4种茴鱼属鱼类形态差异比较

Comparison of morphological differences among four species of the genus Thymallus

中文关键词: 黑龙江茴鱼  北极茴鱼  下游黑龙江茴鱼  鸭绿江茴鱼  形态差异

英文关键词: Thymallus grubii  Thymallus arcticus  Thymallus tugarinae  Thymallus yaluensis  Morphological differences

中文摘要:

      为查明中国现存茴鱼属(Thymallus)鱼类形态差异，以黑龙江茴鱼(T. grubii)、北极茴鱼(T. arcticus)、鸭绿江茴鱼(T. yaluensis)和下游黑龙江茴鱼(T. tugarinae)为研究对象，采用传统形态学方法和框架度量法结合的方式，对茴鱼属鱼类的10项分节特征和32项标准化可量性状进行了统计分析。结果显示：(1)鸭绿江茴鱼全部分节特征与黑龙江茴鱼均无显著性差异(P>0.05)，黑龙江茴鱼、北极茴鱼和下游黑龙江茴鱼两两之间均存在5项以上分节特征差异显著(P<0.05)。(2)差异系数分析显示，除尾柄长/体长外，鸭绿江茴鱼与黑龙江茴鱼之间形态特征差异均属种内地理种群间的差异水平。(3)主成分分析共筛选出8项特征值大于1的主成分，累积贡献率达81.170%，其中，贡献率最高的第一、二主成分分别主要解释了茴鱼属鱼类之间的躯干部和头部差异，构建第一、二主成分散点图发现，鸭绿江茴鱼与黑龙江茴鱼个体交叉程度较高且无法单独进行区分，下游黑龙江茴鱼与黑龙江茴鱼的个体交叉程度次之，可以部分被区分开，仅北极茴鱼可以被单独区分开。(3)判别分析共筛选出14项标准化可量性状用于建立Fisher线性判别函数，个体被正确判入各自群体的判别率高达97.30%。(4)聚类分析显示，与黑龙江茴鱼相比，鸭绿江茴鱼与其相似度最高，下游黑龙江茴鱼次之，北极茴鱼与黑龙江茴鱼相似程度最低。综合分析表明：(1)鸭绿江茴鱼不应被定为有效种，其学名应修订为黑龙江茴鱼。(2)黑龙江茴鱼、北极茴鱼和下游黑龙江茴鱼的形态差异主要体现于其分节特征以及躯干部和头部的可量性状上。本研究将为茴鱼属鱼类的物种分类和进化关系研究提供参考。

英文摘要:

      The genus Thymallus, belonging to the Salmoniformes, Salmonidae and Thymallinae, is distributed in three main areas in China, namely, the Irtysh River Basin, the Heilongjiang River Basin and the Yalu River Basin. Research has shown that the diversity of extant Thymallus in China is much higher than that in the vast European and North American regions, but the taxonomic results of some species are still controversial. Among them, those whose taxonomic status has been clarified and whose nomenclature is not controversial are T. arcticus, T. grubii and T. tugarinae, and the one that is still controversial is T. yaluensis. Named by Mori in 1928, T. yaluensis is mainly distributed in the Yalu River Basin and is geographically isolated from the T. arcticus, T. grubii and T. tugarinae. In 2007, a study on the comparison of countable traits of Thymallus found that the countable traits of the T. yaluensis were in the middle between the T. grubii and T. tugarinae, and the validity of the taxonomic status of T. yaluensis has been formally questioned ever since; in 2008, a study using mitochondrial DNA control region sequences to study the evolutionary relationships of fishes in the genus Thymallus pointed out that the T. yaluensis is synonymous with the T. grubii. In 2016, researchers used mitochondrial genome data to confirm once again that there was no difference between the T. yaluensis and the T. grubii. However, this conclusion does not seem to be accepted by the academic community, and in recent years, there are still some scholars who regard the T. yaluensis as an independent species. Morphological methods are the most commonly used methods in species identification, which can be categorized into traditional morphological method and framework measurement method. The traditional morphological method mainly analyzes the horizontal and vertical traits of the fish body, and it is mostly limited to the head and tail traits, which can't measure the whole surface of the fish body comprehensively. The framework measurement method, however, is based on a certain number of anatomical coordinate points and measures the entire fish body in multiple directions, which can provide a more comprehensive response to the morphological differences of the fish body. So far, the studies on the interspecific differences of Thymallus in China have mostly focused on the molecular biology level, while the morphological differences have been less studied, only in T. grubii and T. tugarinae. The rapid development of molecular marking technology provides an important auxiliary means for species classification, but the apparent morphological differences are still recognized as the most intuitive basis for species classification. In order to clarify the morphological differences of Thymallus in China, this study comprehensively used traditional morphological methods and framework measurement method, and took the T. grubii, T. arcticus, T. yaluensis and T. tugarinae as the research objects, Statistical analysis was conducted on their 10 segmentation characteristics and 32 standardized metric features. The results showed that: (1) there was no significant difference (P>0.05) between all the subsection characteristics of T. yaluensis and T. grubii, and there were significant differences (P<0.05) in more than five segmentation characteristics between T. grubii, T. arcticus and T. tugarinae. (2) The coefficient of variation analysis showed that except for caudal peduncle length/body length, the differences in morphological characters between T. yaluensis and T. grubii were at the level of differences between geographic populations within species. (3) The principal component analysis screened out eight principal components with eigenvalues greater than 1, and the cumulative contribution rate reached 81.170%, among which the first and second principal components with the highest contribution rate mainly explained the differences in trunk and head between Thymallus, respectively. The construction of scatter plots of the first and second principal components revealed that the individual crossover between T. yaluensis and T. grubii had a high degree and could not be distinguished individually, while T. tugarinae and T. grubii show a lower level of overlap and partial distinction. Only T. arcticus can be distinctly separated. (3) Discriminative analysis was used to screen out 14 standardized measurement features to establish the Fisher linear discriminant function, and the discriminative rate of individuals being correctly assigned to their respective groups was as high as 97.30%. (4) Cluster analysis showed that compared with T. grubii, T. yaluensis had the highest degree of similarity with it, followed by T. tugarinae, and T. arcticus had the lowest degree of similarity with T. grubii. The comprehensive analysis showed that: (1) T. yaluensis should not be designated as a valid species and its scientific name should be revised to T. grubii. (2) Morphological differences among T. grubii, T. arcticus and T. tugarinae are mainly reflected in their segmentation characteristics and the measurement characteristics of trunk and head. The results of this study will provide a reference for the study of species classification and evolutionary relationships of the genus Thymallus.