evolution

how do we reconstruct phylogeny

anatomical, genetic, behvioural, fossil, other data

computer algorithms- find pattern (phylogeny) that represents the best estimates of evolutionary patterns

what is phylogeny

• diversification of lineages through evolution

• any scale: populations to massive groups

• temporal or just relative sequence

• not about gross similarity

• emphasises shared novel traits not primitive

uses of phylogenies

• track pattern of evolution of traits

• test for convergent evolution

• examine correlation of trait evolution at any scale

anagenesis

gradual transformation (along branches) of one species into another

cladogensis

rapid splitting of a species into 2+ parts (atnodes)

sources of variation

• mutation -quasi random

• recombnation-quasi random

• phenotypic plasticity- deterministic

• constraints- can reduce or channel variation

modifiers of variation

• natural selection

• sexual selection

• genetic drift

key innovation

Key innovation = novel trait that originated in a particular lineage, providing evolutionary "advantages" such as increased speciation,

adaptive radiation

explosion of speciation in a lineage, that can be causally linked to its key innovation. Involves ecological and phenotypic diversification

alternative explanations for adaptations

1. Phylogenetic constraint or “baggage” 2. Design constraints prevent the optimal 3. Sexual selection 4. Neutral features (“spandrels”) 5. Co-variation with other traits 6. Exaptation 7. Random genetic drift