Isoetes ×blondeaui hyb. nov. (Isoetaceae), a new hybrid quillwort from eastern Quebec, Canada

The hybrid between diploid Isoetes echinospora and tetraploid I. laurentiana is reported from six sites along the St. Lawrence River near Quebec City. Morphological characteristics and distinguishing features are identified, and the binomial I. ×blondeaui, hyb. nov. is proposed. All occurrences are in biogeographically significant freshwater tidal marsh habitat. The hybrid is expected to occur in small numbers within most large I. laurentiana populations.

Isoetes laurentiana, sp. nov. (Isoetaceae) endemic to freshwater tidal marshes in eastern Quebec, Canada

Morphological, phytogeographic, ecological, preliminary genetic, and C-value evidence indicates that populations of Isoetes confined to freshwater tidal marsh habitats along the St. Lawrence River in Quebec, Canada, represent an undescribed endemic species, proposed here as Isoetes laurentiana sp. nov. The combination of short velum coverage (ca. 10%) over a plain (unstreaked) sporangium, broad (ca. 1.0 mm) erect leaves, small megaspores (ca. 459 μm) with more densely convoluted-reticulate, almost echinate ornamentation, and its occurrence within an exceptional habitat, readily distinguish I. laurentiana from I. tuckermanii A.Braun with which it was formerly combined. Isoetes laurentiana is one of a series of endemic taxa of the floristically extraordinary St. Lawrence River estuary. Some populations of I. laurentiana are immense; in cultivation it demonstrates the capacity for prolific production of new individuals, which is presumably necessary to sustain such local abundance. Isoetes laurentiana is of national and global phytogeographic significance, but is not considered to represent a species at risk according to standards from the International Union for Conservation of Nature.

Distribution and Diversity ofGallionella-Like Neutrophilic Iron Oxidizers in a Tidal Freshwater Marsh

ABSTRACTMicrobial iron oxidation is an integral part of the iron redox cycle in wetlands. Nonetheless, relatively little is known about the composition and ecology of iron-oxidizing communities in the soils and sediments of wetlands. In this study, sediment cores were collected across a freshwater tidal marsh in order to characterize the iron-oxidizing bacteria (FeOB) and to link their distributions to the geochemical properties of the sediments. We applied recently designed 16S rRNA primers targetingGallionella-related FeOB by using a nested PCR-denaturing gradient gel electrophoresis (DGGE) approach combined with a novel quantitative PCR (qPCR) assay.Gallionella-related FeOB were detected in most of the samples. The diversity and abundance of the putative FeOB were generally higher in the upper 5 to 12 cm of sediment than in deeper sediment and higher in samples collected in April than in those collected in July and October. Oxygen supply by macrofauna appears to be a major force in controlling the spatial and temporal variations in FeOB communities. The higher abundance ofGallionella-related FeOB in April coincided with elevated concentrations of extractable Fe(III) in the sediments. Despite this coincidence, the distributions of FeOB did not exhibit a simple relationship to the redox zonation inferred from the geochemical depth profiles.