Panarctic Flora

410101-04 The Polygonum aviculare aggregate P. aviculare, P. boreale, P. microspermum, P. neglectum

Geography: Amphi-Atlantic - European - Asian (W).

Notes: Polygonum aviculare s. lat. is an intricate complex with several taxa at two ploidy levels. The taxa are largely sympatric today, possibly due to anthropogenic spread, and may represent different basic diploid genomes in different combinations. Karlsson (2000c) argued for treatment as races of one species because of a probable reticulate variation pattern and some transitions. Elven et al. (2005) and others have followed this proposal. Tzvelev (in comments and elsewhere) rather prefers to treat the group as an aggregate (series) of species. An argument for his solution is that the taxa are largely sympatric and often grow in mixtures without many obvious transitions (perhaps due to predominant inbreeding). They do not well fit the concept of races. For the Checklist, we accept rank as species.

Four taxa (species) reach or approach the Arctic in northwestern Europe. Three of these are widespread adventives also in other regions but a critical study of the material is needed before reliable accounts can be made for areas outside northwestern Europe. Help to do this can be found in the keys and extensive descriptions of Karlsson (1997, 2000c). Several studies address the problems in this group in Europe and North America (e.g., Pauwels 1959; Styles 1960, 1962; Mertens and Raven 1965; McNeill 1981; Wolf and McNeill 1987).