Isolation and characterization of polymorphic microsatellite loci in Asiatic sand sedge,Carex kobomugi Ohwi (Cyperaceae)

Fourteen polymorphic microsatellite loci were isolated from Asiatic sand sedge, Carex kobomugi Ohwi (Cyperaceae), a clonal perennial herb predominant in sandy coast vegetation in Japan. Polymorphism was surveyed for 24 ramets within a single population and for eight distinct individuals from six populations. Within a population, between two and eight alleles were found per locus, and expected heterozygosity ranged from 0.041 to 0.720. Among populations, a higher level of polymorphism was observed. The microsatellite loci were shown to be useful for the study of spatial genetic structure at fine scale and genetic differentiation among populations.     

Clonal structure and hybrid susceptibility to a smut pathogen in microscale hybrid zones of northern wetland Carex (Cyperaceae)

Interspecific hybrid taxa, especially those with the potential for clonal spread, may play important roles in community dynamics and plant-pathogen interactions. This study combines the mapping of clonal structure for two rhizomatous sedges (Carex limosa, C. rariflora) and their nearly sterile interspecific hybrid with an investigation of the relationship between these taxa and a nonsystemic floral smut pathogen (Anthracoidea limosa) in six subarctic fens in Nouveau-Québec, Canada. We used allozyme polymorphisms in 14 of 18 putative loci to confirm hybrid identification and to distinguish among genotypes for mapping. The incidence of A. limosa was 5-20 times greater on hybrids than on parental taxa across all sites at two spatial scales (intensive extent = 10.5 m(2), extensive extent = entire fens). Spatial autocorrelation was detected in smut incidence; however, its statistical removal did not alter the strong association between hybrids and smut infection. Smut incidence on both C. limosa and hybrids was greater when they were growing in areas of high hybrid density. Our study provides evidence that disease can help maintain boundaries between species. We suggest explanations for hybrid susceptibility and provide evidence for a model in which hybrids act as a source for reinfection for all three taxa during subsequent years.     

Growth pattern of Carex arenaria (Cyperaceae)

The origin of the orthotropic aerial shoot from the plagiotropic, horizontal rhizome of Carex arenaria L. (Cyperaceae) was studied. A previously proposed adnation or fusion of the first internode of the orthotropic shoot and the fourth internode of the plagiotropic shoot could not be anatomically confirmed. The rhizome branches sympodially and the point of branching results from intercalary meristematic activity in the plagiotropic shoot.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 145–151.     

福建薹草(莎草科)的考证

在整理和鉴定浙闽薹草属Carex植物的过程中,发现福建薹草Cares fokienensis Dunn较早发表但并未被注意。通过文献查阅、模式标本研究和野外观察,认为闽清薹草C.minqingensis Z．P.Wang、九仙山薹草C jiuxiangshanensis L.K．Dai＆Y.Z．Huang、苍绿薹草C.pallideviridis K．L．Chv（裸名）在果囊和雌花鳞片等鉴别性特征上与福建薹草并没有区别,应该处理为福建薹草的异名。     

Carex, subgenus Carex (Cyperaceae) – A phylogenetic approach using ITS sequences

To evaluate the sectional classification in Carex, subgenus Carex, the ITS region of 117 species belonging to 32 sections was analyzed with Neighbor Joining (NJ) and Markov chain Monte Carlo (MCMC) methods. In our analyses (1) species of subgenus Indocarex appear as a statistically well supported group within subgenus Carex. (2) The representatives of sections Vesicariae, Hirtae, Pseudocypereae, Ceratocystis, Spirostachyae, Bicolores, Paniceae, Trachychlaenae, Scirpinae, Atratae and Albae group in statistically supported clades with higher support in MCMC than in NJ. (3) C. rariflora clusters with representatives of section Limosae, however only weakly supported. (4) Taxa of section Phacocystis are divided in two statistically supported subclusters that are closely related to a core group of section Hymenochlaenae. (5) Species of sections Montanae, Pachystylae, Digitatae, Phacocystis, Rhomboidales, Careyanae and Frigidae are segregated into two or more clusters each. (6) Five species of section Frigidae cluster together, whereas the seven others are in scattered positions. Based on these results, delimitation of sections is discussed.     

浙江薹草属（莎草科）新分类群

摘要描述及图解了浙江薹草属Carex 5新种和1新变种,它们是：灰帽薹草组sect. Mitratae Kükenth.的天目山薹草Carex tianmushanica C. Z. Zheng & X. F. Jin和拟三穗薹草C. pseudotristachya X. F. Jin & C. Z. Zheng;匏囊薹草组sect. Lageniformes (Ohwi) Nelmes的密毛薹草C. densipilosa C. Z. Zheng & X. F. Jin;菱形果薹草组sect. Rhomboidales Kükenth.的浙南薹草C. austrozhejiangensis C. Z. Zheng & X. F. Jin和朝芳薹草C. chaofangii C. Z. Zheng & X. F. Jin;疏花薹草组sect. Laxiflorae Kunth的无芒长嘴薹草C. longerostrata C. A. Mey. var. exaristata X. F. Jin & C. Z. Zheng。     

Fine-scale spatial genetic structure within continuous and fragmented populations of Trillium camschatcense

Spatial genetic structure (SGS) within populations was analyzed for the ling-lived understory perennial herb Trillium camschatcense using allozyme loci. We used Sp statistics to compare SGS between 2 life-history stages, juveniles (J) and reproductives (R), as well as between 2 populations, continuous and fragmented, with different habitat conditions. In the continuous population, significant SGS was detected in both stages but the extent was greatly reduced with the progress of the stage (J, Sp = 0.0475; R, Sp = 0.0053). We inferred that limited seed dispersal and subsequent random loss of individuals from the family patches are responsible for the J and R stage structures, respectively. The fragmented population differed in the patterns of SGS; significant structure was detected in the R stage, but not in the J stage (J, Sp = 0.0021; R, Sp = 0.0165) despite significant positive inbreeding coefficients (J, F(IS) = 0.251). The observed differences in the J-stage structures between populations may be explained by habitat fragmentation effects because reduced recruitment in the fragmented population prevents the development of maternal sibling cohort. Such comparative analysis between populations and life-history stages can be useful to understand the different underlying causes of SGS.     

Clonal diversity and spatial genetic structure of Potamogeton pectinatus in managed pond and river populations

Higher levels of genetic diversity of river macrophytes are expected in downstream parts because of potential accumulation of various genotypes from upstream sites. We assessed the clonal diversity and spatial genetic structure of fennel pondweed (Potamogeton pectinatus or Stuckenia pectinata) populations with emphasis on the estimation of dispersal via clonal propagules along a river in connection to upstream ponds. We analysed genetic diversity of 354 plant shoots sampled in 2005 and 2006 at three pond and five river sites in the Woluwe river catchment (Belgium). Nine microsatellite DNA markers revealed 88 genets of which 89% occurred in only one site. Clonal propagule dispersal was detected up to 10 km along the river. Few multilocus genotypes were repeatedly present along a major part of the river indicating vegetative spread. Populations of ponds contained a higher amount of clonal diversity, indicating the importance of local seed recruitment. A fine-scaled spatial genetic structure indicated that most seedling recruitment occurred at a distance <5 m in pond populations whereas clones in river sites were unrelated and showed no spatial autocorrelation. The clonal diversity decreased along the river from upstream to downstream due to establishment of few large clones.     

Mycorrhizal status of the genus Carex (Cyperaceae)

The Cyperaceae have generally been considered nonmycorrhizal, although recent evidence suggests that mycotrophy may be considerably more widespread among sedges than was previously realized. This study surveyed 23 species of Carex occurring in upland and wetland habitats in northeastern Illinois. Mycorrhizal infection by arbuscular fungi was found in the roots of 16 species of Carex and appears to occur in response to many factors, both environmental and phylogenetic. While some species appear to be obligately nonmycorrhizal, edaphic influences may be responsible for infection in others. In five of the seven Carex species that were nonmycorrhizal, a novel root character, the presence of bulbous-based root hairs, was identified. The taxonomically patchy distribution of the distinctive root hair trait suggests that these structures may have evolved several times within the genus. Evidence of multiple independent origins of the root hair trait lends support to the hypothesis that root hairs represent an adaptation to nonmycotrophy. Although taxonomic position does seem to be of importance in determining the mycorrhizal dependence of sedges, the pattern may be a patchwork of both mycorrhizal clades and clades that have adapted to the nonmycorrhizal state.     

Allozyme variation and genetic relationships among species in the Carex willdenowii complex (Cyperaceae)

A taxonomic study by Naczi, Reznicek, and Ford (American Journal of Botany, 85, 434-447, 1998) has determined that three species (Carex willdenowii, C. basiantha, and C. superata) can be recognized within the C. willdenowii complex. To determine the amount of genetic divergence within and between these species, allozyme analyses were conducted on 14 populations distributed from Pennsylvania to eastern Texas. Seventeen loci were surveyed, 13 of which were polymorphic, with all populations being polymorphic at one or more loci. Interspecific genetic identities ranged from 0.560 (C. willdenowii and C. basiantha) to 0.807 (C. basiantha and C. superata). Alleles for the isozymes Aat-1, Dia-1, Idh-2, Mdh-2, Per-1, Pgm-1, and Pgm-2 served to distinguish C. willdenowii from C. basiantha and C. superata. Carex basiantha and C. superata were recognized by alleles of Mdh-2, Pgm-1, and Tpi-2. The genetic identities of populations within species were high and exceeded 0.957. A caespitose growth habit and perigynia in close proximity to the staminate flowers suggest adaptations for selfing and therefore low levels of heterozygosity. Paradoxically, the values for expected heterozygosities (Hexp) were always lower than those obtained by direct count (Hobs): F values were highly negative, indicating heterozygous excess. Disassortative mating and selection are discussed as possible mechanisms for maintaining heterozygous excess within populations.     

Genetic consequences of plant edaphic specialization to solfatara fields: Phylogenetic and population genetic analysis of Carex angustisquama (Cyperaceae)

Edaphic specialization is one of the main drivers of plant diversification and has multifaceted effects on population dynamics. Carex angustisquama is a sedge plant growing only on heavily acidified soil in solfatara fields, where only extremophytes can survive. Because of the lack of closely related species in similar habitats and its disjunct distribution, the species offers ideal settings to investigate the effects of adaptation to solfatara fields and of historical biogeography on the genetic consequences of plant edaphic specialization to solfatara fields. Here, genome‐wide single nucleotide polymorphisms were used to reveal the phylogenetic origin of C. angustisquama, and 16 expressed sequence tag–simple sequence repeat markers were employed to infer population demography of C angustisquama. Molecular phylogenetic analysis strongly indicated that C. angustisquama formed a monophyletic clade with Carex doenitzii, a species growing on nonacidified soil in the sympatric subalpine zone. The result of population genetic analysis showed that C. angustisquama has much lower genetic diversity than the sister species, and notably, all 16 loci were completely homozygous in most individuals of C. angustisquama. Approximate Bayesian computation analysis supported the model that assumed hierarchical declines of population size through its evolutionary sequence. We propose that the edaphic specialist in solfatara fields has newly attained the adaptation to solfatara fields in the process of speciation. Furthermore, we found evidence of a drastic reduction in genetic diversity in C. angustisquama, suggesting that the repeated founder effects associated with edaphic specialization and subsequent population demography lead to the loss of genetic diversity of this extremophyte in solfatara fields.     

Effects of zoochory on the spatial genetic structure of plant populations

Spatial genetic structure (SGS) of plants results from the nonrandom distribution of related individuals. SGS provides information on gene flow and spatial patterns of genetic diversity within populations. Seed dispersal creates the spatial template for plant distribution. Thus, in zoochorous plants, dispersal mode and disperser behaviour might have a strong impact on SGS. However, many studies only report the taxonomic group of seed dispersers, without further details. The recent increase in studies on SGS provides the opportunity to review findings and test for the influence of dispersal mode, taxonomic affiliation of dispersers and their behaviour. We compared the proportions of studies with SGS among groups and tested for differences in strength of SGS using Sp statistics. The presence of SGS differed among taxonomic groups, with reduced presence in plants dispersed by birds. Strength of SGS was instead significantly influenced by the behaviour of seed dispersal vectors, with higher SGS in plant species dispersed by animals with behavioural traits that result in short seed dispersal distances. We observed high variance in the strength of SGS in plants dispersed by animals that actively or passively accumulate seeds. Additionally, we found SGS was also affected by pollination and marker type used. Our study highlights the importance of vector behaviour on SGS even in the presence of variance created by other factors. Thus, more detailed information on the behaviour of seed dispersers would contribute to better understand which factors shape the spatial scale of gene flow in animal‐dispersed plant species.     

Trans-Atlantic dispersal and large-scale lack of genetic structure in the circumpolar, arctic-alpine sedge Carex bigelowii s. l. (Cyperaceae)

Paradoxically, several of the ecologically most important plant groups in the Arctic are little understood in terms of taxonomy and biogeographic history. The circumpolar Carex bigelowii s. l. (Cyperaceae) is abundant in the Arctic and is one of the most complicated arctic plant groups. While its ecology and population genetics have been extensively studied, its taxonomy is largely unexplored. We analyzed the large-scale geographical structuring of amplified fragment length polymorphisms (AFLPs) covering most of the distribution range. We detected high levels of genetic variation, most (66%) within populations, and a fairly weak genetic structure. Only the Central Asian populations, referred to as C. orbicularis, were strongly divergent. For the remaining populations, Bayesian clustering separated three distinct clusters (one European, one amphi-Atlantic, and one broadly amphi-Beringian), probably reflecting different major glacial refugia and recent transoceanic dispersal. The isolated central European populations were most closely related to those from a larger distribution area in northern Europe. Differences in genetic diversity suggest that the Alpine and Tatra populations have experienced strong bottlenecks, whereas the Krkono?e population may have been part of a continuous distribution area during the cold stages of the Pleistocene. Finally, we discuss the relevance of our results for a uniform, range-wide taxonomic concept.     

Central Asian origin of and strong genetic differentiation among populations of the rare and disjunct Carex atrofusca (Cyperaceae) in the Alps

Aim Carex atrofusca has an arctic–alpine distribution in the Northern Hemisphere, with only a few, disjunct localities known in the European Alps. These alpine populations are declining in number and size. In contrast, C. atrofusca has a wide circumpolar distribution range and is abundant in large parts of the Arctic. The degree of genetic differentiation of the alpine populations and their importance for the conservation of the intraspecific genetic variation of the species is unknown. Location Eurasia and Greenland, with emphasis on the European Alps. Methods We applied amplified fragment length polymorphism (AFLP) fingerprinting and sequences of chloroplast DNA to determine the position of the alpine populations in a circumpolar phylogeography of C. atrofusca and to unravel the patterns of genetic diversity and differentiation within the Alps. Results Two distinct major groups were detected in a neighbour‐joining analysis of AFLP data and in parsimony analysis of chloroplast DNA sequences: one consisting of the populations from Siberia and Greenland and one consisting of all European populations as sister to the populations from Central Asia. Within Europe, the populations from the Tatra Mountains and those from Scotland and Scandinavia formed two well‐supported groups, whereas the alpine populations did not constitute a group of their own. The genetic variation in the Alps was almost completely partitioned among the populations, and the populations were almost invariable. Main conclusions The alpine populations possibly originated due to immigration from Central Asia. The strong differentiation among them suggests that genetic drift has been strongly acting on the populations, either as a consequence of founder events during colonization or due to subsequent reduction of population sizes during warm stages of the Holocene.     

Status of Carex bergrothii (Cyperaceae) on Gotland, SE Sweden

Material of Carex oederi s.lat. was studied at four localities on the Baltic island of Gotland. Each locality included material referable to C. bergrothii , i.e., tall sedges with long leaves and with comparatively large and broad utricles, as well as material of C. oederi s.str., i.e., short sedges with smaller utricles. Univariate and multivariate statistical analyses show continuous variation in C. oederi s. lat. on Gotland and it is concluded that C. bergrothii cannot be recognised as a separate species. However, a large proportion of the phenotypic variance in C. oederi s. lat. on Gotland is due to genotypic differentiation, and C. bergrothii is considered as an extreme ecorype of C. oederi . This ecotype is apparently adapted to grow in deep water on calcareous clay among loose stands of Cladium mariscus .     

Inferring recruitment history from spatial genetic structure within populations of the colonizing tree Albizia julibrissin (Fabaceae)

Comparative analyses of spatial genetic structure (SGS) among species, populations, or cohorts give insight into the genetic consequences of seed dispersal in plants. We analysed SGS of a weedy tree in populations with known and unknown recruitment histories to first establish patterns in populations with single vs. multiple founders, and then to infer possible recruitment scenarios in populations with unknown histories. We analysed SGS in six populations of the colonizing tree Albizia julibrissin Durazz. (Fabaceae) in Athens, Georgia. Study sites included two large populations with multiple, known founders, two small populations with a single, known founder, and two large populations with unknown recruitment histories. Eleven allozyme loci were used to genotype 1385 individuals. Insights about the effects of colonization history from the SGS analyses were obtained from correlograms and Sp statistics. Distinct differences in patterns of SGS were identified between populations with multiple founders vs. a single founder. We observed significant, positive SGS, which decayed with increasing distance in the populations with multiple colonists, but little to no SGS in populations founded by one colonist. Because relatedness among individuals is estimated relative to a local reference population, which usually consists of those individuals sampled in the study population, SGS in populations with high background relatedness, such as those with a single founder, may be obscured. We performed additional analyses using a regional reference population and, in populations with a single founder, detected significant, positive SGS at all distances, indicating that these populations consist of highly related descendants and receive little seed immigration. Subsequent analyses of SGS in size cohorts in the four large study populations showed significant SGS in both juveniles and adults, probably because of a relative lack of intraspecific demographic thinning. SGS in populations of this colonizing tree is pronounced and persistent and is determined by the number and relatedness of founding individuals and adjacent seed sources. Patterns of SGS in populations with known histories may be used to indirectly infer possible colonization scenarios for populations where it is unknown.     

Demography of Carex brevicuspis (Cyperaceae) rhizome populations: a wetland sedge that produces both elongated and shortened rhizomes

The wetland sedge Carex brevicuspis reproduces vegetatively by producing short rhizomes to form clumping ramets phalanx) and long rhizomes to form spreading ramets (guerrilla), resulting in a combined growth form. As an initial step towards understanding the adaptation of Carex growth strategies to seasonal fluctuations in wetland habitats, we investigated the density and composition of C. brevicuspis rhizome populations immediately after flooding (November), in winter (January), in spring (March), and before flooding (May) in the Dongting Lake wetlands, China. The total rhizome density peaked in winter and was lowest before flooding. A large rhizome population in winter may enable C. brevicuspis to survive the seasonal cold weather and recruit a shoot population in the spring. A small rhizome population before flooding may optimize reproductive allocations and be a strategy for enduring the long flooding season. Regardless of date, short rhizomes comprised the majority of the rhizome population (73.0% in March to 98.2% in May). This indicates that C. brevicuspis primarily uses a phalanx growth strategy to utilize locally abundant resources in wetlands. The percentage of long rhizomes in the rhizome population varies significantly between seasons (1.8% in May to 27.0% in March), indicating that growth form also changes with seasonal fluctuation of wetland habitats. The results show that C. brevicuspis may adapt to seasonal changes in wetland habitats through changes in demography of rhizome populations.