Instituto de Botánica Darwinion C.C. 22, B1642HYD, San Isidro, Provincia de Buenos Aires, Argentina.
Department of Biology and Bean Life Science Museum, Brigham Young University 4102 LSB, Provo, Utah, 84602, USA.
Ecol Evol. 2014 Nov;4(22):4270-86. doi: 10.1002/ece3.1268. Epub 2014 Oct 24.
The Patagonian steppe is an immense, cold, arid region, yet phylogeographically understudied. Nassauvia subgen. Strongyloma is a characteristic element of the steppe, exhibiting a continuum of morphological variation. This taxon provides a relevant phylogeographical model not only to understand how past environmental changes shaped the genetic structure of its populations, but also to explore phylogeographical scenarios at the large geographical scale of the Patagonian steppe. Here, we (1) assess demographic processes and historical events that shaped current geographic patterns of haplotypic diversity; (2) analyze hypotheses of isolation in refugia, fragmentation of populations, and/or colonization of available areas during Pleistocene glaciations; and (3) model extant and palaeoclimatic distributions to support inferred phylogeographical patterns. Chloroplast intergenic spacers, rpl32-trnL and trnQ-5'rps16, were sequenced for 372 individuals from 63 populations. Nested clade analysis, analyses of molecular variance, and neutrality tests were performed to assess genetic structure and range expansion. The present potential distribution was modelled and projected onto a last glacial maximum (LGM) model. Of 41 haplotypes observed, ten were shared among populations associated with different morphological variants. Populations with highest haplotype diversity and private haplotypes were found in central-western and south-eastern Patagonia, consistent with long-term persistence in refugia during Pleistocene. Palaeomodelling suggested a shift toward the palaeoseashore during LGM; new available areas over the exposed Atlantic submarine platform were colonized during glaciations with postglacial retraction of populations. A scenario of fragmentation and posterior range expansion may explain the observed patterns in the center of the steppe, which is supported by palaeomodelling. Northern Patagonian populations were isolated from southern populations by the Chubut and the Deseado river basins during glaciations. Pleistocene glaciations indirectly impacted the distribution, demography, and diversification of subgen. Strongyloma through decreased winter temperatures and water availability in different areas of its range.
巴塔哥尼亚草原是一个广阔、寒冷、干旱的地区，但在生物地理学方面的研究较少。Nassauvia 亚属 Strongyloma 是草原的一个特征元素，表现出形态变异的连续体。这个分类群不仅为了解过去环境变化如何塑造其种群的遗传结构提供了一个相关的生物地理学模型，而且还为探索巴塔哥尼亚草原大地理尺度上的生物地理学情景提供了一个相关的生物地理学模型。在这里，我们：(1) 评估塑造当前基因型多样性地理格局的人口过程和历史事件；(2) 分析在更新世冰川期避难所隔离、种群碎裂和/或可用地区殖民化的假说；(3) 对现存和古气候分布进行建模，以支持推断的生物地理学模式。对来自 63 个种群的 372 个个体进行了叶绿体基因间空间、rpl32-trnL 和 trnQ-5'rps16 的测序。嵌套聚类分析、分子方差分析和中性检验用于评估遗传结构和范围扩张。目前的潜在分布进行了建模，并投射到末次冰期最大值（LGM）模型上。在所观察到的 41 个单倍型中，有 10 个在与不同形态变体相关的种群中共享。在巴塔哥尼亚中西部和东南部发现了具有最高单倍型多样性和特有单倍型的种群，这与更新世期间在避难所中长期存在相一致。古模拟表明，在 LGM 期间，海向古海岸线转移；在冰川期，暴露的大西洋海底平台上出现了新的可用区域，随后种群退缩。片段化和随后的范围扩张的情景可能解释了草原中心观察到的模式，这一模式得到了古模拟的支持。北部巴塔哥尼亚种群在冰川期被丘布特河和德塞多河盆地与南部种群隔离。更新世冰川期通过降低不同地区的冬季温度和水资源可用性，间接地影响了 Strongyloma 亚属的分布、人口动态和多样化。
