Comparison Of Gene Flow Among Species That Occur Within The Same Geographic Locations Versus Gene Flow Among Populations Within Species Reveals Introgression Among Several Elymus Species

Elymus(Elymus L.)affiliated with grass family(Poaceae)grain subfamily(Pooideae)of Triticeae,there are a lot of the genus morphology variation,frequent natural hybridization between species.Introgression through hybridization is a creative evolutionary process,which can produce and accumulate genetic novelties faster than through mutation alone and plays critical roles in driving speciation.Natural hybridization and polyploidization have long been recognized as important causes of plant diversification and speciation.Interspecific or intergeneric hybridization is widespread and evolutionarily important phenomena in plants,which play important roles in the formation of new species.When closely related species in the same geographic distribution,the hybridization phenomenon may occur,genes from one genus or species through hybridization and backcross or introgressive hybridization and other variety of ways to enter other gene bank,which makes the original varieties in morphological characteristics and biological characteristics,etc.One of the challenges in evolutionary biology is to understand the evolution of speciation with incomplete reproductive isolation as many taxa have continued gene flow both during and after speciation.Comparison of population structure between sympatric and allopatric populations can reveal specific introgression and determine if introgression occurs in a unidirectional or bidirectional manner.Simple sequence repeat markers were used to characterize sympatric and allopatric population structure of plant species,Elymus alaskanus(Scribn.and Merr.)L?ve,E.caninus L.,E.fibrosus(Schrenk)Tzvel.,and E.mutabilis(Drobov)Tzvelev.Our results showed that genetic diversity(HE)at species level is E.caninus(0.5355)> E.alaskanus(0.4511)>E.fibrosus(0.3924)> E.mutabilis(0.3764),suggesting that E.caninus and E.alaskanus are more variable than E.fibrosus and E.mutabilis.Gene flow between species that occurs within the same geographic locations versus gene flow between populations within species was compared to provide evidence of introgression.Our results indicated that gene flow between species that occur within the same geographic location is higher than that between populations within species,suggesting that gene flow resulting from introgressive hybridization might have occurred among the sympatric populations of these species,and may play an important role in partitioning of genetic diversity among and within populations.The migration rate from E.fibrosus to E.mutabilis is highest(0.2631)among the four species studied.Asymmetrical ratesof gene flow among four species were also observed.The findings highlight the complex evolution of these four Elymus species.