Plant survival in relation to seed size along environmental gradients: a long-term study from semi-arid and Mediterranean annual plant communities
Plant survival in relation to seed size along environmental gradients: a long-term study from semi-arid and Mediterranean annual plant communities
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DOI：
10.1111/j.1365-2745.2010.01652.x
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发表时间：
2010-05-01
影响因子：
5.5
通讯作者：
Tielboerger, Katja
中科院分区：
文献类型：
--
作者：
Metz, Johannes;Liancourt, Pierre;Tielboerger, Katja
P>1。种子大小与随后的后代存活率之间的正相关关系是有关生活史策略的生态理论的一个关键假设。然而，这种关系对于终生生存而言是不确定的，因为只有早期幼苗阶段才存在可靠的证据。此外，环境在空间和时间上的变化以及对比植物功能群对这种关系的影响还很少被研究。2．在这里，我们研究了其中的生存率和年际变化。我们测试了它们与种子大小的关系（i）是否一直维持到繁殖，（ii）随环境梯度的变化以及（iii）功能组（草、豆类、禾本科植物）之间的差异。3。在 7 年的自然条件下，沿着陡峭的降雨梯度的三个地点，对 49 个一年生物种的存活率进行了监测，从已建立的幼苗到繁殖植物。然后，我们将每个物种的平均存活率和存活率的年际变化与种子大小、沿梯度的位置和功能组联系起来。4。种子尺寸越大，存活率越高，年间变异越小。在整个降雨梯度范围内，我们没有发现种子大小与存活率之间的关系存在差异；然而，在最湿润的地点，年份之间的变化最低，没有观察到年份之间的变化与种子大小的关系。与禾本科植物相比，豆科植物的存活率较低，年际变异较高。5．我们的研究结果表明，较大的种子尺寸提供了从幼苗建立到一年生物种繁殖的生存优势。较大的种子大小还可以在暂时不可预测的环境中提供对冲策略。沿环境梯度增加的非生物有利性可能对存活率影响不大，但减少了年份之间的存活差异，从而降低了较大种子尺寸的赌注对冲效益。我们认为豆科植物和禾本科植物的不同反应可能部分是由于它们种子休眠的差异造成的。6．合成。当前的植物生活史理论可以通过考虑更大种子尺寸、更高成活率和赌注对冲的好处来完善。需要沿着环境梯度进行研究，以概括整个生态系统的研究结果，并预测不断变化的环境条件下植物性状和植物性能的模式。
P>1. A positive relationship between seed size and subsequent offspring survival is a key assumption in ecological theory concerning life-history strategies. Yet, this relationship is uncertain in respect to lifetime survival because sound evidence only exists for early seedling stages. Furthermore, the effect of environmental variation in space and time, and of contrasting plant functional groups, on this relationship has been scarcely examined.2. Here, we investigated survival and between-year variation therein. We tested for both whether their relationship to seed size (i) is maintained up until reproduction, (ii) changes along environmental gradients and (iii) differs between functional groups (grasses, legumes, forbs).3. Survival was monitored from established seedlings to reproductive plants in 49 annual species under natural conditions during 7 years in three sites along a steep rainfall gradient. We then related average survival per species and between-year variation in survival to seed size, site along the gradient and functional group.4. Larger seed size was associated with higher survival and lower between-year variation. Across the rainfall gradient, we detected no difference in the seed size-survival relationships; however, variation between years was lowest in the most mesic site where no relationship for between-year variation with seed size was observed. Legumes showed lower survival and higher between-year variation than grasses.5. Our findings indicate that larger seed size provides survival advantages beyond seedling establishment up until reproduction among annual species. Larger seed size also provides a bet-hedging strategy in temporally unpredictable environments. Increased abiotic favourability along environmental gradients may have little effect on survival rates but reduces survival variation between years and thus reduces the bet-hedging benefit of larger seed size. We suggest that the contrasting response of legumes and grasses may partly result from their disparity in seed dormancy.6. Synthesis. Current plant life-history theory can be refined by accounting for both benefits of larger seed size, higher survival rates and bet-hedging. Studies along environmental gradients are needed to generalize findings across ecosystems and to predict patterns of plant traits and plant performance under changing environmental conditions.