# Comparative Analysis of Gut Microbiota in Two Cucurbit Leaf Beetles Reveals Divergent Adaptation Strategies Linked to Host Plant Range

## TL;DR

This study compares gut microbes in two beetles with different diets, revealing how their gut bacteria reflect their feeding habits and adaptation strategies.

## Contribution

The study reveals divergent gut microbiota strategies in polyphagous and oligophagous beetles, linking microbial composition to host dietary breadth.

## Key findings

- A. indica has higher culturable bacterial abundance and diversity, dominated by Proteobacteria and Actinobacteria.
- A. lewisii shows higher overall gut microbiota richness and diversity via sequencing, with Proteobacteria and Firmicutes.
- A. indica's gut microbiota is enriched in core metabolic pathways like carbohydrate and amino acid metabolism.

## Abstract

The relationship between insects’ dietary habits and their gut microbiota remains poorly understood. We compared the gut microbiomes of two closely related beetles: the polyphagous Aulacophora indica and the oligophagous Aulacophora lewisii. Using cultivation, we found that A. indica had a higher abundance and diversity of culturable bacteria. In contrast, high-throughput sequencing revealed that A. lewisii possessed a richer and more diverse overall gut microbiota. Their community compositions differed notably at the genus level. Functional prediction further showed that A. indica had higher gene abundances in core metabolic pathways, such as carbohydrate and amino acid metabolism. These results highlight distinct, diet-adapted gut microbial strategies between a polyphagous and an oligophagous beetle.

Insects’ gut microbiota and their hosts share a mutually dependent symbiotic relationship. However, how insect dietary breadth relates to microbial diversity remains unclear. This study compared the gut bacterial communities of the polyphagous Aulacophora indica and the oligophagous Aulacophora lewisii. Using an integrated approach of cultivation, 16S rRNA high-throughput sequencing, and bioinformatic analyses, we assessed their composition, diversity, and functional potential. Using cultivation-based methods revealed that A. indica showed a greater abundance and diversity of culturable bacteria, dominated by Proteobacteria and Actinobacteria, compared to A. lewisii (Proteobacteria and Firmicutes). In contrast, high-throughput sequencing revealed the opposite pattern: A. lewisii exhibited significantly higher overall species richness and diversity. This apparent paradox highlights the methodological complementarity between cultivation and sequencing. Furthermore, the community composition differed notably at the genus level. Functional prediction via PICRUSt2 v2.2.0 indicated that core metabolic pathways, including carbohydrate metabolism, amino acid metabolism, and energy metabolism, were more enriched in A. indica. In summary, this study reveals systematic multi-dimensional differences in the gut microbiomes of these beetles, providing a theoretical foundation and microbial resources for understanding ecological adaptation and developing targeted control strategies based on gut microbiota.