Quantitatively effective seed dispersers of three species of <i>Rubus</i>, in a Japanese cedar plantation, Central Japan

Most Rubus species (Rosaceae) are pioneer shrubs that quickly invade and increase when open conditions form in suitable habitat, and are typical endozoochorous plants, whose fruits are consumed by a variety of birds and mammals. Quantitative seed dispersal is characterized as the number of fruits removed from plants by wildlife. By use of camera-traps, we recorded fruit removal from three species of Rubus (R. hirsutus, R. palmatus, and R. crataegifolius), and identified the wildlife species of quantitatively effective seed dispersers in a cedar plantation. The study was conducted from May 9 to July 10, 2019, on Rubus that established after thinning in a cedar plantation at the Forestry Experimental Station of Ishikawa Agriculture and Forestry Research Center in Ishikawa Prefecture, Central Japan. Camera traps (Ltl Acorn6210MC) recorded fruit removal by frugivores of 108 fruits on the branches for R. hirsutus, 489 fruits on the branches and 32 fruits on the ground for R. palmatus, and 168 fruits on the branches for R. crataegifolius. Most of the fruits monitored were rapidly removed from the trees for all three Rubus species: 83% of monitored fruits were removed after three weeks. The top species with high fruit removal were Japanese Macaque Macaca fuscata (30.4% of the total number of fruits removed), Japanese Badger Meles anakuma (27.8%), and Brown-eared Bulbul Hypsipetes amaurotis (19.0%) for R. hirsutus, H. amaurotis (59.7%) and M. fuscata (37.4%) for R. palmatus, and H. amaurotis (78.2%) and M. fuscata (20.4%) for R. crataegifolius. The germination rate of R. crataegifolius seeds dispersed by Hypsipetes amaurotis was 3.2% (N=189). Due to the high number of fruits removed, we concluded that these frugivore species are highly effective as quantitative dispersal of these Rubus species. We assumed the effectiveness of the three frugivores as qualitative (germination performance of seeds) seed dispersers because they disperse intact seeds in a dispersal area ranging from tens of hectares to several square kilometers, depending on species.