The Length and Density of Prickles on &amp;lt;i&amp;gt;Zanthoxylum ailanthoides&amp;lt;/i&amp;gt; (Rutaceae): A Comparison of Japanese Islands with Different Sika Deer Browsing Pressures

Tatsuya Fukuda,Jun Yokoyama,Ryo Arakawa,Satoru Yamada,Hiroshi Hayakawa,Katsura Ito,Shin-Ichi Tebayashi,Shogo Takei,Kazuhiro Yoshioka

doi:10.4236/ajps.2014.53046

Abstract

To determine the effects of sika deer (Cervus nippon) browsing on the physical defences of the Japanese pricklyash “Zanthoxylum ailanthoides Sieb. et Zucc.” (Rutaceae), we compared the length and density of prickles on Japanese islands which were under different browsing pressures. We measured the length and density of prickles on the midribs, leaf rachis, and stems. We found that the prickles of Z. ailanthoides on Kashima island were not significantly longer or at higher densities than those in the neighbouring areas; the longest pickles at the highest densities were found on Akune island. The density of sika deer on Akune (ca. 520-600/km2) was higher than that on Kashima (ca. 38.5/km2), and consequently, Akune was under greater browsing pressure. Our results suggest that the increased length and density of prickles on Akune is a response by Z. ailanthoides to the high density of sika deer found on the island.

Highlights

Plants have developed numerous physical and chemical defences against herbivores
We investigated whether Z. ailanthoides plants on Kashima have developed long prickles to resist browsing by sika deer, as have R. sieboldii plants
Z. ailanthoides samples were collected from Kashima and Akune, and 5 areas close to Kashima (Komo Cape, Yokonami, Kurotaki, Hitsuzan, and Muroto) in 2012 and 2013 (Figure 1, Table 1)

Summary

Introduction

Plants have developed numerous physical and chemical defences against herbivores. Such defences are considered beneficial because they reduce herbivory, and increase plant fitness [1]. The physical defences of plants are required to withstand abiotic factors, such as wind damage, and biotic factors, such as herbivory. The Japanese sika deer (Cervus nippon) eats a wide variety of plants and is a gregarious species. Sika deer have a large impact on agricultural and forested vegetation in Japan [2], and on the islands of southern Japan, are important in seed dispersal, the small seeds of graminoids [6,7]

Objectives

Methods

Results