History of the terrestrial isopod genus Ligidium in Japan based on phylogeographic analysis

Abstract

Background Phylogeographical approaches explain the genetic diversity of local organisms in the context of their geological and geographic environments. Thus, genetic diversity can be a proxy for geological history. Here we propose a genus of woodland isopod, Ligidium, as a marker of geological history in relation to orogeny and the Quaternary glacial cycle. Results Mitochondrial analysis of 721 individuals from 97 sites across Japan revealed phylogenetic divergence between the northeastern and southwestern Japan arcs. It also showed repeated population expansions in northeastern Japan in response to Quaternary glacial and interglacial cycles. Genome-wide analysis of 83 selected individuals revealed multiple genetic nuclear clusters. The genomic groupings were consistent with the local geographic distribution, indicating that the Ligidium phylogeny reflects its regional history. Conclusion Ligidium DNA sequence analysis can provide insight into the geological, geographical, and paleoenvironmental history of the studied region.

Hidden diversity in eastern North America: The genus Ligidium (Oniscidea, Ligiidae) in the southern Appalachian Mountains

“…The authors suggest that the observed high genetic differentiation may result from strict ecological specialization to very humid soil habitats, causing strong geographic isolation in a relatively dry region such as the Eastern Mediterranean. However similar patterns have been found among temperate, subtropical and montane climates in regions of Japan (Harigai et al, 2020(Harigai et al, , 2023Yoshino & Kubota, 2022) and China, where several new species have been delimited with the help of molecular data (Li, 2017;Wang et al, 2022). Overall, this suggests that Ligidium species have limited dispersal capacities, favouring genetic lineage differentiation and eventually speciation, most likely by allopatric isolation coupled with ecological niche conservatism (Wiens, 2004).…”

“…The genus Ligidium has proven to be more diverse than initially expected in several parts of the Holarctic, after the integration of dense sampling and molecular data (Harigai et al, 2023;Klossa-Kilia et al, 2006;Wang et al, 2022). Integrative taxonomic approaches have found the existence of truly cryptic Ligidium species, hardly diagnosable based on morphological characters (Wang et al, 2022).…”