Responses of the haploid-to-diploid ratio of isomorphic biphasic life cycles to time instability.

Previous modelling of the haploid-to-diploid ratio (H:D) in biphasic life cycles relied on estimates of the stable population growth rate and structure. This is a projective analysis that estimates the population dynamics given current conditions. However, the environment is rarely constant and has both periodicity and random instabilities. The objective of this work was to unveil how the H:D responds to them. It was found that ploidy phase dissimilarities on the demographic matrix and/or in the initial population structure cause an inevitable H:D time variability as a consequence of the life-cycle structure and independent of the environmental seasonal cycle. This variability depends on the type of life strategy, demographic processes involved and ploidy dissimilar vital rates. Furthermore, ploidy dissimilar fertility or growth rates cause cyclic oscillations mismatching the seasonal cycle, whereas ploidy dissimilarities in the ramet looping rates (survival related) induce a monotonical variation.