台灣北部溪流蛙類資源分配與人為干擾對資源利用影響之研究

Abstract

摘要 共域物種如何利用有限資源，降低彼此的競爭以達到共存，一直是生態學家感興趣的課題。台灣擁有高度生物多樣性和多樣化的棲地類型，特別適合探討物種資源利用相關研究。本研究自2004年4月至2005年8月，在台北縣石碇鄉的烏塗庫溪對河道中共域蛙種進行資源分配的研究調查，利用生態棲位寬度與生態棲位重疊度指數估算出物種在時間、空間及食性等資源利用上的差異，探討共域蛙種間資源分配利用的策略。此外亦探討人為干擾所造成的棲地變化，對溪流蛙類優勢種的褐樹蛙，在時間、空間及食性資源利用上的影響。 研究期間，共記錄到3科7種蛙類：盤古蟾蜍（Bufo bankorensis）、腹斑蛙（Rana adenopleura）、古氏赤蛙（Rana kuhlii）、拉都希氏赤蛙（Rana latouchi）、斯文豪氏赤蛙（Rana swinhoana）、面天樹蛙（Chirixalus idiootocus）及褐樹蛙（Buergeria robustus）。由於腹斑蛙、古氏赤蛙與面天樹蛙等三個物種樣本數不足，本研究將不列入分析。利用IRI相對重要指數分析各物種最重要的食物類型發現，在褐樹蛙和拉都希氏赤蛙為鱗翅目幼蟲、在盤古蟾蜍為倍足綱的馬陸，而斯文豪氏赤蛙則為蜚蠊目的昆蟲。在生態棲位寬度方面，拉都希氏赤蛙在時間資源（BA = 0.502）、棲地資源（BA = 0.403）與食性資源（BA = 0.418）方面具有最大的寬度；在生態棲位重疊度方面，盤古蟾蜍與拉都希氏赤蛙之間具有最大的時間棲位重疊度（O = 0.778），褐樹蛙與斯文豪氏赤蛙之間具有最大的棲地棲位重疊度（O = 0.854），褐樹蛙與拉都希氏赤蛙間在食性資源利用上較為相近（O = 0.779）。共域物種間在一項資源利用的重疊度高時，則其餘資源的重疊度會有降低的現象，顯示物種間會以不同資源項目減少競爭。 人為干擾造成的棲地差異中，環境中底石組成與隱蔽場所的多寡發生變化，會影響褐樹蛙出現的數量；在食性資源利用上，環境中植被多寡會影響攝食比例，並改變褐樹蛙的食性組成。結果顯示，蛙種間主要以食性資源利用上的差異達到共存。有限度的環境干擾，對溪流蛙類而言並非只有負面的影響。Abstract Ecologists are interesting to know how sympatric species can coexist to decrease interspecific competition. Because of having high specie and habitat diversity in Taiwan, it is appropriate to investigate about resource partitioning among species in a community. This study was conducted from April 2004 to August 2005, in Wu-too-ku stream of Taipei County .The main purpose of this research was to investigate the resource partitioning among sympatric frogs in a stream by using the index of niche breadth and niche overlap. Meanwhile we also explored the effects of human disturbance in resources utilization of Buergeria robustus in Wu-too-ku stream. A total of 7 species were recorded from study site, Rana adenopleura, Rana kuhlii and Chirixalus idiootocus, were present only in small numbers. Their data were not analyzed. The major food items of Buergeria robustus and Rana latouchi were Lepidoptera larvae, Chilognatha for Bufo bankorensis, Blattodea for Rana swinhoana, calculated by the IRI index. Indexes of niche breadth indicated that the temporal (0.502), habitat (0.403), and diet (0.418) breadth of Rana latouchi were the widest among 4 species. Indexes of niche overlap indicated that the highest niche overlap was seen between Bufo bankorensis and Rana latouchi in temporal aspect (0.778), Buergeria robustus and Rana swinhoana with the greatest niche overlap in habitat aspect (0.854), and Buergeria robustus and Rana Rana latouchi with the greatest niche overlap in diet aspect (0.779).Results from our study suggests that sympatric species reduce interspecific competition by shifting in niche overlap in various aspects. The component of rocks and difference in vegetation along riparian zones were considered the main reasons which decrease on amphibian abundance in human disturbance area. The density of vegetation affected the components of diet on Buergeria robustus. These findings suggest that difference in feeding habitats is the main mechanism to decrease the interspecific competition among sympatric frog species in a stream. It seems that human disturbance may provide some benefits for certain species of frogs.