Thermal Stress and Its Effects on the Gut Microbiome of Parthenium Beetles

The gut microbiota plays a vital role in nutrient and energy utilization, as well as in the host's ability to adapt its immune system to environmental changes. As a biological control agent for the invasive Parthenium weed, the Parthenium beetle Zygogramma bicolorata (Z. bicolorata) Pallister is often exposed to fluctuating temperatures, which may induce stress in its natural habitat. This study utilized 16S amplicon sequencing to explore the impact of temperature stress on the gut microbiome of Z. bicolorata under cold (15°C), control (27°C), and hot (35°C) conditions. A total of 11 bacterial phyla and 149 genera were identified, with Firmicutes, Proteobacteria, and Cyanobacteria being the most abundant. Temperature treatments significantly influenced the diversity of the gut microbiota, as evidenced by alpha diversity measures. Principal coordinate analysis further revealed substantial variations in microbiome composition across the different temperature conditions. Additionally, PICRUSt2 analysis suggested that the gut microbiota is linked to metagenomic functions related to amino acid and carbohydrate transport, inorganic ion metabolism, and cellular processes. Our findings suggest that thermal stress alters the gut microbiome of Parthenium beetles, offering new insights into how these beetles may have ecologically adapted to temperature fluctuations, while also highlighting the potential role of gut microbes in maintaining beetle health under environmental stress.