中国科学院海洋研究所机构知识库

满月蛤目 Lucinida 是双壳纲在化能生态系统中多样性最高的类群。由于其中大多物种具有特殊的化能生活方式、广泛分布在不同地理区域和生态环境，在深海和浅海栖息地都具有较高的多样性，满月蛤目成为化能共生、种群遗传以及深浅海适应和演化等研究的良好材料，具有极高的研究价值。但中国海满月蛤目的现有研究十分不足，缺乏系统的、与国际最新研究接轨的分类学研究，导致很多物种仍在使用无效种名、存在错误鉴定，物种的分类特征和物种间亲缘关系较为模糊，据估计还有很多种类尚未被发现和报道。国内基础研究的缺乏限制了对该类群进一步的研究和利用，因此对中国海满月蛤目系统性的分类学研究十分有必要。

本研究通过广泛调查标本及文献记录，整理出最新的中国海满月蛤目物种名录，共包含39种，其中满月蛤科 Lucinidae 6亚科22属35种，索足蛤科 Thyasiridae 2属4种；修改了我国以往沿用的分类系统，修改异名10种；为中国满月蛤目物种名录新增15种，其中一个是在南海深海冷泉喷口处发现的新种：椭满月蛤 Elliptiolucina subovalis。对其中大部分类群进行了详细的形态描述和讨论，同时记录了相关的生境、分布等信息，提供了各阶元对应的分类检索表。通过对大量样品的观察，认为南海皱满月蛤 Rugalucina vietnamica 种内形态变异较大，我国原本记录在海南的豌豆毛满月蛤 Pillucina neglecta 为错误鉴定。

通过最大似然法和贝叶斯法对159个物种三个基因（18S rRNA、28S rRNA和Cytb）串联的数据进行系统演化分析，结果显示满月蛤目分为满月蛤科和索足蛤科，满月蛤科又分为七个单系分支，对应着七个亚科；其中各科和亚科之间的演化关系较为明确，但许多属仍存在分子结果与形态相似性不一致的问题。针对其中椭满月蛤属 Elliptiolucina 的多系问题进行了研究讨论，结合形态及分子证据提出椭满月蛤和 E. williamsae 与该属模式物种 E. magnifica 更相近，而巨椭满月蛤 E. ingens 可能非该属物种。通过系统演化分析，结合物种的分布深度，发现满月蛤科起源于浅海，其中多个谱系分别入侵至深海并演化形成了较高的多样性，随后这些深海分支中有部分物种又重新回到浅海，从而形成了满月蛤复杂的深浅海演化关系。

在厘清分类系统的基础上，本研究对两种南海广布满月蛤物种，斯氏印澳蛤 Indoaustriella scarlatoi 六个群体119个个体和南海皱满月蛤 Rugalucina vietnamica 四个群体92个个体，利用COI基因作为分子遗传标记进行了比较谱系地理学研究。遗传多样性参数计算结果显示两物种在南海均表现出高单倍型多样性（I. scarlatoi, h = 0.881; R. vietnamica, h = 0.674）和低核苷酸多样性（I. scarlatoi, π = 0.00277; R. vietnamica, π = 0.00217），这表明它们在近期发生了瓶颈效应后的快速种群扩张，很可能与最近的冰期间冰期海平面变化有关，中性检验和错配分布曲线的结果也基本支持这一推论。分化系数和单倍型网络图显示斯氏印澳蛤在南海的大多种群之间存在大且显著的遗传分化（F_ST > 0.25, p < 0.05），尤其以北部湾各种群和南海其他种群之间基因交流障碍最明显，完全没有共享单倍型，这再一次印证了琼州海峡作为海洋生物群体遗传断点的论断。推测影响琼州海峡两侧基因交流的原因可能是冰期海平面下降导致的地理隔离和多种海流因素导致的基因交流受限，如穿越琼州海峡的海流常年自东向西流动且在东部湾口处存在许多影响幼虫扩散的涡旋、穿越琼州海峡的海流难以到达北部湾湾顶等。阳江海陵岛种群与其他种群之间也存在显著的分化（F_ST = 0.4375-0.5798, p < 0.05）。南海皱满月蛤群体随地理距离变化表现出较小（或无）到中等的遗传分化（F_ST = -0.0314-0.2645），与斯氏印澳蛤相比，单倍型网络图、分化系数和遗传距离等分析均显示琼州海峡并未对其造成显著的基因交流障碍，这可能是由于该物种除大量生活在红树林附近栖息地外，还可以分布在较浅的潮下带中的海草床及其他软泥底质中。相比于斯氏印澳蛤受红树林影响的斑块分布，南海皱满月蛤在南海的分布更连续，因此受上述基因交流障碍的影响较小。

本研究通过系统分类学厘清并修订了中国海满月蛤目的物种名录和分类系统，梳理了中国海已报道的满月蛤目种类，澄清了以往报道中混淆种、疑难种、误鉴定种的分类地位，为以后的准确鉴定提供了信息；通过两种南海广布满月蛤的种群遗传学研究确定了琼州海峡对海洋生物基因交流的阻碍作用以及两物种对相同地理和水文障碍产生不同群体遗传结构的原因。本文为我国满月蛤目的研究打下基础，有助于改善我国对满月蛤目分类和系统演化关系的认知，而且对理解海洋生物的分化与演化、海洋生物多样性形成亦有重要价值。

Lucinida is the most diverse bivalves reported from chemoautotrophic habitats. Because of their unique chemosynthetic lifestyle of most species, wide distribution in different geographic regions and ecological environments, high diversity in both deep-sea and shallow-water habitats, Lucinida is an excellent model for research on chemosymbiosis, population genetics, and the evolutionary pattern between onshore and offshore species. But research on Lucinida in China is lacking, and there is a lack of systematic research in line with the latest international research. This has led to many misidentifications in domestic research reports. Many characteristics of identification and relationships within Lucinida are still unclear in China, and it is estimated that many species remain undiscovered in China Seas. The lack of basic research of Lucinida in China limits further study and utilization of this group, which makes systematic taxonomic research on the Lucinida in China Seas essential.

This study compiled a checklist of Lucinida in China through extensive investigation of specimens and literature records. A total of 39 species were identified, including 6 subfamilies, 22 genera, and 35 species in Lucinidae, as well as 4 species in 2 genera in Thyasiridae. This study revised the classification system previously used in our country, modified synonyms of 10 species, and added 15 species to the checklist. Among the new added species, a new species, Elliptiolucina subovalis, was found in 2018 from a deep-sea cold seep in the South China Sea. The morphology, habitat, distribution, and other information of most taxa were described and discussed in detail, and taxonomic keys were provided for each level of classification. Based on observation of a large number of samples, it was concluded that there is significant morphological variation within Rugalucina vietnamica. Pillucina neglecta, previously reported to occur in Hainan, was determined to be a misidentification of R. vietnamica.

The concatenated data of three genes (18S rRNA, 28S rRNA, and Cytb) of 159 species were used to elucidate the phylogenetic relationships of Lucinida by Maximum Likelihood and Bayesian inference. The results showed that Lucinida is divided into Lucinidae and Thyasiridae. Lucinidae is further divided into seven monophyletic branches, corresponding to seven subfamilies. The relationships among families and subfamilies of Lucinida were relatively clear, however, molecular relationships and morphological similarities sometimes contradict in some genera. The present study focused on the polyphyletic problem within the genus Elliptiolucina, and based on morphological and molecular evidence, it suggested that E. subovalis and E. williamsae were more closely related to the type species of the genus, E. magnifica, while E. ingens may not belong to this genus. By combining the species distribution depth and phylogenetic results, it is found that Lucinidae was originated in the shallow sea, but multiple lineages invaded the deep-sea habitats and diverse here, some species of deep-sea clades returned to the shallow sea. Showed a complex evolutionary pattern between onshore and offshore species.

On the basis of clear taxonomic system, a comparative phylogeographic analysis was conducted on two widely distributed lucinids in the South China Sea, 119 individuals of six populations of Indoaustriella scarlatoi and 92 individuals of four populations of Rugalucina vietnamica, by a molecular genetic marker of COI. We found that both species exhibited high haplotype diversity (I. scarlatoi, h = 0.881; R. vietnamica, h = 0.674) and low nucleotide diversity (I. scarlatoi, π = 0.00277; R. vietnamica, π = 0.00217) in the South China Sea by genetic diversity parameters, indicating rapid population expansion following a recent bottleneck effect that was likely related to changes in sea level during the recent glacial periods. Results of neutrality tests and mismatch distributions were also supporting the above inference. Significant genetic differentiations were observed among most populations of I. scarlatoi in the South China Sea, particularly between the Beibu Gulf populations and other populations in the South China Sea (F_ST > 0.25, p < 0.05), which confirmed the hypothesis that the Qiongzhou Strait serves as a genetic breakpoint for marine species once again. The main reasons for the divergence of species on both sides of the strait may be complete geographical isolation caused by the decrease in sea level during the glacial periods and restricted gene flow due to the various ocean currents factors here: 1) year-round east-to-west currents passing through the strait, 2) many vorticity affecting larval diffusion at the eastern entrance of this strait, 3) it is difficult for the current through the Qiongzhou Strait to reach the top of the Beibu Gulf. Significant weakening of gene flow was also observed between the Yangjiang population and other populations of the South China Sea (F_ST = 0.4375-0.5798, p < 0.05). The genetic differentiations among different populations of R. vietnamica were small compared with I. scarlatoi (F_ST = -0.0314-0.2645). Genetic isolation caused by the Qiongzhou Strait had a relatively minor impact on R. vietnamica, as evidenced by haplotype networks, genetic differentiation coefficients, and genetic distances. This may be due to the fact that this species is capable of surviving in seagrass beds and soft sediments of shallow seas, although it is more commonly found near mangroves. Compared with the patch distribution of I. scarlatoi affected by mangroves, the distribution of R. vietnamica in the South China Sea is more continuous, which may result in less impact from the above barriers of gene flow.

This study clarified and revised the species checklist and taxonomic system of Lucinida in the China Seas by systematic research. We summarized the species of Lucinida in China, clarified the classification status of previously confused, complex, and misidentified species, and provided necessary information for accurate identification. The population genetic study of two widely-distributed lucinids in the South China Sea revealed the obstructive effect of semi-closed straits, islands, ports on gene flow in marine organisms, and the reasons for the different responses of two species to the same geographical and hydrological obstacles. This study lays the foundation for research on Lucinida in China, which contributes to improving our understanding of the classification and evolution of Chinese lucinids and thyasirids. Moreover, it has significant value for understanding the differentiation and evolution of marine organisms and the formation of marine biodiversity.

第1章 绪论 1

1.1 满月蛤目简介 1

1.1.1 生活习性 2

1.1.2 形态及解剖学特征 2

1.2 满月蛤目研究概述 6

1.3 中国海满月蛤目及相关种群遗传研究现状 9

1.3.1 中国海满月蛤目的系统分类研究 9

1.3.2 南海广布满月蛤的比较谱系地理研究 10

1.4 研究目的及意义 13

第2章 中国海满月蛤目分类及满月蛤目系统发育研究 15

2.1 中国海满月蛤目名录及形态分类研究 15

2.1.1 材料与方法 15

2.1.2 研究结果 15

2.2 满月蛤目的系统演化研究 88

2.2.1 材料与方法 88

2.2.2 研究结果 90

2.3 讨论 96

2.3.1 中国海满月蛤目的分类研究 96

2.3.2 满月蛤目的系统发育研究 100

第3章 南海广布满月蛤的种群遗传研究 103

3.1 材料与方法 103

3.1.1 样品采集 103

3.1.2 DNA提取、扩增与测序 104

3.1.3 数据处理与分析 104

3.2 研究结果 105

3.3 讨论 111

3.3.1 遗传多样性及种群历史动态 111

3.3.2 南海群体间的分化和隔离 112

第4章 研究结论与展望 115

参考文献 117

附录一 中国海满月蛤目物种名录 131

附录二 满月蛤目系统演化研究所用序列信息 133

致谢 141

作者简历及攻读学位期间发表的学术论文与其他相关学术成果 143