Ecology Letters (2012) 15 : 329–337
Parasites of invading species undergoing range advance may be exposed to powerful new selective forces. Low host density in range‐edge populations hampers parasite transmission, requiring the parasite to survive longer periods in the external environment before encountering a potential host. These conditions should favour evolutionary shifts in offspring size to maximise parasite transmission. We conducted a common‐garden experiment to compare life history traits among seven populations of the nematode lungworm ( Rhabdias pseudosphaerocephala) spanning from the parasite population core to the expanding range‐edge in invasive cane toads ( Rhinella marina ) in tropical Australia. Compared to conspecifics from the population core, nematodes from the range‐edge exhibited larger eggs, larger free‐living adults and larger infective larvae, and reduced age at maturity in parasitic adults. These results support a priori predictions regarding adaptive changes in offspring size as a function of invasion history, and suggest that parasite life history traits can evolve rapidly in response to the selective forces exerted by a biological invasion.