Mechanism Of Reproductive Isolation Between Closely Related Species Of Aquilegia (Ranunculaceae)

Speciation is a central theme in evolutionary biology and reproductive isolation is condition and result of speciation.The genus Aquilegia L.has been emerged as a model system for study of speciation and adaptive evolution.Pollinator and ecogeographic isolation are the main mechanisms of speciation differentiation and maintenance of this genus in North America and Europe respectively,but its main isolation mechanism lacks exploration in Asia yet.Phylogenetic evidences suggested that four Chinese endemic species of A.yabeana,A.rockii,A.kansuensis and A.ecalcarata represent a monophyletic clade.All four species of this clade were used as the research material to explore main mechanisms between species.Here were the main conclusions:1.Ecogeographic isolation is an important isolation mechanism among the four species,but contribution to reproductive isolation varies greatly.Main isolation mechanism of A.yabeana and A.rockii are ecogeographic isolation.However,A.ecalcarata and A.kansuensis have large habitat of overlap and incomplete niche differentiation in environmental factors,suggesting ecogeographic isolation is not main isolation mechanism of this related species.2.Multiple isolation mechanisms work together in sympatric populations of A.ecalcarata and A.kansuensis,interspecific gene flow of A.ecalcarata with A.kansuensis blocked by pollinators and post-pollination isolation mainly.Incomplete reproductive isolation of A.kansuensis with A.ecalcarata blocked by pollinator isolation.3.A.ecalcarata and A.kansuensis have different mating systems,both species have capacity of autonomous selfing,prior selfing of A.kansuensis and delayed selfing of A.ecalcarata.Autonomous selfing may play an important role in maintaining species integrity and reproductive isolation.