Analytical biogeography of land snails of Mount Kinabalu

This study examined the biogeography of land snail in Kinabalu Park (emphasised on Mt. Kinabalu) from the aspects of space (environmental factors) and time (historical factors). Sampling (land snails and environmental parameter) were done in 142 plots along the elevation gradient of Mt. Kinabalu and Mt. Tambuyokon. Both mountains support more than one-third (126 species) of the total number land snail species that were recorded in Sabah. The assemblage of land snails exhibited zonation along the elevation belts (500 - 1500 m; 1500 - 2600 m; 2600 - 3500 m; and 3500 - 4000 m). Each zone support its unique fauna and most of the Mt. Kinabalu's endemic were found at the zone above 2600 m. The species richness, diversity, evenness and shell's size decreased with increasing elevation. The species-area relationship between log number of species and log area of elevation zone was described by the z-value (0.193). The distribution ranges (elevation range) for the land snail of Mt. Kinabalu and Mt. Tambuyokon were not complied with the Rapoport's rule. The high elevation with relative younger age (of the area), smaller area and harsher environment than the lower elevation caused the low diversity, richness and evenness of the land snail at the top of the mountains. The small snails were better adapted to high elevation habitat than the large snails. For the ecogeography analysis, land snail from genus Everettia; and slugs were used to explore the\ud relationships between environmental parameter with their distribution. From all the parameters that had been examined, elevation was the main factor that determined the distribution of the snail and slug. Also, vegetation was related to the slug distribution. However, the environment was not the sole factor that was determining their distribution. Thus, phylogeny of Everettia (snail) and Meghimatium (slug) were constructed by using the 16S mt DNA. Both genus' phylogenetic trees were compatible, where the highland (above 2600 m) endemics (Everettia corrugata and Meghimatium uniforme) diverged from first from their middle and lower elevation congeners during the first upward move of Kinabalu batholith during the late Pliocene (ca. 1.5 mya). The Everettia spi and Meghimatium striatum that are endemic to Mt. Kinabalu (2000 - 2500 m) were split from the lowland congeners at middle Pleistocene (1 mya) during intrusion of ultrabasic rocks which caused by the second intensive upward movement of Kinabalu batholith. The glaciation and deglaciation during the middle to late Pleistocene also separated the population with the ice-flow (i. e. Meghimatium uniforme uniforme and Meghimatium uniforme 'kotal'). Besides, the boundaries between species were clear, which have been maintained by the isolating mechanisms that lie in the genitalia differences (i. e. Meghimatium spp. ) and possible environment (elevation = climates). Results from this study suggested that the biogeographical patterns of land snail of the Mt. Kinabalu and Tambuyokon had resulted from the geology activities during the middle Miocene - Holocene, and have been maintained by the present-day environment (climates, vegetation and etc.). Therefore, the whole elevation ranges of the mountains need to be protected for their remarkable diversity and evolutionary process of land snail