Comparative Analysis of Prickles on Rubus sieboldii (Rosaceae) between Grazed and Ungrazed Areas in Southwestern Shikoku, Japan

Abstract

Kashima Island (32º57′N, 132º27′E) is a very small island (45.1 ha) in southwestern Shikoku, Japan with a high density (ca. 38.5/km 2) of Sika deer (Cervus nippon). To examine induced defences of plants against the Sika deer, we conducted morphological analyses of prickles of Rubus sieboldii Blume (Rosaceae) between grazed (Kashima Island) and ungrazed areas (neighbour locations) in southwestern Shikoku. The length and density of prickles on leaves and around stems were measured. The prickles of the plants on Kashima Island were significantly longer and denser than those of the other areas, implying that the increased length and density of prickles were an induced defence of R. sieboldii on Kashima Island.