Faculté des sciences

Effect of triploid fitness on the coexistence of diploids and tetraploids

Felber, François ; Bever, James D.

In: Biological Journal of the Linnean Society, 1997, vol. 60, no. 1, p. 95-106

The conditions for the coexistence of diploids, triploids and tetraploids in a single population were investigated with a deterministic model under the assumptions that diploids might produce 2n gametes, and that triploids had a lower fitness than other cytotypes and generated equal proportions of haploid and diploid gametes. When diploids produced only haploid gametes, the dynamics of the... Plus

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    Summary
    The conditions for the coexistence of diploids, triploids and tetraploids in a single population were investigated with a deterministic model under the assumptions that diploids might produce 2n gametes, and that triploids had a lower fitness than other cytotypes and generated equal proportions of haploid and diploid gametes. When diploids produced only haploid gametes, the dynamics of the cytotypes were similar to that of heterozygote disadvantage with two alleles at a single locus, with triploids being equivalent to the heterozygotes. Production of 2n gametes by diploids increased the pool of diploid gametes and created a stable equilibrium involving a majority of diploids and a minority of polyploids. When the fitness of tetraploids was equal to or higher than that of diploids, increased triploid fitness decreased the threshold of 2n gametes necessary to deterministically fix tetraploids in the population. Conversely, when tetraploids were less fit than diploids, the rate of 2n gamete production leading to the exclusion of diploids first decreases and then increased with increasing triploid fitness. Triploids are repeatedly found in diploid-tetraploid hybridizations and are rarely totally sterile. They might play a determinant role in the future of multiple cytotype populations. The effect of triploids depends on the relative fitness of diploids and tetraploids and is also a function of their fitness.