祁连山鸡类物种多样性及其成因

青藏高原祁连山孕育了丰富的鸡类物种多样性,有2科11种5个亚种,是我国鸡类分布中心之一,也是珍稀特有物种分布中心之一。祁连山鸡类多样性的成因主要有以下几方面:悠长的进化时间产生新的分类阶元;残存分布和迁入定居丰富了祁连山鸡类多样性;环境空间异质性,为不同生境要求的鸡类提供了适宜生境和可利用的生态位,以及鸡类生态位分化维持了祁连山鸡类的多样性;已建自然保护区为祁连山鸡类多样性提供了良好保护。

Diversity and evolutionary origins of Gallinaceans in the Qilian Mountains

The Qilian Mountains are situated on the northeastern edge of the Qinghai-Tibet Plateau and are home to diverse rare and endemic gallinacean bird species. These include eleven species and five subspecies of gallinaceans belonging to two families; nine of these species are polytypic in the Qilian Mountains. This diversity arose from speciation events, in part because the Qilian Mountains have experienced several ice ages. Over time, the size of the glaciers decreased until almost no valley glacier was present, leading to allopatric speciation due to spatial and temporal separation. Furthermore, the Qilian Mountains have served as a refuge for some birds during the Pleistocene glaciations, which also led to the differentiation of subspecies due to isolation. For example, the chukar partridge (Alectoris chukar), Tibetan partridge (Perdix hodgsoniae), blood pheasant (Ithaginis cruentus), and common pheasant (Phasianus colchicus) each have two subspecies in the Qilian Mountains. Pairs of subspecies are distributed in the eastern and western regions, or the southern and northern slopes, representing geographical speciation. Furthermore, gallinacean species diversified due to the residual distribution of native birds and the arrival of birds from elsewhere. The forest gallinaceans gradually withdrew from the plateau surface with the plateau uplift that occurred during the Quaternary glacial period. The eastern Qilian Mountains were affected by the East-Asian Monsoon, and humid air led to increased precipitation, resulting in a cold-temperature coniferous forest at an altitude of 2500-3300 m. Thus, the native forest gallinaceans remained in the Qilian Mountains. Since the middle Pleistocene, a dry and cold climate has led to the development of an alpine sub-ice-snow vegetation zone at the top of the mountain, which is a suitable habitat for grassland gallinaceans. Birds such as the Tibetan snow cock (Tetraogallus tibetanus), Himalayan snow cock (Tetraogallus himalayensis), chukar partridge, and Tibetan partridge originated from different parts of the world, enriching gallinacean diversity of this region. Diversity has also been achieved due to complex spatial heterogeneity and niche differentiation, meaning that suitable habitats and niches are available to meet different habitat requirements. For example, the habitats of the blue-eared pheasant (Crossoptilon auritum), blood pheasant, and Chinese grouse (Tetrastes sewerzowi) are similar, but their spatial nesting, foraging, and nutritional niches differ. Six types of shrub-grassland-meadow gallinaceans, belonging to three genera and composed of three closely related herbivorous species, are observed. In addition to competition for food, their habitats were replaced with each other. Thus, despite competition, species can coexist due to niche differentiation, maintaining species diversity. Finally, gallinacean diversity is well protected in nature reserves. At present, 10 nature reserves, including six national and four provincial, are located in the Qilian Mountains. Each gallinacean species and subspecies has been found among these protected areas. On the basis of the geographic approach to protect biological diversity (GAP) analysis, we found the existing nature reserves in the Qilian Mountains to be sufficient for protection of gallinacean species diversity.