Lira-Noriega Andrés, Toro-Núñez Oscar, Oaks Jamie R, Mort Mark E
Biodiversity Institute and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, Kansas 66045 USA.
Am J Bot. 2015 Jan;102(1):149-64. doi: 10.3732/ajb.1400277. Epub 2014 Dec 30.
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A recurrent explanation for phylogeographic discontinuities in the Baja California Peninsula and the Sonoran Desert Region has been the association of vicariant events with Pliocene and Pleistocene seaway breaks. Nevertheless, despite its relevance for plant dispersal, other explanations such as ecological and paleoclimatic factors have received little attention. Here, we analyzed the role of several of these factors to describe the phylogeographic patterns of the desert mistletoe, Phoradendron californicum.•
Using noncoding chloroplast regions, we assess the marginal probability of 19 a priori hypotheses related to geological and ecological factors to predict the cpDNA variation in P. californicum using a Bayesian coalescent framework. Complementarily, we used the macrofossil record and niche model projections on Last Glacial Maximum climatic conditions for hosts, mistletoe, and a bird specialist to interpret phylogeographic patterns.•
Genealogical reconstructions revealed five clades, which suggest a combination of cryptic divergence, long-distance seed dispersal, and isolating postdivergence events. Bayesian hypothesis test favored a series of Pliocene and Pleistocene geological events related to the formation of the Baja California Peninsula and seaways across the peninsula as the most supported explanation for this genealogical pattern. However, age estimates, niche projections, and fossil records show dynamic host-mistletoe interactions and evidence of host races, indicating that ecological and geological factors have been interacting during the formation and structuring of phylogeographic divergence.•
Variation in cpDNA across the species range results from the interplay of vicariant events, past climatic oscillations, and more dynamic factors related to ecological processes at finer temporal and spatial scales.
研究前提：对于下加利福尼亚半岛和索诺兰沙漠地区系统发育地理间断现象的一种反复出现的解释是，替代事件与上新世和更新世的海道断裂有关。然而，尽管其对植物扩散具有相关性，但其他解释，如生态和古气候因素，却很少受到关注。在这里，我们分析了其中几个因素的作用，以描述沙漠槲寄生（Phoradendron californicum）的系统发育地理模式。
方法：利用非编码叶绿体区域，我们评估了19个与地质和生态因素相关的先验假设的边际概率，以使用贝叶斯合并框架预测加州槲寄生的cpDNA变异。作为补充，我们利用大化石记录以及末次盛冰期气候条件下宿主、槲寄生和一种鸟类专家的生态位模型预测来解释系统发育地理模式。
主要结果：系统发育重建揭示了五个分支，这表明存在隐秘分化、远距离种子传播和分化后隔离事件的组合。贝叶斯假设检验支持了一系列与下加利福尼亚半岛形成以及半岛上海道相关的上新世和更新世地质事件，认为这是对这种系统发育模式最有力的解释。然而，年龄估计、生态位预测和化石记录显示了动态的宿主 - 槲寄生相互作用以及宿主种族的证据，表明生态和地质因素在系统发育地理分化的形成和结构过程中一直在相互作用。
结论：整个物种分布范围内cpDNA的变异是由替代事件、过去的气候振荡以及在更精细的时间和空间尺度上与生态过程相关的更动态因素相互作用的结果。
