Host-related genetic differentiation in the anther smut fungus Microbotryum violaceum in sympatric, parapatric and allopatric populations of two host species Silene latifolia and S. dioica

Abstract

We investigated genetic diversity in West European populations of the fungal pathogen Microbotryum violaceum in sympatric, parapatric and allopatric populations of the host species Silene latifolia and S. dioica, using four polymorphic microsatellite loci. In allopatric host populations, the fungus was highly differentiated by host species, exhibiting high values of FST and RST, and revealed clear and distinct host races. In sympatric and parapatric populations we found significant population differentiation as well, except for one sympatric population in which the two host species grew truly intermingled. The mean number of alleles per locus for isolates from each of the host species was significantly higher in sympatric/parapatric than in allopatric populations. This suggests that either gene flow between host races in sympatry, or in case of less neutral loci, selection in a more heterogeneous host environment can increase the level of genetic variation in each of the demes. The observed pattern of host‐related genetic differentiation among these geographically spread populations suggest a long‐term divergence between these host races. In sympatric host populations, both host races presumably come in secondary contact, and host‐specific alleles are exchanged depending on the amount of fungal gene flow.

Glacial Refugia in Pathogens: European Genetic Structure of Anther Smut Pathogens on Silene latifolia and Silene dioica

“…Hybridization between MvSl and MvSd has been suggested previously [105]. However, we showed recently in a study investigating the divergence process between the two species using the same dataset as in the present work that hybridization was very rare in natural populations [52].…”

Life history determines genetic structure and evolutionary potential of host–parasite interactions

“…Thus, strong local spatial genetic structure in the anther smut Microbotryum violaceum is associated with locally restricted insect dispersal [64]. Host preferences shown by vectors might also play a role in sympatric pathogen race formation by promoting reproductive isolation among host-specific strains [65]. Similarly, for parasites of animal species, patterns of host dispersal have the potential to strongly influence parasite gene flow [66].…”

Mating System of the Anther Smut Fungus Microbotryum violaceum : Selfing under Heterothallism

“…The nature of the reproductive isolation among the different sibling species of the complex M. violaceum sensu lato has thoroughly been investigated (18,72,73,96,106,107). Despite the broad geographic overlap among the pathogen lineages adapted to different hosts, indirect isolation could result if pollinators were specialists and transmitted fungal spores only to members of the same host species.…”