Graves' Beach Plum (Prunus maritima var. gravesii) has been notable for its unique morphological form since a single individual was first discovered on Esker Point in Groton, Connecticut and formally described in 1897. This original clone is now extinct in the wild and is presently kept in cultivation on the University of Connecticut campus, with no additional wild plants discovered in 120 years. It was distinguished morphologically based primarily on its distinctive orbicular leaves, which differ from the ovate leaves found in P. maritima var. maritima. Prior studies have shown few morphological differences between P. maritima var. gravesii and P. maritima var. maritima and full reproductive compatibility has been experimentally observed between the two taxa. However, the few unique characteristics of P. maritima var. gravesii merit further investigation to determine if it has unique molecular differences relative to var. maritima that might lead to the prioritization of conservation and possible reintroduction efforts. Twelve polymorphic microsatellite markers were used to evaluate the genetic composition of 40 P. maritima var. maritima plants from three regional populations (Milford, Connecticut, Waterford, Connecticut, and Weekapaug, Rhode Island) and one additional individual from the type locality of P. maritima var. gravesii. High levels of allelic diversity and heterozygosity were observed among the forty-one samples. Additionally, low levels of genetic differentiation were observed among populations sampled, suggesting regular gene flow occurs among populations. Of the 12 loci studied, P. maritima var. gravesii possessed only one private allele existing in the heterozygotic condition, sharing all other alleles across loci with the P. maritima var. maritima samples. Further evaluations of genetic structure, including principal coordinates analysis and population assignment analysis, revealed the genotypic identity of P. maritima var. gravesii placed it within populations of P. maritima var. maritima and not as a discrete taxon. Therefore, we propose that the current variety classification be changed, and P. maritima var. gravesii should now be considered a naturally occurring but exceptionally rare morphological variant of the widespread P. maritima var. maritima, as P. maritima forma gravesii.

Relationships between the flora and vegetation of northern Europe and the northeastern United States have been long noted but little studied. Here, quantitative sampling of high, low, and mid-marsh zones was carried out in 20 marshes along a gradient from non-tidal freshwater via tidal freshwater and brackish to salt marshes in each of two large river systems, the Elbe in Europe (Germany) and the Connecticut in North America (southern New England, USA). The composition of each zone of each marsh type in the two river systems is described. The marsh floras are compared, and possible reasons for differences in vegetation composition, non-native species occurrences, species richness patterns, and the origin of marsh floras are discussed. Twenty-two species occurred in both river systems, nearly 10% of the total marsh flora. Shared species were found in all four marsh types and occasionally in more than one marsh type. Introduced taxa are not prominent in either river system except for Spartina anglica C. E. Hubb. in the salt marshes and Acorus calamus L. in the non-tidal freshwater marshes of the Elbe and Typha angustifolia L. and Phragmites australis (Cav.) Trin. ex Steud. in the brackish marshes along the Connecticut. Asteraceae and Poaceae were the largest (most species rich) families in the marshes of both rivers. These descriptions and comparisons of the marsh flora and vegetation of a European and an American river should serve as benchmarks for future comparisons and assessments of changes in times of rapid environmental and associated ecological change.

The Credit River Watershed contains a mosaic of habitat types, which support a large number of lichen species; however, no detailed inventories of the lichen diversity in this region exist. We present a checklist of 124 species of lichens and allied fungi discovered in the watershed. We report new collections of Illosporium carneum, Microcalicium ahlneri, and Pseudoschismatomma rufescens, which are provincially rare. In this checklist, twelve species are ranked as S1 (critically imperiled), S2 (imperiled), or S3 (vulnerable) in Ontario by the Natural Heritage Information Centre. Local municipalities and conservation authorities can use these baseline data to help monitor changes in populations and in determining areas of high biodiversity in the watershed.