Department of Biological Sciences, University of Idaho, 875 Perimeter Dr. MS 3051, Moscow, Idaho, 83844-3051, USA.
Institute for Bioinformatics and Evolutionary Studies, University of Idaho, 875 Perimeter Dr. MS 3051, Moscow, Idaho, 83844-3051, USA.
Am J Bot. 2019 Jul;106(7):958-970. doi: 10.1002/ajb2.1328. Epub 2019 Jul 10.
At the intersection of ecology and evolutionary biology, community phylogenetics can provide insights into overarching biodiversity patterns, particularly in remote and understudied ecosystems. To understand community assembly of the high alpine flora in the Sawtooth National Forest, USA, we analyzed phylogenetic structure within and between nine summit communities.
We used high-throughput sequencing to supplement existing data and infer a nearly completely sampled community phylogeny of the alpine vascular flora. We calculated mean nearest taxon distance (MNTD) and mean pairwise distance (MPD) to quantify phylogenetic divergence within summits, and assessed whether maximum elevation explains phylogenetic structure. To evaluate similarities between summits, we quantified phylogenetic turnover, taking into consideration microhabitats (talus vs. meadows).
We found different patterns of community phylogenetic structure within the six most species-rich orders, but across all vascular plants phylogenetic structure was largely not different from random. There was a significant negative correlation between elevation and tree-wide phylogenetic diversity (MPD) within summits: overdispersion degraded as elevation increased. Between summits, we found high phylogenetic turnover driven by greater niche heterogeneity on summits with alpine meadows.
Our results provide further evidence that stochastic processes may also play an important role in the assembly of vascular plant communities in high alpine habitats at regional scales. However, order-specific patterns suggest that adaptations are still important for assembly of specific sectors of the plant tree of life. Further studies quantifying functional diversity will be important in disentangling the interplay of eco-evolutionary processes that likely shape broad community phylogenetic patterns in extreme environments.
在生态学和进化生物学的交叉点上，群落系统发生学可以深入了解总体生物多样性模式，尤其是在偏远和研究不足的生态系统中。为了了解美国锯齿山脉国家森林高海拔植物区系的群落组装，我们分析了九个山顶群落内部和之间的系统发生结构。
我们使用高通量测序来补充现有数据，并推断出高海拔维管束植物近乎完全采样的群落系统发生。我们计算了平均最近分类单元距离（MNTD）和平均成对距离（MPD），以量化山顶内部的系统发生分歧，并评估最大海拔是否解释了系统发生结构。为了评估山顶之间的相似性，我们量化了系统发生周转率，同时考虑了微生境（碎石场与草地）。
我们发现六个最丰富的分类阶元内的群落系统发生结构存在不同的模式，但在所有维管植物中，系统发生结构在很大程度上与随机没有区别。山顶内部的海拔与树宽系统发生多样性（MPD）之间存在显著的负相关关系：随着海拔的升高，离散度降低。在山顶之间，我们发现由于高山草甸上的生态位异质性较大，系统发生周转率较高。
我们的结果进一步证明，在高海拔生境中，随机过程也可能在维管植物群落的组装中发挥重要作用。然而，特定阶元的模式表明，适应仍然是植物生命树特定部门组装的重要因素。进一步研究量化功能多样性将有助于理清可能塑造极端环境中广泛群落系统发生模式的生态-进化过程的相互作用。
