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

Abstract

Climate warming is predicted to increase the frequency of invasions by pathogens and to cause the large-scale redistribution of native host species, with dramatic consequences on the health of domesticated and wild populations of plants and animals. The study of historic range shifts in response to climate change, such as during interglacial cycles, can help in the prediction of the routes and dynamics of infectious diseases during the impending ecosystem changes. Here we studied the population structure in Europe of two Microbotryum species causing anther smut disease on the plants Silene latifolia and Silene dioica. Clustering analyses revealed the existence of genetically distinct groups for the pathogen on S. latifolia, providing a clear-cut example of European phylogeography reflecting recolonization from southern refugia after glaciation. The pathogen genetic structure was congruent with the genetic structure of its host species S. latifolia, suggesting dependence of the migration pathway of the anther smut fungus on its host. The fungus, however, appeared to have persisted in more numerous and smaller refugia than its host and to have experienced fewer events of large-scale dispersal. The anther smut pathogen on S. dioica also showed a strong phylogeographic structure that might be related to more northern glacial refugia. Differences in host ecology probably played a role in these differences in the pathogen population structure. Very high selfing rates were inferred in both fungal species, explaining the low levels of admixture between the genetic clusters. The systems studied here indicate that migration patterns caused by climate change can be expected to include pathogen invasions that follow the redistribution of their host species at continental scales, but also that the recolonization by pathogens is not simply a mirror of their hosts, even for obligate biotrophs, and that the ecology of hosts and pathogen mating systems likely affects recolonization patterns.

The tempo and modes of evolution of reproductive isolation in fungi

“…Surprisingly, however, the degree of syngamy compatibility did not continue to decrease at larger genetic distances, remaining quite high. That inhibition of interspecific gamete fusion does not further decrease at higher genetic distance is intriguing given the evolution of postsyngamy isolation, with continual increase of hybrid inviability and sterility at these genetic distances, and the overlapping ranges of the species (Bucheli et al, 2000;Le Gac et al, 2007a, b;Hood et al, 2010;Gladieux et al, 2010b;Vercken et al, 2010). One may think that reinforcement would have kept on occurring to avoid producing unfit hybrids, especially at the greatest genetic distances where postsyngamy isolation is the strongest.…”

Genetic and geographic structure of an insect resistant and a susceptible type of Barbarea vulgaris in western Europe

“…In support of the first scenario, it is now well documented that several European plant species are strongly structured genetically by previous occupancy in different glacial refugias (Hewitt 2000; for a recent review, see Vercken et al 2010). Several refugia have been identified, notably in Iberia, Italy, and the Balkans, and others have been suggested in the northern and eastern part of Europe (Bhagwat and Willis 2008;Stewart et al 2010).…”

Contributions of ancestral inter-species recombination to the genetic diversity of extant Streptomyces lineages

“…Glaciation has had strong impacts on the biogeography and genetic diversity of a range of terrestrial species (Conroy and Cook, 2000;Milá et al, 2006;Wilson and Eigenmann Veraguth, 2010;Pointing et al, 2014;Newman and Austin, 2015) and has been shown to impact microbial diversity in soil (Vercken et al, 2010;Boyd et al, 2011;Park et al, 2011;Eisenlord et al, 2012;Stibal et al, 2012;Hamilton et al, 2013). Rapid demographic expansion resulting from glacial retreat has had profound impacts on the genetics of species (Hewitt, 1996;Conroy and Cook, 2000;Hewitt, 2000Hewitt, , 2004Wilson and Eigenmann Veraguth, 2010).…”