Skip to main content
Dryad

Data for: Latitudinal gradients in the species diversity of Japanese earthworms

Nendai, Noriko1; Sato, Chika2; Sota, Teiji2; Okuzaki, Yutaka3; Nagata, Nobuaki4; Minamiya, Yukio5; Miyano, Jun1; Ikeda, Hiroshi6

Published May 14, 2026 on Dryad. https://doi.org/10.5061/dryad.b8gtht7nd

Data files

May 14, 2026 version files 891.41 KB

Click names to download individual files

Abstract

Although a latitudinal gradient of species diversity is known for diverse animal groups, few detailed studies on this topic exist for soil animals. Our study aimed to clarify the formation process of latitudinal gradients in the species diversity of soil animals in terms of dispersal and evolutionary processes using terrestrial earthworms. We used 4074 earthworms collected from 131 sites in the Japanese archipelago between 31.7°N and 45.1°N. Because morphological classification was difficult for these earthworms, especially for juveniles, we employed a DNA-based method for species delimitation. We used the DNA data for phylogenetic diversity indices and population genetic analysis in subsequent community-ecological analyses. We analysed latitudinal changes in local and regional species diversity and the replacement and nested structures among species assemblages using phylogenetic diversity indices and examined whether environmental factors and the ecological traits of earthworms related to dispersal ability contribute to geographic diversity patterns. Our earthworm samples comprised 113 megascolecid and nine lumbricid molecular operational taxonomic units (MOTUs). The species assemblage of Megascolecidae presented higher γ-, β- and α-diversity at lower latitudes affected by temperature, precipitation and snow depth. Overall β-diversity was greater at lower latitudes, reflecting greater spatial turnover due to greater γ-diversity with more local species at lower latitudes. In contrast, relatively high nestedness was observed at highest latitudes, where γ-diversity and overall β-diversity were lowest and spatial turnover was minimal, suggesting that high-latitude species assemblages were formed through the range expansion of a subset of species from lower latitudes. Such range expansion was likely facilitated for potentially parthenogenetic species. In contrast, Lumbricidae presented greater γ-diversity at higher latitudes and a converse nested structure from high to low latitudes. Our study demonstrated that DNA-based species delimitation is necessary to understand the exact geographic diversity pattern and its formation process for organisms whose morphological classification is difficult. The contradistinctive species-assemblage patterns between related earthworm groups might be considered to have resulted from their low dispersal ability, different biogeographical histories, and characteristic topography in the Japanese Archipelago, which covers a latitudinally wide range.