A taxometric analysis ofLimonium (Plumbaginaceae) in Western Europe

A taxometric analysis ofLimonium species in Western Europe has provided evidence for the subgeneric groupings proposed by other authors. A cluster analysis suggests that the origin of sexual and agamospermous species has taken place separately. Sexual and agamospermous species are usually clustered separately. The lack of a sexual process in many agamospermous species, as indicated by the distribution of incompatibility morphs and by very low pollen fertility, suggests that the evolution of sexual and agamospermous taxa has been by different processes. It is suggested that following the origin of agamospermous species or species groups by hybridisation, subsequent evolution in the agamospermous taxa has occurred by asexual means. Evidence from the distribution of pollen/stigma incompatibility morphs, especially the existence of self-compatible agamospermous species supports this hypothesis.     

The taxonomic treatment of agamosperms in the genusLimonium mill. (Plumbaginaceae)

Agamospermous species account for a large proportion of the species ofLimonium. Agamospermy is indicated by uneven polyploidy or aneuploidy, low pollen stainability and by the presence of monomorphic self-incompatible populations. The taxonomic treatment of agamospermous taxa varies from recognition of all of them at the same specific rank or by utilising a range of ranks in the taxonomic hierarchy. The influence of evolutionary hypotheses on taxonomic systems is considered. Molecular data provide a means of measuring the genetical relationships of taxa and establishing groups in a taxonomic hierarchy.     

Molecular phylogenetics of Paphiopedilum (Cypripedioideae; Orchidaceae) based on nuclear ribosomal ITS and plastid sequences

Phylogenetic relationships in the genus Paphiopedilum were studied using nuclear ribosomal internal transcribed spacer (ITS) and plastid sequence data. The results confirm that the genus Paphiopedilum is monophyletic, and the division of the genus into three subgenera Parvisepalum, Brachypetalum and Paphiopedilum is well supported. Four sections of subgenus Paphiopedilum (Pardalopetalum, Cochlopetalum, Paphiopedilum and Barbata) are recovered as in a recent infrageneric treatment, with strong support. Section Coryopedilum is also recovered, with low bootstrap but high posterior probability values for support of monophyly. Relationships in section Barbata remain unresolved, and short branch lengths and the narrow geographical distribution of many species in the section suggest that it possibly underwent rapid radiation. Mapping chromosome and genome size data (including some new genome size measurements) onto the phylogenetic framework shows that there is no clear trend in increase in chromosome number in the genus. However, the diploid chromosome number of 2n = 26 in subgenera Parvisepalum and Brachypetalum suggests that this is the ancestral condition, and higher chromosome numbers in sections Cochlopetalum and Barbata suggest that centric fission has possibly occurred in parallel in these sections. The trend for genome size evolution is also unclear, although species in section Barbata have larger genome sizes than those in other sections. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 170 , 176–196.     

Genetic diversity in Cypripedium calceolus (Orchidaceae) with a focus on north-western Europe, as revealed by plastid DNA length polymorphisms

Background and Aims

Cypripedium calceolus, although widespread in Eurasia, is rare in many countries in which it occurs. Population genetics studies with nuclear DNA markers on this species have been hampered by its large nuclear genome size. Plastid DNA markers are used here to gain an understanding of variation within and between populations and of biogeographical patterns.

Methods

Thirteen length-variable regions (microsatellites and insertions/deletions) were identified in non-coding plastid DNA. These and a previously identified complex microsatellite in the trnL-trnF intergenic spacer were used to identify plastid DNA haplotypes for European samples, with sampling focused on England, Denmark and Sweden.

Key Results

The 13 additional length-variable regions identified were two homopolymer (polyA) repeats in the rps16 intron and a homopolymer (polyA) repeat and ten indels in the accD-psa1 intergenic spacer. In accD-psa1, most of these were in an extremely AT-rich region, and it was not possible to design primers in the flanking regions; therefore, the whole intergenic spacer was sequenced. Together, these new regions and the trnL-trnF complex microsatellite allowed 23 haplotypes to be characterized. Many were found in only one or a few samples (probably due to low sampling density), but some commoner haplotypes were widespread. Most of the genetic variation was found within rather than between populations (83 vs. 18%, respectively). Two haplotypes occurred from the Spanish Pyrenees to Sweden.

Conclusions

Plastid DNA data can be used to gain an understanding of patterns of genetic variation and seed-mediated gene flow in orchids. Although these data are less information-rich than those for nuclear DNA, they present a useful option for studying species with large genomes. Here they support the hypothesis of long-distance seed dispersal often proposed for orchids.Key words: Biogeography, Cypripedium calceolus, genome size, plastid microsatellites, population genetics, seed dispersal     

Characterisation of Rubus niveus: a prerequisite to its biological control in oceanic islands

This study is intended to inform the search for a biocontrol solution to stem the spread of Rubus niveus, a morphologically-diverse and invasive Rubus species which has become an aggressive invader in areas of the world outside its native range. The fragile biodiversity of islands can be especially threatened by this plant – exemplars of this are the Galápagos archipelago and Hawaii. This report focuses on the morphological and molecular work carried out to establish the homogeneity or intra-specific variation of R. niveus populations within the Galápagos Islands, as well as their kinship with plants of the same name found in Asia. The premise of this study is that genetic closeness between these populations offers increased probability that pathogens of R. niveus in its native range will also provide effective control in the target environment. Increased knowledge of the genetic make-up of R. niveus in both its native and naturalised locations will also help to assess the feasibility of using organisms which have been found to be effective against other Rubus species, but not hitherto considered for R. niveus itself.     

Speciation and evolution in the Gagea reticulata species complex (Tulipeae; Liliaceae)

For the 12 named taxa in the Gagea reticulata species complex, 609 cloned sequences of the low-copy nuclear gene malate synthase (MS) were used to investigate species relationships, using standard phylogenetic tools and network analyses. Three (homologous) copies of MS locus were present in each individual analyzed, and multiple alleles were present at most of these loci. Duplication of MS occurred after divergence of the G. reticulata complex. After comparisons, 591 sequence types (i.e. haplotypes) were identified, requiring implementation of novel statistical analyses to group haplotypes in a smaller number of groups/lineages to enable further study. Haplotype groups/lineages are not fully congruent with species limits with some widely present among species. MS genotypes at the root of the network are those of G. setifolia from central Iran, with more derived sequences in this species found in the west and northwest. Presence of ancestral genotypes in several other taxa may indicate either the retention of "ancestral" polymorphisms, more recent introgressive hybridization, or both. The relative DNA content of specimens was estimated with flow cytometry (FCM). The FCM analyses revealed two levels of DNA content (putatively "diploid" and "tetraploid"), but no correlation between number of MS gene copies and ploidy was found.     

Genome size diversity in orchids: consequences and evolution

Background

The amount of DNA comprising the genome of an organism (its genome size) varies a remarkable 40 000-fold across eukaryotes, yet most groups are characterized by much narrower ranges (e.g. 14-fold in gymnosperms, 3- to 4-fold in mammals). Angiosperms stand out as one of the most variable groups with genome sizes varying nearly 2000-fold. Nevertheless within angiosperms the majority of families are characterized by genomes which are small and vary little. Species with large genomes are mostly restricted to a few monocots families including Orchidaceae.

Scope

A survey of the literature revealed that genome size data for Orchidaceae are comparatively rare representing just 327 species. Nevertheless they reveal that Orchidaceae are currently the most variable angiosperm family with genome sizes ranging 168-fold (1C = 0·33–55·4 pg). Analysing the data provided insights into the distribution, evolution and possible consequences to the plant of this genome size diversity.

Conclusions

Superimposing the data onto the increasingly robust phylogenetic tree of Orchidaceae revealed how different subfamilies were characterized by distinct genome size profiles. Epidendroideae possessed the greatest range of genome sizes, although the majority of species had small genomes. In contrast, the largest genomes were found in subfamilies Cypripedioideae and Vanilloideae. Genome size evolution within this subfamily was analysed as this is the only one with reasonable representation of data. This approach highlighted striking differences in genome size and karyotype evolution between the closely related Cypripedium, Paphiopedilum and Phragmipedium. As to the consequences of genome size diversity, various studies revealed that this has both practical (e.g. application of genetic fingerprinting techniques) and biological consequences (e.g. affecting where and when an orchid may grow) and emphasizes the importance of obtaining further genome size data given the considerable phylogenetic gaps which have been highlighted by the current study.Key words: AFLP, C-value, chromosome, evolution, genome size, guard cell size, Orchidaceae, Robertsonian fission, Robertsonian fusion     

Polymorphism in the Aegean "five-loculed" species of the genus Campanula, Section Quinqueloculares (Campanulaceae)

Population variation in species of Campanula Section Quinqueloculares and related taxa has been studied. 19 species and 48 populations from the Aegean region have been sampled. There are few distinct character states available for analysis so that metric variables have been scored. 11 leaf variables and 19 flower variables have been measured in up to 683 plants. Regressions of variables with overall size have been calculated and where significant allometric variation has been detected residual scores have been used as variables. Hierarchical analysis of variance has indicated that a large part of the total variation is found between populations within species rather than within populations. Between the 10 most closely related species there is a considerable overlap in population means of variables. Multivariate analysis also fails to identify distinct species clusters. In particular principal components analysis provides additional evidence of overlap between species. It is suggested that a detailed study of genetic variation within and between species is required in order to establish the presence of any distinct phylogenetic lineages.