云南横断山区小型兽类多样性的空间分布格局

Study on spatial distribution patterns of small mammals diversity in Hengduan Mountains, Yunnan, China

本文就云南西部横断山区北纬21°-29°，海拔100m-5，000m之间目前所知小型兽类（含啮齿目、食虫目、攀驹目、兔形目和小型食肉目）5目、11科、58属、187种（亚种）的水平和垂直分布资料追行综合整理、统计分析。小型兽类属、种丰富度沿纬度的变化，基本呈现了随纬度增加先逐步增高後降低的分布格局，高峰值主要在中纬度高度24°N-27°N区间；它们沿海拔梯度的变化，也呈现了随海拔增加先增高後降低的偏峰分布格局，丰富度高峰值主要在中海拔高度约1，500—3，000米区域之间。小型兽类属和种β多样性（Cody指数）沿纬度梯度变化基本呈双峰分布格局，其高峰位置主要位于北纬24°N（Ⅳ带）和25°N（Ⅴ带）、26°N（Ⅵ带）与27°）N（Ⅵ带）梯度带之间，高峰的地理位置分别处于当地气候沿纬度梯向的中亚热带与暖温带、温带与寒温带气候的过渡地带；小型兽类属和种p多样性随海拔的升高都呈三峰分布格局，高峰的具体位置分别在海拔1，500m-2，000m（C—D）带之间、2，500m-3，000m（E—F）带之间和3，500m-4，000m（G—H）带之间，其位置约为当地气候由海拔分布向的南亚热带与中亚热带、暖温带与寒温带、温带与寒带气候的过渡地带。上述结果说明横断山小型兽类β多样性空间分布格局及物种的组成与地理环境和气候条件的变化有关。聚类结果显示：（1）沿纬度梯度分布的小型兽类属及种基本分为3大类：第一类包含纬度较低和海拔较低的21°N-24°N（Ⅰ—Ⅳ梯度带）；第二类包含了25°N-26°N（Ⅴ—Ⅵ梯度带）；第三类包含了27°N-28°N（Ⅶ—Ⅷ梯度带）。它们分别反映和代表了当地横断山区及小型兽类沿纬度梯度向水平分布的3个主要地域及区系类型，即柬洋区系、东洋与古北区系的过渡区和古北区系，东洋与古北区系两者交汇或过渡区位置约在23°N-27°N之间，并在25°N-26°）N之间形成两大区系交汇和分异的中心。（2）沿海拔梯度分布的小型兽类属及种也被聚为3人类：第一类包含100m-1，500m（A—C梯度带）；第二类包含了2，000m-2，500m（D，E梯度带）；第三类包含了3，000m-4，500m（F—I带）。它们也分别反映出了横断山区及小型兽类沿海拔梯度向垂直分布的3个主要地域及区系类型，即东洋区系、东洋与古北区系的遏渡区和古北区系，两区系过渡或交错区的范围约在海拔1，500m-3，500m之间，并约在2,000m-3，000m的区域形成交汇和分异的中心。上述25°-26°N和海拔2，000m-3，000m的区域地处了两大区系物种交汇、过渡和分异的中心，在此区域内，由于边缘效应和复杂的地理景观，形成了小型兽类具有较高生物多样性的特徵。此外，在横断山南部家鼠鼠疫流行区区域内，可以看出随着小型兽类多样性沿纬度和海拔梯度向的增高，鼠疫的发病率呈减少的趋势，说明鼠疫的发生和分布与宿主动物多样性及其空间分布格局有一定的关系。

To inquire into the basic rules and distinction of the spatial distribution pattern of small mammalian diversity, to explore the main ecological factors affecting their distribution and its correlation with the plague occurrence. 187 species （subspecies） of small mammals belonging to 58 genera and 11 families were collected in the Hengduan Mountains which lie in at the latitudes of 21 °-29° and at the altitude of 100 m-5,000 m in western Yunnan, China. Based on the latitudinal and altitudinal distribution of small mammals （Rodentia, Insectivora, Scandentia, Lagomorpha, Carnivora）, that area was divided into 8 （ Ⅰ -Ⅷ） regions by latitudinal gradient and 9 （A-I） regions by altitudinal gradient. All of the data were analyzed synthetically with statistics. The richness of small mammals in families, genera and species increased gradually and then decreased with the increasing latitude; the numbers peaking at 24°N-27°N at the mid-latitude zone. A leaning peak distribution pattern according to elevation was observed. The peak occurred at about 1,500-3,000 m at mid-altitude zone and then decreased by degrees with the increasing altitude. Genus and species β diversity （Cody index） of small mammals. The latitudinal gradient showed that there were two peak distribution patterns, and they lie in 24°N-25°N and 26°N-27°N latitudes, which is at the transition zone from the mid-subtropical zone to the warm-temperate zone, from the temperate zone to the frigid zone. With reference to the altitudinal aspects, the Genus and species β diversity of small mammals were present at three peaks distribution patterns. They appeared at 1,500-2,000 m, 2,500-3,000 m and 3,500-4,000 m, which are all in the transition zone （from the south subtropical zone to the mid-subtropical zone, from the warm-temperate zone to the cool temperate zone and from the temperate zone to frigid zone）. The spatial β diversity distribution and community composition of these species of small mammals reflect the influence of the geographical environment and climate. The cluster analysis showed： （1） The genera and species of small mammals according to latitudinal distribution were classified into 3 main ecological types, 21°N-24°N （I-IV）, 25°N-26°N （V-VI）, 27°N-28°N （Ⅶ-Ⅷ.）. These grouping results correspond to the three main regional and faunal characteristics based on the horizontal distribution in Hengduan Mountains those are Oriental fauna, the transitional association between Oriental fauna and Palaearctic fauna and Palaearctic fauna, and formed an overlap zone and divergence center in 23°N-27°N. The zones from 25°N to 26° N are the center of differentiation and overlap the two realms. （2） The genera and species of small mammals according to altitudinal distribution were classified into 3 main ecological types, 100 m-1,500 m （A-C）, 2,000 m-2,500 m （D-E）, 3,000 m-4,500 m （F-I）, they are Oriental fauna, the transitional association between Oriental fauna and Palaearctic fauna and Palaearctic fauna, and formed an overlap zone and divergence center in 1,500 m-3,500 m. The zones in 2,000 m-3,000 m are the center of differentiation and overlaps the two realms. The zones from 25°N to 26° N and from 2,000 m to 3,000 m in Hengduan Mountains were the center of differentiation and overlap of the two realms. Because of the edge effect and complex landscape, the families, genera and species of small mammals there all showed high diversity. In the popular rodent plague region in Southern Hengduan Mt., the disease incidence rate of the plague seems to decrease according to the great diversity of the small mammals that live in that region. This drop in disease incidence also seems to be affected by the varying latitudes and altitudes of the area. This preliminary investigation correlates with earlier research that the host and vector diversity and community composition corresponds with the decrease in the incidence of the infectious disease.