贵南沙蜥洞穴空间分布与昆虫资源分布特征的关系

Correlation between the spatial distribution of active cave and insect resources in Phrynocephalus guinanensis(Lacertilia: Agamidae)

贵南沙蜥分布在青海省贵南县的一片长×宽约为30 km×20 km的连续沙丘,该沙丘被周缘草地隔离,贵南沙蜥主要在沙地与草地接触带的沙地一侧活动。采用3条样线共150个陷阱研究贵南沙蜥在草地与沙地交界线两侧的活动洞穴空间分布特征与潜在的可利用性昆虫食物资源多样性,并分析洞穴空间分布特征与昆虫种类以及数量分布的关系。研究共捕获1236个昆虫个体,隶属于2纲10目26科42种,其中昆虫纲有7目21科37种978个,蛛形纲有3目5科5种258个;草地采集的昆虫有2纲9目22科37种570个,沙地有2纲9目21科33种666个。草地昆虫的Shannon-Wiener,Simpson多样性指数与均匀度指数均大于沙地,表明草地的昆虫食物资源较丰富且分布均匀。研究表明贵南沙蜥在沙地环境活动洞穴数量较多,且离交界线越近洞穴分布数量越多;草地生境活动洞穴空间分布与离交界线距离无相关性,相对沙地数量较少且空间上分布较均匀。草地样方捕获的昆虫种类和数量以及沙地样方捕获的昆虫数量都与离分界线的距离无关,但沙地上昆虫种类与离分界线的距离呈高度负相关。研究表明贵南沙蜥沙地活动洞穴空间分布与昆虫种类分布特征显著相关。

The toad-headed lizard （Phrynocephalus guinanensis） exclusively distributes in an area of sand dunes with approximately 20 km wide and 30 km long in Guinan County of Qinghai Province. While the above sand dunes were geographically isolated by surrounded grasslands, relatively larger number of active lizards were encountered in sand dunes than in grassland in the contact area of sand and grass habitats. Three line transects with 150 traps were used to study the spatial distribution of active caves and the potentially available insect resources for P. guinanensis in grassland and sand dunes in both sides of the contact area. The relationship between cave distribution and insect resource availability was analyzed. We successfully captured 1236 individual insects belonging to 2 classes, 10 orders, 26 families, and 42 species. Among them, 978 Insecta individuals were observed, comprising 7 orders, 21 families, and 37 species, while the remaining 258 Arachnoidea individuals comprised 3 orders, 5 families, and 5 species. We also discovered that among the 570 individuals captured in the grassland, 2 classes, 9 orders, 22 families, and 37 species were present, whereas 666 individuals were captured in sand dunes and included 2 classes, 9 orders, 21 families, and 33 species. The Shannon-Wiener diversity index, Simpson diversity index, and an evenness index for grassland insects were all larger than the corresponding indexes for the insects in sand dunes, which indicated that the insect resources were more abundant and homogeneous in grasslands. Our results also showed that more active caves existed in sand dunes than in grasslands, and their quantity in sand dunes increased with a decrease in the distance to the grassland-sand dune boundary; however, no correlation was found between the quantity of active caves in grasslands and their distance to the boundary, which supports the idea that a homogeneous spatial distribution of caves exists in grasslands. Moreover, we found no correlation between the distance to the boundary, and the number of insect species and individuals in grassland and the number of insect individuals in sand dunes; however, a significantly negative correlation was obtained between the distance to the boundary and the number of insect species in sand dunes. Therefore, our results concluded that a close relationship exists between the spatial distribution of active caves of P. guinanensis and the distribution of insect species in sand dunes.