Panarctic Flora

3309075-086 The Phacocystis complex

Notes: The Phacocystis complex includes mainly species of mires, swamps, and freshwater shores but most of its species also reach the uppermost parts of seashores. Also the species of the Phacocystis complex seem to hybridize fairly freely where they meet but perhaps not fully as freely as those of the Temnemis complex and perhaps with less fertile hybrids. The number of northern species and subspecies proposed in the Phacocystis complex is rather large. Some of these may be closely related and their circumscription is often less certain than in the Temnemis complex. There is, however, little experimental work yet that support a merger of species (but see Nakamatte and Lye 2008; Schönswetter et al. 2008).

In a phylogenetic analysis of several species of Phacocystis based on ITS and ETS markers, Dragon and Barrington (2008) identified four clades: an European and amphi-Atlantic clade with C. acuta, C. elata All. (non-arctic), C nigra s. lat., and C. trinervis Degl. (non-arctic); a clade with C. bigelowii and two related, more southern North American species; a mainly North American clade with C. aquatilis, C. lenticularis s. lat., C. rufina, and a few others; and a mainly East Asian clade with, e.g., C. eleusinoides. Dragon and Barrington (2009), in a study including more species, found much of the same associations as did Nakamatte and Lye (2008). One drawback in the study of Nakamatte and Lye (2008), partly also in those of Dragon and Barrington (2008, 2009), is that there is little documentation that the samples analysed under a name have been thoroughly checked as to identity. Such a check is mandatory in a group with as complex morphology as this one.