Species Diversity And Zoogeography Of Land Snails In Maolan Karst Forest Nature Reserve, Guizhou, China

The aim of the study was to assess the distribution pattern of land snails in different kinds of habitat and its zoogeographical structure in Maolan Karst Forest Nature Reserve, Guizhou, China. An additional aim was to explore the relationship between distribution pattern of land snails and their habitat. The work was undertaken in three districts -Dongsai, Yaogu and Banzhai - which ordinally locates in the east, north-west and south of Maolan Karst Forest Nature Reserve. Within each district, several sites were studied in different habitats, such as forest covered by good vegetation, brush, bamboo, meadow, farmland and habitats of the village. A total of 123 sites with 50X50cm per plot were studied. Large specimens were collected within each site during the fieldwork. Small specimens were extracted from litter and surface soil (depth from 0~5cm) by using 2mm ~ 0.5mm mesh sieves. Statistical analysis was performed using Excel and SPSS11 (2002 edition) softwares. The distribution pattern in different kinds of habitat and the zoogeographical structure were analyzed comparatively. Principal component analysis (PCA) and cluster analysis of 12 habits was based on the occurrence of land snails and their distribution in Maolan Karst Forest Nature Reserve. The abundance of species of common land snails collected from 12 habitats and their co-relation were discussed. The fauna of land snails in Maolan Karst Forest Nature Reserve was quite abundant including Central China district, South- Western China district, Southern China district, Northern China district and Mongolian-Xinjiang district and some other widespread species. In addition, species distributed in Central China district were 48 that accounted for 43. 2% of the total. Species distributed in Southern China district and Central China districtwere 35 and accounted for 31. 5% of total.Principal component analysis (PCA) and cluster analysis were used to analyze the land snail species in different habitats. Similar results were obtained when the 12 plots were grouped into three categories -village and farmland; brush, bamboo and meadow; and forest covered by good vegetation. This indicated that vegetation structure and human disturbance could be the main factors of influencing land snails' community composition and distribution in Maolan.During the period of 1998, 2000—2001, and 2004, a total of 10,077 land snails were collected. The diversity analysis shows that Maolan Karst Nature Reserve has a good species diversity of land snails in different taxonomic levels, 111 species, 42 genus, 16 families, 3 orders and 2 subclasses. Separately, Dongsai has the most abundant diversity considering species, genera and family compared with Yaogu and Banzhai. There is a higher individual number in Banzhai compared with Yaogu but the latter has more species and genus. Among the 12 habitats studied, the forest with good vegetation cover generally has the highest species, genus and families. On the contrary, the habitats of the village and farmland have the lowest species diversity. The condition of land snail diversity in brush, bamboo and meadow is much better than that of the village and farmland but not as good as in the forest.The analysis of the species distribution in different habitats, and correlation analysis among common species were conformed. Similar results were obtained: where common species have an obvious tendency to occupy different habitats.Land snails diversity in Maolan Karst Forest Nature Reserve declined with vegetation and thus follows the widespread pattern shown by most groups of organism. However, faunal variation appears to be more closely related to vegetation, than to the disturbances of human activity. The effects of vegetation on land snails could either be direct, or indirect via its effects on soils or humidity or other ecological factors. The effects from the disturbances of human activity on land snails should beindirect via its effects on the environment, but it could be ruinous for the biodiversity once formed without control. Thus, high abundance of land snails and their natural communities in Maolan karst area can be preserved only when the original vegetation is well protected and the disturbances of human activity are effectively limited.