Distribution of soil testate amoeba assemblages along an elevation gradient on Mount Fuji (Japan)

Elevation gradients have been useful to study distributional patterns of soil organisms since the time of Humboldt but only recently these patterns have been studied for soil microorganisms. Here we report the results on species diversity and composition of soil- and moss-dwelling testate amoeba assemblages along a 1400 m elevation gradient (904-2377 m a.s.l.) on Mount Fuji (Japan) from temperate forest to alpine vegetation. In total, 95 testate amoeba taxa belonging to 29 genera were identified. The core of testate amoeba assemblages was formed by ubiquitous species such as Trinema lineare, Euglypha laevis, Cryptodifflugia oviformis, and Trinema complanatum. However, several taxa with limited geographic distribution were also observed (e.g., Centropyxis latideflandriana, C. stenodeflandriana, Plagiopyxis cf. barrosi, Heleopera rectangularis, and Distomatopyxis couillardi). Species diversity indices (species richness and Shannon's index) were characterised by bell-shaped patterns peaking at ∼ 1700 m in the subalpine mixed conifer-deciduous forest. The species composition of testate amoeba assemblages was best explained by the vegetation types which accounted for 12.3% of the total variation. Overall, these findings indicate that elevation effects on species composition of testate amoeba assemblages are strongly mediated by vegetation.