NATURAL AND EXPERIMENTAL HYBRIDIZATION IN ARMERIA (PLUMBAGINACEAE) - A-VILLOSA SUBSP CARRATRACENSIS

An experimental crossing program was carried out in order to test the hypothesis that Al-mel-in villosa subsp. carratracensis, a serpentine endemic from Southern Spain, is of hybrid origin. Fruit-set and mainly pollen stainability data in artificial hybrids demonstrate that inter nal interspecific barriers are weak. Two generations of backcrossing w ith the two putative parents -A. colorata and A. villosa subsp. longia ristata- can restore pollen stainability to an average of 83.2 and 68. 7, respectively. A morphometric analysis of 148 specimens belonging to parental species, different artificial hybrid generations and wild pu tative hybrid race shows that (1) morphological characters have a stro ng genetic basis and thus are good markers in identifying hybrids and introgression in Armeria; (2) artificial backcrossing produces in morp hometrical characters a variation which conforms in both trend and mag nitude to what is commonly attributed in the wild to introgression; (3 ) the position of the putative hybrid race is intermediate between the two parental species used in the program. These results are in accord ance with the hypothesis of hybrid origin of A. villosa subsp. carratr acensis.