Taxonomy and genetic diversity of Achaea janata (L.) (Lepidoptera: Erebidae) from Karnataka, India

The semilooper, Achaea janata (Linnaeus) (Lepidoptera: Erebidae), is a major defoliator pest of castor and several other crops across tropical and subtropical regions of India. It is known to possess several colour morphs in the larval and adult stages, making it difficult to identify. The present study was conducted to investigate the morphological variation, and genetic diversity of A. janata populations collected across the state of Karnataka, India, and to determine the presence of any closely related species. Among all the collected samples, six colour morphs in the larval stage and two morphs in adults were documented. Larval description was made based on external morphology, chaetotaxy and arrangement of crochets. Adult description was based on the external morphology and the male and female genitalia structures. All the samples collected were identified as A. janata. The mitochondrial cytochrome oxidase I (mtCOI) gene was used for molecular identification and analysis of genetic diversity. The nucleotide composition revealed a high A + T bias (69.71%), and substitution analysis showed a predominance of transitions over transversions. Pairwise genetic distances ranged from 0.0000 to 0.01227, suggesting low genetic divergence among populations. Phylogenetic analysis, although it grouped the Karnataka populations into four clades with high bootstrap support, is not conclusive that all the clades are regionally aligned. Haplotype analysis yielded 11 haplotypes from 32 sequences, of which eight were from Karnataka, showing higher haplotype diversity (Hd = 0.80769) compared to populations outside Karnataka. The study offers the first extensive taxonomic and molecular data on A. janata populations from Karnataka, emphasizing the morphological polymorphism and low genetic divergence.