Climate Heterogeneity Shapes the Diversity of Specialist Beetle Species Across Mountains in Malaysia

The importance of maintaining biodiversity is well recognized, although the impacts of the ongoing climate crisis on biodiversity are still poorly understood for many groups, including insects. Therefore, the objectives of this study are (1) to identify the climatic niche breadth of beetle species among nine different Malaysian mountains, (2) to characterize the role of environmental (climatic) factors in niche determination, and (3) to relate the climatic niche of the species to the mountain environmental heterogeneity. The Outlying Mean Index (OMI), which compares the multivariate distance between the average environmental conditions of a given area and the specific range of conditions in which each species occurs (marginality), was used to quantify the niche parameters. Among the 875 species, only 130 presented significant responses to the nine tested parameters, 113 of which were identified as specialists, whereas 17 were classified as generalists of the climate environment. The remaining 745 species were not related to the environmental variables under study. Mountains with more heterogeneous climates and greater climate variation between sampling sites or elevations had fewer specialist beetles. Conversely, mountains with more homogeneous climates had a greater number of specialist beetles.