Reproductive barriers between different species of Armeria are mostly external, leading to extensive hybridization. We have studied two molecular markers in populations from Sierra Nevada, an E-W aligned massif in Southeast Spain reaching 3500 m, where four taxa occur at different altitudes under several ecological conditions. These are A. splendens, A. filicaulis ssp. nevadense, A. villosa ssp. bernisii, and A. filicaulis ssp. trevenqueana. Fourty populations (with at least five individuals per population) were sampled for ITS1-5.8S-ITS2 and chloroplast trnL-trnF spacer sequences. Morphologically, the four taxa are easily distinguished not only using qualitative characters but also quantitative, as revealed by a principal components analysis based on twenty characters. The ITS sequences are represented in the area by one common ribotype present in all samples regardless of their taxonomic identification. Additionally, at least two other ribotypes, differing on three nucleotide positions plus a 1-bp indel, are present in the area. Despite the occurrence of concerted evolution in the genus, these additional ribotypes occur in some individuals of the two putative hybrid taxa (A. filicaulis nevadense and A. villosa bernisii), besides the common ribotype. In contrast, A. splendens, occurring on alpine meadows, bears a single ribotype. In the cpDNA, sequences from trnL-F intergenic spacer display a haplotype variability independent from ITS and morphology. Six different haplotypes are found within the massif, their distribution being correlated with the altitude. While A. splendens populations show a single haplotype, A villosa bernisii shows four different haplotypes across the massif. Our results are consistent with the hypothesis that A. filicaulis nevadense and A. villosa bernisii have a hybrid origin. A. splendens, or an immediate ancestor, seems to be one of the parental taxa.

Key words: Armeria, hybrids, ITS, Plumbaginaceae, reticulate evolution, trnL-trnF