Functional Similarity Among Isomorphic Life‐history Phases of Polycavernosa Debilis (Rhodophyta, Gracilariaceae) 1

Morphologically identical but different life‐history phases of the red alga Polycavernosa debilis (Forsskål) Fredericq and J. Norris showed no conspicuous differences in physiological or ecological performances. The costs and benefits of ploidy level, as measured by net photosynthesis, calorific content, structural makeup and resistance to predation, were not sufficient to result in statistically significant differences (P > 0.05 ANOA) for the various reproductive phases [haploid male or female (including cystocarps) and diploid tetrasporic]. The lack of measurable functional responses leads to two hypotheses: (1) that adaptive ecological‐physiological differences between life‐history phases are subtle, or (2) that predominantly genetic / reproductive factors are implicated in maintaining isomorphic life‐history phases.