Evolutionary Biology BIOL 3350 Dr Lisa Rapaport Lecture 15 Part 2 Notes What is A Species I Ecological Speciation in Allopatry A There was no barrier before but now all of the sudden there is a B Each population will diverge either through genetic drift or adaption C The hybrid typically has a lower fitness level than either of the barrier to the different habitats parental species D Individuals that do not make those mistakes will have higher fitness Is the distribution of the chameleon clade reflective of vicariance the break up of Gondwana or oceanic dispersal A The oldest clades are in Madagascar B Derived lineages occur in Madagascar Africa and India C Africa and South America were the first to break off of the major land group of Gondwana and then they broke off from each other D Australia broke off much later than Africa Seychelles Tiger Chameleon Distribution Explained by Dispersal A The ocean currents would have favored drifting B They were carried by ocean currents on floating vegetation rather than on continents C Both agrees and disagrees with Raxworthy D A phylogeny is a hypothesis E We now believe that they originated in Africa rather than Madagascar F New information can change phylogenies Sympatric Speciation A Population A is adapting to one type of habitat and population B is adapting to another but they also have an overlap B Assortative mating like mates with like Size Assortative Mating Leads to Byproduct Reproductive Isolation A Three spine sticklebacks 1 Benthic mainly eats invertebrates large body and few short gill 2 Limnetic primarily exploits plankton small body and many long rakers gill rakers II III IV V 3 Benthic prefers to breed with benthic while limnetic prefers to breed with limnetic 4 They is very little cross breeding between the 2 species VI VII Speciation by Sexual Selection A A link between female preference and male expression of the trait Sexual Selection Lake Malawi Cichlids 1 A The species that inhabit deep water have opsins that are more B sensitive to red light In some cases natural selection and sexual selection can combine in order to create new species VIII How do new species arise A The most basal of this salamander group is found in northern California B Scientists think that there was an adaptive radiation down the eastern side of California and an adaptive radiation down the coastal side of California C This is called a ring species D With these salamanders natural selection has favored local adaptation as the clade has radiated out sexual selection has changed females mating preferences this change in preferences causes the populations to become very different form one another sexual selection and natural selection are going hand in hand E Less and less hybridization as time goes on F Natural selection and sexual selection are acting in concert Premating Isolation Mechanism Reproductive Isolation Reinforced Through Song Preferences and Inbreeding A B Their parental species did not participate in inbreeding C The females did not like the weird song that neighboring males were Inbreeding was exceedingly rare prior to this lineage signing so the females bred with their relative males who were signing the song that they liked IX 2