Reinterpretation of an endangered taxon based on integrative taxonomy: The case of Cynara baetica (Compositae)

The Strait of Gibraltar, the gateway between the Atlantic Ocean and the Mediterranean Sea, has a convulsive geological history, with recurring closing and opening events since the late Miocene. As a consequence, this region has played a major role in the evolutionary history of many species. Cynara baetica (Compositae) is a diploid perennial herb distributed in both sides of this strait. It is currently subdivided into two subspecies: C. baetica subsp. baetica for the Spanish populations, and C. baetica subsp. maroccana for the Moroccan ones. Following three different approximations of species delimitation, including phylogenetic and population genetic analyses (based on three AFLP primer combinations and two intergenic spacers of cpDNA), ecological niche modeling (ENM) and morphological studies, this taxon is investigated and reinterpreted. The results obtained showed a clear genetic, morphological and ecological differentiation between the two taxa and the important role played by the Strait of Gibraltar as a geographical barrier. Based on this evidence, the current taxonomic treatment is modified (both taxa should recover their specific rank) and specific conservation guidelines are proposed for the newly delimited taxa.

直布罗陀海峡作为连接大西洋与地中海的门户，自中新世晚期以来历经多次周期性开合事件，地质历史动荡剧烈。该区域在诸多物种的演化历程中发挥了关键作用。刺苞菜蓟（Cynara baetica，菊科Compositae）为二倍体多年生草本植物，分布于该海峡两岸。目前该物种被划分为两个亚种：分布于西班牙种群的西班牙亚种（C. baetica subsp. baetica）以及分布于摩洛哥种群的摩洛哥亚种（C. baetica subsp. maroccana）。本研究采用物种界定的三种不同方法，包括基于3组AFLP（Amplified Fragment Length Polymorphism）引物组合与2个cpDNA（叶绿体DNA）基因间隔区的系统发育与群体遗传分析、生态位建模（ENM）以及形态学研究，对该分类单元进行了调查与重新诠释。研究结果表明，两个分类单元在遗传、形态与生态层面均存在显著分化，同时证实直布罗陀海峡作为地理屏障发挥了重要作用。基于上述证据，本研究修订了当前的分类学处理方案，两个分类单元均应恢复物种等级，并为新界定的分类单元提出了针对性的保护指南。