Parasites, pathogens, and invasions by plants and animals

Abstract

Biological invasions cause billions of dollars in economic damage each year and are a serious threat to native biodiversity. Introduced animals and plants may escape 75% or more of the parasite and pathogen species from their native range. While they do accumulate novel parasite species from their new location, this number is generally only a fraction of the number lost. Individual plants and animals are also generally less frequently infected (prevalence minus percent individuals infected) in introduced compared to native conspecific populations. In conjunction with other biological and physical factors, release from parasites helps explain the increased demographic performance of invasive species, potentially accounting for much of the damage they cause.

Cryptosporidium spp. and Enterocytozoon bieneusi in introduced raccoons (Procyon lotor)—first evidence from Poland and Germany

“…Some studies have shown that species introduced into a novel environment often lose their own parasites during the course of a new population establishment (Torchin et al 2003; Torchin and Mitchell 2004) but also encounter and accumulate parasites that occur in newly colonized areas. In addition, there may be a significant probability of raccoons introducing some new parasite species, recorded previously in individuals from North America, into European ones.…”

Comparative impacts of aboveground and belowground enemies on an invasive thistle

“…This is of particular interest for invasive plants undergoing range expansion, as the interactions between a host plant and its enemies can be an important determinant of future spread. The Enemy Release Hypothesis is a well-established explanation for the success of many invasive plants, whereby the invader benefits from reduced enemy pressure in the invaded range as a consequence of leaving behind species-specific herbivores and pathogens during the invasion process (Elton, 1958;Keane & Crawley, 2002;Torchin & Mitchell, 2004).…”

Analyzing Disease Risks Associated with Translocations

“…More information on the number, identity, distribution, and pathogenicity of parasites would be needed to enable, or prioritize, assessment of novel parasites at the hazard-identification stage and to reduce the number of parasites requiring assessment. Research on parasite loss and persistence in non-native species (Torchin et al 2003;Torchin & Mitchell 2004;MacLeod et al 2010) and wild animals in trade (Smith & Daszak 2009) may suggest which parasite groups are most likely to be source hazards given their ability to persist in translocated populations. So far, such research has identified only host factors that are strongly associated with parasite persistence (Macleod et al 2010).…”

“…We defined parasites as infectious agents, including viruses, bacteria, fungi, protozoa, helminths, and ectoparasites. Some translocated organisms have fewer parasites than others, and therefore may have higher fitness (Torchin et al 2003;Torchin & Mitchell 2004) than conspecifics in the organism's source range. For example, House Sparrows (Passer domesticus) introduced to North America from Europe have fewer genera and species of parasites than House Sparrows in Europe (Dobson & May 1986).…”

“…Parasites may play a role in population regulation. If an organism's parasites are not translocated along with their host, the translocated population may be more successful in its new environment than in its original environment (Tompkins et al 2001;Torchin & Mitchell 2004;Smith & Daszak 2009). Translocated species may also be affected by new parasites.…”