Studies On Phylogeography Of Croomia:Evidence From AGT1Gene And Nuclear Microsatellites

The genus Croomia with4-merous tepals flowers belongs to the monocotyledonous family Stemonaceae Engl.. Croomia species are perennial herbages. It comprises of three species. C. japonica distribute in Southeast China and Japan.C. heterosepala endemic to Japan.C. pauciflora distribute in America.The disjunction of Croomia show the eastern Asian-eastern North American floristic disjunct disjunction. A phylogeographic study of Croomia was conducted to address the genetic diversity and population genetic structure of the species. Further, the historical demograph and evolutionary dynamics of Croomia were inferred.We applied nuclear microsatellites (nSSR) and one single-copy nuclear gene (Agtl) to study populations from throughout the species" range to infer current patterns of genetic diversity and affinities of the species in Croomia. Several putative Pleistocene refugia were inferred. The evolution history and strategies for conservation of Croomia were also studied. The main results of our study are as follows:1. SSR primer development and analysisWe first isolated and characterized seven polymorphic microsatellite loci from C. japonica based on a dual-suppression-PCR method.All of these primers were highly polymorphism, specificity, and amplification of stable, highly repetitive. These primers were confirmed could be used in all the three species of Croomia for genetic diversity, population genetic structure and others.2. Single-copy nuclear gene (Agtl gene) sequence analysisAbundant Agtl haplotypes were found in Croomia. There were22haplotyoes detected in18Croomia populations, and14,6and2haplotypes were found in C japonica, C. heterosepala and C. pauciflora. in respectively. The relationships and distribution of Agtl gene haplotypes suggested that Croomia had been widely distributed in ancient eastern Asian and northern American; the origin and distribution center of Croomia were concentrated on the Tianmu mountain. Several putative Pleistocene refugia were inferred. The refugia of Croomia in China concentrated on Tianmu mountain. At least one refuaium was inferred in Florida Peninsula in America.The two Asian species of Croomia were more closely related to each other than either is to Northern American species. C. japonica was presumed as the progenitor species, and C. pauciflora and C. heterosepala were presumed as the derivative species. As significant differentiation among populations, the populations of C.japonica in Japan were closer to C. pauciflora and C. heterosepala than those in China. Isolation with the island environment made Croomia populations more differentiations, and finally in the Japanese islands differentiation into two species.3. Strategies for conservation of CroomiaTianmu Mountain population had the most abundant genetic diversity, and maybe it was the evolution center of Croomia species, so this population must be focus on the protection of the highest priority. Each groups East Asia of Croomia should try to protect:If the conditions do not permit the collection must ex-situ conservation to try to collect little samples from all groups rather than some groups collected a large number of individuals.