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Evolution Notes

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Biology 3466B
Yolanda Morbey

Evolution NotesOct 2011 A polytomy is a branch point on a phylogeny with more than two descendent lineages emerging It is a group that is unresolvedPhylogenetics applications taxonomic classifications answer questions about origins whales HIV test hypotheses about adaptation test hypotheses about speciation test for coevolution of form interactions between species that lead to adaptations Origin of whales Ancestors of whales made transition from terrestrial to aquatic A synapomorphy is a shared derived homologous trait A pulleyshaped astragalus bone is a synapomorphy that defines artiodactyl ungulates from nonartiodactyl ungulates There are two hypotheses One is that whales are a separate clade not closely related to other artiodactyls they are different The other is that hippos are whales closest relatives In the first hypothesis whales and the outgroup dont have astragalus but all the other animals do The tree has one changea gain in pulleyshaped astragalus In the second hypothesis two changes occura gain in pulleyshaped astragalus for all the animals and then a loss at the whales Changes can be either gains or losses On the principle of parsimony the first tree is more parsimonious based on one trait and it would be supportedPhylogenies are hypotheses however and hypotheses require evidence The best phylogenies use data from many traits and they use multiple types of traits such as behavioural morphological physiological and genetic They also use homologous traits Genetic traits vary though depending on the type of loci used DNA has a slow mutation rate and is best for resolving phylogenies among species and higher taxonomic orders Microsatellites have a fast mutation rate and are best for resolving phylogenies among populations and lower taxonomic orders Using DNA sequence data based on character state changes A C G T at 60 nucleotide sites p
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