Analysis of polygenic traits of Microcystis aeruginosa (Cyanobacteria) strains by Restricted Maximum Likelihood (REML) procedures:: 2.: Microcystin net production, photosynthesis and respiration

Phenotypic expression of traits is the result of complex interactions between genotype and environment. A combination of experiments and statistics based oil restricted maximum likelihood (REML) procedures was utilised for estimating the proportion of genetic variability in a series of phenotypic characters (microcystin net production, cell size, dark respiration rate, photosynthetic capacity, maximum quantum yield and growth rate), as well as their genetic and nongenetic correlations, measured on 18 Microcystis aeruginosa (Cyanobacteria) strains. Results indicated that the phenotypic variability found in these traits were principally due to genetic differences among strains. Thus, the estimated genetic variability ranged from approximate to 50% for dark respiration rate to > 90% in cell size or maximum quantum yield. These results support the conclusions that (1) genetic factors are the main cause of the spatial-temporal heterogeneity observed in quantum yield, respiration and toxin production, and (2) light harvesting and toxin production are not under intense natural selection, both having a low adaptive value. The high variance in toxin production resulting from genetic effects introduces a source of unpredictability in water-supply toxic early warnings. In addition, no significant genetic correlations were found between quantum yield and either maximal growth rate or mean cell diameter.