Soltis et al. 1987 (Article) Tillandsia

GENETIC VARIATION IN THE EPIPHYTES TILLANDSIA IONANTHA AND T. RECURVATA (BROMELIACEAE)

Author(s):—D.E. Soltis, A.J. Gilmartin, L. Rieseberg & S. Gardner

Publication:—American Journal of Botany 74(4): 531-537. (1987) — DOI

Abstract:—The genetic structure of two epiphytic species, Tillandsia ionantha and T. recurvata, was investigated using enzyme electrophoresis. Electrophoretic data suggest that T. ionantha and T. recurvata differ in breeding system, in agreement with predictions based on their strikingly different floral morphologies. Electrophoretic data suggest extremely high levels of inbreeding for T. recurvata, whereas Tillandsia ionantha exhibits characteristics of an outcrossing species. Values of P, H, and mean number of alleles per locus are much higher in T. ionantha than in T. recurvata. The mean value of FIS for T. ionantha is low (0.056), closely approaching expectations at Hardy-Weinberg equilibrium. In contrast, the mean value of FIS in T. recurvata (1.000) indicates a complete absence of heterozygotes. The two species also differ in genetic structure. Low FST values for T. ionantha indicate little variation in allele frequencies among populations. In contrast, FST values are high for T. recurvata, suggesting substantial genetic heterogeneity among populations. In addition, the mean value of I is higher in T. ionantha (0.995) than in T. recurvata (0.931). Population genetic data are in agreement with the suggestion of Benzing (1978), who proposed that extreme epiphytes such as T. recurvata, would be characterized by increased autogamy ensuring high seed set. Due to high chromosome numbers in Bromeliaceae (most taxa have x = 25), the family has been considered polyploid. However, with the exception of an additional isozyme for PGM in T. recurvata, the two species are isozymically diploid.