Disjunctions in Bryophytes

Abstract

In spite of the more general distribution of many bryophytes, dramatic disjunctions exist, many of them similar to those shown by vascular plants. Various explanations have been offered to explain these disjunctions including continental drift, long-distance dispersal, and the fragmentation of a once more continuous distribution. No single hypothesis is sufficient to accommodate all species within any disjunctive pattern. The most serious difficulty is tlie inadequacy of exploration of considerable areas of the globe.Various bryophyte disjunctions are mapped in 51 distribution maps, and details of sexual patterns and dispersal mechanisms are assessed.Most bryophytes are widely distributed. In the Northern Hemisphere more than 60% of the flora of arctic and boreal regions is made up of the same species.Within this wide range, however, each species has highly specific requirements and some are exceedingly local.Becavise bryophytes have air-borne diaspores their means of dissemination would appear to guarantee a wide distribution of all species. That disjunctions exist at all would seem somewhat anomalous, yet such disjunctions do exist, some of them very dramatic. The explanation of these disjunctions has led to numerous intriguing hypotheses, many of which have been derived from similar studies of flowering plant disjunctions.In North America tlie disjunctions that have received the greatest attention

Morphology informed by phylogeny reveals unexpected patterns of species differentiation in the aquatic moss Rhynchostegium riparioides s.l.

“…Differences in sporophytic features, and especially spore size, could not be characterized owing to the minimal number of fertile specimens investigated here, but were not reported in Wynn's (2006) monograph. The presence of R. aquaticum in Kentucky can be interpreted as an event of irradiation of the Neotropical flora into North America, a process that is well documented for other bryophyte (Schofield and Crum, 1972) and angiosperm (Wood, 1972) species disjunct between the Appalachian valleys and the Neotropics. From the specimens surveyed in this study, it appears, however, that R. aquaticum is rare in North America.…”

Aerial dispersal of lichen soredia in the maritime Antarctic

“…Despite much discussion of the origin of the Antarctic cryptogam flora (Lindsay, 1977;Smith, 1984), cryptogam distribution mechanisms and the possibility of effective long-distance dispersal (Crum, 1972;Culberson, 1972;Schofield & Crum, 1972;During, 1979;van Zanten & Pocs, 1981) there have been few field studies on airborne transport of cryptogam propagules in the Antarctic (Rudolph, 1970;Hooker, 1977;Smith, 1985;Harmata & Olech, 1991). Of these only Rudolph (1970) and Harmata & Olech (1991) were able positively to identify specific propagules.…”

Phylogeographic Structure and Cryptic Speciation in the Trans-Antarctic Moss Pyrrhobryum Mnioides

“…This pattern is thought to be common in bryophytes (Bischler and Boisselier-DuBayle 1997;Wyatt et al 1997;Shaw 2001). Many conspecific bryophyte populations may be found in regions separated by ancient vicariance, suggesting cryptic speciation (Schofield and Crum 1972). Bryophytes reproduce by potentially highly dispersible spores, however, meaning that intercontinental migration could account for some disjunctions.…”