Dissertation Research: Effects of the aquatic:terrestrial habitat ratio on an amphibian predator and its prey

生境破坏会改变剩余生境的孤立程度和形状，从而对生物多样性和生态系统的功能产生重大影响。虽然不太受重视，但过度破坏一种类型的栖息地也会改变景观中不同栖息地类型的比例。例如，湿地排水不仅会减少景观中水生栖息地的数量，还会减少水生栖息地与陆地栖息地的比例。对于需要同时使用水生和陆地栖息地类型的生物，如两栖动物，水生和陆地栖息地比率的变化可以改变它们在任一种栖息地的丰度，以及它们的总体种群动态。对一种长寿的两栖动物斑点蜥蜴(Ambystoma Maculata)的初步调查表明，水生栖息地中斑点蜥蜴幼虫的丰度严重取决于水生和陆地栖息地的比率。由于幼虫是无鱼小池塘的顶级捕食者，它们可以对其猎物的群落组成和多样性产生巨大影响；改变水生和陆地栖息地的比例可以改变这种影响的强度。本研究旨在阐明景观中水生与陆生生境比例与斑点幼虫对水生群落的影响之间的关系。它将特别关注斑纹蛙捕食对两种不同程度利用陆生和水生生境的青蛙种群动态的影响，采用标记-重新捕获和人口建模的方法。两栖动物种群下降的研究通常集中在水生栖息地和影响幼体存活和生长的因素上。然而，越来越多的证据表明，陆地栖息地对许多两栖动物种群来说是重要的。要了解两栖动物如何应对不同类型的栖息地破坏(如毁林、湿地流失)，需要考虑两栖动物的整个生命周期，以及景观中水生和陆地栖息地的比例。这项研究将是对保护文献和旨在防止两栖动物未来灭绝的管理努力的及时贡献。

Habitat destruction can change the degree of isolation and shape of remaining habitats, and thus can have dramatic consequences for biodiversity and the functioning of ecosystems. Although less appreciated, disproportionate destruction of one type of habitat will also change the ratio of distinct habitat types in a landscape. For example, wetland draining will not only decrease the amount of aquatic habitat in a landscape, but will also decrease the ratio of aquatic to terrestrial habitats. For organisms that require the use of both aquatic and terrestrial habitat types, such as amphibians, changes in the ratio of aquatic to terrestrial habitats can alter their abundance in either habitat, as well as their overall population dynamics. Preliminary surveys of a long lived amphibian, Ambystoma maculatum (the spotted salamander), indicate that the abundance of larval A. maculatum in aquatic habitats depends critically upon the ratio of aquatic to terrestrial habitat available. Because larval A. maculatum are top predators in small fishless ponds, they can have dramatic effects on community composition and diversity of their prey; alterations to the ratio of aquatic to terrestrial habitats can alter the strengths of this effect. This research seeks to elucidate the relationship between the ratio of aquatic to terrestrial habitats in a landscape and the impacts of larval A. maculatum on the aquatic community. It will specifically focus on the influence, of A. maculatum predation on the population dynamics of two frog species that utilize terrestrial and aquatic habitats to different extents, using mark-recapture and demographic modeling approaches.Studies of declining populations of amphibians typically focus on aquatic habitat and factors that affect larval survivorship and growth therein. Yet, there is increasing evidence of the importance of terrestrial habitat for many amphibian populations. Understanding how amphibians will respond to different types of habitat destruction (e.g., deforestation, draining of wetlands) requires consideration of the entire life-cycle of amphibians, and the ratio of aquatic to terrestrial habitats within the landscape. This research will be a timely contribution to the conservation literature and to management efforts aimed at preventing future extinctions of amphibians.