Coinfection with chytrid genotypes drives divergent infection dynamics reflecting regional distribution patterns

By altering the abundance, diversity, and distribution of species — and their pathogens — globalization may inadvertently select for more virulent pathogens. In Brazil’s Atlantic Forest, a hotspot of amphibian biodiversity, the global trade has facilitated the co-occurrence of previously isolated enzootic and panzootic lineages of the pathogenic amphibian-chytrid (Batrachochytrium dendrobatidis, ‘Bd’) and generated new virulent recombinant genotypes (‘hybrid’). Epidemiological data indicate that amphibian declines are most severe in hybrid zones, suggesting that coinfections are causing more severe infections or selecting for higher virulence. We investigated how coinfections involving these genotypes shaped virulence and transmission. Overall, coinfection favored the more virulent and competitively superior panzootic genotype, despite dampening its transmission potential and overall virulence. However, for the least virulent and least competitive genotype, coinfection increased both ov...