Bridging the molecular gap in one of the world’s most endemic earthworm faunas through a strategic roadmap from India

Abstract

Earthworms are vital ecosystem engineers that sustain soil health and agricultural productivity. India harbors 497 described species (approximately 8.4% of global diversity), with nearly 71% endemism; however, this diversity remains poorly characterized at the molecular level. DNA sequence data are currently available for only 144 species (28.97%), leaving a substantial research gap of 353 species (71.03%). Of the species represented in molecular databases, 116 are supported by sequences generated from Indian specimens, while 28 sequences were generated from specimens collected outside India, primarily representing exotic species. However, among the 144 species sequences, 26 species were sequenced by both Indian and outside-country researchers owing to their peregrine nature. Only three families, predominantly represented by peregrine species, exhibit complete molecular coverage. In contrast, the majority of Indian earthworm diversity is concentrated in three dominant families: Megascolecidae (208 species), Acanthodrilidae (138 species), and Moniligastridae (101 species). These families show substantial molecular gaps, with 152 unsequenced species in Megascolecidae, 104 in Acanthodrilidae, and 77 in Moniligastridae. Megascolecidae represents the largest absolute knowledge gap and therefore constitutes the highest priority for targeted sequencing efforts. A strategic roadmap emphasizing systematic sampling, DNA barcoding, and collaborative genomic initiatives focused on these priority families could substantially increase national molecular coverage, with approximately 80% coverage over the next decade representing an illustrative, resource-dependent target rather than a guaranteed outcome. Such progress would significantly enhance understanding of India’s soil biodiversity in one of the world’s 17 megadiverse countries, encompassing four global biodiversity hotspots, address the declining availability of classical taxonomic expertise, and strengthen ecosystem restoration, soil fertility management, and sustainable agriculture.