Diversity and assemblage patterns of ladybirds (Coccinellidae) in different crop management practices in Peninsular Malaysia

Abstract

Ladybirds (Coleoptera: Coccinellidae) are important predatory insects found in many croplands, but their patterns of diversity and assemblage in diverse crop management practices remain understudied, especially in southeastern Asia. Their existence denotes a crucial need to update the diversity and assemblage pattern in diverse crop management practices. This study aims to (i) delimit ladybird species through DNA barcodes and (ii) compare the abundance of different ladybird taxa from different crop management practices. A total of 2260 ladybirds were collected and barcoded resulting in 12 species representing four subfamilies (Coccidulinae, Coccinellinae, Epilachninae, and Scymninae). Three predatory species dominated and were top contributors to the dissimilarity average for different crop management practices, i.e., Coccinella transversalis, Micraspis discolor, and Cheilomenes sexmaculata. Even though the effect of different crop management practices on ladybird abundance was insignificant (Kruskal Wallis, p-value > 0.05), their diversity significantly varied across different practices (diversity t-test, p-value < 0.05). Organic monocrop resulted in a higher value of Shannon index (H’), and richness than other management practices. Furthermore, monocrops comprised higher ladybird diversity than multicrops. While the species assemblage was not distinct (ANOSIM, p-value > 0.05), a variation in assemblage composition and spatial distribution concerning the different crop management employed (NMDS, stress value = 0.12) was observed. The hierarchical dendrogram distinguished six clusters of ladybirds between organic and conventional management practices. More explorations are required to uncover the various effects of crop management practices on ladybirds’ fitness and survival in different landscapes.