Data from: Genetic and morphometric evidence for the recognition of several recently synonymized species of trans-Andean Rhamdia (Pisces: Siluriformes: Heptapteridae)

A recent taxonomic revision of the Neotropical catfish genus Rhamdia (Pisces: Siluriformes: Heptapteridae) reduced a number of described species to synonymy, especially under a broadly circumscribed R. quelen. Evidence is presented here from DNA sequence data, external morphology, and morphometrics that argues for the recognition of R. guatemalensis in Central and northern South America and R. saijaensis and R. cinerascens in the Pacific drainages of Colombia and Ecuador, respectively. The DNA data indicate that all trans-Andean samples form a monophyletic group, within which there are separate clades corresponding to R. laticauda and the synonymized R. guatemalensis, R. saijaensis, and R. cinerascens. The morphometric data substantiate the phylogenetic groupings, and in external morphology, each putative species has diagnostic characters. Rhamdia guatemalensis is characterized by insertion of the adipose fin closer to the dorsal fin than to the caudal fin and presence of a conspicuous lateral longitudinal dark band; R. saijaensis is characterized by a small head with head length 20.8–23.4% of standard length and by lacking a lateral longitudinal band; and R. cinerascens is characterized by a large head with head length 25.8–30.1% of standard length, base of the adipose fin 30.3–33.3% of standard length, outer mental barbels extending to the base of the pectoral rays, and presence of a faint lateral longitudinal band. The external morphological differences and phylogenetic relationships indicate that these groups are both recognizable and represent independent lineages, which argue for their recognition as species.

近期针对新热带区鱼纲（Pisces）鲶形目（Siluriformes）七鳍鲶科（Heptapteridae）拉姆达鲶属（Rhamdia）的分类学修订，曾将多个已描述物种归为同物异名，其中尤以宽泛界定的奎拉姆达鲶（R. quelen）所涵盖的物种数量为多。本文基于DNA序列数据、外部形态学与形态测量学证据，支持中美洲及南美洲北部的危地马拉拉姆达鲶（R. guatemalensis），以及分别分布于哥伦比亚、厄瓜多尔太平洋水系的萨哈拉姆达鲶（R. saijaensis）与灰拉姆达鲶（R. cinerascens）为独立有效物种。DNA序列分析结果显示，所有跨安第斯样本构成一单系群，该群内包含多个对应不同类群的演化支：宽尾拉姆达鲶（R. laticauda），以及此前被归为同物异名的危地马拉拉姆达鲶、萨哈拉姆达鲶与灰拉姆达鲶。形态测量数据佐证了上述系统发育聚类结果，且在外部形态层面，每一个候选物种均具备专属鉴别特征。危地马拉拉姆达鲶的鉴别特征为：脂鳍起点距背鳍较距尾鳍更近，且具一条清晰可见的侧纵向深色带；萨哈拉姆达鲶的鉴别特征为：头部较小，头长占标准体长的20.8%~23.4%，且无侧纵向深色带；灰拉姆达鲶的鉴别特征为：头部较大，头长占标准体长的25.8%~30.1%，脂鳍基底长占标准体长的30.3%~33.3%，外侧颏须延伸至胸鳍鳍条基部，且具一条不甚明显的侧纵向深色带。上述外部形态差异与系统发育关系表明，这些类群不仅可被有效区分，且代表独立演化谱系，因此支持将其恢复为独立物种等级。