Table 1.

Studies that have compared the rate of evolution of different RI barriers

Taxon	Number of species pairs	Result	Phylogenetic correction	Reference
Darters Etheostoma	13	Sexual isolation accumulates faster than postzygotic RI. Hybrid inviability does not increase over time.	Species pair selected to be strictly phylogenetically independent	(Mendelson 2003)
Stickleback Gasterosteus	5	Sexual and ecological isolation accumulate faster than other barriers	No	(Lackey and Boughman 2017)
Streptanthus	39	Climatic niche differences are substantial early in speciation and evolve faster than differences in phenology and floral morphology.	Node‐weighted average phylogenetic correction, (Fitzpatrick 2002)	(Christie and Strauss 2018)
Nolana	15‐22	Prezygotic pollen–pistile isolation accumulates slower than all postzygotic barriers.	Node‐weighted average phylogenetic correction, (Fitzpatrick 2002)	(Jewell et al. 2012)
Drosophila	72	Prezygotic and postmating‐prezygotic RI accumulate faster than postzygotic barriers.	Random sampling of strictly phylogenetically independent species pairs and bootstrapping	(Turissini et al. 2018)
Glycine	18‐55	Postmating‐prezygotic and postzygotic RI accumulate at similar rates.	Random sampling of strictly phylogenetically independent species pairs and bootstrapping	(Moyle et al. 2004)
Silene	19‐49	Postmating‐prezygotic and postzygotic RI accumulate at similar rates.	Random sampling of strictly phylogenetically independent species pairs and bootstrapping	(Moyle et al. 2004)
Food‐deceptive orchids	110, 125	Premating and postmating‐prezygotic RI show no clear increase over divergence. Postzygotic RI evolves in a clock‐like manner.	Node‐weighted average phylogenetic correction, (Fitzpatrick 2002) and identification of strictly phylogenetically independent species pairs	(Scopece et al. 2007)
Sexually deceptive orchids	36	Strong premating RI but weak postmating RI	Node‐weighted average phylogenetic correction, (Fitzpatrick 2002) and identification of strictly phylogenetically independent species pairs	(Scopece et al. 2007)
Stalk‐eyed flies	12	Hybrid male sterility accumulates faster than premating RI, hybrid inviability, and female hybrid sterility	No	(Charistianson et al. 2005)