Chromosome numbers of plant species from the Canary Islands

Abstract.: Baltisberger M. and Widmer A. 2006. Chromosome numbers of plant species from the Canary Islands. Bot. Helv. 116: 9-30. Chromosome numbers are reported for 66 taxa (101 populations) of flowering plants representing 22 families from the Canary Islands. The chromosome numbers of Kleinia aizoides (Asteraceae, 2n=20) and Polycarpaea nivea (Caryophyllaceae, 2n=18) are given for the first time. Chromosome numbers of another 17 taxa are recorded for the first time from Canarian material. Karyotypes are presented for nine species (six endemic), and phytogeographic and for part of the species systematic aspects are discussed. For Bidens aurea, we provide evidence suggesting that this species might consist of more than one taxo

QTL Analysis of Intraspecific Differences between Two Silene vulgaris Ecotypes

• Background and Aims Serpentine soils provide a highly selective substrate for plant colonization and growth and represent an ideal system for studying the evolution of plant-ecotypes. In the present study the aim was to identify the genetic architecture of morphological traits distinguishing serpentine and non-serpentine ecotypes of Silene vulgaris. • Methods Using an F2 mapping population derived from an intraspecific cross between a serpentine and a non-serpentine ecotype of S. vulgaris, the genetic architecture of 12 morphological traits was explored using a quantitative trait locus (QTL) analysis. • Key Results The QTL analysis identified a total of 49 QTLs, of which 24 were classified as major QTLs. The mean number of QTLs per trait category was found to correspond well with numbers reported in the literature for similar crosses. Clustering of QTLs for different traits was found on several linkage groups. • Conclusions Morphological traits that differentiate the two ecotypes are strongly correlated, presumably as a consequence of the joint effects of extensive linkage of QTLs for different traits and directional selection. The signature of consistent directional selection was found for leaf and shoot trait divergence. Intraspecific ecotype differences in S. vulgaris were found to be distributed across the entire genome. The study shows that QTL analyses on non-model organisms can provide novel insights into the genetic basis of plant diversificatio

Distribution, growth performance and genetic variation of Erigeron annuus in the Swiss Alps

We investigated whether local adaptation has been important in enabling the invasive apomictic species Erigeron annuus to extend its altitudinal range in the Swiss Alps. We first conducted a field survey along several major roads crossing the Swiss Alps to study the distribution and growth performance of E. annuus along an altitudinal gradient. We then used amplified fragment length polymorphism to assess genetic variation within and among populations originating from different altitudes. To complement the molecular analyses, we compared the performance of genotypes with different distributions (i.e. local, occasional, widespread genotypes) in two common gardens at 400m and 1,000m a.s.l. Although E. annuus was seldom found above 1,000m, plant performance in field populations did not decrease with increasing altitude. However, there was a significant decline in genotypic diversity within populations, and highland (711-1,100m) populations were more differentiated (Gst=0.55) than lowland (200-530m) populations (Gst=0.33). In the common garden experiment, local genotypes (i.e. those restricted to a single population) grew less vigorously than widespread genotypes, and were less likely to reproduce. We found no evidence for on-going adaptive changes and conclude that any selection acting on particular genotypes at the altitudinal limit is weak. This leads us to propose that the patterns in the distribution of genotypic diversity in E. annuus are governed by processes of occasional sexual reproduction, dispersal and extinction that are to a large extent independent of altitud

Genetic structure and phylogeography of alpine relict populations of Ranunculus pygmaeus and Saxifraga cernua

Bauert M. R., Kälin M., Edwards P. J. and Baltisberger M. 2007. Genetic structure and phylogeography of alpine relict populations of Ranunculus pygmaeus and Saxifraga cernua. Bot. Helv. 117: 181-196. Ranunculus pygmaeus and Saxifraga cernua are arctic-alpine species with similar disjunct distributions: both occur as small, isolated relict populations in the Alps, while they are more widespread in the Arctic. To improve our understanding of their glacial and postglacial history, we investigated their genetic diversity within and among populations collected in the Alps and in the Arctic using 80 RAPD primers. We found only two genotypes of R. pygmaeus, one in the Alps and one in the Arctic. The absence of genetic diversity within each region is probably the consequence of postglacial colonization from a single source, followed by inbreeding in very small populations. In S. cernua, we found six genotypes among 11 populations in the Alps but no genetic variation within alpine populations. This limited genetic variation probably results from an extreme reduction and fragmentation of populations during successive glacial periods. In contrast, there was a high level of genetic variation both among and within all arctic populations of S. cernua. We suggest that this arose at least partly through the immigration of plants from multiple sources after the last glaciation. The higher genetic diversity of S. cernua compared to R. pygmaeus might also be related to their contrasting breeding systems: R. pygmaeus is an inbreeding diploid which propagates only by seeds, while S. cernua is a clonal polyploid which propagates mainly by vegetative means. Clonal growth, by prolonging the life span of a genotype, might contribute to the maintenance of genetic diversity under conditions which are difficult for sexual reproduction and seedling establishmen

Karyotype evolution supports the molecular phylogeny in the genus Ranunculus (Ranunculaceae)

Karyotype evolution can be reconstructed by the characterization of chromosome morphology, based on the position of centromeres. Different karyotypes often reflect speciation events within phylogenies as they can establish crossing barriers between species. Hence, evolution of karyotypes often is congruent with splits and differentiation of clades within phylogenies of angiosperm genera. Here we study karyotype evolution in the big cosmopolitan genus Ranunculus and in related genera to test the hypothesis that karyotypes are congruent with major clades. We investigated karyotypes on mitoses of 36 species, evaluated literature records for additional 87 species, and reconstructed ancestral states by mapping karyotypes onto a published molecular phylogenetic tree. Altogether ten karyotypes can be discriminated as character states, eight based on the base number x = 8, and two on the base number x = 7. The ancestral type within Ranunculus is characterized by four metacentric and four submetacentric/subtelocentric chromosomes, and dominates in five major basal clades of Ranunculus (R. subg. Auricomus) and in four of the related genera (Coptidium, Halerpestes, Kumlienia, and Trautvetteria). Another four karyotypes are ancestral and predominant in two major clades within Ranunculus (R. subg. Ranunculus), while three further ones occur only on terminal branches of the buttercup phylogeny. Among related genera, Ficaria and Ceratocephala also show derived karyotypes. Karyotype morphology thus supports generic and infrageneric classifications based on molecular and morphological data. Karyotype evolution drives in general to increasing number of chromosomes with asymmetric arms, and to a reduction from x = 8 to x = 7 chromosomes. A review of interspecific homoploid hybridization in sympatric species, and of crossing experiments suggests enhanced crossability of species with the same karyotype and strong crossing barriers between those with different karyotypes. We conclude that karyotype evolution is a major driver of speciation and differentiation of clades within Ranunculus

Chromosome numbers of plant species from the Canary Islands

ISSN:0253-1453ISSN:1420-906