Department of Integrative Biology, University of South Florida, Tampa, FL 33620, USA.
Oecologia. 2012 Mar;168(3):737-48. doi: 10.1007/s00442-011-2117-7. Epub 2011 Sep 20.
The role of predators in shaping prey life histories is a central theme in the ecological literature. However, the association between degree of predation risk and prey reproductive strategies has not been clearly established. We examined reproduction in the sailfin molly (Poecilia latipinna) from small tidal tributaries in a subtropical estuary. Our results revealed a gradient along which females produced many, small offspring at one extreme (mean = 42 offspring, 17 mg each) and fewer, larger offspring at the other (24 offspring, 29 mg each). Reproductive allotment ranged from 14.9-21.5% of maternal biomass. Based on our observation of divergent reproductive strategies, we experimentally tested the null hypothesis of no difference in predation risk among tributaries using a novel quantitative approach to estimate predation. We predicted greater risk in tributaries where mollies produced many, small offspring. Tethering confirmed increasing risk from 16.2 ± 5.3% SE to 54.7 ± 3.6% fish lost h(-1) across sites in agreement with observed variation in reproduction. Predation was unexpectedly higher than predicted at one of the four sites suggesting that additional factors (e.g., food) had influenced reproduction there. Our results provide insight into the well-studied concept of predator-mediated variation in prey reproduction by quantitatively demonstrating differential risk for mollies exhibiting divergent reproductive strategies. While the observed range of variation in reproductive traits was consistent with previous studies reporting strong predator effects, higher than expected predation in one case may suggest that the prey response does not follow a continuous trajectory of incremental change with increasing predation risk, but may be better defined as a threshold beyond which a significant shift in reproductive strategy occurs.
捕食者在塑造猎物生活史中的作用是生态学文献中的一个核心主题。然而，捕食风险程度与猎物繁殖策略之间的联系尚未明确确立。我们检查了亚热带河口小潮汐支流中的帆鳍孔雀鱼（Poecilia latipinna）的繁殖情况。我们的研究结果揭示了一个梯度，在这个梯度上，雌性在一个极端产生许多小的后代（平均值=42 个后代，每个 17 毫克），而在另一个极端产生较少的大的后代（24 个后代，每个 29 毫克）。繁殖分配范围从母体生物量的 14.9-21.5%不等。基于我们观察到的不同繁殖策略，我们使用一种新的定量方法来估计捕食，实验性地检验了支流之间没有捕食风险差异的零假设。我们预测，在那些产生许多小后代的支流中，捕食风险更大。系泊实验证实，随着从 16.2±5.3% SE 到 54.7±3.6% SE 每小时失去的鱼的数量的增加，捕食风险在各个地点都有所增加，这与观察到的繁殖变化一致。在四个地点中的一个地点，捕食出乎意料地高于预测，这表明其他因素（例如食物）影响了那里的繁殖。我们的研究结果通过定量证明了表现出不同繁殖策略的孔雀鱼存在差异的风险，为研究捕食者介导的猎物繁殖变化这一研究已久的概念提供了新的见解。虽然观察到的繁殖特征变化范围与先前报道的捕食者强烈影响繁殖的研究一致，但在一种情况下，捕食出乎意料地高，这可能表明猎物的反应没有随着捕食风险的增加而沿着连续的渐进变化轨迹进行，而是可以更好地定义为一个临界点，超过这个点，繁殖策略就会发生显著变化。
