Instituto de Botánica Darwinion (CONICET-ANCEFN), Labardén 200, C.C. 22, B1642HYD, San Isidro, Provincia de Buenos Aires, Argentina.
Department of Biology and Bean Life Science Museum, 4102 LSB, Brigham Young University, Provo, UT 84602, USA.
Mol Phylogenet Evol. 2019 Jul;136:164-182. doi: 10.1016/j.ympev.2019.03.004. Epub 2019 Mar 8.
Congruence among different sources of data is highly desirable in phylogenetic analyses. However, plastid and nuclear DNA may record different evolutionary processes such that incongruence among results from these sources can help unravel complex evolutionary histories. That is the case of Nassauvia subgenus Strongyloma (Asteraceae), a taxon with five putative species distributed in the southern Andes and Patagonian steppe. Morphometric and phylogeographic information cast doubt on the integrity of its species, and previous molecular data even questioned the monophyly of the subgenus. We tested those questions using plastid and nuclear DNA sequences by the application of different methods such as phylogenetic trees, networks, a test of genealogical sorting, an analysis of population structure, calibration of the trees, and hybridization test, assembling non-synchronous incongruent results at subgenus and species levels in a single reconstruction. The integration of our molecular analyses and previous taxonomic, morphological, and molecular studies support subgenus Strongyloma as a monophyletic group. However, the topology of the nuclear trees and the evidence of polyploids within subgenus Nassauvia, suggest a hypothetical origin and initial radiation of Nassauvia related to an ancient hybridization event that occurred around 17-6.3 Myr ago near the Andes in west-central Patagonia. Plastid data suggest a recent diversification within subgenus Strongyloma, at most 9.8 Myr ago, towards the Patagonian steppe east of the Andes. These processes cause phylogenies to deviate from the species tree since each putative species lack exclusive ancestry. The non-monophyly of its species using both plastid and nuclear data is caused mainly by incomplete lineage sorting occurred since the Miocene. The final uplift of the Andes and Pliocene-Pleistocene glacial-interglacial and its consequences on the landscape and climate structured the genetic composition of this group of plants in the Patagonian steppe. The molecular data presented here agree with previous morphological studies, in that the five putative species typically accepted in this subgenus are not independent taxa. This study emphasizes that adding more than one sequence per species, not combining data with dissimilar inheritance patterns without first performed incongruence tests, exploring data through different methodologies, considering the timing of events, and searching for the causes of poorly resolved and/or incongruent phylogenies help to reveal complex biological underlying processes, which might otherwise remain hidden.
在系统发育分析中，不同数据来源的一致性是非常理想的。然而，质体和核 DNA 可能记录不同的进化过程，因此这些来源的结果不一致有助于揭示复杂的进化历史。这就是 Nassauvia 亚属 Strongyloma（菊科）的情况，该分类群有五个假定的物种分布在安第斯山脉南部和巴塔哥尼亚草原。形态计量学和系统地理学信息对其物种的完整性提出了质疑，而先前的分子数据甚至质疑了该亚属的单系性。我们使用质体和核 DNA 序列通过不同的方法，如系统发育树、网络、谱系分类检验、种群结构分析、树校准和杂交检验，来检验这些问题，在亚属和种水平上将非同步不一致的结果整合到一个单一的重建中。我们的分子分析以及先前的分类学、形态学和分子研究的整合支持 Strongyloma 亚属是一个单系群。然而，核树的拓扑结构和 Nassauvia 亚属内多倍体的证据表明，Nassauvia 与大约 17-6.3 百万年前在安第斯山脉以西的中-巴塔哥尼亚发生的古老杂交事件有关的起源和初始辐射。质体数据表明，Strongyloma 亚属最近在 9.8 百万年前左右，在安第斯山脉以东的巴塔哥尼亚草原发生了多样化。这些过程导致系统发育偏离了物种树，因为每个假定的物种都没有独特的祖先。使用质体和核数据的物种非单系性主要是由于中新世以来不完全谱系分选造成的。安第斯山脉的最终隆起以及上新世-更新世的冰期-间冰期及其对景观和气候的影响，构成了该植物群在巴塔哥尼亚草原的遗传组成。这里呈现的分子数据与先前的形态学研究一致，即通常在这个亚属中接受的五个假定的物种不是独立的分类群。这项研究强调，在每个物种中添加多个序列，在没有先进行不一致性检验的情况下，不要将具有不同遗传模式的数据组合在一起，通过不同的方法探索数据，考虑事件的时间，并寻找解决分辨率差和/或不一致的系统发育的原因，有助于揭示复杂的潜在生物学过程，否则这些过程可能仍然隐藏着。
