Decreasing species richness and positive Rapoport effects of Crambidae (Lepidoptera) on Mount Taibai

The vertical gradient pattern of species richness has been studied
intensively over the past decades. Among these, Rapoport's rule is
one of the important hypotheses of the patterns of species richness and
macroecology, asserting the latitude or altitude distributional width of
animal and plant species gradually narrows from a high latitude or high
altitude area to low latitude or low altitude areas. However, altitudinal
distributions and Rapoport’s rule have rarely been tested for Asian
Lepidopterans. Pyraustinae and Spilomelinae (Lepidoptera: Crambidae) are
widely distributed across the world's major geographic realms and
some species pose serious economic problems. These crambids as model
organisms are extremely diverse in temperate Asia including in Mount
Taibai where is considered as an ideal area for studying the vertical
distribution patterns of insect species and verifying the universality of
Rapoport's rule from the perspective of spatial scale. Based on the
investigation of altitudinal distribution data with identification by
using both DNA barcoding and traditional 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's method, Pagel's method,
Rohde's method, and the cross-species method. Our results show that
the abundance and α-diversity of Pyraustinae and Spilomelinae both
decrease with rising altitude. By contrast, the species distribution
ranges increase with rising altitude. Three of the four methods used to
test Rapoport’s rule yield positive results, while Rohde's results
show a unimodal distribution model and do not support Rapoport's
rule. This may be due to the Mid-Domain effect.