RAPD differentiation between Borderea pyrenaica and B. chouardii (Dioscoreaceae), two relict endangered taxa
As currently circumscribed, the genus Borderea Mieg. comprises two narrowly distributed European taxa, Borderea pyrenaica (Bub.) Mieg. and B. chouardii (Gaussen) Heslot. An accumulation of facts such as that both species share a very close overall morphology, that only a single population of Borderea chouardii is known, and that they live in contrasting environments has led some authors to suggest that B. chouardii is a mere ecotype of the more widespread B. pyrenaica. We tested this hypothesis using RAPD markers in four populations of Borderea, three of them identified as B. pyrenaica and the other one representing the only known population of B. chouardii. Eleven out of twenty assayed pri…
Nuclear and chloroplast DNA variation in Cephalaria squamiflora (Dipsacaceae), a disjunct Mediterranean species
Cephalaria squamiflora is a chamaephyte restricted to rupicolous habitats in islands of the Western (Balearic Islands, Sardinia) and Eastern Mediterranean (Crete and few Aegean islands). Four narrowly distributed races (subspp. squamiflora, mediterranea, ebusitana, balearica) have been described to encompass the morphological variation within the species. We have used nuclear ribosomal ITS and cpDNA sequences to assess how the patterns of molecular differentiation are related to taxonomic and geographic boundaries. Extensive intragenomic ITS variation was detected in samples from all territories, the average sequence divergence among cloned ribotypes was 1.339%. The parsimony network of clo…
Hybridization studies inSilene subgen.Petrocoptis (Caryophyllaceae)
Silene subgenusPetrocoptis comprises sexual diploid taxa and it is restricted to calcareous cliffs in the Iberian peninsula. Artificial crosses involvingSilene pyrenaica (Bergeret)Mayol etRossello (≡Petrocoptis pyrenaica (Bergeret)Walp.),Silene laxipruinosa Mayol etRossello andS. montserratii subsp.crassifolia (Rouy)Mayol etRossello (≡P. crassifolia Rouy) were attempted to assess the extent of barriers developed within the subgenusPetrocoptis. Usually, intraspecific crosses involving allopatric populations were successful, suggesting that geographically isolated populations are not genetically isolated. Cross-compatibility was noted among the polymorphicS. pyrenaica, which developed fertile…
Why Nuclear Ribosomal DNA Spacers (ITS) Tell Different Stories in Quercus
The molecular systematics of Quercus (Fagaceae) was recently assessed by two teams using independently generated ITS sequences. Although the results disagreed in several remarkable features, the phylogenetic trees for either hypothesis were highly supported by bootstrap resampling. We have reanalyzed the ITS sequences used by both teams (eight taxa) to reveal the underlying patterns of this divergence. Within species, conspicuous length and G + C% divergence were evident in most sequence comparisons. In addition, a high rate of substitutions and deletions involving highly conserved motifs in both ITS spacers were present in a set of sequences. This was coupled with a less thermodynamic stab…
Seed isozyme variation in Petrocoptis A. Braun (Caryophyllaceae).
Abstract The electrophoretic patterns of seven isozyme systems (ADH, AMY, AAT, GDH, LAP, MDH, and SOD) obtained from dormant seeds from 44 accessions belonging to 12 Petrocoptis taxa were compared in order to clarify taxonomic relationships within the genus. Overall, electrophoretic zymograms showed the presence of up 28 electromorphs, of which 26 were polymorphic among accessions. Mantel tests revealed a moderate level of correlation between the geographic distance matrix and several dissimilarity matrices based on the isozyme data ( r =0.3052–0.3376). The electrophoretic profiles of seed isozymes did not match closely the analytical taxonomic framework drawn from morphology. Many electrom…
Testing Taxonomic and Biogeographical Relationships in a Narrow Mediterranean Endemic Complex (Hippocrepis balearica) using RAPD Markers
Analyses of RAPD profiles from 17 populations of the Hippocrepis balearica complex revealed a highly structured geographic pattern, not only among continental–insular areas but also within the eastern Balearic islands. In marked contrast to previous morphometric results, a clear separation between continental and insular samples was found, and intermediates between H. balearica and H. valentina samples were not detected. Molecular data indicated that western and eastern Balearic populations of the complex (H. grosii and H. balearica) were more closely related to each other than to continental populations (H. valentina). Multivariate analyses of the RAPD data clearly indicated that the simil…
Phylogeographical structure in the coastal speciesSenecio rodriguezii(Asteraceae), a narrowly distributed endemic Mediterranean plant
Aim Our goals were (1) to assess the levels of chloroplast DNA variation in a narrowly distributed plant restricted to continental islands, (2) to ascertain whether a phylogeographical structure is present in plants restricted to coastal linear systems, and (3) to interpret the results in the light of the known palaeogeography of these islands. Location The Eastern Balearic Islands (Majorca and Minorca) in the Western Mediterranean Basin. Methods Sampling included 134 individuals from 28 populations of Senecio rodriguezii covering the entire range of the species. Sequences of the chloroplast genome (trnT-trnL spacer) were obtained and parameters of population genetic diversity and substruct…
Patterns of genetic variability and habitat occupancy in Crepis triasii (Asteraceae) at different spatial scales: insights on evolutionary processes leading to diversification in continental islands.
International audience; Background and Aims Archipelagos are unique systems for studying evolutionary processes promoting diversification and speciation. The islands of the Mediterranean basin are major areas of plant richness, including a high proportion of narrow endemics. Many endemic plants are currently found in rocky habitats, showing varying patterns of habitat occupancy at different spatial scales throughout their range. The aim of the present study was to understand the impact of varying patterns of population distribution on genetic diversity and structure to shed light on demographic and evolutionary processes leading to population diversification in Crepis triasii, an endemic pl…
Random amplified polymorphic DNA (RAPD) markers detect a single phenotype in Lysimachia minoricensis J.J. Rodr. (Primulaceae), a wild extinct plant
Lysimachia minoricensis is a Mediterranean (Balearic Islands) endemic that is extinct in the wild but extant in botanical gardens. Previously, no variation at 22 isozyme loci was revealed in more than 150 analysed plants. Random amplified polymorphic DNA (RAPD) analysis was used to examine genetic variation among five individuals from each of eight botanical garden accessions (40 plants). No polymorphisms were detected at 201 amplified bands. This is the first report of RAPD monomorphism in a nonapomictic vascular plant. The lack of detectable genetic variation suggests that an extremely reduced gene pool was recovered in the field before its extinction. Although the screening of other geno…
Seed germination and reproductive features of Lysimachia minoricensis (Primulaceae), a wild-extinct plant.
Lysimachia minoricensis is one of the few Mediterranean endemic plants (Minorca, Balearic islands) that has gone extinct in the wild but which persists as extant germplasm or cultivated plants in several botanical gardens. Reproductive features (seed set, number of seeds per capsule, seed weight) and germination responses to constant temperatures, sea water and dry-heat pre-treatments were investigated to determine the extent to which they may have influenced the extinction of the species. Seed set in Lysimachia is not dependent on pollinators, suggesting a functional selfer breeding system. Most plants produced a large mean number of fruits (23.2) and seeds (466), and the mean production o…
Molecular phylogeography ofThymus herba-barona(Lamiaceae): Insight into the evolutionary history of the flora of the western Mediterranean islands
Thymus herba-barona is endemic to Majorca, Corsica, and Sardinia. In order to gain insight into its evolutionary history, we examined the genetic diversity and phylogeography of the species using sequences of the trnT-trnL intergenic spacer from 106 individuals belonging to 15 populations. We detected high within-species genetic diversity and strong among- population differentiation, but no evidence for phylogeographic structure. A haplotype network supported the occurrence of three main clades, the ancestral one being geographically restricted to the Gennargentu massif in Sardinia, while the two derived ones were relatively widespread. Coalescent-based analyses indicated deep divergence ti…