Fierst, J.L., C.P. terHorst, J.E. Kubler, and S. R. Dudgeon. 2005. Fertilization success can drive patterns of phase dominance in complex life histories. Journal of Phycology 41:238-249.
Abstract: Many algal life cycles alternate between two free-living generations. Life histories in which the two generations look identical (isomorphic) are common, particularly in the Rhodophyta. Reports of natural populations dominated by one generation of the life history have sought explanation in terms of phase-specific differences in mortality and reproductive output, yet in many cases identification of these adaptations has been elusive or inconsistent with predictions. We hypothesized that the gametophyte-to-sporophyte ratio of ecologically equivalent isomorphs could result from variation in fertilization rate. We developed two models to test this hypothesis: one representing a generalized isomorphic life history and the other specific to red algae with a Polysiphonia-type life history. Fertilization rate affected the gametophyte-to-sporophyte ratio, especially at low fertilization rates. In the general model, gametophytes dominated the population regardless of fertilization rate unless egg production greatly exceeded meiospore production. In the red algal model, phase dominance depended on the combination of fertilization rate and the number of carpospores produced per fertilization. The generational composition of model multiphasic algal populations results from their inherent reproductive characteristics and the dynamic environment to which fertilization and mortality rates are tied.
Keywords: algae; fertilization; gametophyte dominance; isomorphic; life history; population structure; sporophyte dominance