The relationship between seed mass and mean time to germination for 1037 tree species across five tropical forests
The relationship between seed mass and mean time to germination for 1037 tree species across five tropical forests
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DOI：
10.1111/j.1365-2435.2008.01477.x
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发表时间：
2009-02-01
影响因子：
5.2
通讯作者：
Chave, Jerome
中科院分区：
文献类型：
--
作者：
Norden, Natalia;Daws, Matthew I.;Chave, Jerome
理论模型预测，大种子的物种应该发芽速度比小种子的物种，因为大种子更有可能有更高的后扩散种子捕食比小种子。一个迅速的发芽策略，因此，使大的种子，以减少死亡的风险。为了评估这种预测的种子质量和平均发芽时间（MTG）之间的关系，我们使用了一个荟萃分析发表的数据源。我们的数据库包含了来自全球五个热带地区（巴西，印度，象牙海岸，马来西亚和巴拿马）的1037个树种的这两个性状的信息。对种子质量和MTG的对数转换值进行了种间分析和非遗传独立对比（PIC），在所有5个数据集中，对数种子质量是一个显著的非遗传保守性状。Log-MTG在除马来西亚和印度外的所有地点都是显著的遗传保守的，Log-MTG和对数种子质量在除马来西亚外的所有地点都是显著的正相关。PIC分析显示，在巴西，印度和象牙海岸，但不是在马来西亚和巴拿马显着的正相关关系。当所有地点相结合，PIC分析表明，这两个性状之间的显着正相关。我们的研究结果不支持的假设，大种子发芽速度比小种子，而是小种子发芽速度更快。我们解释我们的研究结果，根据系统发育和生物物理的限制。我们提出了四种替代机制，可以解释所观察到的模式，包括发展的限制，吸水和投资的物理防御。
Theoretical models predict that large-seeded species should germinate more rapidly than small-seeded species, since large seeds are more likely to have higher post-dispersal seed predation than small seeds. A prompt germination strategy would therefore enable large seeds to reduce risks of mortality.To assess this predicted relationship between seed mass and mean time to germination (MTG), we used a meta-analysis of published data sources. Our data base contained information for these two traits for 1037 tree species from five tropical areas worldwide (Brazil, India, Ivory Coast, Malaysia and Panama). Both cross-species analyses and phylogenetically independent contrasts (PIC) were conducted on the log-transformed values of seed mass and MTG.Log-seed mass was a significantly phylogenetically conserved trait in all five data sets. Log-MTG was significantly phylogenetically conserved in all sites except for Malaysia and India.Log-MTG and log-seed mass were significantly positively correlated in all sites except for Malaysia. PIC analyses showed a significantly positive relationship in Brazil, India and Ivory Coast but not in Malaysia and Panama. When all sites were combined, PIC analyses indicated a significant positive relationship between these two traits.Our findings do not support the hypothesis that large seeds germinate faster than small seeds, but rather that small seeds germinate faster. We interpret our results in light of phylogenetic and biophysical constraints. We propose four alternative mechanisms that could account for the observed pattern, including developmental constraints, water absorption and investment to physical defences.