A Model for the Establishment of Polyploidy in Plants: Viable but Infertile Hybrids, Iteroparity, and Demographic Stochasticity

Analysing a mathematical model, a previous study (Rodrı́guez, 1995) found that, when crosses between semelparous plants of different ploidy in deterministic environments produce inviable zygotes, the establishment of polyploids in communities where their deploid ancestors predominate is possible, when fecundity and selfing are high enough and there is a slight niche separation between cytotypes. The present study modifies this model by considering other situations. Results indicate that: (1) when hybrids are viable but infertile the conditions for polyploid establishment are not altered, (2) iteroparity enhances the chances of polyploid invasion, and (3) stochastic effects due to a small number of invaders decrease the chances of invasion, but in biologically reasonable cases there is still a good chance of invasion. The results are discussed in view of patterns reported in empirical studies. It is concluded that the establishment of polyploids in higher plants is not an unlikely event, and this can help to understand its widespread abundance.