Population fluctuation and intraguild predation among ladybug species (Coleoptera: Coccinellidae) on cotton

Abstract

Insects of the Coccinellidae family, known as ladybugs, are generalist and voracious predators widely found in agricultural environments. Due to these characteristics, ladybugs are commonly used in biological control programs worldwide. Recently, Harmonia axyridis invaded South America, and reports of competition and intraguild predation on other native ladybugs are constant. The cotton culture is affected by many pests, and predators are an alternative for pest control. However, information about species diversity, abundance, population dynamics, and ecological interactions are necessary for these agents' successful use. Our objectives are: (i) to identify (using morphological and molecular characters) the species of Coccinellidae in cotton culture; and (ii) to evaluate population fluctuation and the rate of intraguild predation among three different species of Coccinellidae and correlate with the population density of Aphis gossypii and ladybug species. For this, we collected Coccinellidae larvae throughout the cotton cycle and evaluated the density of A. gossypii for 3 years (2017 to 2019). Molecular identifications of Coccinellidae larvae were performed by morphological characters and via sequencing of a fragment of the cytochrome c oxidase subunit I (COI) gene. The next stages of the project's objectives will be the construction of species-specific primers for the species H. axyridis, Cycloneda sanguinea, and Hippodamia convergens for quantification of intraguild predation via molecular identification of a specific species in the intestinal content of another species. With these results, we hope to contribute to understanding the real impact of H. axyridis on two native ladybug species in Brazil.