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.

研究背景与目的
昆虫是全球物种丰富度最高的支系，但目前针对该支系整体的大尺度多样性格局及其潜在驱动因子尚未得到充分研究。本研究旨在探究当代气候、历史气候、生态位保守性（niche conservatism）、分布区重叠（range overlapping）及其他环境因子，对中国全境昆虫物种丰富度与系统发育结构（phylogenetic structure）的地理格局的相对作用。

研究区域
中国。

研究方法
本研究从184个自然保护区收集昆虫数据，针对不同生物地理归属（biogeographic affinities）类群：古北界（Palearctic）物种、东洋界（Oriental）物种及广布种，以及在温暖、寒冷地质历史时期起源的支系（分别称为“温暖支系”与“寒冷支系”），分析其物种丰富度与平均根距离（mean root distance, MRD，用于衡量群落演化发育程度的指标）的地理格局。随后将物种丰富度及MRD与当代气候、历史气候、区域面积、生境异质性（habitat heterogeneity）及人为干扰（human disturbance）进行关联分析，以评估各因子的相对重要性。

研究结果
昆虫总物种丰富度呈现驼峰状纬度梯度格局，在北纬30°~35°区间达到峰值。不同演化类群的丰富度格局存在显著差异：东洋界物种丰富度随纬度升高显著降低，古北界物种则随纬度升高而增加，其余类群的丰富度峰值仍出现在北纬30°~35°区间。中纬度地区不同生物地理类群的分布区重叠，可能是形成驼峰状纬度丰富度格局的重要成因。MRD与纬度呈正相关，且“温暖支系”的MRD增长速率快于“寒冷支系”。对于所有演化类群而言，历史气候因子（尤其是冬季寒冷程度）均是解释物种丰富度与系统发育格局的最强预测因子之一，这表明生态位保守性具有较强的影响。

研究结论
中国昆虫物种丰富度的驼峰状纬度格局，主要由生态位保守性与分布区重叠塑造，并辅以生境异质性与当代气候的调控作用。若仅基于总物种丰富度进行分析，可能会忽略生态位保守性与分布区重叠的作用，这凸显了分别针对不同演化类群开展研究的重要性。