中国田螺科的系统学研究

The Viviparidae Gray, 1847, a group of large-sized and ovoviviparous freshwater gastropods, is nearly cosmopolitan, but absent from South America, reaching their highest diversity in China with 11 genera and 83 species recorded. The traditional taxonomy of viviparids is primarily based on characters of shell morphology, such as shell shape, size and sculpture. But shell morphology exhibits a large amount of plasticity caused by environment variations, which results in a chaotic state of taxonomy of viviparid snails, systematic position, boundary delimitation and validities of many taxa and its phylogeny are still equivocal in studies using shell characters only. This problem is most pronounced in China with the highest number of viviparid species. In this study, we plan to carry out a field survey for viviparid specimens firstly, then delimit boundaries for controversial genus or species, and explore its taxonomic revision using shell morphology, anatomy of soft-part, micro-morphology and molecular systematics with mitochondrial (COI and 16S) and nuclear (H3, 18S and 28S) DNA. The contents of this study are as following: 1) Plasticity of shell morphology and sorting character for taxonomy; 2) Comparative anatomy of soft-part and exploring character for taxonomy; 3) Identification for controversial genera and species based on DNA sequence; 4) Taxonomic and systematic revision of Viviparidae based on morphological and molecular data. We want to reevaluate taxonomical value of triditional morphological characters, sort and explore some new important taxonomical characters, and then make an overall revision for viviparid taxonomy based on comprehensive analysis of morphological and molecular data. The results can not only promote its systematic studies and applications in China, but also provide knowledgical supports for conservation of biodiversity and sustainable utilization of biological resources, control of parasites and invasive species, and biogeography of the Viviparidae.

田螺科是一类大型的卵胎生淡水腹足类软体动物，广泛分布在除南美洲之外的世界各地。中国是田螺科物种多样性最高的地区，已记录的种类达11属83种。传统上田螺科的分类主要依据壳形态特征，但由于壳形态的高度可塑性，导致该科分类十分混乱，一些类群的系统位置、属种的有效性和边界划分存在较大争议。本研究拟在广泛采集田螺科标本的基础上，采用形态学、比较解剖学、微形态学和分子生物学相结合的方法，厘定一些争议属种，开展田螺科的分类研究。内容包括：1）壳形态变异及分类特征筛选；2）软体部分比较解剖及分类特征发掘；3）争议属/种的分子生物学鉴定；4）中国田螺科的分类整理及系统修订。通过综合分析，重新评价形态特征的分类学价值，筛选和发掘出不同阶元的分类特征，对我国田螺科进行全面的分类修订。研究结果不仅能全面推进该科的系统学研究，而且为其资源利用与物种多样性保护、寄生虫与入侵种防治以及生物地理学研究等提供知识支撑。

田螺科软体动物是世界上最濒危的类群之一。但由于壳形态可塑性导致该科一些类群的系统位置、属种的有效性和边界划分仍存在较大争议。本研究对田螺科进行了全面的分类修订。研究结果如下：.1. 壳形态变异及分类特征筛选.发现形态度量特征不能用于物种阶元的分类，而几何形态特征则可以区分出不同的物种；然而，尽管单纯依靠壳形态特征的分类存在很多不足，但描述性特征（尤其是壳的形状和壳饰）在物种鉴定上往往具有关键作用。.2. 软体部分比较解剖及分类特征发掘.（1）软体部分的多数解剖特征比较保守，可用科级及以上阶元的分类，嗅检器的大小、输精管次级分支的数量和开口的位置、肾的形状、怀卵量等特征尽管能相互结合来区分物种，但难以筛选出不同阶元的共性特征；（2）齿舌、胚螺和厣特征难以有效区分所有物种，更适合用于属级及其以上阶元的分类。.3. 争议属/种的分子生物学鉴定.（1）我国传统的环棱螺属证实应是石田螺属；（2）发现狭义螺蛳属不是一个有效属，其物种应归入圆田螺属；（3）与传统形态分类相比，基于分子数据的环棱螺属和圆田螺属物种数明显较少，而河螺属和角螺属的物种数基本一致；（4）我国的田螺属和湄公螺属不是有效属，三带田螺、湄公螺与石田螺属物种聚为一支，而东北田螺与Amuropaludina聚为一支；（5）乌苏里圆田螺不属于圆田螺属，应归入Ussuripaludina。.4. 中国田螺科分类整理及系统修订. （1）我国田螺科有39个有效种，隶属12个属，包括1个新属（环田螺属 Anulapaludina gen. nov.）、2个新纪录属（Ussuripaludina和Amuropaludina）和5个新种（泸沽湖环田螺 Anulaplaudina luguensis sp. nov.、茈碧湖环田螺 Anulaplaudina cibiensis sp. nov.、橄榄河螺Rivularia oleivora sp. nov.、塱原角螺 Angulyagra longvalleynensis sp. nov.和纹角螺 Angulyagra striatulus sp. nov.）；（2）田螺科各类群的物种丰度与分布明显不同，环棱螺属（4种）在我国分布最为广泛，其次是圆田螺属（9种），但圆田螺属多数物种（6种）、河螺属（7种）、角螺属（8种）、玺螺蛳属（2种）、环螺蛳属（2种）和环田螺属（2种）