Evolution as the Basis for Biodiversity

Question 1

What are the major patterns and processes in evolution?

Answer 1

• Phylogeny = pattern of evolution / relationships

Uses of phylogenies:
1. Track pattern of evolution of traits - youngest, oldest, rate of evolution, timing of changes
2. Test for convergent evolution (independent of similar traits)
3. Examine correlation of trait evolution at any scale (eg: species & continents, hosts & parasites, adaptation & diversification)

Patterns of speciation:
- Anagenesis - gradual transformation (along branches) of one species into another (linear)
- Cladogenesis - rapid splitting of species into 2+ parts at nodes (branched)

Processes of evolution:
1. Sources of variation
– mutation (quasi-random)
– recombination (quasi-random)
– phenotypic plasticity / environmental impact that is not passed down (deterministic)
– constraints (can reduce/channel variation)
2. Modifiers of variation
– natural selection (deterministic)
– sexual selection
– genetic drift (quasi-random)

Question 2

How is phylogeny used?

Answer 2

• Can be reconstructed through: anatomical, genetic, behavioural and fossil data or computer algorithms that represent th4e best estimate of evolutionary patterns
• Used to identify the diversification of lineages through evolution on any scale, at any time, through the understanding of shared novel traits (not primitive / gross similarity)
• Phylogenies can be read by looking at 3+ branches and observing how they connect together to create a comparison between species features and how they have evolved

Question 3

What is adaptation, and what about evolution is non-adaptive?

Answer 3

• Adaptation = a trait that enhances (evolutionary) fitness that arose historically as a result of natural selection, for its current biological role - to allow an individual to successfully reproduce to continue its lineage
• Adaptation requires:
  – feature
  –more offspring reproducing
  – favoured by natural selection
  – appeared in conjunction with its current function in its environment (was not previously used for another function)
• Key innovation = novel trait that originated in a particular lineage, providing evolutionary advantages that lead to an adaptive radiation (eg: increased speciation)
• Adaptive radiation = explosion of speciation in a lineage, that can be causally linked to its key innovation (involves ecological and phenotypical diversification)
• Key innovation and adaptive radiation must coincide (by definition) and a phylogeny must be used to test whether they explain a part of biodiversity (eg: Darwin’s finches)

Alternative explanations for adaptations:
1. Phylogenetic constraint/baggage - feature previously used by ancestors but no longer required / no longer possible to use
2. Design constraints preventing the optimal
3. Sexual selection
4. Neutral features
5. Co-variation with other traits - long fingers usually result in long toes
6. Exaptation - good enough to do the job
7. Random genetic drift