A Study On Crabs Diversity And Genetic Diversity In Beibu Gulf Mangrove

A field study had been conducted to identify the brachyuran crabs in the12sampling stations in mangroves of Beibu gulf during July to October2012. A total of39species of brachyuran crabs belonging to11families,23genera were reported. Among them, Perisesarma eumolpe was a new record in China, and P. maipoense was a new record in Hainan province; Ocypodoidea (including8genera and20species) accounted for51.3%, and Grapsoidea (10genera and14species) accounted for35.9%of all species; There were two species in Portunidae and Pilumnidae respectively, and there was one species in Leucosiidae. Among the12sampling stations, the diversity index of crabs (H’) ranges between1.861-3.315, Pielou index (J) ranged between0.587-0.829, Margalef index (D’) ranges between0.892-1.972. The similarity index ranged between0.087～0.632, the maximal value(0.632) appeared in both Daguansha and Leizhou Haijiao village, which was medium similar; the lowest similarity value (0.087) was in both Hainan Qinglan Barbor and Beihai Caotou villege, which was extremely dissimilarity. The results showed that Ocypodoidea and Grapsoidea were two of the largest groups, and the Beibu gulf coastal mangrove crabs belonged to the South China Sea crab fauna. It was mainly composed of tropical and subtropical warm water species and wide temperature species.This paper dealed with the sequence analysis based on mitochondrial16s rRNA genes Grapsoidea (14species of10genera) and Ocypodoidea (20species of8genera) in Beibu gulf mangrove. And phylogenetic tree was constructed by using method of NJ, MP and BI. The results showed that the monophyly of Sesarminae, Varuninae, Grapsinae which including in Superfamily Grapsoidea were divided into three clades. The MP tree and BI tree of Superfamily Ocypodoidea’s topology graph showed that the morphological classification Ocypodoidae was clustered into a clade, and together with Macrophalmidae aggregated into a big clade. The monophyly of Camptandiidae and Dotillidae were respectively together into a clade, while the Mictyridae separated to form a clade far from them. The results of the molecular phylogenetic tree basicly supported the morphological taxonomic classification results.Morphologically metrical characters of9Perisesarma bidens populations which was widely distributed in the mangrove were collected from mangrove of China.23morphological characteristics were measured. And based on the proportional parameters of morphological characters, three multivariation analysis methods were conducted to investigate the morphological variations among nine populations.The results showed that the group of clustering analysis could not bring obvious grouping. Discriminant analysis demonstrated that there were no significant (the total discriminant accuracy was40.8%) among the nine populations. Principal component analysis results showed that trevealed that nine populations were almost overlapped to each other in scatter diagram of the first and the second principal components, indicating only small morphological variations among these populations. The coefficients of difference (CD) of proportional parameters of morphometric characters among the nine populations were always lower than1.28. And the shape of the difference between groups did not reach the subspecies level.Mitochondrial COI gene sequences were analysised among10geographic population Perisesarma bidens with number of186. The results showed that there were31haploid type, which presented a high level of haploid type diversity and low levels of nucleotide diversity characteristics. Network diagram showed "star-like" structure. And the molecular variance (AMOVA) and Fst results indicated that individual difference was greater than the differences among groups within the group level. The genetic distance between groups was very closed. There was no geographical isolation mode. Unimodal curve of mismatch distributions and the observations in conformity with the simulation values which belonged to the poisson’s distribution model suggested a recent population expansion. The neutrality test also supported the result of mismatch distributions.