Distribution Of Ruppia Species Along China Coastline And The Influencing Factors

In this paper, we try to distinguish Ruppia species which distribute along China coastline using molecular markers and morphological characteristics and to infer the potential mechanism affecting the distribution pattern.We chose ITS, rbcL and trnLUAA-trnLUAA-trnFGAA as the main makers, other 4 sequences as supplements (rpS12-rpL20, rpS16, rpL16 and trnD-trnT). We sequenced 204 samples from 20 populations, and found 5 haplotypes. Both the phylogeny obtained by the combination of six sequences and Structure cluster got the same results. According to the molecular information, there are three Ruppia species in China:R. cirrhosa, R. maritima and R. megacarpa.The morphological characteristics were consistent with the molecular classification. R. megacarpa is separated from R. cirrhosa and R. maritima by the width of leaves and rhizome. There were significant difference in length of peduncle and podogyne between R. cirrhosa and R. maritima. Seed of R.maritima was significantly larger than that of R. cirrhosa. R. cirrhosa and R. maritima can be distinguished by morphology, ecophysiology and habitat type.R. cirrhosa distributed more widely than the other two species. It grew mainly in north of China, whereas R. maritima distributed in the south. Difference in heat-tolerance between R. cirrhosa and R. maritima might explain such a distinct distribution pattern. However, directions of sea currents may also contribute to such a pattern. In summer, offshore currents along Jiangsu-Zhejiang and Fujian-Zhejiang changed their directions to north-eastern, and may block dispersal of R. cirrhosa and R. maritima. R. megacarpa, which was previously found only in Australia, was found in two sites Qindao and Yanchen. The record of this species in China was due to long-distance dispersal via migration birds from Australia.