The enemy release hypothesis and Callosciurus erythraeus in Argentina: combining community and biogeographical parasitological studies

Abstract

The enemy release hypothesis (ERH) postulates that during the invasion process an introduced species is released from the natural enemies that regulate its populations, promoting its invasion success in the new environment. Callosciurus erythraeus is a sciurid native to Southeast Asia that has been successfully introduced into Argentina and other Asian and European countries. The aim of this study was to provide new parasitological data on this species and to compare it with studies in native and other introduced ranges under the framework of the ERH. We proposed two working hypotheses: (1) an analysis at the community level to compare the prevalence, abundance and identity of parasites of C. erythraeus and sympatric native mammals in the main invasion focus of Argentina, and ( 2) an analysis at the biogeographical level to compare parasite richness in native and introduced ranges of C. erythraeus and parasite prevalence and richness among introduced regions with different invasion success (using population density and spread as proxy variables). The community analyses indicated that C. erythraeus has lost its specific parasites in Argentina and that it has a lower level of parasitism than other native mammals.

Exotic Pet Trade as a Cause of Biological Invasions: The Case of Tree Squirrels of the Genus Callosciurus

“…This was observed mainly in populations in Japan, where the helminth Strongyloides callosciureus was successfully co-introduced with its original host [133,134] while other Callosciurus-specific nematodes, Brevistriata callosciuri and Gongylonema neoplasticum, were detected in only one to three hosts [134][135][136]. In Argentina, France, Belgium and Italy, the introduction of Callosciurus-specific parasites was detected to a very low extent, possibly resulting in extinction of the parasite in the future [130,131,[137][138][139]. Consequently, in these countries, there is a very low risk of macroparasite spillover from the alien to native rodent species.…”

“…Consequently, in these countries, there is a very low risk of macroparasite spillover from the alien to native rodent species. Since, so far, Pallas's squirrels are only accidentally parasitized by nematodes acquired in their new environment (Table 2), the risk of parasite spillback also seems to be very low (France and Belgium [137], Italy [131] and Argentina [138,139]).…”

Prey naïveté rather than enemy release dominates the relation of an invasive spider toward a native predator

“…As one of the most predominant and intuitive, the enemy release hypothesis posits that nonindigenous species are released from the pressure of predators and parasites once introduced to their exotic ranges (Elton, 1958 ; Keane & Crawley, 2002 ). Introduced species might have advantages over resident species against native enemies by, for example, not being recognized as prey or hosts for parasites in the exotic range (e.g., Cottrell & Shapiro‐Ilan, 2003 ; Gozzi et al., 2020 ; Montes et al., 2020 ; Tierney et al., 2020 ). However, Elton ( 1958 ) mentions that species leaving coevolved predators and parasites from the native areas immediately meet novel potential enemies once introduced in the exotic range.…”

“…Therefore, the enemy release hypothesis as a driving force behind successful invasions should be tested for already established invasive species that are in their spreading phase (i.e., abundant or dominant) in the exotic range. Furthermore, studies investigating the role of enemy release as a causal mechanism of invasiveness are mainly based on invasive plant and vertebrate species (e.g., Carpenter & Cappuccino, 2005 ; Gozzi et al., 2020 ; Hawkes, 2007 ; Hierro et al., 2005 ; van Kleunen et al., 2010 ; Lankau et al., 2004 ; Liu & Stiling, 2006 ; Meijer et al., 2016 ; Montes et al., 2020 ; Schultheis et al., 2015 ; Tierney et al., 2020 ), whereas only a limited number is focused on arthropods (e.g., Aliabadi & Juliano, 2002 ; Juliano et al., 2010 ; Paula et al., 2021 ; Zuharah & Lester, 2010 ).…”

“…might have advantages over resident species against native enemies by, for example, not being recognized as prey or hosts for parasites in the exotic range (e.g., Cottrell & Shapiro-Ilan, 2003;Gozzi et al, 2020;Montes et al, 2020;Tierney et al, 2020). However, Elton (1958) mentions that species leaving coevolved predators and parasites from the native areas immediately meet novel potential enemies once introduced in the exotic range.…”