Abstract

SummaryUnderstanding disease distributions is of fundamental and applied importance, yet few studies benefit from integrating broad sampling with ecological and phylogenetic data. Here, anther-smut disease, caused by the fungus Microbotryum, was assessed using herbarium specimens of Silene and allied genera of the Caryophyllaceae.A total of 42 000 herbarium specimens were examined, and plant geographical distributions and morphological and life history characteristics were tested as correlates of disease occurrence. Phylogenetic comparative methods were used to determine the association between disease and plant life-span.Disease was found on 391 herbarium specimens from 114 species and all continents with native Silene. Anther smut occurred exclusively on perennial plants, consistent with the pathogen requiring living hosts to overwinter. The disease was estimated to occur in 80% of perennial species of Silene and allied genera. The correlation between plant life-span and disease was highly significant while controlling for the plant phylogeny, but the disease was not correlated with differences in floral morphology.Using resources available in natural history collections, this study illustrates how disease distribution can be determined, not by restriction to a clade of susceptible hosts or to a limited geographical region, but by association with host life-span, a trait that has undergone frequent evolutionary transitions.

Highlights

  • Theoretical studies have emphasized that epidemiological and evolutionary dynamics may be heavily influenced by details of the pathogen’s and the host’s life cycles (Anderson & May, 1981; Thrall & Burdon, 2004; Barrett et al, 2008)

  • A total of 42 000 herbarium specimens were examined, and plant geographical distributions and morphological and life history characteristics were tested as correlates of disease occurrence

  • Disease was found on 391 herbarium specimens from 114 species and all continents with native Silene

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Summary

Introduction

Theoretical studies have emphasized that epidemiological and evolutionary dynamics may be heavily influenced by details of the pathogen’s and the host’s life cycles (Anderson & May, 1981; Thrall & Burdon, 2004; Barrett et al, 2008). Surprisingly few examples are available of diseases in natural populations where broad geographical sampling can be combined with ecological and phylogenetic data to understand pathogen distributions. Because endemic pathogens and their hosts are affected by long-term coevolutionary processes, phylogenetic analyses can be combined with ecological and geographical data to identify the population, life history, and genetic traits that contribute to disease spread and persistence. Such an integrated approach can be used to evaluate ecological factors and life history traits that put hosts at risk for the emergence of new diseases. Similar surveys of herbarium specimens have proven increasingly useful for understanding a variety of other naturally occurring diseases (Evans, 1987; Alexander et al, 2007; Malmstrom et al, 2007)

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