Genetic diversity in Mexican wild populations of the Great Curassow (Crax rubra)

Abstract The Great Curassow (Crax rubra) is a Neotropical bird with a wide distribution; it is classified under different threat categories and is listed as a vulnerable species by the IUCN. The Official Mexican Standard, the NOM-059-SEMARNAT-2010, indicates that the Great Curassow is a threatened species, and the subspecies Crax rubra griscomi, which is restricted to the island of Cozumel, is classified as critically endangered. Habitat loss and fragmentation, hunting, overexploitation, and illegal trade are among the main factors that have placed the bird at an endangered status. The objective of the present study was to determine the genetic structure and variation of the species within the Mexican populations of Crax rubra by using three mitochondrial markers, and one nuclear marker (COI, ND2, Cyt b, and MUSK). We used 47 samples obtained by noninvasive collection (feathers) including the two different color phases of the female plumage: dark brown and barred (rare in Mexico). Gene flow between the remaining populations is recent and extensive, even between the continental and the island population (C. r. griscomi). The results indicate that the subspecies C. r. rubra and C. r. griscomi do not present a marked genetic differentiation because the second exhibits an exclusive haplotype and a shared haplotype. With this study, we provide the first genetic-geographic approximation of the curassow in Mexico, where a gradual geographic differentiation is observed between the western and eastern populations of the Isthmus of Tehuantepec, and we provide a baseline for future studies. Finally, the information obtained indicates that important genetic diversity persists in the Mexican populations of the Great Curassow and that sufficient conservation within the ecosystems of these subspecies can be obtained by protecting them from overexploitation and by conserving and restoring their habitat.

摘要 大凤冠雉（Great Curassow，学名*Crax rubra*）是分布广泛的新热带界鸟类，其受威胁等级存在不同划分标准，被世界自然保护联盟（IUCN）列为易危物种。墨西哥官方标准NOM-059-SEMARNAT-2010将大凤冠雉列为受威胁物种，其中仅分布于科苏梅尔岛的亚种*Crax rubra griscomi*被评为极危物种。栖息地丧失与片段化、狩猎、过度利用以及非法贸易是导致该鸟类陷入濒危状态的主要因素。本研究旨在借助三种线粒体分子标记与一种核分子标记（COI、ND2、细胞色素b（Cyt b）及MUSK），解析墨西哥境内大凤冠雉种群的遗传结构及遗传变异。本次研究共采集47份通过无创采样获取的羽毛样本，涵盖雌性羽色的两种色型：深棕色型与横斑型（该色型在墨西哥较为罕见）。现存种群间的基因流发生时间较近且交流规模较大，甚至存在于大陆种群与科苏梅尔岛亚种（C. r. griscomi）的种群之间。研究结果显示，C. r. rubra与C. r. griscomi两个亚种并未出现显著的遗传分化，后者仅存在1种独有单倍型与1种共享单倍型。本研究首次对墨西哥境内的大凤冠雉开展了遗传地理学层面的探究，研究发现特万特佩克地峡东西两侧的种群存在渐进式的地理分化，同时为后续相关研究提供了基准参考框架。最后，本研究获取的数据表明，墨西哥境内的大凤冠雉种群仍保留有丰富的遗传多样性；通过遏制其过度利用、保护并修复栖息地，即可为这些亚种的生态系统提供充分的保护。