Evolution Biol 4802:  Lecture 9

 

Topic for today

Biogeography – the study of species distributions

    1. Ancient patterns
    2. Pleistocene patterns

What factors influence species distributions?

  1. Contemporary factors
    1. Climate
    2. Soils
    3. Biotic interactions
    4. Dispersal
    5. Extinction
  2. Historical factors
    1. Position of the continents
    2. Dispersal
    3. Ancient climates
    4. Vicariance (separation)
    5. Extinction

Historical remnants of artic climate on “shelf” habitats near Lake Superior

  1. Artic-Alpine disjunct species

Questions in the field of biogeography

1.   Historical aspects

    1. Where did groups of organisms originate?
    2. What paths did they follow as they moved?
  1. Contemporary patterns
    1. What factors constrain a species from range expansion?
    2. Why are some species restricted and others widespread?
    3. Why are there more species in the tropics than in the temperate zone?
  2. Tools for understanding
    1. Geology (plate tectonics)
    2. Fossil record
    3. Phylogeny
    4. Ecology

Biogeographic realms of Wallace reflect ancient divisions

  1. Use modern tools to refine our understanding

Testing hypotheses with phylogenies

1.   What phylogenetic pattern would you expect with dispersal?

  1. Build expected phylogeny
  2. Compare to actual phylogeny

Phylogenetic pattern with vicariance?

Extinction complicates matters

Successive division of Gondwanaland forms expectation

1.   Three tests of vicariance hypothesis

  1. What kind of species might you select?

Does the phylogeny chameleons support vicariance?

  1. Distributed in Africa (A), Madagascar (M), India (I), and islands of Indian Ocean (SE)
  2. Chameleons originated in Madagascar and dispersed over water

Does the phylogeny of cichlids support vicariance?

  1. Pattern roughly corresponds
  2. But the timing is off according to molecular clock and fossil record
  3. Suggests that cichlids dispersed after Gondwanan breakup

Does the phylogeny of flightless birds support vicariance?

Phylogeny of flightless birds

  1. Stem from ancient ancestor on Gondwanaland
  2. Consistent patterns?
  3. Not consistent?
  4. Some kind of dispersal?

Hypotheses about human evolution distinguished

  1. Mitochondrial DNA “haplotype”
    1. Maternally inherited
    2. Doesn’t recombine

Which hypothesis is supported by mitochondrial DNA?

  1. Diverse African lineages
  2. One lineage gave rise to all other human populations

Which hypothesis is supported by DNA on Y chromosome?

  1. African lineages older
  2. N & S American lineages younger

Pleistocene change revealed by distribution of mitochondrial haplotypes

  1. Jack Pine glacial refugia revealed through analysis of mtDNA haploytpes