Chapter 4: Speciation and Phylogeny Macroevolution Species and Speciation Phylogenies: Evolutionary Trees

Biological Species Reproductive isolation –Gene flow within species –No gene flow between species Allopatric speciation: results from geographic/environmental isolation –Selection or gene drift will eventually change each population in different directions and eventually they will be incapable of interbreeding

Sympatric Speciation: Niche diversification –Different ways of making a living in the same place. –Specialization toward different resource gathering strategies leads to different selective forces

Time Sympatric Speciation: Niche diversification –Different ways of making a living in the same place. –Specialization toward different resource gathering strategies leads to different selective forces

–Darwin’s finches –Adaptive radiation Other isolation mechanisms –Mechanical isolation –Temporal isolation –Behavioral isolation Seagulls around the World

Phylogenies: Trees of Life Linnaeus: Linnaean System of Classification Based on similarity of traits Hierarchical: –Kingdom –Phylum –Class –Order –Family –Genius –Species K ings P lay C hess O n F ine G rained S and K eep P ots C lean O r F amily G et S ick

Kingdom:Animal Phylum:Cordates (Sub phylum Vertebrata) Class:Mammal Order:Primate Family:Hominid (Super Family Hominoid) GeniusHomo SpeciesSapiens Humans are:

Phylogeny for the Hominoids

Inheritance or Convergence? Homologous = Similar because of common decent (share a recent common ancestor) – Inheritance. Analogous = Similar because of adaptation to the same or similar environmentally stable problem (Bird and Bat wings) - Convergence.

Phylogenies use homologous structures (traits) and must avoid analogous structures Present Past

YesNo Derived Trait Analogous Trait Ancestral Trait (last common ancestor) (convergence) (common ancestor of all 3)

Using Overall Similarity of Traits Leads to the Wrong Family Tree

Using Similarity of Derived Traits Leads to the Correct Family Tree

Systematics: the study that distinguishes ancestral from derived traits Ancestral Traits Appear earlier in embryonic development –Ontology recapitulates phylogeny Appear earlier in the fossil record –Older traits Seen in out-groups –If a trait is absence in one species but seen in other more distant lineages (tails)

Genetic Distance DNA Hybridization Fewer bondsMore bonds Less Related More Related Lower Temp to break Higher Temp to break

Molecular Clock Neutral theory or Natural selection?

How Good are Human Phylogenies Cladistic modeling of skeletal traits do not match the cladistic modeling of DNA distance Human phylogenies are based on skeletal data and are likely to have errors. Some argue for Bastian statistics approach.