Lecture 9 - 3444

Phylogeography studies the geographic distribution of genetic lineages within species, focusing on historical dynamics and gene flow.
It explains evolutionary divergence influenced by historical and contemporary factors such as distance, topography, and physical barriers.

Phylogenetic Tree: Diagram representing evolutionary relationships among organisms or genes.
- Branches: Represent evolutionary lineages.
- Nodes: Common ancestors of the branches.
  - Internal Nodes: Represent common ancestors of descendant branches.
  - Terminal Nodes: End points representing species or genes being studied.
- Root: Base of the tree indicating the most recent common ancestor.
- Branch Lengths: In some trees, they represent evolutionary change or time; in others, they are arbitrary.

Monophyletic Groups: Include a common ancestor and all its descendants.
- Evidence of shared ancestry and valuable for inferring biogeographic histories.
Paraphyletic Groups: Include a common ancestor and some but not all descendants, suggesting asymmetric lineage sorting.
Polyphyletic Groups: Avoided in phylogeography due to artificial grouping; often due to misinterpretation or convergent evolution.

Tools: MEGA, BEAST, RAxML.
Methods: Maximum Likelihood and Bayesian Inference.
- Maximum Likelihood: Finds the best tree with highest likelihood.
- Bayesian Phylogenies: Estimates posterior probabilities of trees, slower and more computationally intense, incorporates uncertainty.

Applications:
- Conservation: Identifying stress responses, historical dynamics, and biodiversity patterns.
- Forensics and wildlife management.
- Understanding pathogen spread and climate change impacts.

mtDNA: High mutation rate; matrilineal inheritance. Limitations reflect only maternal lineages and mask deeper signals.
nuDNA: Biparental inheritance for a comprehensive view of genetics. Lower mutation rates than mtDNA limit its effectiveness for some studies.
cpDNA: Potent for studying long-term dynamics, evolves slowly, but may overlook pollen-mediated gene flow.

Haplotypes: Group of alleles inherited from one parent, useful for tracing maternal/paternal lineages.
Haplotype Networks: Visual representations depicting the relationships among haplotypes, with circles representing haplotypes and lines showing mutational differences.

Diversity measures the probability that two randomly chosen haplotypes are different:
- High values: Indicate diverse populations with long-term stability.
- Low values: Suggest dominance of a single haplotype; not reflective of overall haplotype count.

Measures average nucleotide differences within a population, indicating ancient or evolved diversity within populations. High 𝜋 suggests high gene flow; low 𝜋 indicates recent bottlenecks or limited variability.

Phylogeography correlates genetic data with environmental conditions, aiding understanding of population responses under stress.

Study in a radiated area indicating adaptation to stress, demonstrating unexpected increases in mtDNA diversity despite higher radiation levels.
Response to radiation showcases complexity in evaluating evolutionary impacts under stress.

Colonization: Leads to rapid differentiation and gene flow limitations.
Historical Isolation: Fragmentation influences genetic structure through vicariance and geographic barriers, promoting genetic drift and divergence.
Climate Change and Glacial Cycles: Significant influence on population distribution and genetic diversity.

Estimation methods involve sequencing, with calibration through fossil records, geological events, and biogeographical changes.

Study exemplifies challenges and conservation efforts due to habitat fragmentation and genetic diversity concerns.
Divergence analysis based on mitochondrial markers; insights into population dynamics assist in conservation prioritization.