Elevational patterns of life history and ecological trait diversity of aquatic insects in the middle of the Lancang River: The effects of climate and land use variables

Abstract

Aims: Species respond to environmental changes through functional traits. Exploring the elevational pattern of community functional trait diversity is an important aspect in understanding the spatial distribution and formation mechanisms of biodiversity. Climate change and land use are important factors that affect stream ecosystems, their biodiversity, and community assembly. However, there is still a lack of systematic studies on the elevational distribution of functional trait diversity of aquatic insect assemblage under the effects of climate and land use variables. Methods: We collected aquatic insect community data from 56 stream sites along elevational gradients ranging between 1,000–3,000 m in 2016 and 2018 in the middle of the Lancang River Basin, Yunnan Province, China. We then utilized a linear or quadratic regression model to explore and compare the elevational patterns of life history (voltinism, development, and adult life span) and ecological traits (trophic habit, habit, and thermal preference) diversity indices. Then, we used random forest model to analyze the effects of climatic and land use variables on the diversity of life history and ecological traits of aquatic insect assemblages. Results: Of all life history traits, diversity of semivoltine, nonseasonal, slow seasonal, and long adult life span demonstrated significantly U-shaped elevational patterns. While diversity of fast seasonal, and very short adult life span exhibited significantly hump-shaped elevational patterns, and short adult life span diversity demonstrated a significantly increasing elevational pattern. Of all ecological traits, thermal preference diversity displayed no significant pattern along the elevation gradient. Diversity of clinger and sprawler exhibited a significantly increasing pattern and a U-shaped elevational pattern, while diversity of collector-filter, herbivore, and predator exhibited significantly increasing, decreasing, and U-shaped elevational patterns, respectively. Random forest models revealed that variation of life history trait diversity explained by climate and land use variables were higher than that in ecological trait diversity, with annual mean temperature and percentage of agriculture area as common key factors. Conclusion: In summary, the elevational patterns of functional trait diversity in aquatic insect assemblage differed between life history and ecological trait diversity, in which differences are driven by different natural and human disturbance gradients. These results can provide theoretical supports for aquatic biodiversity maintenance and conservation in the Lancang River Basin.