Infection success data from experimental pairings of cane toad hosts and lungworm parasites

By imposing novel selection pressures on both participants, biological invasions can disrupt evolutionary “arms races” between hosts and parasites. A spatially replicated cross-infection experiment reveals strong divergence in the ability of lungworms (Rhabdias pseudosphaerocephala) to infect invasive cane toads (Rhinella marina) in Australia. In areas colonised for > 20 years, toads are more resistant to infection by local strains of parasites than by allopatric strains. The situation reverses at the invasion front, where super-infective parasites have evolved. Invasion-induced shifts in genetic diversity and selective pressures may explain why hosts win the arms race in long-colonised areas whereas parasites win the arms race at the invasion front.