MODELING REPRODUCTIVE EFFORT IN SUB AND MARITIME ANTARCTIC MOSSES

A comparison is made of the reproductive effort (RE), considered as th e investment in sporophyte relative to gametophyte biomass, of eight s pecies of moss occurring at sub- and maritime Antarctic sites. Six of the species showed smaller sporophytes and gametophytes at the climati cally more extreme maritime Antarctic sites and one species showed no size difference between regions. The remaining species, although showi ng no regional difference, showed some evidence of a reverse pattern, with higher altitude samples having greater biomass than lower altitud e samples. Spore counts indicated a measure of compensation in maritim e Antarctic samples, with no significant decrease in spore output in s everal species despite smaller sporophyte biomass. The relationship be tween sporophyte (S) and gametophyte (G) biomass within samples was de scribed by an allometric curve (S=aG(b)) which gave a better fit than a straight line for six species. This form of model allows comparisons of patterns of RE to be made between samples with non- or partially o verlapping size distributions even when the relationship involves size -dependence. An allometric curve was not appropriate for describing sa mples of one species (Andreaea regularis), and insufficient data were available to identify any relationship in Polytrichum alpinum. The exp onent (b) differed between species, but there were no statistically si gnificant differences between exponents from samples of the same speci es. Samples of two species could further be described by the same coef ficient (a), indicating that they lie on the same curve. However, samp les of three species from sub-Antarctic South Georgia gave significant ly higher coefficients, indicating increased RE relative to maritime A ntarctic populations.