Brita Stedje

Comparison of multivariate methods for the analysis of genetic resources and adaptation in Phytolacca dodecandra using RAPD.

Abstract The extent of genetic differentiation among 17 Ethiopian populations (249 individuals) of Phytolacca dodecandra (Endod) sampled along altitudinal gradients that varied from 1600 to 3000 m was investigated using random amplified polymorphic DNA (RAPD). The populations were classified into three altitude groups: lowland (1600–2100 m), central-highland (2101–2500 m) and highland (2500–3000 m). Seventy polymorphic loci scored from 12 RAPD primers, singly or in combination with ecogeographical variables (altitude, longitude, latitude, temperature and rainfall), were used for principal component, discriminant, correlation, and stepwise multiple regression analyses. Principal component analysis (PCA) clearly differentiated lowland and the central-highland populations from those of the highlands independent of their geographical regions. Canonical discriminant analysis separated the lowland plants from those of the highlands with the central-highland plants being intermediate. Classificatory discriminant analysis corrected classification of 92.8% of the 249 plants into their respective three altitude groups. Multiple regression analysis identified a strong association between some RAPDs and altitude, temperature and rainfall, while the variation in most RAPDs was explained by combinations of the different ecogeographical variables. It is hypothesised that the different altitude groups may be (1) chemical and/or physiological ecotypes produced as a result of complex interactions of altitude with climatic and/or edaphic factors, or (2) different in ploidy levels. The significant correlations obtained between population means from some RAPDs and altitude and temperature as well as the strong association of some RAPDs with the ecogeographical variables in the multiple regression analysis suggest that part of the RAPD polymorphism could be adaptive, and responsive to environmental selection.

Taxonomy and Evolutionary Relationships in the Saxifraga rivularis Complex

Abstract In many arctic-alpine plant groups, reticulate evolutionary histories have resulted in problems with species delimitation and phylogenetic reconstruction. In the Saxifraga rivularis complex (2n  =  26, 52), the number of species accepted ranges from a single polymorphic one (S. rivularis s.l.) to several (the circumpolar S. hyperborea, the amphi-Atlantic S. rivularis, the three amphi-Pacific species S. bracteata, S. flexuosa, and S. arctolitoralis, and S. debilis in the Rocky Mountains). A combination of molecular (AFLPs), flow cytometrical, and morphological data from samples covering most of the distribution range was used to delimit taxonomic species and to unravel their evolutionary relationships. Four lineages with distinct morphological differences were recognized, representing four species: the diploids S. bracteata, S. hyperborea (including S. flexuosa), and S. debilis, and the tetraploid S. rivularis (including S. arctolitoralis). Based on a synthesis of the available data we provide a taxonomic revision of the complex and propose one rank change (S. rivularis subsp. arctolitoralis comb. et stat. nov.). Genome sizes as well as the intermediate position of the S. rivularis lineage in the molecular and morphological analyses suggest a single allopolyploid origin from the S. bracteata and the S. hyperborea lineages, most likely in Beringia.

Finding Evolutionary Processes Hidden in Cryptic Species

Cryptic species could represent a substantial fraction of biodiversity. However, inconsistent definitions and taxonomic treatment of cryptic species prevent informed estimates of their contribution to biodiversity and impede our understanding of their evolutionary and ecological significance. We propose a conceptual framework that recognizes cryptic species based on their low levels of phenotypic (morphological) disparity relative to their degree of genetic differentiation and divergence times as compared with non-cryptic species. We discuss how application of a more rigorous definition of cryptic species in taxonomic practice will lead to more accurate estimates of their prevalence in nature, better understanding of their distribution patterns on the tree of life, and increased abilities to resolve the processes underlying their evolution.

RAPD variation in Solanum anguivi Lam. and S. aethiopicum L. (Solanaceae) in Uganda

Variation in 39 polymorphic RAPD markerswas studied for 18 populations of Solanum anguivi, S. aethiopicum Gilogroup and S. aethiopicum Shum groupin Uganda. UPGMA and PCO analyses of thedata revealed no clear groupingscorresponding to the species and groups. AnAMOVA analysis of the genetic variationshowed that the variation among species andgroups was less than 10%, whereas thevariation within species and groups wasmore than 90%. A Mantel test showed nocorrelation between genetic distance andgeographic distance. The data gives onlyvery weak support for the separation of themore morphologically distinct S.aethiopicum and S. anguivi. TheGilo- and Shum-groups of S.aethiopicum, which were previouslyregarded as two separate species can not beseparated on the basis of RAPD data, and itis most likely that they are keptmorphologically distinct by a strongman-made selection pressure.

Phylogenetic relationships and generic delimitation of sub-SaharanScilla (Hyacinthaceae) and allied African genera as inferred from morphological and DNA sequence data

The genusScilla has recently been split into two genera,Scilla s. str. andLedebouria, based on morphological characters of South African species. This splitting, as well as the phylogenetic relationships between these genera and the related generaDrimia andDrimiopsis, is here discussed in the light of cladistic analyses of morphological and DNA sequence data of species from tropical Africa, the Mediterranean and India. Two chloroplast DNA regions are analysed: the intergenic spacer between thetRNA genesL(UAA) andF(GAA) and theL(UAA) intron.

Chromosome evolution within theOrnithogalum tenuifolium complex (Hyacinthaceae), with special emphasis on the evolution of bimodal karyotypes

Hypotheses on the evolution of the karyotypes of 8 chromosome races (2n = 4, 6, 8, 10, 12, 16-two forms, 26) within theOrnithogalum tenuifolium complex are discussed. Four of the karyotypes are strictly bimodal: 2n = 8 (6 long and two short chromosomes), 2n = 10 (6 long and 4 short chromosomes), 2n = 12 (6 long and 6 short chromosomes) and 2n = 16 (12 long and 4 short chromosomes). The hypotheses are tested by means of measurements of nuclear DNA content, studies of meiosis and pollen fertility of hybrids, and comparisons of karyotype morphology. The results indicate that the E. African 2n = 12 chromosome race is the most primitive and has given rise to the other chromosome races. The 2n = 6 race is found to have a significantly higher fitness than the 2n = 12 race.

Genetic diversity and differentiation in Ethiopian populations of Phytolacca dodecandra as revealed by AFLP and RAPD analyses

Amplified fragment length polymorphism (AFLP) and random amplified polymorphic DNA (RAPD) analyses were performed on six populations (a total of 89 individuals) of Phytolacca dodecandra (endod) collected in Ethiopia. The populations were selected based on our previous investigation to represent two altitude groups: lowland/central-highland (1600–2500 m) and highland (2501–3000 m). A total of 197 AFLP and 68 RAPD markers were scored from 5 primer pairs and 12 random primers, respectively. The overall patterns obtained for AFLPs and RAPDs from diversity, cluster and principal component analyses were very comparable. However, the moderate correlation (r = 0.56) between AFLP and RAPD similarity matrices as well as the discrepancies in diversity estimates between the two techniques in some populations and in the lowland/central-highland plants could be due to differences in sensitivity of reaction conditions, bias in scoring of bands, number of markers used for analyses, and/or parts of the genome surveyed. For both AFLP and RAPD, the lowland/central-highland populations showed higher polymorphism and Shannon information measure (H) than the highlands. Cluster and principal component analyses performed for both marker types have also clearly demonstrated the differentiation of all the lowland/central highland plants from those of the highlands, in agreement with our previous conclusion. Markers scored from any of the five AFLP primer pairs were sufficient to clearly distinguish the two altitude groups; with RAPD, selection of about 8 informative markers produced by seven random primers was needed for the same purpose.

Phylogenetic relationships in the genus Crinum (Amaryllidaceae) with emphasis on tropical African species : evidence from trnL-F and nuclear ITS DNA sequence data

The subfamily Thalictroideae, which is clearly defined by its chromosome characters, contains nine or ten genera. Here we use sequences of chloroplast rbcL and matK genes as well as non-coding trnL-F and nuclear ITS regions to reconstruct the generic level phylogeny of this subfamily. Our data recognize three major groups within Thalictroideae: (1) Thalictrum, Leptopyrum, Paropyrum, and Paraquilegia; (2) Urophysa, Semiaquilegia, and Aquilegia; and (3) Dichocarpum, Enemion, and Isopyrum. Isopyrum anemonoides, the sole species of Paropyrum, and Paraquilegia form a clade sister to Leptopyrum; together they make up the first group. Isopyrum manshuricum and I. thalictroides form another clade within the third group. Isopyrum anemonoides is sister to the monophyletic Paraquilegia. Our data suggest that Isopyrum is polyphyletic and support the segregate genus Paropyrum. Reconstruction of petal evolution suggests a secondary loss of petals in Enemion and Thalictrum, in contrast with the view that apetalous taxa are the most primitive. Petals with longer stalks in Dichocarpum are shown to be derivative, refuting the viewpoint that this type is a primitive condition. The flat petals in Paraquilegia may be derived from the tubular-type petals in Paropyrum and Leptopyrum, and spurred petals are thought to have originated from a single ancestor.

A new low chromosome number forOrnithogalum tenuifolium (Hyacinthaceae)

A new chromosome number (2n=4) forOrnithogalum tenuifoliumDelaroche is reported. The new chromosome race is postulated to have originated by a Robertsonian translocation from a Southern African chromosome race with six chromosomes, and represents thus the final step in a series of decreasing basic number of the species.

Ledebouria, Resnova and Drimiopsis : a tale of three genera

The monophyletic status of Ledebouria, Resnova and Drimiopsis (Hyacinthaceae) was investigated using cladistic analyses of morphological characters as well as by combined trnL-F and morphology dataset. Based on morphology alone, numerous synapomorphies support Ledebouria, Resnova and Drimiopsis as three separate clades. In contrast, trnL-F data in a reduced taxon sample suggest that Resnova and Drimiopsis are imbedded within Ledebouria, while in combination with morphology again suggest them to be separate. The analysis of morphological data shows that the majority of morphological characters listed by Manning & al. (2004) to support Ledebouria s.1. are homoplasious or symplesiomorphies. A revised taxonomy of Ledebouria, Resnova and Drimiopsis is premature.