Molecular tools provide new insights into phylogenetic relationships of plant species, and by relating phylogenetic groups to their geographical distribution, we can cast light upon the evolution history of plant clades. In the current study, we evaluated the phylogenetic position of the Sinai endemic Brassica deserti (Brassicaceae), later renamed as Erucastrum deserti, based on morphological data and 5.8S rDNA and ITS (Internal Transcribed Spacer) regions. Our results indicate that B. deserti belongs to an East-Mediterranean – Saharo Arabian clade and was not assigned to the core Brassica and Erucastrum clades, respectively, which evolved in the West Mediterranean area. We tentatively conclude that Brassica deserti evolved independently of core Brassica and Erucastrum.
The winter annuals Brassica tournefortii and Raphanus raphanistrum (Brassicaceae) share similar habitats and life-history traits, but differ in their reproduction system (self-compatibility vs. self-incompatibility, respectively). The two phylogenetically close species offer means to assess the effect of reproductive biology on genetic diversity between and within populations. In general, genetic diversity between populations of B. tournefortii was higher than that found between populations of R. raphanistrum, while higher genetic diversity indices were evident within populations of R. raphanistrum. In addition, the results of pairwise genetic distances indicated that the genetic distances between populations can be associated to the species’ reproductive biology and not to the population’s distribution pattern. We discuss whether knowledge of reproductive and habitat characteristics can be used to predict genetic diversity when planning sampling scheme for ex situ conservation.