Gruenstaeudl Michael, Santos-Guerra Arnoldo, Jansen Robert K
Section of Integrative Biology, University of Texas at Austin, 1 University Station C0930, Austin, TX 78713, USA.
Unidad de Botánica - ICIA, Retama 2, 38400 Puerto de la Cruz, Tenerife, Spain.
Cladistics. 2013 Aug;29(4):416-434. doi: 10.1111/cla.12005. Epub 2012 Nov 5.
The plant genus Tolpis (Asteraceae) has been the subject of several investigations on the evolution of oceanic island plants. Its insular species were utilized in studies of artificial hybrid fertility, testing the validity of Baker's law, the application of DNA barcodes, and the phylogenetic utility of inter-simple sequence repeat markers. Despite this considerable interest in Tolpis, little is known about its phylogenetic history. Past investigations were unable to resolve most of the interspecific relationships, especially within the Canary Islands, where the genus is particularly diverse. Incomplete taxon sampling, the use of ambiguous outgroups and the limited utility of slowly evolving chloroplast DNA markers precluded detailed reconstructions. The present investigation presents a comprehensive molecular phylogeny of Tolpis. By utilizing highly variable nuclear DNA markers and a comprehensive taxon set, we have resolved the majority of interspecific relationships in the genus. Evaluations of competing tree topologies and ancestral area reconstructions complemented the analyses. Our results highlight the presence of three dominant mechanisms of island plant evolution-island colonization, adaptive radiation and interspecific hybridization-in Tolpis: (i) the extant distribution of the genus is the result of two independent colonization pathways, (ii) Tolpis has colonized at least one archipelago multiple times, (iii) the present insular diversity is the product of adaptive radiation, (iv) potential hybridization was detected between species now inhabiting different islands and archipelagoes, indicating sympatric historical distributions, and (v) several undescribed species await taxonomic recognition.
托尔皮斯属植物（菊科）一直是海洋岛屿植物进化领域多项研究的对象。其岛屿物种被用于人工杂交育性研究、检验贝克法则的有效性、DNA条形码的应用以及简单序列重复区间标记的系统发育效用研究。尽管对托尔皮斯属植物有着浓厚的兴趣，但人们对其系统发育历史却知之甚少。过去的研究未能解决大多数种间关系，尤其是在加那利群岛地区，该属植物在那里特别多样化。分类群抽样不完整、使用不明确的外类群以及进化缓慢的叶绿体DNA标记效用有限，都妨碍了详细的系统发育重建。本研究展示了托尔皮斯属植物全面的分子系统发育情况。通过使用高度可变的核DNA标记和完整的分类群集合，我们已经解决了该属植物中的大多数种间关系。对相互竞争的系统发育树拓扑结构的评估和祖先分布区域的重建完善了分析。我们的研究结果突出了托尔皮斯属植物中岛屿植物进化的三种主要机制——岛屿定殖、适应性辐射和种间杂交：（i）该属植物目前的分布是两条独立定殖途径的结果；（ii）托尔皮斯属植物至少多次定殖于一个群岛；（iii）目前的岛屿多样性是适应性辐射的产物；（iv）在现今栖息于不同岛屿和群岛的物种之间检测到了潜在的杂交现象，这表明它们具有同域历史分布；（v）有几个未描述的物种有待分类鉴定。
