In the Bromeliaceae, hybrids have been engineered for horticultural purposes; in addition, hybrids have been observed in natural habitats. We investigated the hybridization potential of three sympatric species of Tillandsia inhabiting secondary forests and shaded coffee plantations in the central mountains of Veracruz, Mexico. The studied species (T. juncea, T. polystachia and T. variabilis) show overlap in flowering phenology and are believed to share pollinators. We compared the floral morphology of the species, performed controlled intra-and interspecific pollinations, and recorded pollen tube growth, fruit and seed set, as well as seed germination. Flower size differed among the species, but stamen and stigma heights were similar between pairs of species, which would facilitate interspecific pollen exchange. Pollen tubes reached the ovary in interspecific crosses. The three species showed interspecific crosscompatibility, as all crosses resulted in development of mature fruit and viable seeds. Tillandsia juncea achieved the highest fruit set, whereas T. variabilis showed the highest seed set. Seed set as a result of agamospermy, autogamy, geitonogamy and interspecific cross-pollination did not differ among the species. The findings suggest that pre-and post-pollination barriers are weak among the three species of Tillandsia, which thus could potentially hybridize in natural sympatric populations.
K E Y W O R D Sfruit and seed set, interspecific crosses, intraspecific crosses, seed germination, Tillandsia species
| INTRODUCTIONPlant hybridization involves the mating of two closely or distantly related taxa, followed by the production of viable seeds, germination and growth of seedlings (Marques, Roselló-Graell, Draper, & Iriondo, 2007;Soltis & Soltis, 2009). The genetic and demographic effects derived from hybridization are among the leading causes of population decline (