Department of Microbiology and Plant Biology, University of Oklahoma, Norman, Oklahoma, USA.
University and Jepson Herbaria, University of California, Berkeley, Berkeley, California, USA.
Mol Ecol. 2023 May;32(9):2301-2319. doi: 10.1111/mec.16889. Epub 2023 Mar 10.
The lowland Amazon rainforest houses some of the greatest tree diversity on Earth. While the vast majority of these species are rare, a small number are common and widespread and thus considered to play a disproportionate role in many of the global ecosystem services provided by the Amazon. However, the extent to which dominant Amazonian tree species actually include multiple clades, each on their own unique evolutionary trajectory, is unknown. Here we investigate the extent to which lineage divergence may be occurring within Protium subserratum (Burseraceae), a common and widespread tree species that is monophyletic with populations exhibiting genotypic and phenotypic differences associated with soil and geography. Utilizing a combination of phylogenomic and population genomic methods with sampling from across the range, we found that P. subserratum contains at least eight distinct clades. Specialization onto white-sand soils has evolved independently at least twice within the species; however, phenotype is not correlated with soil type. Finally, cryptic diversity at the base of the Andes is associated with elevational shifts. Together these results lend support to the hypothesis that common and widespread Amazon tree species may not represent evolutionary cohesive units. Instead, these dominant species may more commonly represent species complexes, undergoing evolutionary transitions on a trajectory to become multiple range-restricted, specialist species.
低地亚马逊雨林拥有地球上最丰富的树种多样性。尽管这些物种中的绝大多数都很罕见，但也有一小部分是常见且分布广泛的，因此被认为在亚马逊地区提供的许多全球生态系统服务中发挥了不成比例的作用。然而，主导亚马逊树种实际上是否包含多个分支，每个分支都有自己独特的进化轨迹，这一点尚不清楚。在这里，我们调查了在 Protium subserratum（Burseraceae）中可能发生的谱系分化程度，Protium subserratum 是一种常见且分布广泛的树种，它与具有与土壤和地理相关的基因型和表型差异的种群具有单系性。我们利用来自整个分布范围的系统基因组学和群体基因组学方法的组合，发现 P. subserratum 至少包含八个不同的分支。至少有两次在该物种内独立进化到白沙土壤的特化；然而，表型与土壤类型没有相关性。最后，安第斯山脉底部的隐种多样性与海拔变化有关。这些结果共同支持了这样一种假说，即常见和广泛分布的亚马逊树种可能不是进化上有凝聚力的单位。相反，这些优势物种可能更常见地代表物种复合体，在成为多个范围受限的特化物种的轨迹上经历进化转变。
