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首页> 外文学位 >Introduced bullfrogs (Rana catesbeiana) in British Columbia: Impacts on native Pacific treefrogs (Hyla regilla) and red-legged frogs (Rana aurora).
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Introduced bullfrogs (Rana catesbeiana) in British Columbia: Impacts on native Pacific treefrogs (Hyla regilla) and red-legged frogs (Rana aurora).

机译：在不列颠哥伦比亚省引入了牛蛙（Rana catesbeiana）：对本地太平洋树蛙（Hyla regilla）和红脚蛙（Rana aurora）的影响。

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Introduced species are considered one of the greatest threats to biodiversity, next only to habitat destruction. I studied the ecology, distribution, and impacts of one such introduced species: the American bullfrog (Rana catesbeiana). Bullfrogs were introduced to British Columbia in the 1930's for the farming of frog legs. The frog farms were not economically successful and the bullfrogs were introduced to the wild. Call surveys and information from naturalists and the public was collated to map the current distribution of bullfrogs in British Columbia. Populations of bullfrogs are found in southern British Columbia, on Vancouver Island, on the Lower Mainland, in the Gulf Islands and in the Okanagan.; Natural history data and observations on marked populations in the Greater Victoria area were used to study the ecology of bullfrogs. The population ecology of bullfrogs was very similar to that in their native range in eastern North America and was governed by seasonal rhythms of air and water temperature. Bullfrog populations are expanding their range due to introduction by humans into new habitats and through migration.; Bullfrogs are considered a key species in structuring the anuran community composition in their native habitat. I examined the impact of bullfrogs on native Pacific treefrogs (Hyla regilla) and red-legged frogs (Rana aurora), focusing mainly on larval competitive interactions. Using Capture-Mark-Recapture techniques, I estimated survival of treefrog tadpoles in ponds with and without bullfrogs. I was unable to detect a difference caused by bullfrogs over the natural variation in treefrog tadpole survival rates among ponds. In artificial pond experiments I was able to show that bullfrog tadpoles had a negative effect on the development rate of the two native tadpoles and on the growth rate of red-legged frog tadpoles. Bullfrogs did not affect the survival rate of the native tadpoles in these experiments.; The demography of bullfrog populations was studied using four marked populations in the Greater Victoria area. The life-cycle of the bullfrog consisted of two alternate larval development trajectories. Tadpoles could either metamorphose after a year in the larval stage (fast-track) or spend two years in the larval stage (slow-track). Bullfrogs attained sexual maturity two years following metamorphic transformation. Linear, stage-based matrix models were used to assess the factors controlling bullfrog population growth rate. Population growth rates were most sensitive to the proportion of tadpoles entering the fast-track option of the larval life-cycle and to early post-metamorphic survival rates.; This study adds to previous published studies that have documented negative effects of bullfrogs on native species. I assessed the most effective methods of bullfrog population control. Based on logistics and on perturbation analysis of population matrix models, the most effective stages to cull are the early post metamorphic stages: metamorphs and juveniles. However, all bullfrog control efforts are bound to be expensive and labour intensive. Habitat modification to favour native species and permit coexistence with bullfrogs may be the more effective long-term management option.
机译：引入物种被认为是对生物多样性的最大威胁之一，仅次于栖息地破坏。我研究了一种这样的引进物种：美国牛蛙（Rana catesbeiana）的生态，分布和影响。牛蛙在1930年代被引入不列颠哥伦比亚省，用于养殖蛙脚。蛙场在经济上并不成功，牛蛙被引入野外。整理了来自自然学家和公众的电话调查和信息，以绘制不列颠哥伦比亚省牛蛙目前的分布图。在不列颠哥伦比亚省南部，温哥华岛，中低陆平原，海湾群岛和欧肯娜根发现了牛蛙种群。大维多利亚地区的自然历史数据和对标记种群的观察被用来研究牛蛙的生态。牛蛙的种群生态与北美东部的原生动物非常相似，并且受空气和水温的季节性节律的控制。由于人类被引入新的栖息地并通过迁徙，牛蛙种群的范围正在扩大。牛蛙被认为是在其原生栖息地构建无脊椎动物社区组成的关键物种。我研究了牛蛙对本地太平洋树蛙（Hyla regilla）和红脚蛙（Rana aurora）的影响，主要侧重于幼虫竞争性相互作用。使用Capture-Mark-Recapture技术，我估计了有或没有牛蛙的池塘中树蛙t的存活。我无法发现牛蛙对池塘中树蛙t存活率自然变化的影响。在人工池塘实验中，我能够证明牛蛙t对两个天然t的发育速度和红脚蛙t的生长速度具有负面影响。在这些实验中，牛蛙并没有影响天然t的存活率。使用大维多利亚地区的四个标记种群来研究牛蛙种群的人口统计学。牛蛙的生命周期由两种幼体发育轨迹组成。 could可能在幼虫期一年后（快速繁殖）变态，或在幼虫期花费两年（缓慢繁殖）变质。牛蛙在变态转化后两年就达到了性成熟。基于阶段的线性矩阵模型用于评估控制牛蛙种群增长率的因素。人口增长率对entering进入幼虫生命周期的快速通道选择的比例以及早期的变态后存活率最敏感。这项研究增加了以前已发表的研究，这些研究已经证明了牛蛙对本地物种的负面影响。我评估了牛蛙种群控制的最有效方法。根据后勤和人口矩阵模型的扰动分析，最有效的剔除阶段是变态后的早期阶段：变态和幼体。但是，所有的牛蛙控制工作注定都是昂贵且劳动密集的。改变栖息地以有利于本地物种并允许与牛蛙共存可能是更有效的长期管理选择。

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