The Genetic Diversity and Phylogeography of the Iberian Endemic Steppe Plant Moricandia moricandioides (Boiss.) Heywood, Inferred from ISSR, Plastid DNA, and ITS Sequences

Moricandia moricandiodes is an endemic species found in the south and east of the Iberian Peninsula. Five subspecies have been recognized, and all exist as fragmented populations on limestones and marls with salt and gypsum intrusions under a continental Mediterranean climate, except for one of the subspecies, which inhabits semi-arid and hotter environments. In this study, we sampled populations covering the distribution area of the species and performed a population and phylogeographic study to assess the evolutionary history of populations and the taxonomic relationships of subspecies. ISSR markers, nrITS, and plastid sequences were used in the analyses. The results revealed that, in general, southern populations showed higher genetic diversity than northern populations, suggesting that the former are located in glacial refugia. Furthermore, we did not find clear differences between subspecies, except for M. moricandioides subsp. pseudofoetida, which showed exclusive haplotypes and an exclusive ribotype. Isolation and rapid divergence are discussed as the probable causes of differentiation, whereas bottlenecks and secondary contact between populations would explain the absence of differentiation among the other subspecies. Finally, we propose a few guidelines for the conservation of M. moricandioides.