Genetic relationships and population structure within taxa of the endemicSideritis pusilla (Lamiaceae)assessed using RAPDs

Abstract

RAPD analysis has been performed for 15 plant populations, covering eight different infraspecific taxa ofSideritis pusilla(Lange) Pau, member of the Lamiaceae endemic to southeastern Spain, and their putative parental speciesSideritis hirsutaL. andSideritis leucanthaCav. Genetic distances, together with the presence of numerous fixed molecular markers differentiatingS. pusillafrom its putative ancestors, indicate that it should be considered as a true species. Cladistic and populational analysis led to the allocation ofS. pusillapopulations into three major groups—osteoxylla, flavovirensandpusilla/almeriensis—which include taxa previously described as ranging from the varietal to the specific level. Low genetic differentiation among groups revealed by a reduced number of specific molecular markers justify their assignment under the infraspecific range. Moreover, the existence of both morphological and biogeographical differences, supports a status for these groups as subspecies ofS. pusilla.Highly significant (P<0.002) variance partitioning data (AMOVA) extracted from the analysis of individuals withinS. pusillapopulations show that, of the total genetic diversity, 68.8% was attributable to individual differences within populations, 19.9% to populational differences within groups, and only 11.3% to divergence between groups. This distribution is in agreement with the outcrossing nature of these plants. Comparative analysis of variance within populations reveals a reduced genetic variation for theosteoxyllagroup, thus supporting its previous consideration as an endangered taxon.