320115-17 The Juncus bufonius aggregate J. bufonius, J. minutulus, J. ranarius
Geography: Circumboreal-polar.
Notes: Juncus bufonius s. lat. is either one complex species or a species complex with three main northern taxa and a few more southern ones (see, e.g., Loenhoud and Sterk 1976; Cope and Stace 1978, 1983, 1985; Kirschner et al. 2002c; Snogerup 2006). Our decision for the Checklist is as three species: J. bufonius s. str., J. ranarius, and J. minutulus. They differ in several characters (e.g., number of culm leaves, structure of inflorescence, shape and relative size of outer and inner perianth segments, width of hyaline margin on perianth segments, number of stamens, and size and relative length of anthers) and they differ ecologically. They are centered on three ploidy levels: J. ranarius on 2n = ca. 30-40 (presumed diploid), J. minutulus on 2n = ca. 70-80 (presumed tetraploid), and J. bufonius on 2n = ca. 100-120 (presumed hexaploid). The ploidally intermediate J. minutulus is not morphologically transitional between J. ranarius and J. bufonius. The three taxa are largely sympatric. Egorova (PAF proposal, in comments) accepted three species as did Kirschner et al. (2002c) and Snogerup (2006, in comments).
The problem is that there are lots of more or less fertile plants transitional in morphology and with intermediate level chromosome numbers, as shown by Snogerup and others. Brooks and Clemants (2000) expressed an opinion opposite to that of the authors above: "Insufficient evidence exists upon which to base the segregation of the plethora of taxa that have been recognized out of this group in the past". In our opinion, that conclusion is too defaitistic, at least as concerns the plants found in the boreal and arctic regions. The characters reported to separate between species largely hold true, e.g., the low-ploid J. ranarius has several features not shared with the two more high-ploid species and is mostly easily recognized. Waiting for a combined morphological and molecular analysis, the hypothesis is that the high-ploid plants are allopolyploids from different, but related diploid genomes, so that there is some interfertility.
Higher Taxa
- Juncus [3201,genus]