Comparative Morphology of Prickles of Rubus croceacanthus (Rosaceae) in Kashima Island and Its Neighbouring Areas

Abstract

Kashima Island (32° 57′ N, 132° 27′ E) is a small island of southern Japan with high population density of sika deer (Cervus nippon). To ascertain whether heavy sika deer browsing has resulted in increased plant defences on the island, we conducted a morphological comparison of Rubus croceacanthus H. Lév. (Rosaceae) on Kashima Island and in the neighbouring areas on the mainland. We measured the length and density of the leaf and stem prickles. We found that the prickles of R. croceacanthus on Kashima Island were significantly longer and at a higher density than those in the neighbouring areas, suggesting that increased prickle length and density is an adaptive defence against sika deer browsing.

Morphological Study of <i>Glochidion obovatum</i> under Heavy Browsing Pressure by Sika Deer

“…G. obovatum has no prickles on its leaves and stems and instead develop spine-like branches [15] (Figure 2(b)). Thus, the spine-like branch of this species is morphologically and embryologically different from the prickles of the Rubus species, which were previously reported by Takei et al 2013Takei et al , 2014b [13].…”

“…38.5/km 2 ) [11], and therefore, the population of two Rubus species, R. sieboldii Blume and R. croceacanthus H. Lév., has recently increased in this island [12] [13]. These plant species may have increased physical defence by changing of prickles under the high browsing pressure by sika deer because they have many prickles on leaves and stems, and the differences between individuals in the spinescence induced by browsing sika deer indicate phenotypic variation.…”

Nonglandular prickle formation is associated with development and secondary metabolism‐related genes in Rosa multiflora

“…Moreover, prickles are found to increase in size and number in the presence of herbivory (Milewski et al 1991; Perevolotsky & Haimov 1991; Young et al 2003). For example, Rubus croceacanthus bears significantly long and dense prickles and Zanthoxylum ailanthoides display long prickles to protect from sika deer browsing, suggesting that the increase in prickle length and density is an adaptive defense strategy (Takei et al, 2014a, 2014b).…”

“…Zanthoxylum ailanthoides display long prickles to protect from sika deer browsing, suggesting that the increase in prickle length and density is an adaptive defense strategy (Takei et al, 2014a(Takei et al, , 2014b.…”