Decreasing Species Richness with Increase in Elevation and Positive Rapoport Effects of Crambidae (Lepidoptera) on Mount Taibai

Rapoport's rule proposes that a species' range size increases with the increase in a gradient (such as latitude, altitude or water depth). However, altitudinal distributions and Rapoport's rule have rarely been tested for Asian Lepidoptera. Pyraustinae and Spilomelinae (Lepidoptera: Crambidae) are extremely diverse in temperate Asia, including on Mount Taibai, which is considered a hotspot area for studying the vertical distribution patterns of insect species. Based on the investigation of altitudinal distribution data with identification by using both DNA barcoding and the morphological classification of Pyraustinae and Spilomelinae, this paper determines the altitudinal gradient pattern for these two subfamilies on the north slope of Mount Taibai, and provides a test of the universality of Rapoport's rule in Lepidoptera by using four methods, including Stevens' method, Pagel's method, Rohde's method, and the cross-species method. Our results show that the alpha diversity of Pyraustinae and Spilomelinae both decrease with rising altitude. By contrast, the species' ranges increase with rising altitude. Three of the four methods used to test Rapoport's rule yielded positive results, while Rohde's results show a unimodal distribution model and do not support Rapoport's rule. Our findings fill the research gap on the elevational diversity of Lepidoptera in temperate Asia.