Ectoparasite extinction in simplified lizard assemblages during experimental island invasion

Abstract

Introduced species can become invasive, damaging ecosystems and disrupting economies through explosive population growth. One mechanism underlying population expansion in invasive populations is ‘enemy release’, whereby the invader experiences relaxation of agonistic interactions with other species, including parasites. However, direct observational evidence of release from parasitism during invasion is rare. We mimicked the early stages of invasion by experimentally translocating populations of mite-parasitized slender anole lizards ( Anolis apletophallus ) to islands that varied in the number of native anoles. Two islands were anole-free prior to the introduction, whereas a third island had a resident population of Gaige's anole ( Anolis gaigei ). We then characterized changes in trombiculid mite parasitism over multiple generations post-introduction. We found that mites rapidly went extinct on one-species islands, but that lizards introduced to the two-species island retained mites. After three generations, the two-species island had the highest total density and biomass of lizards, but the lowest density of the introduced species, implying that the ‘invasion’ had been less successful. This field-transplant study suggests that native species can be ‘enemy reservoirs’ that facilitate co-colonization of ectoparasites with the invasive host. Broadly, these results indicate that the presence of intact and diverse native communities may help to curb invasiveness.

Sex-biased parasitism and expression of a sexual signal

“…Both sexes can be heavily parasitized (Fig. 1) by both endo-and ectoparasites (Telford, 1974;Cox et al, 2020), including the trombiculid mite (Eutrombiculus c.f. alfreddugesi., Lance Durden pers.…”

“…We sought to understand how ecology, morphology, and energetics can impact ectoparasitic infection in a sex-specific fashion in the Panamanian slender anole (Anolis apletophallus; hereafter, slender anole). The slender anole possesses a dramatic sexual signal (the dewlap), can be heavily parasitized by trombiculid mites (Cox et al, 2020), and is sexually monomorphic in body size (Andrews & Stamps, 1994). In other anole species with male-biased sexual size dimorphism, testosterone circulates at higher levels in males (Lovern et al, 2001;Cox et al, 2009a;Cox et al, 2017), expression of the dewlap can be condition-dependent and is regulated by testosterone (Lovern et al, 2004;Cox et al, 2009b;Cox et al, 2015a;Curlis et al, 2017), and males suffer from increased ectoparasitism (Zippel et al, 1996;Reedy et al, 2016).…”

Sex-specific microhabitat use is associated with sex-biased thermal physiology in Anolis lizards

“…Despite these differences in habitat structure and sexual size dimorphism, brown anoles and slender anoles have broadly similar ecologies and life histories. Both species are territorial, generalist arthropod-predators that have nearly annual population turnover and breed during northern hemisphere summers (Andrews et al, 1989;Andrews and Nichols, 1990;Andrews and Stamps, 1994;Calsbeek, 2009;Cox et al, 2020a;Logan et al, 2014;Losos, 2009;Sexton, 1967;Sexton et al, 1972). The differences and similarities between these two species render them an ideal system for testing hypotheses regarding the ecological factors favoring sexual dimorphism in thermal physiology.…”

Habitat structure mediates vulnerability to climate change through its effects on thermoregulatory behavior

“…We randomized the order of exposure to different physiological assays in both species to eliminate potential order effects, and all lizards were given a minimum of 90 minutes rest between experiments. After no more than 72 h, lizards were either released back to their spot of capture or transplanted to experimental islands as part of a separate, ongoing experimental evolution study (e.g., Cox et al, 2020). We compared thermal tolerance limits between populations using general linear models with either CT min or VT max as dependent variables and “body mass” and “species” as independent variables.…”

“…After no more than 72 h, lizards were either released back to their spot of capture or transplanted to experimental islands as part of a separate, ongoing experimental evolution study (e.g., Cox et al, 2020). We compared thermal tolerance limits between populations using general linear models with either CT min or VT max as dependent variables and "body mass" and "species" as independent variables.…”