Recent dispersal and diversification within the clingfish genus Acyrtus (Actinopterygii: Gobiesocidae), with the description of a new western Atlantic species

Abstract The genus Acyrtus (Gobiesocidae) is represented by four valid species distributed in the western Atlantic, and a recently described fifth species from the eastern Pacific. Here, we describe a new species endemic to Trindade Island, Brazil, and provide the first phylogenetic inference for the genus including all representatives. The new species can be distinguished from all its congeners by meristic and morphometric characters, as well as genetic differences. It presents low genetic diversity and, contrarily to other Trindade Island endemic fishes, shows no evidence of recent population growth. Our phylogeny reveals cryptic species and the paraphyletic nature of Acyrtus, which included Arcos nudus (western Atlantic) in a clade that separated from Arcos erythrops (tropical eastern Pacific) around 20 Mya. The three species found in the Brazilian Province, including one that remains undescribed, form a monophyletic clade which colonized the western South Atlantic around 2.6 Mya. Our study suggests that Arcos nudus should be placed in Acyrtus, and that the relationships among the closely-related Gobiesocidae genera Acyrtus (mostly from the Atlantic Ocean) and Arcos (from the Pacific Ocean) need further investigation.

摘要 棘腹盘鱼属（Acyrtus，喉盘鱼科Gobiesocidae）目前包含4个有效物种，均分布于西大西洋，另有1个近年新描述的东太平洋第五个物种。本研究记述了1种特生于巴西特林达迪岛的新物种，并首次针对该属所有代表类群开展系统发育推断。该新种可通过计数性状、形态测量特征以及遗传差异，与所有同属物种相区分。其遗传多样性较低，且与特林达迪岛其他特有鱼类不同，未表现出近期种群增长的迹象。我们的系统发育分析结果揭示了该属存在隐存物种，且棘腹盘鱼属为并系群：原隶属于阿科斯盘鱼属（Arcos）的Arcos nudus（西大西洋）所在的演化支，与东太平洋热带物种Arcos erythrops的分化时间约为2000万年前。分布于巴西生物地理区的3个物种（含1个尚未正式描述的物种）构成单系演化支，该类群约于260万年前拓殖至南大西洋西部。本研究建议将Arcos nudus归入棘腹盘鱼属，同时亲缘关系密切的喉盘鱼科两属——主要分布于大西洋的棘腹盘鱼属与太平洋的阿科斯盘鱼属之间的系统发育关系仍需进一步探究。