We studied the phylogeography of Chinese yew (Taxus wallichiana), a tree species distributed over most of southern China and adjacent regions. A total of 1235 individuals from 50 populations from China and North Vietnam were analysed for chloroplast DNA variation using polymerase chain reaction-restriction fragment length polymorphism of the trnL-F intron-spacer region. A total of 19 different haplotypes were distinguished. We found a very high level of population differentiation and a strong phylogeographic pattern, suggesting low levels of recurrent gene flow among populations. Haplotype differentiation was most marked along the boundary between the Sino-Himalayan and Sino-Japanese Forest floristic subkingdoms, with only one haplotype being shared among these two subkingdoms. The Malesian and Sino-Himalayan Forest subkingdoms had five and 10 haplotypes, respectively, while the relatively large Sino-Japanese Forest subkingdom had only eight. The strong geography-haplotype correlation persisted at the regional floristic level, with most regions possessing a unique set of haplotypes, except for the central China region. Strong landscape effects were observed in the Hengduan and Dabashan mountains, where steep mountains and valleys might have been natural dispersal barriers. The molecular phylogenetic data, together with the geographic distribution of the haplotypes, suggest the existence of several localized refugia during the last glaciation from which the present-day distribution may be derived. The pattern of haplotype distribution across China and North Vietnam corresponded well with the current taxonomic delineation of the three intraspecific varieties of T. wallichiana.

The attributes of codominance, reproducibility and high resolution have all contributed towards the current popularity of nuclear microsatellites as genetic markers in molecular ecological studies. One of their major drawbacks, however, is the development phase required to obtain working primers for a given study species. To facilitate project planning, we have reviewed the literature to quantify the workload involved in isolating nuclear microsatellites from plants. We highlight the attrition of loci at each stage in the process, and the average effort required to obtain 10 working microsatellite primer pairs.

Summary The genome evolution of ferns has been considered to be relatively static compared with angiosperms. In this study, we analyse genome size data and chromosome numbers in a phylogenetic framework to explore three hypotheses: the correlation of genome size and chromosome number, the origin of modern ferns from ancestors with high chromosome numbers, and the occurrence of several whole‐genome duplications during the evolution of ferns. To achieve this, we generated new genome size data, increasing the percentage of fern species with genome sizes estimated to 2.8% of extant diversity, and ensuring a comprehensive phylogenetic coverage including at least three species from each fern order. Genome size was correlated with chromosome number across all ferns despite some substantial variation in both traits. We observed a trend towards conservation of the amount of DNA per chromosome, although Osmundaceae and Psilotaceae have substantially larger chromosomes. Reconstruction of the ancestral genome traits suggested that the earliest ferns were already characterized by possessing high chromosome numbers and that the earliest divergences in ferns were correlated with substantial karyological changes. Evidence for repeated whole‐genome duplications was found across the phylogeny. Fern genomes tend to evolve slowly, albeit genome rearrangements occur in some clades.

Chloroplast DNA sequences were obtained from 331 Asplenium ceterach plants representing 143 populations from throughout the range of the complex in Europe, plus outlying sites in North Africa and the near East. We identified nine distinct haplotypes from a 900 bp fragment of trnL-trnF gene. Tetraploid populations were encountered throughout Europe and further afield, whereas diploid populations were scarcer and predominated in the Pannonian-Balkan region. Hexaploids were encountered only in southern Mediterranean populations. Four haplotypes were found among diploid populations of the Pannonian-Balkans indicating that this region formed a northern Pleistocene refugium. A separate polyploid complex centred on Greece, comprises diploid, tetraploid and hexaploid populations with two endemic haplotypes and suggests long-term persistence of populations in the southern Mediterranean. Three chloroplast DNA (cpDNA) haplotypes were common among tetraploids in Spain and Italy, with diversity reducing northwards suggesting expansion from the south after the Pleistocene. Our cpDNA and ploidy data indicate at least six independent origins of polyploids.

No abstract

To examine the performance and information content of different marker systems, comparative assessment of population genetic diversity was undertaken in nine populations of Athyrium distentifolium using nine genomic and 10 expressed sequence tag (EST) microsatellite (SSR) loci, and 265 amplified fragment length polymorphism (AFLP) loci from two primer combinations. In range-wide comparisons (European vs. North American populations), the EST-SSR loci showed more reliable amplification and produced more easily scorable bands than genomic simple sequence repeats (SSRs). Genomic SSRs showed significantly higher levels of allelic diversity than EST-SSRs, but there was a significant correlation in the rank order of population diversities revealed by both marker types. When AFLPs, genomic SSRs, and EST-SSRs are considered, comparisons of different population diversity metrics/markers revealed a mixture of significant and nonsignificant rank-order correlations. However, no hard incongruence was detected (in no pairwise comparison of populations did different marker systems or metrics detect opposingly significant different amounts of variation). Comparable population pairwise estimates of F(ST) were obtained for all marker types, but whilst absolute values for genomic and EST-SSRs were very similar (F(ST) = 0.355 and 0.342, respectively), differentiation was consistently higher for AFLPs in pairwise and global comparisons (global AFLP F(ST) = 0.496). The two AFLP primer combinations outperformed 18 SSR loci in assignment tests and discriminatory power in phenetic cluster analyses. The results from marker comparisons on A. distentifolium are discussed in the context of the few other studies on natural plant populations comparing microsatellite and AFLP variability.

Little is known about the mode of transmission of chloroplasts in ferns, despite the importance of such knowledge for molecular phylogenetic and biosystematic studies. Andersson‐Kötto (1930, 1931) inferred from crossing experiments that chloroplasts are inherited biparentally in Asplenium scolopendrium L. Here we present evidence from artificial hybridisation that demonstrates maternal inheritance of chloroplast DNA in the genus Asplenium (Aspleniaceae, Pteridophyta) using length variation in a non‐coding spacer (trnLUAA‐trnFGAA) in the chloroplast DNA.

In this paper we demonstrate that, by investigating polyploid complexes in d.\p/enium, it is possible to locate the areas in Europe that are southern glacial rcfugia, and arc likely to have been so since the tjcginning of the Plcistoccnc during the consecutive cold and warm periods in Europe. Identification and consenation of thrsc specific areas that s e n e as safe havens for plants, and perhaps animals, is of paramount importance for the maintcnancc of European liiodiversity because hlan's activities arc resulting in an ever-increasing loss of natural habitats and putting diversity at risk. The genus A.\pl~nium in Europe comprises some 50 taxa: half of these are diploid while the other half are polyploids derived from thr diploids. All aspleniums in Europe are (small) rock ferns with high suhstratc specificity. Today, most of mainland Europe, Scandinavia and the British Isles has been colonized by polyploid dsplenium species, while the diploids that gavc rise to these polyploids are distributed around (and more or less confined to) the hfcditcrrancan Basin. In the tetraploids genetic variation is partitioned mostly between sites, whereas diploids show a high dcp-cc of genetic variation both within and between sites. The tctraploid taxa seem capable of single spore colonization via intragametophytic selling, but the diploid taxa appear to he predominantly outbreeding, For most diploids at least two gametophytes, produced by different spores, have to tic prcscnt to achieve fertilization and subsequent sporophyte formation for the successful colonization of a new site. This results in a slower rate of colonization. The formation of auto-and allopolyploid taxa from diploid communities appears to have been a recurrent and common fcaturc in Europe. Minority cytotypc exclusion is likely to prevent the establishment of tetraploids within the diploid communities, but spores from tetraploids can cstaldish populations outside the diploid communities. The differences between colonization abilities of tetraploid and ancestral diploid taxa, resulting from their differcnt hrccding systems, has prevented thc merging and mingling of their ranges and led to the establishment of contact/ hybrid zoncs. This has resulted in the restriction of diploid populations to ancient glacial rcfugia and the colonization of the rest of Europe by polyploids. Mapping the rurrrnt distribution of these diploid communities and comparing the genetic diversity within and between outbrccding diploid i-l.cp/zninm taxa allows us to dcfinc the area, age and historical biogeography of thcsc rrfugia and to assess thrir importance for present day genetic and species diversity in Europe. 0 lW9 'l'tir Liiiiiriiii Socirt! 111 1.11ii1i11ii