Moharrek Farideh, Sanmartín Isabel, Kazempour-Osaloo Shahrokh, Nieto Feliner Gonzalo
Department of Plant Biology, Faculty of Biological Sciences, Tarbiat Modares University (TMU), Tehran, Iran.
Department of Biodiversity and Conservation, Real Jardín Botánico (CSIC), Madrid, Spain.
Front Genet. 2019 Jan 21;9:698. doi: 10.3389/fgene.2018.00698. eCollection 2018.
The Irano-Turanian floristic region spans a topographically complex and climatically continental territory, which has served as a source of xerophytic taxa for neighboring regions and is represented by a high percent of endemics. Yet, a comprehensive picture of the abiotic and biotic factors that have driven diversification within this biota remains to be established due to the scarcity of phylogenetic studies. is an important component of the subalpine steppe flora of the Irano-Turanian region, containing c. 200 cushion-forming sub-shrubby pungent-leaved species. Our recent molecular phylogenetic study has led to enlarging the circumscription of this genus to include eight mono- or oligospecific genera lacking the characteristic life-form and leaves. Using the same molecular phylogeny, here we investigate the tempo and mode of diversification as well as the biogeographic patterns in this genus, to test the hypothesis that a combination of key morphological innovations and abiotic factors is behind high species diversity. Molecular dating analysis indicates that s.l. started to diversify between the Late Miocene and the Pliocene and the biogeographic analysis points to an Eastern Iran-Afghanistan origin. Macroevolutionary models support the hypothesis that the high diversity of the genus is explained by accelerated diversification rates in two clades associated with the appearance of morphological key innovations such as a cushion life-form and pungent leaves; this would have favored the colonization of water-stressed, substrate-poor mountainous habitats along the newly uplifted IT mountains during the Mio-Pliocene. Given the apparent similarity of mountain habitats for most species of , we hypothesize that its current high species diversity responds to a scenario of non-adaptive radiation fueled by allopatric speciation rather than evolutionary radiation driven by ecological opportunity. Similar scenarios might underlie the high diversity of other speciose genera in the topographically complex Irano-Turanian landscape, though this remains to be tested with fine-grained distribution and climatic data.
伊朗 - 图兰植物区系跨越地形复杂且气候大陆性的区域，它是邻近地区旱生分类群的来源，且以高比例的特有种为代表。然而，由于系统发育研究的匮乏，驱动该生物群多样化的非生物和生物因素的全面图景仍有待建立。[该属]是伊朗 - 图兰地区亚高山草原植物区系的重要组成部分，包含约200种形成垫状的亚灌木状具刺激性叶子的物种。我们最近的分子系统发育研究导致该属的范围扩大，纳入了八个缺乏典型生活型和叶子的单种或寡种属。利用相同的分子系统发育，我们在此研究该属的多样化速度和模式以及生物地理模式，以检验关键形态创新和非生物因素的组合是其高物种多样性背后原因的假设。分子年代测定分析表明，广义[该属]在中新世晚期和上新世之间开始多样化，生物地理分析指向伊朗东部 - 阿富汗起源。宏观进化模型支持这样的假设，即该属的高多样性可由与垫状生活型和具刺激性叶子等形态关键创新出现相关的两个分支中加速的多样化速率来解释；这可能有利于在中新世 - 上新世期间沿着新隆起的伊朗 - 图兰山脉的水分胁迫、底物贫瘠的山区栖息地的定殖。鉴于[该属]大多数物种的山地栖息地明显相似，我们假设其当前的高物种多样性是对由异域物种形成推动的非适应性辐射情景的响应，而非由生态机会驱动的进化辐射。类似情景可能是地形复杂的伊朗 - 图兰景观中其他物种丰富属的高多样性的基础，尽管这仍有待用细粒度分布和气候数据进行检验。
