Ecological impacts of invading species: Do parasites of the cane toad imperil Australian frogs?

Abstract

Parasite transfer to native fauna is a potentially catastrophic impact of invasive species. Introduced cane toads in Australia frequently host the nematode lungworm Rhabdias pseudosphaerocephala, which reduces viability of metamorph toads. If native frogs are vulnerable to this South American parasite, cane toad invasion may affect native species via this route; but if the native taxa are not vulnerable, we may be able to exploit the parasites for managing toads. Our laboratory experiments show that infective larvae can penetrate the body of all seven species of Australian frogs (five hylids: Cyclorana longipes, Litoria caerulea, Litoria dahlii, Litoria nasuta, Litoria rothii, one myobatrachid: Opisthodon ornatus, and one limnodynastid: Limnodynastes convexiusculus) we tested, but most did not host the adult worms at the end of the trials, and none showed major impairment of growth, survival or locomotor performance. One native tree-frog (L. caerulea) retained high infection levels with few ill effects, suggesting that we might be able to use this taxon as a reservoir species to build up local parasite densities for toad management. However, the interspecific variation in lungworm retention suggests that generalizations about parasite effects on native frogs will be elusive.

Diversity and host specificity of coccidia (Apicomplexa: Eimeriidae) in native and introduced squirrel species

“…through predation or introduction of lethal pathogens) or indirectly (e.g. through competition, including the parasite-mediated competition) (Clavero and Garcia-Berthou 2005;Hartigan et al 2011;Pizzatto and Shine 2011;Zavaleta et al 2001). Moreover, invasive species and the pathogens they spread represent a threat for human health (Hulme 2014).…”

“…Although majority of parasites are host-specific (Pizzatto and Shine 2011;Poulin 2007), a range of examples of successful invasion (i. a. avian malaria to Hawaii, Fascioloides magna to Europe, spreading of chytridiomycosis in amphibian populations) suggests that the interspecific transmission of parasites can be more frequent than expected (Atkinson et al 2014;Marzal et al 2015; a total of 540 faecal samples from 466 animals (S. vulgaris 206 samples/143 individuals, S. carolinensis 164/164, C. erythraeus 170/159), some individuals were screened repeatedly.…”

Invasive species as drivers of evolutionary change: cane toads in tropical Australia

“…Invasive species allow us to explore the initial stages of parasite–host coevolution, before adaptive shifts obscure interactions (Pizzatto et al. 2010; Pizzatto and Shine 2011a,b).…”

Frogs in the spotlight: a 16‐year survey of native frogs and invasive toads on a floodplain in tropical Australia

“…; but see Bleach et al. ); and toads can transmit parasites to frogs (Pizzatto and Shine ) or take up parasite larvae that would otherwise infect frogs (Lettoof et al. ).…”

“…Laboratory and field-enclosure experiments have documented a diverse array of ecological interactions between cane toads and Australian frogs, within both aquatic and terrestrial phases of the life history (reviewed by Shine 2014). For example, thousands of tadpoles of native frogs are fatally poisoned when they attempt to ingest the toxic eggs of cane toads (Crossland et al 2008) and metamorph frogs die when they try to eat metamorph toads (Greenlees et al 2010); the presence of toads can modify activity levels and habitat selection of frogs (Greenlees et al 2007; but see Bleach et al 2014); and toads can transmit parasites to frogs (Pizzatto and Shine 2011) or take up parasite larvae that would otherwise infect frogs (Lettoof et al 2013). Indirect ecological interactions may be even more important; for example, toads reduce predation pressure on frogs by virtually extirpating local populations of large carnivorous lizards (Brown et al 2013b).…”