Table 1

Modes of speciation.

stages in the speciation processinitiation of intrinsic reproductive isolation
strengthening and increased genomic extent of isolation
completion of reproductive isolation

for each stage:possible modesnotes
what is the spatial context?sympatry (m≈0.5)a continuum. Position on the continuum
parapatry (0<m<0.5)allopatry (m≈0)commonly varies through the speciation process
what is the driving force for divergence?chance (mutation, hybridization, drift)non-exclusive and interacting categories
natural selection (ecology)
sexual selection or sexual conflict
what is the genetic basis of isolation?genetic or non-genetic (learning or plasticity)intrinsic incompatibility versus maladaptationone-gene, one-allele and two-allele mechanismswith or without restricted recombinationnon-exclusive and interacting categories. May apply simultaneously to different barriers (habitat choice, assortative mating, postzygotic). See Kirkpatrick & Ravigné (2002) and Gavrilets (2004) for further discussion