Gomez-Mestre Ivan, Warkentin Karen M
Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA.
Oecologia. 2007 Aug;153(1):197-206. doi: 10.1007/s00442-007-0708-0. Epub 2007 Mar 21.
Risk-sensitive hatching is adaptive for species facing a trade-off between egg-stage and post-hatching risks, and environmental variation in one or both stages. Such plasticity has been found in amphibians, fishes, reptiles and spiders, with red-eyed treefrogs (Agalychnis callidryas) being the best-studied case. We assessed hatching plasticity and egg- and larval-stage risks in a closely related, syntopic species, the gliding leaf-frog (Agalychnis spurrelli). We found a lower hatching response to egg-eating snakes in A. spurrelli (9-28% of embryos escaped) than in A. callidryas (59-80% escaped). Levels of snake predation were similarly high for clutches of both species monitored at a pond in Costa Rica, and in fish predation experiments early-hatched A. spurrelli tadpoles were more vulnerable than later hatchlings, as has been shown for A. callidryas. A. spurrelli thus face a risk trade-off similar to A. callidryas, and likely would benefit from predator-induced hatching; their lower responsiveness to snakes appears nonadaptive. A. spurrelli embryos showed a stronger hatching response (57% hatched in 1 h) to submergence underwater than to snake attacks even though submergence is a less frequent risk. This suggests they have a greater capacity for early hatching than is expressed in the context of snake attacks, but have much lower sensitivity to snake cues than to flooding cues. Development in A. spurrelli is accelerated compared to syntopic A. callidryas, and spontaneous hatching is earlier and more synchronous. This is congruent with predictions based on selection by egg predators in the absence of a strong escape hatching response.
风险敏感型孵化对于面临卵期风险与孵化后风险之间权衡以及一个或两个阶段环境变化的物种而言具有适应性。这种可塑性已在两栖动物、鱼类、爬行动物和蜘蛛中被发现，其中红眼树蛙（红眼树蛙属）是研究得最为透彻的案例。我们评估了一种近缘同域物种——滑翔叶蛙（红眼树蛙属）的孵化可塑性以及卵期和幼体期风险。我们发现，滑翔叶蛙对食卵蛇的孵化反应（9% - 28%的胚胎逃脱）低于红眼树蛙（59% - 80%逃脱）。在哥斯达黎加一个池塘监测的两种蛙的卵块中，蛇的捕食水平同样很高，并且在鱼类捕食实验中，如红眼树蛙一样，早产的滑翔叶蛙蝌蚪比晚产的更易受到伤害。因此，滑翔叶蛙面临着与红眼树蛙类似的风险权衡，并且可能会从捕食者诱导的孵化中受益；它们对蛇的较低反应性似乎是非适应性的。尽管被淹没是一种较不常见的风险，但滑翔叶蛙胚胎对水下淹没的孵化反应（1小时内57%孵化）比对蛇攻击的反应更强。这表明它们具有比在蛇攻击情况下所表现出的更大的早期孵化能力，但对蛇的线索的敏感性远低于对洪水线索的敏感性。与同域的红眼树蛙相比，滑翔叶蛙的发育加速，自发孵化更早且更同步。这与在没有强烈的逃避孵化反应的情况下基于卵捕食者选择的预测一致。
