Effects of different environmental factors on altitude distribution pattern of functional trait diversity in locust communities

Functional traits are the concrete embodiment of the relationship between species and ecosystems, and exploring the altitudinal pattern of functional trait diversity of species is an important part of the study to reveal the spatial distribution pattern and formation mechanism of biodiversity. Environmental factors such as climate and land-use changes under altitudinal gradients are important factors affecting the distribution pattern and assembly mechanism of locust communities. However, there is a lack of systematic research on the vertical distribution pattern of functional traits in locust communities.

In this study, we conducted a survey from June to September 2022 in the Yongren area of the Jinsha River Basin within the altitude range of 1200 m to 2400 m. Based on the data of locusts collected in 84 sample plots by sweep net method, we explored and compared the distribution characteristics of locust community-weighted average trait diversity indices along the altitude gradient of functional traits (individual size, relative wing length, body colour, life type, and feeding habit) by using linear and quadratic regression models. We also used a random forest model to analyse the effects of climate, soil, vegetation productivity and land-use variables on the vertical distribution pattern of locust trait diversity along the altitudinal gradient.

The results showed that: (1) The diversity of traits among medium-sized and graminivorous feeding habits locusts followed a significant 'U'-shaped distribution pattern along the altitude gradient. The diversity of traits among brachypterous relative wing length and green body color locusts showed a significant linear decrease along the altitude gradient. Finally, the diversity of traits among mixed-feeding feeding habits locusts showed a significant single-peak distribution pattern along the altitude gradient. (2) The altitudinal gradient was found to have a significant linear decreasing effect on the functional richness index, functional homogeneity index, and functional dispersion index. (3) The analysis of the random forest model revealed inconsistent responses of different locust traits to environmental factors. The proportion of grassland area, NDVI (Normalized Difference Vegetation Index), and water vapour pressure were identified as the common key explanatory factors for multiple traits.

In conclusion, the study found that the altitudinal pattern of locust functional trait diversity varied in the Jinsha River dry-hot valley, and that the distribution of different natural environmental gradients and land-use types were the main influencing factors. These results provide a theoretical basis for biodiversity conservation and ecological restoration in the Jinsha River valley.