Characterization of Seven (CTT)n Microsatellite Loci in the Pyrenean Endemic Borderea pyrenaica (Dioscoreaceae): Remarks on Ploidy Level and Hybrid Origin Assessed through Allozymes and Microsatellite Analyses

We present the identification and characterization of microsatellite loci in the Pyrenean endemic Borderea pyrenaica Miégeville (Dioscoreaceae). Seven microsatellite loci were isolated from a (CTT)(n)-enriched partial genomic library. Electropherograms patterns suggest that B. pyrenaica is a tetraploid species, as is its congener B. chouardii. One microsatellite locus was monomorphic, whereas the remaining ones presented from 2 to 10 alleles when analyzed in a sample of 60 individuals. Microsatellites have revealed higher levels of genetic variability than those in previous studies based on allozymes. Levels of genetic diversity are discussed in terms of tetrasomic (autotetraploidy) or duplicated disomic (allotetraploidy) modes of allele segregation. According to the first hypothesis, mean levels of genetic variability (H(min)-H(max)) range between 0.36 and 0.41, whereas, according to the second hypothesis, the 7 primer pairs amplified 11 chromosomal loci, and mean levels of observed and expected heterozygosities were 0.217 and 0.229, respectively, and did not differ significantly from HW expectations. These results suggest a hybrid allopolyploid origin for the Borderea taxa.