Molecular and morphological evidence for hybridization between endemic Canary Island Convolvulus

摘要

Morphological data and molecular data from the chloroplast trnH-psbA region and nuclear ribosomal ITS region areused to test the hypothesis that the problematic Canary Island endemic Convolvulus floridus var. virgatus is a hybridbetween the endemic species C. floridus and C. scoparius. Analysis of mean leaf length and width of 58 individualsindicates that accessions referable to C. floridus var. virgatus are intermediate between the parental taxa in leafdimensions. Direct sequencing of the ITS region of C. scoparius and C. floridus revealed two species-specific ribotypesdistinguished by 10 base differences. Examination of ITS chromatograms for putative hybrids revealed poly-morphisms at those sites that are diagnostic between species in all except one putative hybrid. Morphologicalintermediacy and ITS additivity therefore support the hybrid status of C. floridus var. virgatus. An analysis ofintraindividual ITS variation confirmed the co-occurrence of both parental ribotypes in putative hybrids and dem-onstrated that some hybrid individuals contained chimaeric ITS types. It is proposed that chimaeric ITS types arethe result of recombination following backcrossing. Sequencing of the trnH-psbA region revealed four haplotypes.Three were, for the most part, confined to C. floridus and putative hybrids although one C. scoparius accession wasalso found to share this haplotype. The remaining haploype was only found in C. scoparius and putative hybrid acces-sions. Patterns of haplotype distribution between parental and hybrid accessions suggest multiple, bidirectionalhybridization events between C. floridus and C. scoparius. The nomenclature of the hybrid is discussed and the nec-essary new name C. x despreauxii is proposed.