Biodiversity of beetles: The phylogenetic composition of beetle communities across tropical forests of the world

Abstract

This thesis examines the phylogenetic diversity patterns of beetle (Coleoptera) communities across tropical forests by developing and implementing molecular methodologies. A novel protocol for authenticating amplicon sequence variants was designed using 10,395 specimens representing 98 families from 11 countries, integrating abundance-based filtering with phylogenetic placement to achieve an authentication success rate of 82.34%. Multivariate analysis identified preservation methodology (χ² = 145.00, p < 0.001) and sequencing protocols (χ² = 287.45, p < 0.001) as primary determinants of authentication outcomes. Machine learning frameworks were implemented to automate sequence authentication, with DNA barcoding and metabarcoding pipelines achieving an accuracy of 99.80%. Field applications in Thailand's protected areas yielded 1,800 specimens (71 families) processed via mitogenomics (187 mitogenomes), DNA barcoding (584 sequences), and metabarcoding (608 operational taxonomic units, or OTUs). Phylogenetic analysis revealed that Thai specimens (1.54% of the global dataset) contributed disproportionately to total phylogenetic diversity (3.23%, p<0.01). Community structure analysis revealed significant phylogenetic clustering at Khao Yai National Park (NRI = 1.875207, p < 0.001) and overdispersion at Sakaerat Environmental Research Station (NRI =-0.82255, p < 0.01). Comprehensive phylogenetic analysis integrated 12,320 mitochondrial genome sequences, establishing sequential infraorder diversification in Polyphaga spanning approximately 56 million years (254.3-198.5 Ma). The lineages-through-time analysis identified an inflexion point at approximately 120 MYA, coinciding with angiosperm radiation. This research advances the understanding of beetle diversity while establishing methodological frameworks for molecular biodiversity assessment in hyperdiverse taxa.Open Acces