Chromosomal features of Fosterella species (Bromeliaceae, Pitcairnioideae)

Abstract

Fosterella (Bromeliaceae) comprises 31 species with rosulate leaves and mostly small, whitish flowers. Previous karyological studies were restricted to chromosome counts. In the present study, chromosomal variation in Fosterella was analysed using CMA3/DAPI staining and/or fluorescence in situ hybridization (FISH) using 45S and 5S rDNA probes, generating data for nine taxa with either 2n = 50 or 100 chromosomes. A single chromosome pair containing one CMA+/DAPI− band was identified in all diploid species. In the tetraploid Fosterella hatschbachii one pair had a CMA+/DAPI− band, whereas the other tetraploid studied, Fosterella yuvinkae, had two pairs with proximal bands. The presence of two CMA+/DAPI− pairs in F. yuvinkae may indicate a recent polyploidization event. This paper also reports the application of FISH in Bromeliaceae. FISH using 45S rDNA as the probe revealed one pair of terminal sites in most species and a co-localization with CMA+/DAPI− bands in all analysed species. The 5S rDNA sites were terminal in the tetraploid F. hatschbachii and proximal in all other species studied. Our data indicate that Fosterella species have little heterochromatin and it is largely restricted to the vicinity of the nucleolus organizer region. The data also indicate that hybridization (sometimes associated with polyploidy) has probably played an important role in the evolution of Fosterella.