| Abstract: |
The Indo-Burma biodiversity hotspot is one of the most biologically diverse regions of the world and supports highly heterogeneous tropical and subtropical ecosystems. While its above-ground biodiversity has received considerable scientific attention, knowledge of below-ground fauna, particularly earthworms, remains fragmented. Earthworms are important ecosystem engineers that regulate organic matter decomposition, nutrient mineralization, soil aggregation, aeration, infiltration and microbial activity. The present study reviews and quantitatively synthesizes available information on the taxonomic diversity, biogeographical status and habitat preferences of earthworms in the Indian component of the Indo-Burma biodiversity hotspot, with particular emphasis on north-eastern India. Published inventories report 128 earthworm species/subspecies belonging to 26 genera and nine families, including 72 endemic, 18 near-endemic, five native peregrine and 32 exotic taxa. More recent ecological synthesis has documented approximately 125 species representing 28 genera and 10 families across north-eastern India, with recorded richness varying considerably among states and habitats. Forest ecosystems generally support greater species diversity and a higher representation of native taxa, whereas agricultural, plantation and anthropogenically disturbed habitats are frequently characterized by adaptable and peregrine species. In Assam, reported earthworm densities ranged from approximately 65 to 238 individuals m⁻² and biomass from 1.1 to 5.4 g m⁻² across different habitats. Comparative observations in Manipur recorded 12 species in natural mixed forest compared with only four in an oak plantation. Mixed forests across the region have reported Shannon diversity values of approximately 1.76–2.72, whereas highly disturbed municipal waste habitats may show values as low as 0.42. Recent discoveries of previously unknown Eutyphoeus, Metaphire, Perionyx and Drawida species further demonstrate that the region's earthworm diversity remains inadequately explored. Soil moisture, organic carbon, pH, temperature, litter quality, vegetation heterogeneity, elevation and land-use intensity emerge as important determinants of earthworm distribution. The findings highlight the importance of integrating morphological taxonomy, DNA barcoding, ecological monitoring and habitat conservation to protect soil biodiversity in the Indo-Burma hotspot. |
