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Oat sterile dwarf virus (OSDV) is a fijivirus whose genome segments 7 to 10 were sequenced earlier. In the current study, the complete genome was sequenced. To confirm the genome ends, rapid amplification and sequencing of cDNA ends were performed. The complete OSDV genome consists of 10 double-stranded RNA (dsRNA) segments with a total size of 28,686 bp. The sense strand sequence of all segments has the terminal consensus sequence motif 5’-AACGA(5–7)… U(6–8)(A/U)GUC-3’, in which the length of the stretches of A and U varies, being slightly shorter for segments 1–4 and longer for segments 5–10. The 3’ end of segment 3 is …UGUC, not AGUC as in the other segments. Segments 5, 7, and 10 contain two small ORFs, while each of the other segments contains one long ORF. ORF7-2 and ORF9 are slightly longer than annotated before. Phylogenetic analysis based on amino acid sequences of the RNA-directed RNA polymerase (RdRP) placed OSDV between the plant fijiviruses and Nilaparvata lugens reovirus (NLRV), an insect fijivirus that does not replicate in plants. OSDV RdRP shares 48–49% sequence identity with other plant-infecting fijivirus RdRPs and 30% identity with that of NLRV. OSDV has earlier been reported in several Northern and Central European countries. The sequencing of the complete genome serves as a reference for identifying all segments in future high-throughput sequencing datasets, enabling the investigation of the molecular epidemiology and evolution of OSDV. [ABSTRACT FROM AUTHOR]

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Locally adapted ecotypes can constitute an important part of the biodiversity, especially in young floras with few endemic species. However, the origins, distinctness and conservation value of many ecotypes remain uncertain because genetic data are lacking or no common-garden study has been carried out. In the present study, we evaluated the distinctness and genetic structure of a phenotypically deviating morph of Rhinanthus angustifolius, growing in calcareous spring fens on the Baltic island of Gotland. Using data from a common-garden experiment and analyses of nuclear microsatellite variation, we compared fen populations on Gotland with conspecific populations from habitats more typical of the study species. We also included the fen specialist R. osiliensis from the Baltic island of Saaremaa in the molecular analyses to make further inferences about the origin of the Gotlandic fen morph. Our data indicate that the Gotlandic fen populations constitute a phenotypically and genetically distinct ecotype that most likely has evolved at least two times on Gotland after the last ice age. In congruence with previous studies, we also infer that fen ecotypes have evolved independently on Gotland and Saaremaa. We propose a varietal status for the Gotlandic fen ecotype and give recommendations for the conservation of this taxon. [ABSTRACT FROM AUTHOR]

Phenotypic variation may be genetically determined or reflect phenotypic plasticity. More common plants are expected to be less differentiated between and within regions and more adapted than less common ones. However, such differences might not develop in hybridizing species which cannot evolve completely independently. We collected 311 genets of Carex flava, 215 of C. viridula and 46 of their hybrid C. × subviridula from 42 natural populations in cold temperate Estonia, mild temperate Lowland Switzerland and alpine Highland Switzerland. Three plantlets from each genet were planted to three experimental gardens, one in each region. We measured survival, growth, reproduction and morphological traits. The experimental transplants showed strong plasticity and grew smallest in the alpine garden. The less common C. viridula was slightly more differentiated between regions of origin than the more common C. flava and the hybrid. However, this depended on the experimental garden. Significant origin-by-garden-by-taxon and taxon-by-garden interactions suggest differential adaptation among populations and taxa. Regional differed from non-regional plants in several traits indicating both adaptations and, especially for C. viridula, maladaptations to the home regions. For C. flava, plant seed production was higher when mean annual temperature and precipitation were more similar between population of origin and garden, suggesting local adaptation to climate. Hybrids were intermediate between parental taxa or more similar to one of them, which was retained across gardens. We conclude that plasticity, genetic variation and genotype-environment interactions all contributed to regional differentiation of the closely related species. Hybridization did not completely align evolutionary patterns, and the less common species showed slightly more genetic differentiation between populations and more maladapted traits than the more common one. [ABSTRACT FROM AUTHOR]

Rarer species are expected to show stronger geographic differentiation than more common species. However, if rare species hybridize with common species, differentiation may be quite similar between the two due to genetic admixing via backcrossing. We studied morphological differentiation of plants of 21 natural populations of the more common Carex flava, 16 of the less common Carex viridula and 6 of their hybrids from 27 sites in three climatically different regions, Estonia, Lowland Switzerland and Highland Switzerland. Univariate ANOVA and multivariate principal component analysis of 14 morphological characters, describing both vegetative and reproductive characters, allowed to clearly distinguish C. flava from C. viridula. Carex viridula populations showed stronger regional variation than C. flava. Hybrids had both intermediate and transgressive characters in Switzerland and Estonia. On average, hybrids from Lowland Switzerland were more similar to Swiss C. flava than to C. viridula, while hybrids from Estonia were morphologically intermediate between plants of Estonian populations of the parental species. The results suggest that within-region genetic admixing between species has limited potential to lead to region-specific similarity between species, at least in our model system of the C. flava complex. We conclude that C. flava and C. viridula are clearly distinct species and that, despite hybridization, geographic differentiation is more pronounced in the less common C. viridula than in C. flava. [ABSTRACT FROM AUTHOR]

The intricate genus Rhinanthus L. contains many taxonomically unresolved taxa. The assessment of genetic diversity may clarify the differentiation and taxonomic relationships between species and help to determine their mating system, which is important for understanding the future prospects of populations and species. Isozymes were used to assess the mating system, genetic diversity, and differentiation in R. rumelicus, R. osiliensis, R. wagneri, R. alectorolophus, and R. angustifolius from sect. Cleistolemus and R. minor from sect. Rhinanthus. Genetic diversity at species level was found to be higher in widespread R. angustifolius and R. rumelicus compared with insular endemic R. osiliensis. Positive inbreeding coefficient revealed dominant inbreeding in endemic R. osiliensis and R. wagneri. We also detected a significant departure from Hardy-Weinberg equilibrium in some populations of R. rumelicus and R. angustifolius. The common R. alectorolophus and R. minor and several populations of R. rumelicus and R. angustifolius displayed a mixed mating mode. Six studied species divided into three distinct clusters. Rhinanthus alectorolophus was the most differentiated taxon among the investigated species. The species of sect. Cleistolemus formed two distinct groups. The first cluster consisted only of R. alectorolophus while another comprised R. rumelicus, R. osiliensis, R. wagneri, and R. angustifolius, indicating their close affinity. Thus, our isozyme results call into question the monophyly of section Cleistolemus and the taxonomic position of R. alectorolophus. [ABSTRACT FROM AUTHOR]

Genetic diversity is affected by breeding systems, life history traits and the distribution of species. Generally, inbred species with restricted geographic distribution have lower genetic variation compared to common outbreeding plant species. Rhinanthus osiliensis is a narrow endemic growing in calcareous spring fens on the island Saaremaa, Estonia. Presumably the closest congener of R. osiliensis is R. rumelicus, which is widely distributed in Eastern and Central Europe and the Balkan Peninsula. Isozymes were used to describe the mating system, levels of genetic variation and differentiation between the populations of R. osiliensis and R. rumelicus. Genetic diversity was found to be higher in widespread R. rumelicus compared to the endemic R. osiliensis. A significantly higher inbreeding coefficient with a low germination rate indicated substantial autogamy in R. osiliensis, whereas R. rumelicus displayed a mixed mating mode with a moderate inbreeding coefficient and a high germination rate. The low genetic differentiation between R. osiliensis and R. rumelicus confirmed their close affinity and the short evolutionary period of both taxa after the postglacial colonization. Considering the restricted geographic range and inbreeding in populations of R. osiliensis, this species may face a loss of genetic variation in the future. [ABSTRACT FROM AUTHOR]

Carex magellanica subsp. irrigua is a wet habitat taxon that is extinct or declining in the Baltic States and Central Europe, but still quite common in northern areas, in Fennoscandia and Alaska. We investigated the extent of genetic variation within and among populations and geographic regions of this subspecies. Isozyme electrophoresis in polyacrylamide gels was applied to characterize genetic diversity with allozymes as genetic markers. Of the nine putative isozyme loci assessed, five (56%) were found to be polymorphic. The genetic diversity in small and fragmented Estonian populations was lower ( He = 0.034) than in larger Fennoscandian and Alaskan populations (average He = 0.082). All standard genetic parameters ( Ae, Ho, He, P, Fis, t) showed the lowest values in Estonian populations. The heterozygosity level in Fennoscandian populations was low ( Ho = 0.01), whereas no heterozygotes were found in Estonian and Alaskan populations. High Fis values indicate that C. magellanica subsp. irrigua is predominantly inbreeding. The main reason for its decline in Estonia is the destruction of suitable habitats. More attention to the protection of Estonian habitats is needed to maintain genetic diversity and stop further decline of this taxon. [ABSTRACT FROM AUTHOR]

1. Loss of plant species induced by adverse human influence and habitat fragmentation might be delayed due to a slow response to changed environmental conditions. This phenomenon is known as extinction debt, which can lead to the underestimation of actual threats to biodiversity. To adequately estimate the condition of recently fragmented plant communities and avoid future loss of species, good indicators of forthcoming extinctions are needed. 2. We studied the behaviour of genetic diversity of a relatively common habitat specialist grass Briza media in fragmented calcareous grasslands in which the extinction debt has been previously documented. Species richness in this system is shown to be determined by historical landscape patterns and human population densities prevailing centuries ago. We hypothesize that genetic diversity in this grassland system is related to current landscape patterns and contemporary human impact since genetic diversity might react more quickly to environmental changes than species diversity. 3. In contrast to species diversity, genetic diversity was indeed best described by current connectivity of grasslands. Additionally, genetic diversity was negatively related to current human population density, indicating an adverse effect of contemporary human settlements on studied species. The faster response of genetic diversity to changed environmental conditions compared to species richness was further supported by the absence of an expected correlation between species richness and genetic diversity. 4. Human population density a century ago had a positive effect on genetic diversity. A similar effect has been demonstrated for species richness in these grasslands, indicating that traditional land use in the past has supported the development of both genetic and species diversity. 5. Synthesis. Genetic diversity of Briza media in fragmented communities is reacting quickly to changes in landscape structure and anthropogenic pressure. Our results confirm that plant species can be prone to genetic deterioration due to habitat fragmentation and negative anthropogenic impact even if the decline in species richness has been delayed by extinction debt. Thus, a decrease of population genetic diversity in fragmented communities can be taken as the first indication of future species losses. [ABSTRACT FROM AUTHOR]