Walls Susan C
Department of Biology, The City College of The City University of New York, Convent Avenue at 138th Street, 10031, New York, NY, USA.
Oecologia. 1995 Jan;101(1):86-93. doi: 10.1007/BF00328904.
The aquatic larvae of two species of salamanders coexist as a result of differences in their competitive abilities: Ambystoma talpoideum is a superior aggressor, whereas A. maculatum is a superior forager. I examined the behavioral mechanisms that permit these species to coexist with their predatory congener, A. opacum. I asked whether the two prey species differ in their vulnerability to predation and in their use of structural and spatial refugia when under the risk of predation; such inter-specific variation may allow predation to contribute indirectly to prey coexistence. Larval A. maculatum (the superior forager) was more vulnerable to predation by A. opacum than was A. talpoideum, and only the latter species significantly increased its use of structural refugia (leaf litter) in the presence of the predator. In pond enclosures, both species of prey exhibited diel patterns of microhabitat use; significantly more larvae occupied shallow regions of enclosures during the day and migrated to deeper water (a spatial refugium) at night. However, when considered separately, neither (1) the presence of a predatory larval A. opacum nor (2) an increased density of intra- and interspecific competitors significantly altered this habitat shift for either prey species. Rather, diel microhabitat usage in A. talpoideum was significantly affected by an interaction between predator presence and competitor density. My results demonstrate the importance of refugia to coexistence in this predator-prey assemblage. Furthermore, predation by A. opacum may mediate prey competition; that is, preferential consumption of A. maculatum may reduce the competitive impact of this superior forager on A. talpoideum, thus enhancing their coexistence.
墨西哥钝口螈是更强的攻击者，而斑泥螈是更强的觅食者。我研究了使这些物种与其捕食性同类——不透钝口螈共存的行为机制。我探讨了这两种猎物物种在被捕食的易感性以及在面临捕食风险时对结构和空间避难所的利用方面是否存在差异；这种种间差异可能使捕食间接促成猎物的共存。与墨西哥钝口螈相比，斑泥螈幼体（更强的觅食者）更容易被不透钝口螈捕食，并且只有后者在有捕食者存在时显著增加了对结构避难所（落叶层）的利用。在池塘围栏中，两种猎物都表现出微生境利用的昼夜模式；白天有更多的幼体占据围栏的浅水区，晚上则迁移到更深的水域（一个空间避难所）。然而，单独考虑时，（1）捕食性不透钝口螈幼体的存在以及（2）种内和种间竞争者密度的增加都没有显著改变任何一种猎物物种的这种栖息地转移。相反，墨西哥钝口螈的昼夜微生境利用受到捕食者存在和竞争者密度之间相互作用的显著影响。我的结果证明了避难所在这种捕食者 - 猎物组合中共存的重要性。此外，不透钝口螈的捕食可能会调节猎物之间的竞争；也就是说，对斑泥螈的优先捕食可能会降低这种更强的觅食者对墨西哥钝口螈的竞争影响，从而增强它们的共存。
