Tolerance of desiccation was examined in three species of moss, Grimmia ant
arctici Card., Ceratodon purpureus (Hedw.) Brid. and Bryum pseudotriquetrum
(Hedw.) Gaertn., Meyer et Scherb. collected from two sites of contrasting
water availability in the Windmill Islands, continental Antarctica. Physiol
ogical tolerance to desiccation was measured using chlorophyll fluorescence
in plugs of moss during natural drying in the laboratory. Differences in r
elative water content, rate of drying and the response of photosynthesis to
desiccation were observed among the three species and between sites. Of th
e three species studied, G. antarctici showed the lowest capacity to sustai
n photosynthetic processes during desiccation, B. pseudotriquetrum had an i
ntermediate response and showed the greatest plasticity and C. purpureus sh
owed the greatest capacity to sustain photosynthesis during desiccation. Th
ese results fit well with the known distribution of the three species with
G. antarctici being limited to relatively wet sites, C. purpureus being com
mon in the driest sites and B. pseudotriquetrum showing a wide distribution
between these two extremes. Levels of soluble carbohydrates were also meas
ured in these samples following desiccation and these indicate the presence
of stachyose, an oligosaccharide known to be important in desiccation tole
rance in seeds, in B. pseudotriquetrum. Both gross morphology and carbohydr
ate content are likely to contribute to differences in desiccation toleranc
e of the moss species. These results indicate that if the Casey region cont
inues to dry out, as a result of local geological uplifting or global clima
te change, we would expect to see not only reductions in the moss community
but also changes in community composition. G. antarctici is likely to beco
me more limited in distribution as C. purpureus and B. pseudotriquetrum exp
and into drying areas.