A Behavioral Trade-Off and Its Consequences for the Distribution of Pseudacris Treefrog Larvae
A Behavioral Trade-Off and Its Consequences for the Distribution of Pseudacris Treefrog Larvae
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假树蛙幼虫分布的行为权衡及其后果
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发表时间：
1995
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通讯作者：
D. Skelly
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作者：
D. Skelly
幼虫合唱青蛙（Pseudacris triseriata）和春季偷窥者（P.十字花科）显示出显着的差异，它们的分布格局，合唱青蛙往往发生在较低的永久性池塘捕食者密度较低，和春季偷窥者往往发生在更永久的池塘捕食者密度较高。为了理解这种模式，我在两个层面上进行了实验。首先，在社会层面上，我评估的重要性，竞争，捕食，和池塘持久性的幼虫性能的模式。第二，在行为层面，我提出了一个假设，即收益和风险之间的权衡是否构成了生态相互作用的基础，并最终构成了这些物种的表现和分布模式。我采用了现场操作，以评估在不同的池塘，不同的持久性的竞争和捕食的贡献。为了研究种间竞争的影响，围栏包含单独的或在其他物种的同等密度的存在下的每种蝌蚪物种;这些围栏被放置在两个临时池塘，两个中间池塘，和两个永久池塘。蝌蚪放养密度反映了当地的自然密度。该竞争处理与操纵捕食者的存在或不存在的捕食者处理交叉（其中"存在"表示每个池塘内自然发生的密度）。相对性能的模式是一致的相对分布模式，整个池塘的持久性梯度：合唱青蛙表现最好的相对于春季偷窥者在临时池塘，而春季偷窥者表现最好的相对合唱青蛙在永久性池塘（性能测定为生存和增长）。死亡率的主要来源是池塘干燥的临时池塘和捕食更永久的池塘。与以往大多数无尾类幼体的实验研究相反，竞争对蝌蚪的表现影响很小。从现场实验的结果表明，池塘干燥和捕食可能是重要的决定因素的性能，这两个物种是不同的敏感性，这些死亡因素。在一组实验室实验中，我评估了一个假设，即通过活动（移动所花费的时间比例）介导的觅食增益和捕食风险之间的权衡可能解释了Pseudacris分布模式。在这两个物种中，个体在笼中捕食者存在下的活动减少，相应的生长速度下降。一般来说，幼虫合唱蛙也往往更活跃，更快的增长和发展比春天偷窥。这些结果提供了支持的存在的权衡，并表明，种间活动的差异可能有助于模式的幼虫的性能和池塘之间的分布。这种权衡的一般性质表明，它在其他系统中也可能很重要。
Larval chorus frogs (Pseudacris triseriata) and spring peepers (P. crucifer) show marked differences in their distribution patterns, with chorus frogs tending to occur in less permanent ponds containing lower predator densities, and spring peepers tending to occur in more permanent ponds with higher predator densities. In order to understand this pattern I performed experiments at two levels. First, at the community level, I evaluated the importance of competition, predation, and pond permanence for patterns of larval performance. Second, at the behavioral level, I asked whether a hypothesized trade-off between gain and risk underlies ecological interactions, and ultimately, patterns of perfor- mance and distribution of these species. I employed a field manipulation to assess the contributions of competition and predation within different ponds that varied in permanence. In order to examine the effect of inter- specific competition, enclosures contained each tadpole species either alone or in the pres- ence of an equal density of the other species; these enclosures were placed in two temporary ponds, two intermediate ponds, and two permanent ponds. Tadpole stocking densities re- flected local natural densities. This competition treatment was crossed with a predator treatment manipulating the absence or presence of predators (with "presence" representing the naturally occurring density within each pond). Patterns of relative performance were consistent with relative distribution patterns across the pond permanence gradient: chorus frogs performed best relative to spring peepers in temporary ponds while spring peepers performed best relative to chorus frogs in permanent ponds (performance was measured as survivorship and growth). The dominant sources of mortality were pond drying in temporary ponds and predation in more permanent ponds. In contrast to most previous experimental studies of larval anurans, competition had small effects on tadpole performance. Results from the field experiment suggest that pond drying and predation may be im- portant determinants of performance, and that the two species are differentially susceptible to these mortality agents. In a set of laboratory experiments I evaluated the hypothesis that a trade-off between foraging gain and predation risk mediated through activity (proportion of time spent moving) might explain patterns of Pseudacris distribution. In both species, individuals facultatively reduced activity in the presence of a caged predator with a cor- responding drop in growth rate. In general, larval chorus frogs also tend to be more active and faster growing and developing than spring peepers. These results provide support for the existence of the trade-off and suggest that interspecific differences in activity may contribute to patterns of larval performance and distribution among ponds. The general nature of this trade-off suggests that it may also be important in other systems.