Cytological studies on meiotic configurations of intraspecific aneuploids ofCarex blepharicarpa (Cyperaceae) in Japan

Chromosome configurations at meiotic metaphase I ofCarex blepharicarpa were determined for 245 individuals collected from 11 localities in the Chugoku District of Japan. Nine intraspecific aneuploids, 2n=26–33 and 41, were found. The most common diploid number was 29, and found in 73 individuals. No clear geographical pattern was suggested by a distribution of these aneuploids. A consecutive series of chromosome numbers from 2n=26 to 32 was found in two populations from Okayama Prefecture. At meiotic metaphase I, univalents and multivalents were found, and one to three trivalents were observed in each aneuploid. Heteromorphic chain trivalents comprising large, medium and small chromosomes were prevalent. Homomorphic trivalents, which are thought to be originated from chromosome duplications caused by unreduced gametes, were found in only one individual with 2n=41. The high frequency of heteromorphic trivalents in this species indicates that most aneuploidy probably results from fission and/or fusion of chromosomes.     

Using genomics to guide seed‐sourcing at the right taxonomical level for ecological restoration projects: The complex case of Carex bigelowii s.lat. in Norway

There is a growing demand for ecological restoration using suitable seeds following international standards or national legal demands for local seed‐sourcing. However, before selecting the appropriate geographic origin of seeds, it is vital to explore taxonomic complexity related to the focal taxa. We used ddRAD‐seq to screen genomic diversity within Carex bigelowii s.lat. focussing on Norway. This species complex is considered a candidate for seeding, but presents considerable morphological, ecological, and genetic variation. The genetic structure of 132 individuals of C. bigelowii s.lat., including Carex nigra as an outgroup, was explored using ordinations, clustering analyses, and a genetic barrier algorithm. Two highly divergent clusters were evident, supporting the recognition of two taxonomic units “C. dacica” and C. bigelowii “subsp. bigelowii”. Previously defined seed‐sourcing regions for C. bigelowii s.lat. did not consider the known taxonomic complexity, and therefore interpreted the overall genetic structure as seed‐sourcing regions, not taxa. We estimated genetic neighborhood sizes within each taxon to be 100–150 km and 300 km, respectively, indicating species‐specific delimitations of local seed‐sourcing regions. Frequent hybrids, local genetic distinctiveness, and suggested ecotypes add complexity to the discussed seed‐sourcing regions. Our results show how genomic screening of diversity and structure in a species complex can alleviate the taxonomic impediment, inform practical questions, and legal requirements related to seed‐sourcing, and together with traditional taxonomic work provide necessary information for a sound management of biodiversity.     

New Material of Carex Subgenus Vignea from China

In addition, two new sections, Echinochlomorphae Y. L. Chang and Thomsonianae Y. L. Chang, two new combinations, C. duriuscula subsp. rigescens (Franch.) S. Y. Liang et Y. C. Tang (=C. stenophylla var. rigescens Franch.) and C. rochebrunii Franch. Subsp. reptans (Franch.) S. Y. Liang et Y. C. Tang (=C. remotae L. var. reptans Franch.) are made, and C. stenophylloides V. Krecz. is reduced to C. duriuscula subsp. stenophylloides (V. Krecz.) S. Y. Liang et Y. C.Tang.     

Effect of microrelief and vegetation on methane emission from wet polygonal tundra, Lena Delta, Northern Siberia

The effect of microrelief and vegetation on methane (CH₄) emission was investigated in a wet polygonal tundra of the Lena Delta, Northern Siberia (72.37N, 126.47E). Total and plant-mediated CH₄ fluxes were measured by closed-chamber techniques at two typical sites within a low-centred polygon. During the study period, total CH₄ flux averaged 28.0±5.4mgm^–2d^–1 in the depressed polygon centre and only 4.3±0.8mgm^–2d^–1 at the elevated polygon rim. This substantial small-scale spatial variability of CH₄ emission was caused by strong differences of hydrologic conditions within the microrelief of the polygon, which affected aeration status and organic matter content of the soils as well as the vegetation cover. Beside water table position, the vegetation cover was a major factor controlling CH₄ emission from polygonal tundra. It was shown that the dominant vascular plant of the study area, Carex aquatilis, possesses large aerenchyma, which serve as pathways for substantial plant-mediated CH₄ transport. The importance of plant-mediated CH₄ flux was strongly influenced by the position of the water table relative to the main root horizon. Plant-mediated CH₄ transport accounted for about two-thirds of the total flux in the wet polygon centre and for less than one-third of the total flux at the moist polygon rim. A clipping experiment and microscopic-anatomical studies suggested that plant-mediated CH₄ transport via C. aquatilis plants is driven only by diffusion and is limited by the high diffusion resistance of the dense root exodermes.     

Flooding tolerance of Carex species in relation to field distribution and aerenchyma formation

The flooding tolerance of Carex species was studied in relation to their field distribution and their capacity to form root aerenchyma under controlled conditions. In an alpine meadow, six Carex species were selected which were distributed in a clear zonation correlating with water content of the soil. Carex sempervirens and C. ferruginea were only found on nonflooded soil, the latter species preferring moister conditions. Carex davalliana and C. nigra were both associated with water-saturated soil, whereas C. limosa and C. rostrata preferred partially submerged conditions. Carex davalliana and C. limosa were bound to flooded soils with a relatively high redox potential and horizontally flowing groundwater. Carex rostrata and C. nigra grew in stagnant soil-flooded conditions with low soil redox potentials. The amount of aerenchyma in the roots of all species increased when grown in oxygen-deficient stagnant agar. This increase in root porosity, combined with increased root diameter, presumably improved internal aeration of the roots. Although all species survived experimental soil flooding, partial submergence was lethal to C. sempervirens and, surprisingly, also to the wetland species C. davalliana. Carex ferruginea showed a reduced growth rate during partial submergence. The three other species, all wetland plants, reached highest biomass production under soil-flooded and partially submerged conditions, with slower growth on free-draining soil. It is concluded that aerenchyma is not constitutive in the Carex species under study, and is best developed in Carex species from wetlands. Species with less aerenchyma perform poorly when soil-flooded, but conditions of partial submergence could even affect species with a considerable amount of root aerenchyma.     

Within-species variation among populations of the Carex flava complex as a function of habitat conditions

Background: Variable habitat conditions contribute to morphological variability that plays a substantial part in evolution of plants. Understanding the extent of phenotypic plasticity has important implication for assigning individuals to taxa.

Aims: I analysed morphological variability among populations within species of the Carex flava group and tested to what extent morphological variability was associated with habitat conditions.

Methods: A total of 571 specimens from 20 populations of four species from the C. flava complex were sampled in Poland and tested by Discriminant Function Analysis (DFA). The relationship between morphological characters and habitat factors was explored by means of the redundancy analysis (RDA).

Results: Variability of the generative and vegetative traits was fairly similar in Carex lepidocarpa, C. flava and Carex demissa, while it was somewhat higher in Carex viridula. The morphological traits were mostly related to soil organic matter content, calcium and carbonate, as well as to habitat fertility (C:N ratio), elevation and habitat disturbance. The results obtained do not support the separation of C. viridula var. pulchella from C. viridula var. viridula.

Conclusions: Phenotypic variability in the species of the C. flava complex is related to habitat conditions and this can lead to the differentiation of morphotypes within species.