Alpha and beta diversities of Trichoptera (Insecta) assemblages in natural and rural subtropical streams

Abstract: Aim The aim of this study was to determine the diversity of Trichoptera in subtropical streams and the effects of environmental variables and geographical position on alpha and beta diversity in natural and rural streams. Methods We collected Trichoptera with a Surber sampler in 12 small order subtropical streams (six streams with apparent absence of anthropic disturbance and six streams with rural activity in their drainage areas) and measured limnological variables. We evaluated the effects of environmental variability and geographical distance on the dissimilarity of the assemblage and calculated the contribution of alpha and beta diversity for each stream. Results We collected a total of 1,264 Trichoptera larvae distributed in 17 genera and 11 families. The genera Phylloicus and Smicridea were found in almost all streams. We observed a positive effect of environmental variability on biological variability but not of geographical distance. The environmental variability was basically generated by the influence of higher concentrations of dissolved organic carbon and nutrients. We observed the greatest contribution of the alpha diversity of the Trichoptera assemblages in natural streams and of beta diversity in the rural streams. Conclusions Our results demonstrate that the variability of Trichoptera is affected by environmental characteristics, but not by geographical position.

摘要：本研究旨在探明亚热带溪流中毛翅目（Trichoptera）昆虫的物种多样性，以及环境变量与地理位置对天然溪流和乡村溪流的α多样性、β多样性的影响。研究方法：采用索伯采泥器（Surber sampler）对12条小型亚热带溪流开展毛翅目昆虫采样，其中6条溪流无明显人为干扰，剩余6条溪流的流域存在乡村人类活动；同时测定相关湖沼学变量。本研究评估了环境异质性与地理距离对昆虫群落相异性的影响，并计算了各溪流的α多样性与β多样性贡献占比。研究结果：本次研究共采集到1264头毛翅目幼虫，隶属于11科17属。其中Phylloicus属与Smicridea属在几乎所有采样溪流中均有分布。结果显示，环境异质性对昆虫群落的生物变异存在显著正向影响，而地理距离无显著影响；环境异质性主要由较高浓度的溶解有机碳与营养盐所驱动。天然溪流中毛翅目群落的α多样性贡献占比最高，乡村溪流则以β多样性贡献占比为最高。研究结论：本研究结果表明，毛翅目昆虫的群落变异主要受环境特征调控，而非地理位置因素。