Diversity of coccinellid beetles (Coleoptera: Coccinellidae) of northern Kerala

Abstract

Coccinellid beetles, commonly known as ladybirds or lady beetles, belong to the family Coccinellidae of order Coleoptera, are species rich and play a significant and multifaceted role in agriculture. Coccinellids are ecologically and morphologically diverse and exhibit a wide range of food habits spanning kingdoms and trophic levels. Most of the coccinellids are predaceous on various agricultural pests, whereas a few are phytophagous, and some are mycophagous. The research work on “Diversity of coccinellid beetles (Coleoptera: Coccinellidae) of northern Kerala” was undertaken in the Department of Agricultural Entomology, College of Agriculture, Padannakkad during 2021-2023 for the documentation of the species composition and estimation of diversity indices of coccinellid beetles in different agro-ecological zones of northern Kerala and to generate DNA barcodes and carry out molecular analysis of coccinellids associated with different cropping systems. Purposive surveys were conducted across four different agro-ecological zones, viz., coastal plain, midland laterites, foothill, and high hill, covering Kasaragod, Kannur, Kozhikode, and Wayanad districts. Different cropping systems, viz., rice, vegetables, fruits, and plantation crops were covered during the survey. A total of 27 species of coccinellids belonging to six tribes were recorded. Among these, three were phytophagous viz., Afidenta misera, Henosepilachna septima, and H. vigintioctopunctata and two were mycophagous viz., Illeis bielawskii and Illeis cincta and rest of 22 species were predacious in nature. Total number of coccinellid species recorded from rice, vegetables, plantation crops and fruits were seven, 18, 11 and eight, respectively. Among different agroecological zones, high hills recorded maximum number of coccinellids (20) followed by coastal plain (19), midland laterites (14) and foothills (10). Diversity indices to assess species richness, diversity, dominance and evenness were estimated. The most abundant coccinellid species was H. vigintioctopunctata, with a relative abundance of 29.86 per cent. The predominant predatory coccinellid was Cheilomenes sexmaculata (11.88%), followed by Coccinella transversalis (11.72%). Among various cropping systems the vegetable cropping system displayed highest species richness, while rice showed lowest richness. High hills showed the highest richness and least rich was foot hills. Species diversity was estimated in terms of Shannon-Wiener index (H) and the most diverse cropping system was plantation crops (1.96) and least diverse was rice (1.15) ecosystem. Among the agroecological zones, high hill (2.47) was the most diverse, and the foothill was the least diverse zone (1.91). Species dominance was studied by using Simpson’s index. The highest value of Simpson’s index was observed in rice (0.46) and lowest value in plantation crops (0.17). Among agroecological zones, coastal plain was least diverse with highest dominance value (0.21) and lowest dominance value was in midland laterites (0.11). Pielou's evenness index (J) estimated how evenly species are distributed in a community. The vegetable cropping system had the lowest species evenness (0.39) while the plantation crops had the highest (0.65). The species were more evenly distributed in midland laterites (0.75), while less evenly in coastal plains (0.42). Total genomic DNA was isolated and mitochondrial Cytochrome Oxidase 1 (CO1) locus was amplified using LCO1490 /HCO2198 primers. DNA sequencing was done by outsourcing. The forward and reverse COI sequences were trimmed using BioEdit Sequence Alignment Editor software and assembled using CAP3 sequence assembler. Molecular analysis of 20 sequences representing 17 species was done using MEGA11 software. Homology analysis of 14 DNA sequences, encompassing 13 distinct species using Nucleotide BLAST of NCBI revealed a substantial similarity of over 98 per cent when compared to sequences present in the NCBI database. Six sequences of four species showed less than 90 per cent similarity to other sequences in the NCBI database. Phylogenetic trees were constructed using MEGA11 software with the Maximum likelyhood method and a bootstrap value of 1000. The analysis incorporated 20 generated sequences in this study and 20 sequences (including Amphix laevigatus as outgroup) retrieved from the NCBI database. The tree formed two major clades, one includes I. cincta and all other species formed the second major clade. Within the second major clade, members of each tribe formed as separate clade except for S. sp. nr. posticalis. Twenty accessions of 17 species were submitted to NCBI and BOLD databases