Discuss The Taxonomy Of Huaxi Crab Based On Multiple Morphological Characteristics

Sinopotamon Bott,1967 is an endemic freshwater crab genus of Potamidae in China mainland including 80 species(and 4 subspecies).It is known to be one of the highest diversity species of freshwater crabs and the most extensive inland freshwater crabs of the genus in China.The extant crabs in Sinopotamon were divided into four major species groups including acute lobes,rounded lobes,obtuse lobes,concaved lobes groups and two other species(Sinopotamon introdigitum and S.cochlearidigitum with distinct spoon-like terminal in the cheliped,we call it spoon cheliped group in this article)based on the morphological differences of the male first gonopod(G1)according to Dai in Fauna Sinica(Decapoda,Potamidae),especially its last segment.However,division into the four species groups and the spoon cheliped group and the relationship between them still lack of experiment and evidences to verify and support based on all sampling groups.In today's morphological taxonomy study,meta-analysis using all groups and multiple morphological classification characteristics,it can establishes a classification system closer to nature.We have extracted identify morphological traits within the genus and multiple classification morphological characteristics among species groups and species(a total of 25 quantitative traits and 33 qualitative traits).Sample 72 species of the Sinopotamon including the four species groups and the spoon cheliped group for the study(85%of total).We discussed the species groups and the systematic relationship in Sinopotamon,and the existing classification system was combed by multivariate statistical analysis and phylogenetic analysis.The taxa and their morphological characters used in this paper comes from 232 populations of the various species distribution,including a total number of 1,121 specimens(806 males and 315 females),and the obtained morphological data totalling 65,018.The results showed that:1)On the species groups level,all species of spoon cheliped group(including one new species to be published)cluster into a separate branch(or gather together).The 8 rounded lobes group species of S.yaanense,S.chishuiense,S.pingshanense,S.fuxingense,S.kwanhsienense,S.davidi,S.emeiense and S.ebianense distributed in the Sichuan Basin and its surrounding mountains(abbreviate as Basin)cluster into one branch(or gather together),and are significantly different from the rest species of rounded lobes group and other species groups.So called they Basin rounded lobes group.All species of concaved lobes group cluster into a branch(or gather together).The species in rounded lobes group except Basin rounded lobes group species,all species of obtuse lobes and acute lobes groups all can not cluster into a separate branch.Among them,the rest species of rounded lobes group,the species of obtuse lobes and concaved lobes groups are dispersed in some branches of the acute lobes group(tight sandwiches-like or interspersed).The shape of terminal GI of S.linhuaense,S.siguqiaoense,S.yushanense and S.jichiense divided into rounded lobes group in former classification system are not blunt but more closely to the description of acute lobes group.This study supports these 4 species classified into acute lobes group.2)Summary the meta-analysis results of multiple morphological characteristics,this paper proposed the establishment of a new species group in Sinopotamon,and named it Basin rounded lobes group.And described its identify morphological characteristics and geographical distribution etc.in detail.Although the rest species of rounded lobes group in the shape of terminal in the male first gonopod(Gl)is different from Basin rounded lobes group,we recommended that these species remains in rounded lobes group because their shape also belong to blunt type.Until now,there are 6 species groups in Sinopotamon.The 6 species groups are spoon cheliped group,Basin rounded lobes group,obtuse lobes group and the obtuse lobes group,rounded lobes group(except the species of Basin rounded lobes group),acute lobes group.But results of analysis in this study does not support the division for the three groups in the back.As to whether they will be merged or subdivided,remains to be integrated more morphological and molecular data.3)On the species level,S.davidi in Basin rounded lobes group,S.acutum,S.yangtsekiense,S.shensiense and S.honanense in acute lobes group are typical non-monophyletic species in Sinopotamon.Meta-analysis based on multiple morphological characteristics provide new evidences for the taxonomy and species delimitation in Sinopotamon.