Department of Biological Sciences, University of Bergen, PO Box 7803, 5020, Bergen, Norway.
Bjerknes Centre for Climate Research, 5020, Bergen, Norway.
Sci Rep. 2024 Aug 2;14(1):17940. doi: 10.1038/s41598-024-67650-1.
Spatio-temporal assessment of phylogenetic diversity gradients during the Holocene (past 12,000 years) provides an opportunity for a deeper understanding of the dynamics of species co-occurrence patterns under environmental fluctuations. Using two robust metrics of phylogenetic dispersion (PD) and 99 fossil pollen sequences containing 6557 samples/assemblages, we analyse spatio-temporal variation in PD of angiosperms and its relationship with Holocene climate in central Asia. Overall, PD throughout the Holocene decreases linearly with increasing latitude, except for a rise in mean nearest taxon distance from ca. 25 to 35° N. This indicates that phylogenetically divergent taxa decrease progressively with increasing latitude, leaving more phylogenetically closely related taxa in the assemblages, thereby increasing phylogenetic relatedness among the co-occurring taxa. The latitudinal gradient of PD has not been consistent during the Holocene, and this temporal variation is concordant with the Holocene climate dynamics. In general, profound temporal changes in the latitudinal PD toward higher latitudes implies that the major environmental changes during the Holocene have driven considerable spatio-temporal changes in the phylogenetic assembly of high-latitude angiosperm assemblages. Our results suggest that environmental filtering and the tendency of taxa and lineages to retain ancestral ecological features and geographic distributions (phylogenetic niche conservatism) are the main mechanisms underlying the phylogenetic assembly of angiosperms along the climate-latitudinal gradient. Ongoing environmental changes may pose future profound phylogenetic changes in high-latitude plant assemblages, which are adapted to harsh environmental conditions, and therefore are phylogenetically less dispersed (more conservative or clustered).
全新世（过去 12000 年）期间系统发育多样性梯度的时空评估为深入了解环境波动下物种共存模式的动态提供了机会。使用两种稳健的系统发育离散度（PD）度量指标和包含 6557 个样本/组合的 99 个化石花粉序列，我们分析了中亚地区被子植物 PD 的时空变化及其与全新世气候的关系。总体而言，整个全新世的 PD 随纬度呈线性下降，除了从大约 25°到 35°N 的平均最近分类单元距离上升。这表明系统发育上差异较大的类群随着纬度的增加而逐渐减少，使得组合中更多的类群具有系统发育上的亲缘关系，从而增加了共存类群之间的系统发育亲缘关系。在全新世期间，PD 的纬度梯度并不一致，这种时间变化与全新世气候动态一致。总的来说，PD 沿纬度向高纬度的深刻时间变化表明，全新世期间的主要环境变化导致了高纬度被子植物组合的空间和时间上的显著变化。我们的结果表明，环境过滤以及类群和谱系保留祖先生态特征和地理分布的趋势（系统发育生态位保守性）是沿气候-纬度梯度构建被子植物系统发育组合的主要机制。正在进行的环境变化可能会对适应恶劣环境条件的高纬度植物组合产生未来深远的系统发育变化，因此系统发育上的离散度（更保守或聚类）较低。
