赤腹寄居姬蜘（Argyrodes miniaceus）之寄主選擇

Abstract

本研究的目的在於了解赤腹寄居姬蜘（Argyrodes miniaceus）如何選擇寄主，包括搜尋寄主時期是否有能力辨別寄主？入侵蛛網後是否會被寄主排斥？以及寄主蛛網上食物資源與同種密度對寄居姬蜘滯留蛛網時間的影響。實驗於2006年6月至2008年4月進行，共分為四部份：（1）野外調查：了解樣區內寄居姬蜘的寄主偏好，並監測其在寄主蛛網移入移出的狀況；（2）選擇實驗：製作迷宮測試寄居姬蜘是否會利用嗅覺搜尋蛛網？是否會偏好某種寄主或同種個體的蛛絲？（3）滯留時間與寄主種類：將寄居姬蜘引入不同種類蜘蛛網上，測驗寄居姬蜘的滯留時間是否受寄主種類或寄主存在影響？（4）滯留時間與食物資源及同種密度：將寄居姬蜘引入不同食物資源與同種個體密度的人面蛛網上，測驗食物資源與同種密度對滯留時間的影響。根據野外調查的結果，雖然樣區中數量最多、蛛網總面積最大的兩種結網性蜘蛛為人面蜘蛛（Nephila pilipes）與大銀腹蜘（Leucauge magnifica），但超過90%的赤腹寄居姬蜘分布於人面蜘蛛網上。標記監測的結果顯示移入人面蛛網上的寄居姬蜘數量顯著高於移出者。寄居姬蜘不偏好有人面蛛網的路徑，行走時都是沿著蛛絲行走，但不偏好跟隨大銀腹蜘或人面蜘蛛留下的蛛絲。將寄居姬蜘引入人面或大銀腹存在的蛛網時，人面蜘蛛發現寄居姬蜘後並沒有驅趕行為，大銀腹蜘則展現強烈的驅趕行為，直到寄居姬蜘離開，因此受寄主驅趕可能是造成寄居姬蜘分布差異的主要原因。但寄居姬蜘滯留於無主的大銀腹蛛網的時間顯著小於滯留在無主的人面蛛網的時間，顯示寄居姬蜘仍有主動選擇的偏好。同種個體密度不影響寄居姬蜘在網上的滯留時間，但食物資源越少，寄居姬蜘滯留於人面蛛網上的時間越短，同時滯留時間與獵捕行為的比例有顯著的正相關，顯示食物獲取是影響寄居姬蜘停留時間的重要因子。本研究顯示造成自然環境中赤腹寄居姬蜘在人面蜘蛛的蛛網上的數量遠大於在大銀腹蜘蛛網上的主要原因有3個：（1）寄主反應的差異，（2）赤腹寄居姬蜘選擇寄主蛛網的差異，（3）食物獲取率的差異。

The goal of this research was to study how the red abdomen Argyrodes（Argyrodes miniaceus）select their two hosts Nephila pilipes and Leucauge magnifica by conducting: (1) field survey: to investigate host preference and to monitor the numbers of A. miniaceus; (2) selection experiments: to test whether A. miniaceus would search and select webs by olfaction or by following their silks; (3) Introduction test 1: to test whether host species or host existence would affect remaining time of A. miniaceus on webs; and (4) Introduction test 2: to test whether different level of food availability and density of A. miniaceus would affect remaining time of A. miniaceus. Over 90% A. miniaceus were found on the webs of N. pilipes, and web monitoring revealed that immigration rate was greater than emigration rate. Selection experiments indicated that A. miniaceus preferred walking along silks, but did not show preference for any kinds of silks. When A. miniaceus was introduced to the web of two hosts, L. magnifica showed intensive expelling behavior until A. miniaceus left, whereas N. pilipes hardly showed such behavior. Therefore host response may be an important factor of host preference. Furthermore, the remaining time that A. miniaceus stayed on webs of L. magnifica without host was significantly shorter than that on webs of N. pilipes without host, suggesting that A. miniaceus may able to actively differentiate host. The higher level of food supply on webs, the longer A. miniaceus would stay, and there was a significant positive correlation between forging time of A. miniaceus and their remaining time, suggesting that food intake may affect the remaining time of A. miniaceus. Based on the results, this research concluded that the following factors: (1) response of hosts, (2) active selection of A. miniaceus on the web, and (3) food availability are the most possible reasons why A. miniaceus prefer the webs of Nephila pilipes.