Tetraploid inheritance has two extremes: disomic in allotetraploids and tetrasomic in autotetraploids. The possibility of mixed, or intermediate, inheritance models has generally been neglected. These could well apply to newly formed hybrids or to diploidizing (auto)tetraploids. We present a simple likelihood-based approach that is able to incorporate disomic, tetrasomic, and intermediate inheritance models and estimates the double-reduction rate. Our model shows that inheritance of microsatellite markers in natural tetraploids of Rorippa amphibia and R. sylvestris is tetrasomic, confirming their autotetraploid origin. However, in F 1 hybrids inheritance was intermediate to disomic and tetrasomic inheritance. Apparently, in meiosis, chromosomes paired preferentially with the homolog from the same parental species, but not strictly so. Detected double-reduction rates were low. We tested the general applicability of our model, using published segregation data. In two cases, an intermediate inheritance model gave a better fit to the data than the tetrasomic model advocated by the authors. The existence of inheritance intermediate to disomic and tetrasomic has important implications for linkage mapping and population genetics and hence breeding programs of tetraploids. Methods that have been developed for either disomic or tetrasomic tetraploids may not be generally applicable, particularly in systems where hybridization is common.

The ecological implications of a Yakutian mammoth's last meal van General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. AbstractPart of a large male woolly mammoth (Mammuthus primigenius) was preserved in permafrost in northern Yakutia. It was radiocarbon dated to ca. 18,500 14 C yr BP (ca. 22,500 cal yr BP). Dung from the lower intestine was subjected to a multiproxy array of microscopic, chemical, and molecular techniques to reconstruct the diet, the season of death, and the paleoenvironment. Pollen and plant macro-remains showed that grasses and sedges were the main food, with considerable amounts of dwarf willow twigs and a variety of herbs and mosses. Analyses of 110-bp fragments of the plastid rbcL gene amplified from DNA and of organic compounds supplemented the microscopic identifications. Fruit-bodies of dung-inhabiting Ascomycete fungi which develop after at least one week of exposure to air were found inside the intestine. Therefore the mammoth had eaten dung. It was probably mammoth dung as no bile acids were detected among the fecal biomarkers analysed. The plant assemblage and the presence of the first spring vessels of terminal tree-rings of dwarf willows indicated that the animal died in early spring. The mammoth lived in extensive cold treeless grassland vegetation interspersed with wetter, more productive meadows. The study demonstrated the paleoecological potential of several biochemical analytical techniques.

The frequency of polyploidy increases with latitude in the Northern Hemisphere, especially in deglaciated, recently colonized areas. The cause or causes of this pattern are largely unknown, but a greater genetic diversity of individual polyploid plants due to a doubled genome and/or a hybrid origin is seen as a likely factor underlying selective advantages related to life in extreme climates and/or colonization ability. A history of colonization in itself, as well as a recent origin, and possibly a limited number of polyploidization events would all predict less genetic diversity in polyploids than in diploids. The null hypothesis of higher gene diversity in polyploids has to date hardly been quantified and is here tested in self-incompatible Rorippa amphibia (Brassicaceae). The species occurs in diploid and tetraploid forms and displays clear geographical polyploidy in Europe. On the basis of eight microsatellite loci it can be concluded that the level of gene diversity is higher in tetraploids than in diploids, to an extent that is expected under neutral evolution when taking into account the larger effective population size in the doubled cytotype. There is thus no evidence for reduced genetic diversity in the tetraploids. The evidence presented here may mean that the tetraploids' origin is not recent, has not been affected by bottlenecks and/or that tetraploids were formed multiple times while an effect of introgression may also play a role.

This study aims to identify genetically diverged clone mates in apomictic dandelions. Clone mates are defined as individuals that may have diverged as a result of mutation accumulation and that have undergone only clonal reproduction since their most recent common ancestor. Based on distinctive morphology and an aberrant and rare chloroplast haplotype, northwest European individuals of Taraxacum section Naevosa are well suited for the detection of clonal lineages in which mutation has occurred. In the case of strictly clonal reproduction, nuclear genetic variability was expected to be hierarchically organized. Nucleotide polymorphisms in internal transcribed spacer (ITS) sequences, however, were incompatible with a clonal structure of the Norwegian individuals, probably due to persistent ancestral polymorphisms that pre-date the origin of the Naevosa clone. This interpretation is supported by the presence of ITS variants in section Naevosa that were also found in distantly related dandelions. In contrast to the ITS sequence data, amplified fragment length polymorphisms (AFLPs), isozymes and microsatellites strongly supported the contention of prolonged clonal reproduction and mutation accumulation in Norwegian Naevosa. Because these markers are generally considered to be more variable and more rapidly evolving than ITS sequences, mutations in these markers probably evolved after the origin of the clone. Within the Norwegian clone, a surprising number of markers distinguished the clone mates. As a consequence, incorporation of mutation in the detection of clone mates is anticipated to have a big impact on estimates of size, geographical range and age of clones as well as on experimental designs of studies of clonal plants.

The five tetraploid (2n = 36) species in the Californian genus Microseris illustrate three very different evolutionary scenarios.1 The perennial M. scapigera of Australia and New Zealand has arisen from a hybrid between an annual and a perennial species in North America after chromosome duplication and long-distance dispersal (Chambers 1955;Van Houten et al. 1993). Chloroplast DNA analysis (Wallace & Jansen 1990) suggests that the maternal parent of this hybrid was ancestral to the present-day annuals, and morphological evidence suggests that the paternal parent is related to the present-day M. borealis (Chambers 1955). M. scapigera therefore exemplifies the accidental arrival of a new genetic entity in a geographically isolated Keywords: chloroplast DNA, concerted evolution, extinct parent, ITS, Microseris, polyploids, RAPD 13 September 1996; revision received 23 January 1997; 4 February 1997 Molecular Ecology 1997 Figure 1, from Chambers (1955), summarizes the possible relationships among the various annuals. Recognition of the two tetraploid entities was a key factor in his analysis. Except for the strictly coastal species, M. bigelovii, the ecological differentiation among the Californian annuals of Microseris is very subtle and they occur frequently in mixed populations. Artificial hybrids among the diploids are at least partially fertile, and the distribution of chloroplast genomes is not congruent with the species borders (Roelofs & Bachmann 1995, 1997. Still, all of these species appear to retain their identity. ReceivedThe tetraploids may be as crucial to an understanding of factors involved in the origin and maintenance of the species listed under (3) as they were for the elucidation of their taxonomy. Molecular data provide new sources of evidence for polyploid evolution (Doyle et al. 1990;Soltis & Soltis 1993;Soltis et al. 1995;Lowe & Abbott 1996). This investigation was designed to use molecular data to determine the exact parentage of M. acuminata and M. campestris including evidence for a unique origin or a repeated local origin. This information is essential for a search for factors involved in the apparently stable coexistence of the ecologically similar Californian annuals of Microseris. agarose gels and blotted on to Qiabrane plus membranes. DNA digested with HinfI (four base-pair recognition site) was separated on 6% polyacrylamide sequence gels and electroblotted using the methodology described by Van Houten et al. (1993). Hybridization was performed with radioactively labelled Lettuce SacI chloroplast clones described by Jansen & Palmer (1987). PCR amplifications for RAPD analysis with DNA mini preparations from one leaf (Hombergen & Bachmann 1995) were performed with Super Taq polymerase (HT Biotechnologies) in a MJ Research PTC-100/96 thermal cycler as previously described (Roelofs & Bachmann 1995). Primer kits A, C and H from Operon Technologies (USA) were screened for reliably reproducible polymorphic RAPD markers. The amplification products were separated on 1.5% agarose gels and ...

The disjunct allotetraploid lineage of the North American genus Microseris in New Zealand and Australia originated from one or a few diaspores after a single introduction via long‐distance dispersal. The plants have evolved into four morphologically distinct ecotypes: ‘fine‐pappus’, ‘coastal’, ‘murnong’, and ‘alpine’, from which the first two are grouped as Microseris scapigera, mainly from New Zealand and Tasmania, and the latter two as M. lanceolata, endemic to the Australian mainland. Three chloroplast (cp) DNA types were distinguished in each of the species, but their distribution, especially in M. lanceolata, showed discrepancies with ecotype differentiation. Here, we analyse the genetic structure of the nuclear (n) DNA among two plants of each of 55 New Zealand, Tasmanian, and Australian Microseris populations for amplified fragment length polymorphisms (AFLPs). The nuclear genetic structure is compared to geographical, ecotype, and cpDNA distribution, in order to resolve and illustrate the early process of adaptive radiation. The strongest signal in the AFLP pattern was related to geographical separation, especially between New Zealand and Australian accessions, and suggested an initial range expansion after establishment. The ecotypic differentiation was less‐well reflected in the AFLP pattern, and evidence was found for the occurrence of hybridization among plants at the same geographical region, or after dispersal, irrespective of the cpDNA‐ and ecotypes. This indicated that the ecotype characteristics were maintained or re‐established by selection. It also showed that genetic differentiation is not an irreversible and progressive process in the early stage of adaptive radiation. Our results illustrate the precarious balance between geographical isolation and selection as factors that favour differentiation, and hybridization as factor that reduces differentiation.

We developed microsatellites for the bromeliads Tillandsia fasciculata and Guzmania monostachya, epiphytes of Central‐American montane rain forests. Fragments obtained using amplified fragment length polymorphism (AFLP) pre‐amplification were enriched by hybridization with biotin‐labelled repeat sequences, and subsequently cloned and sequenced. Primers were designed for 15 loci; seven produced interpretable and repeatable amplification products and five were polymorphic in one or both species. We will use these primers to study the population structure of Bromeliaceae in relation to their breeding system as well as to their role in (re‐)colonization of secondary rain forests.

No abstract