies in which hawthorns that emerge between both peak periods do less well than other hawthorns. Flies show strong preference for one fruit type. Incipient species are populations that have diverged but are not isolated, which indicates there is some gene flow. A difference in colour can be caused by a single nucleotide substitution in a gene regulating melanin. If one population occupies a niche, selection leads to adaptation to that niche and new environment, causing divergence. Sexual selection concentrates on the phenotypic variation among individuals in their ability to obtain mates. Sexual selection affects mating success and gene flow and can result in divergence of species. Reproductive isolation can lead to divergent traits that. Female choice or incompatible genitalia can prevent interbreeding.
