Invasion history and demographic pattern of Cryphonectria hypovirus 1 across European populations of the chestnut blight fungus

Sarah F Bryner,Daniel Rigling,Patrick C Brunner

doi:10.1002/ece3.429

Abstract

We reconstructed the invasion history of the fungal virus Cryphonectria hypovirus 1 (CHV-1) in Europe, which infects the chestnut blight fungus Cryphonectria parasitica. The pattern of virus evolution was inferred based on nucleotide sequence variation from isolates sampled across a wide area in Europe at different points in time. Phylogeny and time estimates suggested that CHV-1 was introduced together with its fungal host to Europe and that it rapidly colonized the central range along the south facing slopes of the Alps and the north-east facing slopes of the Dinaric Alps. These central populations were the source for two waves of simultaneous invasions toward the southern Balkans and Turkey, as indicated by migration rates. Our results showed that the evolutionary scenarios for CHV-1 and C. parasitica were spatially congruent. As infection with CHV-1 reduces the pathogenicity of C. parasitica toward the chestnut tree, CHV-1 invasions of the newly established C. parasitica populations probably prevented the development of devastating chestnut blight epidemics in Europe. We propose that in this, and supposedly in other pathosystems, geographic, vegetation-related, demographic, economic, and political factors may help explain the correlated invasion pattern of a parasite and its host.

Highlights

In modern time, global travel and trade have repeatedly facilitated the introduction of foreign species and their establishment in new environments (Perrings et al 2002)
Our results strongly suggest that the evolution of Cryphonectria hypovirus 1 (CHV-1) is spatially, but not temporally, congruent with the evolution of its host C. parasitica
This is the first investigation of CHV-1 genome sequences obtained from a wide area in Europe

Summary

Introduction

Global travel and trade have repeatedly facilitated the introduction of foreign species and their establishment in new environments (Perrings et al 2002). The majority of DNA viruses are persistent, transmitted vertically (to offspring) or sexually, and their virulence is often low (Villarreal et al 2000; Holmes 2008). They have an evolutionary rate similar to that of their host and their evolution is mostly congruent with that of their host on both the spatial and the temporal scale. RNA viruses that depend on horizontal transmission between hosts have often the same geographic distribution as their host, and show an evolutionary pattern congruent with that of their host on a spatial scale (Real et al 2005; Biek et al 2007; Nadin-Davis et al 2010; Torres-Perez et al 2011)

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