Ecology's cruel dilemma, phylogenetic trait evolution and the assembly of Serengeti plant communities
Ecology's cruel dilemma, phylogenetic trait evolution and the assembly of Serengeti plant communities
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DOI：
10.1111/j.1365-2745.2011.01795.x
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发表时间：
2011-05-01
影响因子：
5.5
通讯作者：
Olff, Han
中科院分区：
文献类型：
--
作者：
Anderson, T. Michael;Shaw, Joey;Olff, Han
P > 1。生态学家就物种共存模式的中性解释和基于生态位的解释的重要性以及小规模数据是否可以为群落的生态理解提供信息进行了辩论，McNaughton [ecology Monographs, 1983,53,291]将其称为“生态学的残酷困境”。系统发育关系、性状和物种共现的研究试图解决这个问题，结果相当复杂。我们提出了一个假设，即植物群落的组装受到生态梯度上的性状相似性的影响，这影响了物种在站点内的平均系统发育距离（MPD）。我们分析了塞伦盖蒂草地的比叶面积（SLA）、最大株高和系统发育关系。塞伦盖蒂草地是一个非常适合研究群落聚集的系统，因为在这个系统中，主要的植物胁迫从干旱转向了光竞争。系统发育群落组装理论预测，MPD在干旱地区最低（欠分散），在高降雨量地区最大（过度分散）。同样，理论预测，低土壤养分浓度应该过滤不耐的物种，因此MPD预计在不育的低海拔地区分散不足，而在肥沃的高海拔地区过度分散。然而，由于整个塞伦盖蒂的降雨量和土壤肥力梯度彼此相反，这种共变如何影响MPD.4尚不清楚。令人惊讶的是，各性状表现出不同的进化模式：SLA表现为趋同进化，而最大株高表现为布朗进化。正如预测的那样，统计上不分散的组合发生在降雨量较少的不育地点，而统计上过度分散的组合发生在降雨量较多的肥沃地点。然而，所有样地的模式都很弱，大多数样地没有MPD.5的统计模式。利用结构方程模型进行多变量分析，统计控制了环境效应之间的协变，揭示了环境变化对MPD的复杂直接和间接影响，包括抵消了SLA和最大株高因其性状进化模式不同而产生的直接影响。合成。在塞伦盖蒂平原上，湿度和土壤肥力的空间抵消梯度，结合性状演化的对比模式，模糊了MPD与任何单一环境变量之间的关系。我们的研究表明，整合跨生态梯度的性状和系统发育关系可以深入了解决定群落组成的生态机制，但可能需要多变量技术来适当地揭示这些模式。
P>1. Ecologists debate the importance of neutral versus niche-based explanations for patterns of species coexistence and whether small-scale data can inform ecological understanding of communities, referred to by McNaughton [Ecological Monographs, 1983, 53, 291] as 'ecology's cruel dilemma.' Research on phylogenetic relationships, traits and species co-occurrence has attempted to address this topic, with results considerably mixed.2. We address the hypothesis that plant community assembly is influenced by trait similarity across ecological gradients and this affects mean phylogenetic distance (MPD) of species within sites. We analysed specific leaf area (SLA), maximum plant height and phylogenetic relationships among Serengeti grasses, a system ideally suited to study community assembly because of an ecological gradient in which the dominant plant stress shifts from drought to light competition.3. Phylogenetic community assembly theory predicts that MPD would be lowest (under-dispersed) at dry sites and greatest (over-dispersed) at sites with higher rainfall. Similarly, theory predicts that low soil nutrient concentrations should filter intolerant species, so that MPD is expected to be under-dispersed at infertile, low-elevation sites and over-dispersed at fertile, higher-elevation sites. However, as gradients of rainfall and soil fertility run counter to one another across the Serengeti, it was unclear how this covariation would influence MPD.4. Surprisingly, traits showed different evolutionary patterns: SLA displayed convergent evolution while maximum plant height displayed Brownian evolution across the phylogeny. As predicted, statistically under-dispersed assemblages occurred at lower rainfall, infertile sites while statistically over-dispersed assemblages occurred at higher rainfall, fertile sites. However, the pattern across all plots was weak, with most plots showing no statistical pattern of MPD.5. Multivariate analyses using structural equation modelling, which statistically controlled for covariation among environmental effects, revealed complex direct and indirect effects of environmental variation on MPD, including offsetting direct effects of SLA and maximum plant height due to their different patterns of trait evolution.6. Synthesis. Spatially counteracting gradients of moisture and soil fertility across the Serengeti, combined with contrasting patterns of trait evolution, obscured the relationship between MPD and any single environmental variable. Our study shows that integrating trait and phylogenetic relationships across ecological gradients yields considerable insight into the ecological mechanisms that determine community composition, but that multivariate techniques may be required to appropriately reveal such patterns.