Assessing the Role of Light and Bioclimatic Factors in the Distribution and Abundance of Nocturnal Insects in Urban and Semi-Urban Areas of Faisalabad and Sahiwal

Abstract

The influence of light pollution and bioclimatic factors on nocturnal insect diversity is key knowledge for biodiversity conservation in fast urbanizing areas. Here we assess whether artificial light intensity and environmental variability, including abiotic and biotic variables, drive nocturnal insect community composition in two contrasting regions: Faisalabad (urban) and Sahiwal (semi-urban), Punjab, Pakistan. Spodoptera litura, Helicoverpa armigera, Plusia orichalcea, and Gryllus bimaculatus were the key species whose abundance was significantly affected by the light intensity, while the others had weak or no significant responses with the increase in light intensity, as revealed by regression analysis. Results Boxplots and scatterplots showed higher variability of light pollution and lower species richness in Faisalabad, and a weak negative trend between Shannon Diversity Index and light intensity promote that light pollution might help in biodiversity losses. By using multivariate analyses such as Principal Component Analysis (PCA) and Canonical Correspondence Analysis (CCA), each region was found to have a unique composition of species and environmental factors. The higher degree of environmental heterogeneity in Faisalabad was most likely driven by urbanization-related processes such as habitat fragmentation and change in local microclimates. Correlation heatmaps and hierarchical clustering additionally emphasized this complexity in species interactions and species interactions with environmental variables. These results highlight the relative importance of environmental heterogeneity and light pollution as local-scale drivers of nocturnal insect diversity. Our study highlights the need to manage increasing light pollution and environmental heterogeneity to promote insect conservation, particularly in urbanizing landscapes. This knowledge provides clearer understanding in the impacts of anthropogenic change on nocturnal ecosystems and informs urban and biodiversity management moving forward.