320125-27 The Juncus arcticus aggregate J. arcticus, J. balticus, J. haenkei
Notes: The Juncus arcticus aggregate is a polymorphic group for which treatments differ widely. We follow Tolmachev (1963), Snogerup (1980), Kirschner et al. (2002c), and Elven et al. (2005) and accept three species - Juncus arcticus, J. balticus, and J. haenkei - the two former with subspecies. In the most recent North American treatment, Brooks and Clemants (2000) recognized only a collective J. arcticus with three varieties, two to reach the Arctic: var. alaskanus (including J. haenkei) and var. balticus. We can all support their remark that this is "a wide-ranging and obviously polymorphic complex that has not read the literature. It is abundantly clear that the systematics of the group will not be solved on the basis of morphology alone and that resolution of the problem is ripe for molecular investigations".
Kirschner et al. (2002c) and Kirschner (in comment) argued for the amphi-Pacific J. haenkei as a species apart from J. arcticus/balticus, differing in several characters and overlapping in geographical range with almost no intermediates. Similar arguments have been forwarded by, e.g., Snogerup concerning the amphi-Atlantic J. balticus vs. the circumpolar J. arcticus. Both were originally described by Willdenow from northern Europe where they (except for Iceland) differ in general habit, in many features of detail, and in ecology and distribution. When comparing a series of northwestern European plants, few would doubt them as two different species. Only a single putative hybrid clone (sterile) is known within their range overlap in northern Norway (Snogerup in comment), whereas both J. arcticus and J. balticus very frequently produce sterile clonal hybrids with the morphologically much more different J. filiformis. The hybrid J. arcticus x filiformis is even candidate for inclusion in the Checklist as it often occurs in localities and even regions from where J. arcticus is absent, perhaps due to an assumed strong Holocene reduction in the range of J. arcticus. Snogerup et al. (2002) argued for J. arcticus and J. balticus as two species, each with several subspecies.
For Iceland, see subsp. intermedius below.
- Juncus [3201,genus]