Forage plants of Lagopus muta japonica at Mt. Hiuchi identified using DNA metabarcoding

Abstract

Abstract: Mt. Hiuchi, in Niigata Prefecture, central Honshu, Japan, lies at the northern range limit of Japanese rock ptarmigan, Lagopus muta japonica. The rapid growth of gramineous plants in the area has reduced the forage available to Japanese rock ptarmigan, and a project to remove these plants is ongoing. To determine the effectiveness of these efforts, it is necessary to characterise how Japanese rock ptarmigan use available forage species. To identify forage plant use at Mt. Hiuchi, we conducted DNA metabarcoding of the rbcL gene on 96 ptarmigan faecal samples from May-July and October, 2019. The resulting sequences were analysed against a combined database of 136 species derived from samples collected from Japanese rock ptarmigan habitats, and the National Center for Biotechnology Information (NCBI). In all, we found evidence of 40 taxa, of which 32 could be identified to species, 4 to genus, 3 to family and 1 to order. Based on rarefaction and extrapolation sampling curves using the exponential of Shannon entropy, we estimated that 98.2% of available forage taxa were sampled over the study period. Of the 12 plant families represented in the combined database, the most foraged were the Apiaceae (found in 62.5% of faecal samples), followed by the Saxifragaceae (53.1%), Ericaceae (52.1%) and Rosaceae (50.0%). In the faecal samples examined, the most frequently encountered plant species were Ligusticum holopetalum (38.5%), Rubus vernus (38.5%), Tiarella polyphylla (37.5%), Micranthes fusca var. kikubuki (36.5%) and Alnus alnobetula subsp. maximowiczii (30.2%). The high foraging frequency of plants in the Apiaceae and Saxifragaceae at Mt. Hiuchi is anomalous among Japanese rock ptarmigan habitats, indicating high local specificity. Our survey further supports the potential of the gramineous plant removal project, to contribute to the restoration and conservation of major ptarmigan forage species. The major forage plants in this area grow around the summit of Mt. Hiuchi and along the margins of Pinus pumila and Alnus alnobetula subsp. maximowiczii communities. Therefore, the growth and expansion of these tree species—and the associated loss of marginal habitat—may also reduce the quality of the feeding environment for Japanese rock ptarmigan. Controlling these tree species should also be considered, along with the continued removal of gramineous plants.