Miguel A. González-Pérez

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.

Patterns of genetic diversity in Phoenix canariensis, a widespread oceanic palm (species) endemic from the Canarian archipelago

Understanding how genetic diversity is structured on oceanic island taxa requires the integration of physical, biological and anthropomorphic factors. Founder effects coupled with limited dispersal over sea barriers typically result in low levels of genetic variation in island populations. In widespread species, restriction in gene flow across large areas leads to patterns of isolation by distance (IBD), but recent population-based studies indicate that genetic structure on islands can be complex even at local scales. Here, we investigated the patterns of genetic variation in a widespread island palm (Phoenix canariensis) displaying reproductive syndromes associated with extensive dispersal (wind pollination and zoochory). Genetic variation was assessed at eight nuclear microsatellite loci in 330 individuals of 15 Canarian populations. Our results showed that levels of within-population genetic diversity in P. canariensis depend on the island considered, with a strong decreasing pattern from the easternmost and oldest island to the westernmost and youngest islands. A Mantel test supported a stepping-stone model of differentiation across the archipelago that fits the sequence of island emergence, and results from ABC and clustering analyses also corresponded with this progression rule. In addition, our analyses were congruent with the idea that the only large population found on Lanzarote has an anthropogenic origin. Despite the high dispersal potential of P. canariensis, our analyses suggest that the geographical configuration of the Canary Islands and a relatively recent pattern of differentiation across islands appear to have had a primary influence on the genetic structure of this island taxon.

Reproductive strategy and ploidy determine the genetic variability of Sorbus aria

Sorbus aria (L.) Crantz (common whitebeam) from the Canary Islands has not been characterised genetically. We analysed the genetic variability of 184 individuals belonging to seven natural populations of S. aria from the Canarian Archipelago and the Iberian Peninsula. Our main aims were to obtain essential information to enable the exploration of the genetic relationship between populations from the Canary Islands and the Iberian Peninsula; to establish the existence of a spatial genetic structure and formulate appropriate management and conservation genetics strategies. Genetic variation was analysed using nine polymorphic microsatellite loci. The Canary Island populations (triploids) were found to have very low genetic variability and to be considerably differentiated from the populations from the peninsula (diploid and triploid), although with a connection to the Sierra Nevada population in the south of the Peninsula. This population, in turn, had many different genotypes, which is indicative of the existence of various origins. The level of genetic diversity was higher in all-diploid populations, which, in addition, presented a greater interpopulation gene flow, possibly the result of a prevalence of sexual reproduction. On the other hand, the triploid populations presented lower levels of genetic variability, with a significant degree of fixed heterozygosity, possibly due to asexual reproduction, mainly by apomixis. The reproductive biology and ploidy appear to be responsible for the levels of genetic variability in S. aria.

Characterization of six microsatellite loci in Myrica faya (Myricaceae) and cross amplification in the endangered endemic M. rivas-martinezii in Canary Islands, Spain

Six novel polymorphic microsatellite markers were isolated from enriched libraries in Myrica faya Ait., recently renamed Morella faya, (fayatree, firetree, or firebush) in order to examine the genetic diversity in natural populations. Also, test cross-specific amplification and genetic diversity in Myrica rivas-martinezii, which is endemic on the Canary islands. Microsatellite loci were screened in 225 individuals of both species from different islands of the Canarian archipelago. All markers were successfully amplified from both Myrica species, with an average number of 6.5 and 9.3 alleles per locus in M. rivas-martinezii and M. faya, respectively. There was no evidence for linkage disequilibrium between loci, and the probability of null alleles ranged from 0.01 to 0.17.