Plant taxa detected in the faeces of the critically endangered Japanese land snail Euhadra murayamai using chloroplast DNA analysis

Understanding the composition of omnivores’ diet in their habitats is difficult, especially in endangered taxa. Faecal DNA metabarcoding could be one of non-invasive methods that may help resolve this problem. The critically endangered Japanese land snail Euhadra murayamai Habe, 1976 has only been recorded from a single vertical limestone cliff, where direct examination of its feeding ecology is physically difficult. We obtained sufficient sequencing reads of a partial chloroplast trnL intron region from faeces of 10 and 4 individuals sampled in July and October, respectively. The operational taxonomic unit (OTU) compositions detected from these samples were similar between these months. In total, 14 of 45 OTUs were assigned at or below the order level using an automated pipeline. Subsequent manual BLAST searches, combined with verification against plant species recorded during field surveys, enabled assignment to 10 different species across eight orders. These results support that E. murayamai eats plant-derived materials from diverse plant taxa in its habitat. Our findings highlight the methodological potential of faecal DNA analysis for investigating the ecological resources of terrestrial molluscs.