Molecular evidence of hybridisation between the endemic Phoenix canariensis and the widespread P. dactylifera with Random Amplified Polymorphic DNA (RAPD) markers

Abstract

We used RAPD markers to test whether morphologically intermediate individuals between the Canarian endemic Phoenix canariensis and the widespread P. dactylifera correspond to hybrids. Consistent with previous allozyme evidence, the scarcity of appropriate RAPD markers to distinguish P. dactylifera and P. canariensis indicated a close genetic relationship among these species. Only two of the 54 ten-mer primers (OPM-8 and OPK-14) tested in 221 individuals from 7 localities in different islands enabled us to unambiguously identify both species. While P. canariensis possesses two exclusive monomorphic bands of 1000 bp and 750 bp (for OPM-8 and OPM-14, respectively), dactylifera is characterised by two bands of 900 bp and 950 bp for the same primers. The additivity of these taxon-specific bands in the individuals that were morphologically intermediate provided, for the first time, firm evidence for their hybrid origin. Because these hybridisation capabilities pose clear threats to the survival of the endemic P. canariensis and some individuals that had been morphologically characterised as pure P. canariensis revealed later a hybrid nature in the RAPD analysis, we suggest that RAPD markers be used to estimate the possible incidence of introgression in the scarce extant natural populations of P. canariensis. This procedure will provide a straightforward means to select target populations to implement the “in situ” conservation strategies suggested previously on the basis of allozyme research.