Neopolyploidy and pathogen resistance

Abstract

Despite the well-documented historical importance of polyploidy, the mechanisms responsible for the establishment and evolutionary success of novel polyploid lineages remain unresolved. One possibility, which has not been previously evaluated theoretically, is that novel polyploid lineages are initially more resistant to pathogens than the diploid progenitor species. Here, we explore this possibility by developing and analysing mathematical models of interactions between newly formed polyploid lineages and their pathogens. We find that for the genetic mechanisms of pathogen resistance with the best empirical support, newly formed polyploid populations of hosts are expected to be more resistant than their diploid progenitors. This effect can be quite strong and, in the case of perennial species with recurrent polyploid formation, may last indefinitely, potentially providing a general explanation for the successful establishment of novel polyploid lineages.

Changes to gene expression associated with hybrid speciation in plants: further insights from transcriptomic studies inSenecio

“…Altered expression of genes involved in response to herbivory has also been demonstrated to vary between two Nicotiana polyploids that share a common ancestor (Qu et al 2004). Increased resistance to herbivores in polyploids compared with their diploid relatives has been proposed (Qu et al 2004) as possibly due to an increase in the number of alleles for resistance genes seen in polyploids (Oswald & Nuismer 2007). Recent research in Gossypium (Liu & Adams 2007) suggests that different adaptive phenotypes such as this could also result from modulated expression of homeologous parental gene copies.…”

The Red Queen Process does not Select for High Recombination Rates in Haplodiploid Hosts

“…Since arthropods are not very well known for adaptive immune systems the MAM was adopted as the interaction model over the IMA and GfG models (Wilfert, Gadau and Schmid-Hempel 2007a). However, since the results of previous studies Oswald and Nuismer 2007;M'Gonigle and Otto 2011) suggest the possibility of interdependence between these factors, the results here remain specific to the MAM.…”

“…The most striking result is the lack of the spread of a recombination modifier and the lack of Red Queen oscillations in haplodiploid host populations. Previous studies analyzed either invasion scenarios (M'Gonigle and Otto 2011), advantages of the host to resistance (Oswald and Nuismer 2007), or conditions favouring parasitism . The host systems of Mgonigle & Otto and Nuismer & Otto were either haploid, diploid (M'Gonigle and Otto 2011); or diploid, tetraploid .…”

“…In further studies, haploidy was found to be beneficial for parasites , whereas higher ploidy levels (diploidy, tetraploidy) were favoured in the host (M'Gonigle and Otto 2011; Oswald and Nuismer 2007). The only exception was the evolution of haploid hosts under the MAM .…”

Host-parasite evolution in male-haploid hosts: an individual based network model

“…The lower fitness observed for diploids under the MAM (and haplodiploids under the IMAM) is similar to that found for the virulence figure. Here, though, the relationship is strictly negative with a gradual reduction in the degree of divergence between fitness under the different interaction models parasite virulence under the MAM, higher fitnesses under the IMAM Oswald and Nuismer 2007; M'Gonigle and Otto 2011). The converse being true for haplodiploid host populations (higher fitnesses under the MAM than the IMAM).…”