Uncertainties and risks in delimiting species of Cambeva (Siluriformes: Trichomycteridae) with single-locus methods and geographically restricted data

Abstract Cambeva contains species with complex taxonomy or poorly delimitated in terms of morphology and geopraphic distribution. We conducted an extensive review of Cambeva populations from coastal drainages of Southern to Southeastern Brazil to evaluate species geographic limits with an integrative analysis including morphological and molecular data (COI). We test if two single-locus methods, Bayesian Poisson Tree Processes (bPTP) and Generalized Mixed Yule Coalescent (GMYC), are efficient to delimit species boundaries in Cambeva by the comparison with the diagnosable morphological units. Using GMYC, we also evaluated the combination of tree and molecular clock priors to reconstruct the input phylogeny and assessed how well the implemented model fitted our empirical data. Eleven species were identified using a morphological diagnosability criterion: Cambeva balios, C. barbosae, C. botuvera, C. cubataonis, C. davisi, C. guaraquessaba, C. iheringi, C. tupinamba, and C. zonata and two treated as undescribed species. In contrast with previous knowledge, many of them have wider distribution and high intraspecific variation. Species delimitation based on single-locus demonstrated incongruences between the methods and strongly differed from the morphological delimitation. These disagreements and the violation of the GMYC model suggest that a single-locus data is insufficient to delimit Cambeva species and the failure may be attributable to events of mitochondrial introgression and incomplete lineage sorting.

摘要：Cambeva（坎贝瓦鱼属）类群包含分类学关系复杂，或在形态与地理分布层面界定模糊的物种。我们针对巴西南部至东南部沿海水系的Cambeva种群开展了系统性综述，结合形态学数据与细胞色素C氧化酶亚基I（Cytochrome C Oxidase Subunit I, COI）分子数据开展整合分析，以明确该属物种的地理分布边界。我们通过与可鉴别形态单元的对比，检验两种单基因座（single-locus）物种界定方法——贝叶斯泊松树过程模型（Bayesian Poisson Tree Processes, bPTP）与广义混合尤尔-合并模型（Generalized Mixed Yule Coalescent, GMYC）——在Cambeva属物种边界界定中的有效性。借助GMYC模型，我们还评估了系统发育树结构与分子钟先验的组合方案以重建输入系统发育树，并检验所采用的模型对实测数据的适配程度。基于形态可鉴别性标准，我们共鉴定出11个物种：Cambeva balios、C. barbosae、C. botuvera、C. cubataonis、C. davisi、C. guaraquessaba、C. iheringi、C. tupinamba、C. zonata，以及2个待描述新物种。与此前的学术认知不同，该属多数物种拥有更广泛的分布范围与较高的种内变异水平。基于单基因座的物种界定结果显示，两种方法间存在不一致性，且与形态学界定结果存在显著差异。这些分歧以及GMYC模型的适配性不佳均表明，单基因座数据不足以完成Cambeva属的物种界定，其界定失败可能与线粒体基因渐渗以及不完全谱系分选事件相关。