speciation

Schluter D & Conte GL 2009 Genetics and ecological speciation. PNAS 106:9955-9962.

• ecological speciation
• the evolution of reproductive isolation between populations, or subsets of a single population, as a result of ecologically-based divergent natural selection
• natural selection acts in contrasting directions between environments, which drives the fixation of different alleles each advantageous in one environment but not in the other

• mutation-order speciation
• populations diverge as they accumulate a different series of mutations under similar selection pressures

• selection favors divergence only under ecological speciation
• divergence occurs by chance under the mutation-order process