FUERTES AGUILAR, JAVIER*, BELéN GUTIéRREZ LARENA, AND GONZALO NIETO FELINER. Real Jardín Botánico, CSIC. 28014 Madrid, Spain. - Reticulate evolution along an altitudinal gradient in Armeria (Plumbaginaceae) inferred from ITS, cpDNA, and morphology.
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