内唇在蜉金龟亚科中用于分属和分族的分类学价值

The taxonomic value of the epipharynx in the Aphodiinae

【目的】蜉金龟亚科(鞘翅目:金龟科)成虫外部形态高度趋同,种间相似性大,属族等高级阶元的鉴别特征混乱,因此构建新的形态指标系统极为重要。近年来内唇形态广泛应用于蜉金龟的分类学研究,并能有效区分部分种类,然而内唇在高级阶元的分类学价值和应用范围仍未可知。【方法】本文选取276属818种金龟为研究对象,其中包括蜉金龟亚科7族259属799种,以及外群样本17属19种(蜣螂亚科13属14种,沙金龟亚科4属5种),利用几何形态学手段量化蜉金龟内唇的形态学信息,评估了属级和族级的区分度,并联合支序系统学方法,重建了蜉金龟祖先内唇形态。【结果】根据主成分分析显示,属级阶元的形态总方差为0.03213127,族级为0.03291463,内唇在属族间变异程度接近(两者相差约3%),揭示了内唇形态在高级阶元间基本保持稳定,适合用于分类鉴定。为了进一步探索内唇在高级阶元的分类归属是否也接近,随之对样本进行判别函数分析。结果显示,仅基于内唇形态,98.49%的属可被正确鉴定,族级有98.41%的正确率,表明内唇在属级阶元间的判别归类略胜于族级阶元,内唇适合应用于高级阶元的判别归类。结合系统发育树,重建的内唇祖先形态显示其多变区域包括上内唇根基部、侧缘,内唇前区和内唇外缘等6个特征,不仅验证了前人对内唇的部分特征应用,也发现了新的形态指标。【结论】本研究利用定量形态学方法证实了内唇适用于蜉金龟高级阶元分类,同时为外部形态趋同类群提供了新的特征筛选与评估范式。

[Objectives]To construct a new morphological index system for the Aphodiinae(Coleoptera:Scarabaeidae),the adults of which are very similar in external morphology complicate accurate classification into genera and tribes.Previous studies have shown that the morphology of the epipharynx can effectively distinguish some species,but it was not known whether the same criteria could be used to identify higher taxa.[Methods]818 species belonging to 276 genera were used as research samples,including 799 species,259 genera and 7 tribes of the Aphodiinae,and 19 species and 17 genera as outgroup samples(13 genera and 14 species of the Scarabaeinae,4 genera and 5 species of the Aegialiinae).Morphological information on the epipharynx was quantified by means of geometric morphometrics.The ability of this information to classify species to the generic and tribal levels was then evaluated,and the morphology of the ancestors of the Aphodiinae was reconstructed using cladistic methods based on epipharyngeal morphology.[Results]Based on Principal Component Analysis,the total morphological variation at the genus and at tribal levels was estimated to be 0.03213127 and 0.03291463,respectively.The degree of epipharyngeal variation among genera and tribes was small(about 3%),which reveals that epipharyngeal morphology has remained basically stable in the higher-level taxa.In order to determine whether the epipharynx is more similar among higher taxa,we also performed a discriminant function analysis.The results showed that 98.49%of genera and 98.41%of tribes can be correctly identified on the basis of epipharyngeal differences,which suggests that,although epipharyngeal differences are slightly better at discriminating genera than tribes,they are generally suitable for the discrimination and classification of the higher taxa of the Aphodiinae.Combined with a phylogenetic tree,the reconstructed ancestral shape of the epipharynx suggests that it has six variable morphological features,including the base,the lateral margin of the epitorma,the corypha and the shape of the epipharyngeal marginal.[Conclusion]The results validate the previous use of some epipharyngeal features to resolve the taxonomy of the Aphodiinae,and also has identified some new morphological indexes.The epipharyngeal features are suitable for the classification of Aphodiinae into genera and tribes using quantitative morphology,and this approach has provided a new paradigm for resolving the taxonomy of groups with a high degree of external morphological convergence.