Biodiversity And Spatial Distribution Of Freshwater Gastropods In Guangxi

Freshwater gastropods represent a substantial component of the benthic invertebrate community,playing a critical role in the regulation of material cycles and energy flow processes within freshwater ecosystems.The Guangxi Zhuang Autonomous Region(hereinafter referred to as Guangxi),situated in southwestern China,harbors abundant freshwater and biological resources.In the current study,we conducted a systematic investigation of the species diversity and spatial distribution patterns of freshwater gastropods in Guangxi based on field surveys carried out in 10 river systems in the region.The field observations were combined with historical document researches and morphological and molecular biological analysis.The main findings are as follows:1.Among the collected gastropods,a total of 44 species(including 12 undetermined species)belonging to 21 genera and 12 families were identified.The majority(38 species)belonged to the Mesogastropoda order of the Prosobranchia subclass,distributed across nine families,with Semisulcospiridae accounting for the highest proportion(14 species)followed by Viviparidae(eight species).In contrast,the Basommatophora order of the Pulmonata subclass was represented by only six species from three families.2.The composition of gastropods varied significantly across the different sub-basin regions.The highest species diversity was found in the Lijiang and Guijiang rivers(27 species),followed by the Hongshui River(24 species),Liujiang River(22 species),Youjiang River(20 species),Zuojiang River(17 species),Beibu Gulf river system(12 species),and Xiangjiang(Guangxi section),Hejiang,Yongjiang-Yujiang,and Qianjiang-Xunjiang river systems(not more than10species).3.Based on species occurrence frequency and the percentage of individual number in the total number of individuals,as well as field investigations and sampling,the dominant species in the study area were Sinotaia purificata,Pomacea canaliculata,Sulcospira tonkiniana,and Oncomelania hupensis.4.Among the different river systems,the Hongshui River system exhibited the highest average taxonomic distinctness index for freshwater gastropods,indicating the most distant affinities among species.The Xiangjiang River system(Guangxi section)demonstrated the highest variation in the taxonomic distinctness index,reflecting a lower degree of uniformity in the classification relationships among gastropods.The gastropods were mainly distributed in rivers located in the northern and northwestern regions of Guangxi,with a lower number of species observed in the main streams than in the tributaries.The gastropods displayed a preference for habitats containing silt and pebbles,with higher richness and abundance observed when the habitats contained a diverse range of substrate species and macrophytes.5.Different families exhibited different distribution ranges across the study region.For example,Thiaridae species were mainly distributed in the southern subtropical region of Guangxi,while Semisulcospiridae species were mainly distributed in northern and northwest of Guangxi.However,Sulcospira tonkiniana(Pachychilidae),along with the species of Viviparidae and Physidae were widely distributed across Guangxi.