Hammer Michael P, Allen Gerald R, Martin Keith C, Adams Mark, Unmack Peter J
Museum and Art Gallery of the Northern Territory, PO Box 4646, Darwin, Northern Territory 0801, Australia..
Zootaxa. 2019 Nov 28;4701(3):zootaxa.4701.3.1. doi: 10.11646/zootaxa.4701.3.1.
The 'maccullochi species group' of rainbowfishes are small and distinctly patterned freshwater fishes of streams and swamps, comprising around eight species. The species from which the group bears its name, Melanotaenia maccullochi Ogilby, 1915, has been thought to comprise three forms occurring in distinct geographic areas, and recent mitochondrial genetic data provides matching patterns of likely inter-specific divergence. Here we undertake a detailed investigation of the taxonomic status of M. maccullochi using a combined lines of evidence approach incorporating multiple nuclear genetic markers (55 allozyme loci), mitochondrial DNA sequence data (1141 bp cytochrome b) and morphology (examination of a suite of 38 morphometric and meristic characters). As all three datasets provide support for a three-way split, we accordingly describe two new species and redescribe M. maccullochi sensu stricto. McCulloch's Rainbowfish M. maccullochi, a species with brown body stripes and red fins occurs in northeast Queensland and is redescribed based on 338 specimens, 13.1-53.0 mm SL. This species was one of the first rainbowfishes to become known in the aquarium hobby. A second form with darker stripes on a contrasting light white-grey body and with distinct sub-marginal black bands in the dorsal and anal fins, distributed across northern and eastern Cape York Peninsula, Torres Strait and southern central New Guinea, is described as Sahul Rainbowfish M. sahulensis sp. nov. based on 267 specimens, 13.4-48.4 mm SL. A diminutive and well geographically isolated form occurring below the escarpment of the Tabletop Range in Litchfield National Park, Northern Territory possessing a more prominent and purplish mid-lateral stripe, is described as the Little Rainbowfish Melanotaenia wilsoni sp. nov. based on 50 specimens, 19.3-33.3 mm SL. A combination of morphological characters is useful for separating the respective taxa with M. wilsoni sp. nov. the most distinctive, typically having fewer vertebrae, lateral scales, cheek scales, procurrent caudal rays and anal rays and proportionally a shorter maxilla and snout than either of the other two species. Useful characters for further separating M. sahulensis sp. nov. from M. maccullochi include slightly higher counts of vertebrae, lateral scales and anal rays and proportionally greater body depth, body width and pre-dorsal distance. Information on the known distribution, habitats and conservation status of the three species is summarised, with the Northern Territory species being a narrow-range endemic with specific environmental requirements.
虹银汉鱼属的“麦卡洛克种群”是生活在溪流和沼泽中的小型淡水鱼，身上有独特的斑纹，包含约8个物种。该种群得名于1915年奥吉尔比命名的麦氏虹银汉鱼（Melanotaenia maccullochi），人们认为它包含三种分布在不同地理区域的形态，近期的线粒体基因数据也显示出可能的种间分化匹配模式。在此，我们采用综合证据法，结合多个核基因标记（55个等位酶位点）、线粒体DNA序列数据（1141bp细胞色素b）和形态学（对38个形态测量和可数性状进行检查），对麦氏虹银汉鱼的分类地位进行详细研究。由于这三个数据集均支持三分法，因此我们据此描述了两个新物种，并重新描述了狭义的麦氏虹银汉鱼。麦卡洛克虹银汉鱼（M. maccullochi）身体有褐色条纹，鳍为红色，分布于昆士兰东北部，基于338个标本（体长13.1 - 53.0毫米）进行重新描述。该物种是最早在水族爱好中为人所知的虹银汉鱼之一。第二种形态分布于约克角半岛北部和东部、托雷斯海峡以及新几内亚中南部，其身体浅白灰色，有深色条纹，背鳍和臀鳍有明显的亚边缘黑色带，基于267个标本（体长13.4 - 48.4毫米）被描述为沙湖虹银汉鱼（M. sahulensis sp. nov.）。一种体型微小且地理隔离明显的形态出现在北领地利奇菲尔德国家公园桌面山脉悬崖下方，有更明显的紫色中侧条纹，基于50个标本（体长19.3 - 33.3毫米）被描述为小虹银汉鱼（Melanotaenia wilsoni sp. nov.）。形态特征组合有助于区分各个分类单元，小虹银汉鱼最为独特，通常椎骨、侧鳞、颊鳞、尾下骨射线和臀鳍射线较少，上颌骨和吻部相对较短。进一步区分沙湖虹银汉鱼和麦氏虹银汉鱼的有用特征包括椎骨、侧鳞和臀鳍射线数量略多，以及相对更大的体深、体宽和背前距。总结了这三个物种的已知分布、栖息地和保护状况，北领地的物种是具有特定环境要求的狭域特有种。
