Molecular phylogenies

Ancestral DNA sequence: ATTGCTATTC DNA sequence changes to: ATTGCTTTTC Mutations can create synapomorphies

Ancestral DNA sequence: ATTGCTATTC DNA sequence changes to: ATTGCTTTTC Reversal to A at 7th position Reversals (‘back mutations’) can remove synapomorphies

rodhocetus

mesonychid ambulocetus rodhocetus basilosaurus

Molecular data used in phylogenetic analysis Immunological distance DNA-DNA hybridization Protein electrophoresis Restriction sites Amino acid sequences DNA sequences

Molecular data used in phylogenetic analysis Immunological distance DNA-DNA hybridization Protein electrophoresis Restriction sites Amino acid sequences DNA sequences

Molecular data used in phylogenetic analysis Restriction sites

Molecular data used in phylogenetic analysis Immunological distance DNA-DNA hybridization Protein electrophoresis Restriction sites Amino acid sequences DNA sequences

Tissues from which ancient DNA has been extracted Type of materialMaximum age Mummies 5000yrs Bog bodies 7500yrs Feathers 130yrs Museum skins 140yrs Naturally preserved skins10000yrs Bones25000+yrs Amber insects ??? Herbaria specimens 118yrs Charred seeds & cobs 4500yrs Mummified seeds & embryos44600yrs

Molecular clocks All phylogenies assume evolutionary differences arise from mutational differences  greater mutational differences = greater evolutionary distance

Molecular clocks If molecular clock assumptions are true, Phylogeny could be inferred from overall similarity of spp If calibrated, could estimate actual time since taxa diverged

Molecular clocks Relative rates Calibrated rates

Molecular clocks Problems Clock rate differs for different taxonomic groups & nucleotide sequences Differences in DNA repair efficiency Differences in metabolic rates Differences in generation time?