Smith Kevin G
Department of Ecology and Evolutionary Biology, The University of Tennessee, 569 Dabney Hall, Knoxville, TN 37996-1610, USA.
Oecologia. 2006 Jun;148(2):342-9. doi: 10.1007/s00442-006-0370-y. Epub 2006 Feb 7.
Predation, competition, and their interaction are known to be important factors that influence the structure of ecological communities. In particular, in those cases where a competitive hierarchy exists among prey species, the presence of certain keystone predators can result in enhanced diversity in the prey community. However, little is known regarding the influence of keystone predator presence on invaded prey communities. Given the widespread occurrence of invasive species and substantial concern regarding their ecological impacts, studies on this topic are needed. In this study I used naturalistic replications of an experimental tadpole assemblage to assess the influence of predatory eastern newts, Notophthalmus viridescens, on the outcome of interspecific competition among native and nonindigenous tadpoles. When newts were absent, the presence of the tadpoles of one invasive species, the Cuban treefrog, Osteopilus septentrionalis, resulted in decreased survival and growth rate of the dominant native species, Bufo terrestris, and dominance of the tadpole assemblage by O. septentrionalis. However, the presence of one adult newt generally reduced or eliminated the negative impacts of O. septentrionalis tadpoles, resulting in comparable survival and performance of native species in invaded and noninvaded treatments. Differential mortality among the tadpole species suggests that newts preyed selectively on O. septentrionalis tadpoles, supporting the hypothesis that newts acted as keystone predators in the invaded assemblage. The presence of nonindigenous larval cane toads, Bufo marinus, did not significantly affect native species, and this species was not negatively affected by the presence of newts. Collectively, these results suggest that eastern newts significantly modified the competitive hierarchy of the invaded tadpole assemblage and reduced the impacts of a competitively superior invasive species. If general, these results suggest that the presence of certain species may be an essential factor regulating the ecological impacts of biological invasions.
捕食、竞争及其相互作用是影响生态群落结构的重要因素。特别是在猎物物种之间存在竞争等级的情况下，某些关键捕食者的存在会导致猎物群落的多样性增加。然而，关于关键捕食者的存在对入侵猎物群落的影响却知之甚少。鉴于入侵物种的广泛存在及其对生态影响的大量关注，需要对此主题进行研究。在本研究中，我使用了实验性蝌蚪组合的自然主义复制品，以评估捕食性东方蝾螈（Notophthalmus viridescens）对本地和非本地蝌蚪种间竞争结果的影响。当没有蝾螈时，一种入侵物种古巴树蛙（Osteopilus septentrionalis）的蝌蚪的存在导致优势本地物种北美蟾蜍（Bufo terrestris）的存活率和生长率下降，并且蝌蚪组合被古巴树蛙占据主导地位。然而，一只成年蝾螈的存在通常会减少或消除古巴树蛙蝌蚪的负面影响，导致本地物种在入侵和未入侵处理中的存活率和表现相当。蝌蚪物种之间的差异死亡率表明蝾螈选择性地捕食古巴树蛙蝌蚪，支持了蝾螈在入侵组合中作为关键捕食者的假设。非本地的甘蔗蟾蜍（Bufo marinus）幼虫的存在对本地物种没有显著影响，并且该物种也没有受到蝾螈存在的负面影响。总体而言，这些结果表明东方蝾螈显著改变了入侵蝌蚪组合的竞争等级，并减少了竞争优势入侵物种的影响。如果具有普遍性，这些结果表明某些物种的存在可能是调节生物入侵生态影响的一个重要因素。
