Geographic patterns of insect diversity across China's nature reserves: The roles of niche conservatism and range overlapping

Aim Insects are the most species‐rich clade in the world, but the
broad‐scale diversity pattern and the potential drivers have not been well
documented for the clade as a whole. We aimed to examine the relative
roles of contemporary and historical climate, niche conservatism, range
overlapping, and other environmental factors on geographic patterns of
species richness and phylogenetic structure, for insects across China.
Location China. Methods We collected insect data from 184 nature reserves
and examined geographic patterns of species richness and mean root
distance (MRD, a metric of the evolutionary development of assemblages)
for different biogeographic affinities (Palearctic, Oriental, and
widespread species) and for clades originated during the warm and cold
geohistorical periods (“warm clades” and “cold clades,” respectively). We
related richness and MRD to contemporary and historical climate, area,
habitat heterogeneity, and human disturbance to evaluate their relative
importance. Results Total species richness revealed a hump‐shaped
latitudinal pattern, peaking between 30°~35°N. Richness patterns differed
markedly among evolutionary groups: Oriental species richness decreased
significantly with higher latitude but Palearctic species increased, while
other groups again peaked between 30°~35°N. The range overlapping of
different biogeographic groups in midlatitudes may be an important
contributor to humped latitudinal richness patterns. MRD was positively
related to latitude and increased more rapidly for “warm clades” than
“cold clades.” Historical climate factors (especially winter coldness)
were among the strongest predictors for both richness and phylogenetic
patterns, for each evolutionary group, suggesting the strong influence of
niche conservatism. Conclusions The hump‐shaped latitudinal pattern of
insect richness in China is mainly shaped by niche conservatism and range
overlapping, supplemented by habitat heterogeneity and contemporary
climate. The role of niche conservatism and range overlapping may have
been overlooked if only total species richness was analyzed, suggesting
the importance of examining different evolutionary groups separately.