Biología Evolutiva, Instituto de Ecología A.C., Apartado Postal 63, 91000 Xalapa, Veracruz, Mexico.
Mol Phylogenet Evol. 2012 Nov;65(2):437-50. doi: 10.1016/j.ympev.2012.06.025. Epub 2012 Jul 7.
A lineage of 12 arid land shrubby species in the gymnosperm genus Ephedra (Gnetales) from North America is used to evaluate the influence of climate on speciation. With a long evolutionary history, and a well documented fossil record this lineage is an ideal model for understanding the process of speciation under a niche conservatism scenario. Using seven DNA molecular markers, Bayesian inference is carried out to uncover sister species and to estimate time of divergence of the lineages. Ecological niche models are generated for four parapatric and sympatric sister species and two analyses of niche evolution are performed, one based on ecological niche models and another using raw data and multivariate analysis. As previous analyses suggest, the diversification of North America Ephedra species may be the result of a recent secondary radiation. Both parapatric and sympatric species diverged mostly in a scenario of climatic niche conservatism. However, we also found strong evidence for niche divergence for one of the sister species pairs (E. californica-E. trifurca). Moreover, the multivariate analysis found environmental differences for some variables between sister species. The estimated divergence time of three pairs of sister species distributed in southwestern North America (E. cutleri-E. aspera, E. californica-E. trifurca and E. torreyana-E. viridis) is inferred to have occurred in the Late Miocene to Pliocene and for the sister species pair E. antisyphilitica-E. coryi distributed in the southern United States and northeastern Mexico, it was inferred from the Pliocene to Pleistocene. The orogenetic and climatic changes documented for these regions related to expansion of arid lands, may have contributed to the diversification in North American Ephedra, rather than adaptations to new climatic conditions.
十二种旱生灌木物种的谱系，这些物种属于北美麻黄属（买麻藤目）的裸子植物，用于评估气候对物种形成的影响。该谱系具有悠久的进化历史和详细的化石记录，是理解在生态位保守主义情景下物种形成过程的理想模型。使用七个 DNA 分子标记，通过贝叶斯推断来揭示姐妹种，并估计谱系的分歧时间。为四个地理上接近的和一个地理上隔离的姐妹种生成生态位模型，并进行两种生态位进化分析，一种基于生态位模型，另一种使用原始数据和多元分析。正如先前的分析表明，北美麻黄物种的多样化可能是近期二次辐射的结果。地理上接近的和地理上隔离的物种大多在气候生态位保守的情景下分歧。然而，我们还发现了一个姐妹种对（E. californica-E. trifurca）的生态位分歧的有力证据。此外，多元分析发现了姐妹种之间一些变量的环境差异。分布在北美西南部的三个姐妹种对（E. cutleri-E. aspera、E. californica-E. trifurca 和 E. torreyana-E. viridis）的估计分歧时间推断发生在中新世晚期到上新世，而分布在美国南部和墨西哥东北部的姐妹种对 E. antisyphilitica-E. coryi 的估计分歧时间则推断发生在上新世到更新世。与干旱地区扩张相关的造山和气候变化，可能促成了北美麻黄属的多样化，而不是对新的气候条件的适应。
