Earthworm diversity in an unexplored Himalayan landscape: Patterns across forest, orchard and crop field ecosystems

The present study was undertaken to explore the earthworm diversity in the Bani Valley, situated at an elevation range of 1200-2000 m above sea level, in the western Himalayan Region. Over the course of two years (March 2021 to January 2023), eight earthworm species were documented in three distinct habitat-types (forest, orchard and crop field), characterised by varying levels of anthropogenic interference. Notably, the crop field habitat exhibited highest earthworm density as well as biomass, while the forest habitat was observed to exhibit least earthworm abundance despite negligible human interference. Year-wise comparison showed that Octolasion tyrtaeum exhibited the highest mean density during both the years [34.31± 2.54 m-² (2021-22) and 27.91 ± 1.88 m-² (2022-23)], while the least density was recorded for Amynthas corticis (2.84 ± 1.06 m-²) during 2021-22, but for Drawida nepalensis (1.60 ± 0.63 m-²) during 2022-23 period. Moreover, an aggressive dominance of exotic earthworm species was observed in the study area with the occurrence of only one native species i.e. Drawida nepalensis. Maximum Likelihood Phylogram analysis of different earthworm species revealed three major clades, largely consistent with classical taxonomy. However, intergeneric clustering between Drawida nepalensis and Octolasion tyrtaeum suggests a potential case of cryptic similarity warranting further investigation. Analysis of Variance followed by multivariate ordination through canonical correspondence analysis suggested that the earthworm community structure was governed by the interactive effects of different soil physico-chemical properties. Despite the valuable insights with regard to earthworm diversity of the Bani Valley, further investigations are required in other unexplored patches to develop a comprehensive inventory of the earthworm fauna of the Himalayan Region.