Abstract:  Determining the vertical distribution of species diversity along altitudinal gradients is of critical importance in biodiversity and conservation research. Across a broad set of taxa, the hump-shaped pattern of species diversity is the most common one, and the vertical distribution of the small mammal community in the Middle Himalayas best fits a hump-shaped pattern. Since the Eastern Himalayas and Middle Himalays share many geographical and climatological conditions, we hypothesize that the vertical pattern of small mammal diversity in the East Himalayas also fit a mid-peak or humped pattern. Therefore, we conducted field surveys of two mammalian orders, Non-flying Small Mammal at an elevation of 2 300 – 5 000m, in the Lebu Valley of the East Himalayas. 45 sampling sites were set up, with each contained 9 segments distributing along an elevational gradient every 300 m. In total, our 16 200 traps  captured 372 specimens, which belonged to 10 species, 5 families and 3 mammalian orders. Our results indicated that the species richness of Non-flying Small Mammal in the Lebu valley reached a peak at an elevation of 2 600 – 2 900 m, and then decreased at higher elevations, displaying a mid-peak pattern. Based on this study, we hypothesize that the vertical distribution and species diversity of small mammals inhabiting valleys in the southern part of the Himalayas will exhibit a similar pattern in response to similar geographical and climatological conditions. Results suggest that geography and climate are key factors in understanding the vertical distribution of species diversity.

Key words: Lebu Valley in Himalayas, Small mammals, Vertical distribution of species diversity, Elevational gradient

摘要： 物种多样性沿海拔梯度的垂直分布格局在生物多样性研究与保护中受到广泛关注，中峰格局是物种多样性垂直分布四类格局中最为普遍的格局。中喜马拉雅沟谷的研究表明，小型兽类的垂直分布格局符合中峰模型。中喜马拉雅和东喜马拉雅具有相似的自然地理和气候条件，由此，推断东喜马拉雅沟谷的小型兽类垂直分布格局可能也符合中峰格局。为此，在东喜马拉雅勒布沟对非飞行小型兽类开展实地调查，选取研究海拔范围为2 300~5 000 m，沿海拔梯度连续设置9个300 m海拔段45个样方采集点，累计布夹16 200次，共采集标本372号，分属 3目5科10种。研究结果显示：该沟谷非飞行小型兽类物种丰富度在2 600~2 900 m海拔段出现峰值，随后随着海拔的升高递减，即从最低海拔到中海拔段上升至峰值后开始递减至趋于平缓，即显示出中峰格局特点。喜马拉雅山脉东西走向导致其南翼各沟谷拥有相似的地理和气候特征，如各沟谷都南北走向，受印度洋暖流气候影响，拥有相似的植被垂直带分布等，这使得非飞行小型兽类物种多样性垂直分布呈现出相似的特点，推论：在大尺度背景下，地理和气候条件可能是影响物种多样性垂直分布格局的关键因素。

关键词: 喜马拉雅勒布沟, 小型兽类, 物种多样性垂直分布, 海拔梯度