Transcript Unit3Day9
Geography of Speciation • Allopatric – Peripatric • Parapatric • Sympatric Fig. 24-6 Sister species in allopatry A. harrisi A. leucurus Peripatric Speciation (like allopatric, but offers drift a bigger role) Divergent natural selection &/or Genetic Drift = Speciation Divergent natural selection &/or Genetic Drift = Speciation Sympatric and Parapatric Speciation • What do we mean by sympatry or parapatry? – In same geographic area (or side-by-side)? – Exchanging gene flow during the speciation process? – How finely should we divide the environment? – Habitat isolation in the same geographic area = real sympatry? Apple maggot fly Sympatric or Micro-allopatric? Pre-mating RIM = host fidelity Post-mating RIM = scent tracking in F1’s http://evolution.berkeley.edu/evosite/evo101/VC1eSympatric.sht ml Parapatric Speciation (sympatric, micro-allopatric?) Mine from mid-1800’s Contamination prevents most plant growth Strong, disruptive selection against interbreeding Different flowering times Anthoxanthum odoratum Mine soils (black): Flowering is earlier (flowers more developed in a point sample) Antonovics, Heredity (2006) 97, 33–37. doi:10.1038/sj.hdy.6800835 • Flowering stage along a transect from mine field (border = dashed line) • Common garden experiment included • Trend persists over 40 years • 40% less mating between forms • Parapatry, sympatry, or micro-allopatry? Mechanisms of Speciation • • • • Mutation Drift Ecological Speciation (Driven by natural selection) Sexual Selection Allopatric Speciation--Mutation http://evolution.berkeley.edu/evosite/history/modsynth2.shtml •Gene Duplication is common •LOF mutation is common •Fixation of alternate mutations can hybrid inviability