Extension of the geographic distribution of Plecturocebus baptista (Pitheciidae, Primates) and a possible hybrid zone with Plecturocebus hoffmannsi: evolutionary and conservation implications

ABSTRACT Titi monkeys (family Pitheciidae) are Neotropical primates highly diversified in morphology, ecology and genetics, with a wide geographic distribution, including the Amazon, Atlantic Forest, Cerrado, Pantanal and Caatinga. This diversity, together with knowledge gaps, generates uncertainties in titi monkey taxonomy and distribution. An example is Plecturocebus baptista, with only 14 occurrence records and an ill-defined distribution based on untested geographical barriers. Here, we report the occurrence of this species at a new locality outside its known range, across the Paraná-Urariá River, which was considered a distributional limit for the species. The new record implies an overlap of P. baptista with the range of P. hoffmannsi. We document the sighting of an apparent hybrid animal. Our observations suggest that i) the distribution of P. baptista needs to be reviewed, and ii) the evolutionary relationships between P. baptista and P. hoffmannsi may be more complex than previously assumed. Since both species share contiguous areas of potential hybridization, we question whether the two species arose via allopatric speciation.

摘要：伶猴（Titi monkeys）隶属于僧面猴科（Pitheciidae），为新热带灵长类动物，在形态学、生态学与遗传学上具有高度多样性，地理分布范围广泛，涵盖亚马逊雨林、大西洋森林、塞拉多稀树草原、潘塔纳尔湿地与卡廷加旱生灌丛区。这种多样性加之研究空白，使得伶猴的分类学与分布范围研究存在诸多不确定性。以巴普蒂斯塔褶尾猴（Plecturocebus baptista）为例，该物种目前仅记录到14次出现，且其分布范围界定模糊，所依据的地理屏障尚未经过验证。本研究报道了该物种在已知分布范围之外的一处新分布点：其跨越了此前被认为是该物种分布上限的巴拉那-乌拉里亚河（Paraná-Urariá River）。此次新记录显示，巴普蒂斯塔褶尾猴的分布范围与霍夫曼褶尾猴（Plecturocebus hoffmannsi）的分布范围存在重叠。本研究还记录到一只疑似杂交个体的观测个体。本次观测结果表明：其一，巴普蒂斯塔褶尾猴的分布范围亟需重新评估；其二，巴普蒂斯塔褶尾猴与霍夫曼褶尾猴之间的演化关系或许比此前设想的更为复杂。由于两个物种存在可发生杂交的毗邻分布区，我们对这两个物种是否通过异域物种形成（allopatric speciation）演化而来提出了质疑。