Abstract Detail

Bryological and Lichenological Section/ABLS

Pressel, Silvia [1], Duckett, Jeffrey G. [1].

Protonemal Diversity: New Insights into Moss Systematics.

Moss protonemata are providing an increasing number of new characters useful at all levels in the taxonomic hierarchy. Certain groups clearly distance themselves from other mosses by having thalloid protonemata rather than ones characterized by tip growing multicellular filaments with regular side branches; these are Andreaea, Sphagnum, Oedipodium, Tetraphis and Diphyscium. The Polytrichales are distinctive in having rhizoidal ropes and chloronemata consisting of quasi-parenchymatous structures somehow reminiscent of those found in Diphyscium. Although the remaining orders all share a basic protonemal structure, a richness of characters remains within this common plan. A striking difference is often the presence or absence of protonemal gemmae. We have examined the distribution of protonemal gemmae, their morphology and abscission mechanisms in over 300 mosses. These are absent in the Polytrichales, Buxbaumiales, Archidiales, Fissidentales, Grimmiales and Splachnales and very rare in the Hypnobryales. Filamentous gemmae, mostly with Tmema cells (TCs), are widespread in the Dicranales whereas in the Pottiales TCs are lacking and gemmae are generally rounded. Protonemal gemmae in the majority of isobryalean (Fontinalis, Cryphaea, Homalia, Leucodon, Neckera) and thuidialean (Myurella, Leskea, Pseudoleskea, Anomodon) genera separate by schizolysis, with the striking exception of Habrodon. Another protonemal feature shared by these two orders, and also the Orthotrichales, is chloronemal side branches arising from the mid point and at right angle to short chloronemal cells forming the main axes. The recent discovery of gemmiferous protonemata in Seligeria carniolica, in an otherwise gemma-free genus, suggests a reevaluation of the generic status of Trochobryum, a notion in line with the absence of stomata and persistent lid-columella attachment unique to this species. At the infraspecific level, in the genus Weissia distinctive protonemal morphology suggests that W. controversa var. densifolia and W. longifolia var. angustifolia may merit elevation to specific status.

1 - Queen Mary, University of London, School of Biological Sciences, London, E1 4NS, UK

Keywords:
asexual reproduction
gemmae
protonemata
taxonomy.

Presentation Type: Paper
Session: 35-2
Location: Ballroom 3 (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 2:15 PM
Abstract ID:422