Accelerated speciation in colour-polymorphic birds

There’s an interesting new study in tomorrow’s issue of nature. Andrew F. Hugall and Devi Stuart-Fox use molecular phylogenies to look at speciation rates of birds. I cite from the abstract:

… we confirm, using species-level molecular phylogenies for five families of non-passerine birds, that colour polymorphism is associated with accelerated speciation rates in the three groups in which polymorphism is most prevalent. In all five groups, colour polymorphism is lost at a significantly greater rate than it is gained. Thus, the general rarity and phylogenetic dispersion of colour polymorphism is accounted for by a combination of higher speciation rate and higher transition rate from polymorphism to monomorphism, consistent with theoretical models where speciation is driven by fixation of one or more morphs. […] Our results provide empirical support for the general proposition, dating from classical evolutionary theory, that colour polymorphism can increase speciation rates.

Figure: Speciation rate (λ1/λ0) ratio from Bayesian Diversitree analyses. Copyright: Nature.

Cool stuff! I specially liked that the authors were trying to link their findings closely to existing theoretical concepts and results – a paper worthwhile reading.

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