Instituto de Botânica, São Paulo, Brazil.
Universidade Estadual de Feira de Santana, Programa de Pós-Graduação em Botânica, Feira de Santana, Brazil.
Mol Phylogenet Evol. 2021 Aug;161:107177. doi: 10.1016/j.ympev.2021.107177. Epub 2021 Apr 16.
The genus Isoëtes is globally distributed. Within the Neotropics, Isoëtes occurs in various habitats and ecosystems, making it an interesting case study to address phylogenetic and biogeographic questions. We sequenced and assembled plastomes and ribosomal DNA (rDNA) sequences to reconstruct phylogenetic relationships in Isoëtes from tropical regions in the Neotropics. The ploidy level of nine taxa was established to address the potential source of phylogenetic incongruence in the genus. Node ages were estimated using MCMCTree. The ancestral range estimates were conducted in BioGeoBEARS. Plastome-based phylogenies were congruent throughout distinct matrices and partition schemes, exhibiting high support for almost all nodes. Whereas, we found incongruences between the rDNA and plastome datasets. Chromosome counts identified three diploids, five tetraploids and one likely hexaploid among Neotropical species. Plastome-based node age estimates showed that the radiation of the crown Isoëtes group occurred at 20 Ma, with the diversification of the tropical American (TAA) clade taking place in the Pleistocene at 1.7 Ma. Ancestral range estimates showed that the ancestor of the TAA clade may have evolved first in the dry diagonal area in South America before reaching more humid regions. In addition, the colonization of the Brazilian semiarid region occurred three times, while the occupation of the Cerrado and Amazon regions occurred twice and once, respectively. Our study showed a large unobserved diversity within the genus in warm-dry regions in the Neotropics. Plastomes provided sufficient genomic information to establish a robust phylogenetic framework to answer evolutionary questions in Isoëtes from the Neotropics.
该属在全球范围内分布。在新热带地区，水韭属存在于各种生境和生态系统中，是解决系统发育和生物地理学问题的有趣案例。我们对来自新热带地区热带地区的水韭属进行了质体和核糖体 DNA(rDNA)序列的测序和组装，以重建系统发育关系。为了解决该属系统发育不一致的潜在来源问题，我们确定了九个分类群的倍性水平。使用 MCMCTree 估计节点年龄。使用 BioGeoBEARS 进行了祖先范围估计。基于质体的系统发育在不同的矩阵和分区方案中始终一致，几乎所有节点都得到了高度支持。然而，我们发现 rDNA 和质体数据集之间存在不一致。染色体计数确定了新热带地区的三种二倍体、五种四倍体和一种可能的六倍体。基于质体的节点年龄估计表明，冠水韭组的辐射发生在 2000 万年前，热带美洲（TAA）分支的多样化发生在 170 万年前的更新世。祖先范围估计表明，TAA 分支的祖先可能首先在南美洲的干燥对角地区进化，然后到达更潮湿的地区。此外，巴西半干旱地区发生了三次殖民化，而塞拉多和亚马逊地区分别发生了两次和一次殖民化。我们的研究表明，在新热带地区温暖干燥地区的属内存在大量未观察到的多样性。质体提供了足够的基因组信息，为建立一个稳健的系统发育框架提供了依据，以回答新热带地区水韭属的进化问题。
