Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
Department of Anthropology and Center for Ecology, Southern Illinois University Carbondale, Carbondale, Illinois, United States of America.
PLoS One. 2022 Mar 31;17(3):e0264519. doi: 10.1371/journal.pone.0264519. eCollection 2022.
Gibbons (Family Hylobatidae) are a suitable model for exploring hybridization in pair-living primates as several species form hybrid zones. In Khao Yai National Park, Thailand, white-handed gibbons (Hylobates lar) and pileated gibbons (Hylobates pileatus) are distributed parapatrically and hybridize in a narrow zone. Their phenotypic characteristics suggest limited inter-species gene flow, although this has never been assessed. To uncover the history and degree of gene flow between the two species, we studied the genetic structure of gibbons in the hybrid zone by analyzing fecal DNA samples, phenotypic characteristics, vocalizations and individuals' social status. We determined eight autosomal single nucleotide variant (SNV) loci, and mitochondrial DNA (mtDNA) and Y-chromosomal haplotypes of 72 gibbons. We compared these markers with reference types of wild pureblood white-handed gibbons (n = 12) in Kaeng Krachan National Park and pureblood pileated gibbons (n = 4) in Khao Soi Dao Wildlife Sanctuary. Autosomal genotypic analyses confirmed the various levels of mixed ancestry for several adult gibbons with or without atypical phenotypic traits in Khao Yai National Park. In some other adult gibbons, the mixed ancestry was not detected in either autosomal SNVs or their phenotypic traits but the mtDNA. Both male and female adult hybrids formed reproductive units mainly with a phenotypic pureblood partner and many of them produced offspring. Taken together, our results suggest that once hybridization occurs, white-handed-pileated-gibbon hybrids can reproduce with either parental species and that the backcrossing and thus introgression may occur in successive generations, with no drastic changes in phenotypic appearance.
长臂猿（Family Hylobatidae）是探索对偶居灵长类动物杂交的合适模型，因为有几个物种形成了杂交带。在泰国考艾国家公园，白掌长臂猿（Hylobates lar）和白颊长臂猿（Hylobates pileatus）呈部分地理分布，并在一个狭窄的区域内杂交。它们的表型特征表明存在有限的种间基因流，尽管这从未得到过评估。为了揭示这两个物种之间的历史和基因流程度，我们通过分析粪便 DNA 样本、表型特征、叫声和个体的社会地位，研究了杂交带中长臂猿的遗传结构。我们确定了 8 个常染色体单核苷酸变异（SNV）位点，以及线粒体 DNA（mtDNA）和 Y 染色体单倍型的 72 只长臂猿。我们将这些标记与考艾国家公园的野生纯种白掌长臂猿（n = 12）和考索伊道野生动物保护区的纯种白颊长臂猿（n = 4）的参考类型进行了比较。常染色体基因型分析证实，考艾国家公园的一些具有或不具有非典型表型特征的成年长臂猿具有不同程度的混合血统。在其他一些成年长臂猿中，无论是常染色体 SNV 还是表型特征，都没有检测到混合血统，但 mtDNA 却检测到了。雌雄成年杂种主要与表型纯种伙伴形成生殖单位，其中许多产生了后代。总的来说，我们的结果表明，一旦发生杂交，白掌-白颊长臂猿杂种可以与父本或母本物种繁殖，并且回交和因此的基因渗入可能在连续几代中发生，而表型外观没有明显变化。
