Living on the Edge: Parasite Prevalence Changes Dramatically across a Range Edge in an Invasive Gecko

Abstract

Species interactions can determine range limits, and parasitism is the most intimate of such interactions. Intriguingly, the very conditions on range edges likely change host-parasite dynamics in nontrivial ways. Range edges are often associated with clines in host density and with environmental transitions, both of which may affect parasite transmission. On advancing range edges, founder events and fitness/dispersal costs of parasitism may also cause parasites to be lost on range edges. Here we examine the prevalence of three species of parasite across the range edge of an invasive gecko, Hemidactylus frenatus, in northeastern Australia. The gecko's range edge spans the urban-woodland interface at the edge of urban areas. Across this edge, gecko abundance shows a steep decline, being lower in the woodland. Two parasite species (a mite and a pentastome) are coevolved with H. frenatus, and these species become less prevalent as the geckos become less abundant. A third species of parasite (another pentastome) is native to Australia and has no coevolutionary history with H. frenatus. This species became more prevalent as the geckos become less abundant. These dramatic shifts in parasitism (occurring over 3.5 km) confirm that host-parasite dynamics can vary substantially across the range edge of this gecko host.

The factors affecting a native obligate parasite, Cuscuta australis, in selecting an exotic weed, Humulus scandens, as its host

“…It is generally thought that the location of a host and subsequent attachment by a dodder are mainly induced by changes in light quantity and quality rather than by volatile chemical cues from host plants 9,10 . Cuscuta seedlings conspicuously grow toward conditions with low red light:far-red light (R:FR) ratios, which are associated with denser canopy environments 9,10 , so the probability of encountering and parasitizing a host plant is much greater for dodder seedlings, which is consistent with previos results that the spread of parasites is mainly driven by host density 11,12 . Furthermore, parasites often prefer hosts with higher nutrient contents, especially nitrogen (N) (such as legumes) as N content is important in parasite performance, although it is not always better on nutrient-rich plants 13–16 .…”

Morphological divergence and reduced ectoparasite prevalence in an introduced population of a Caribbean anole

“…Morphological divergence of dispersal‐related traits in vanguard populations has been observed in amphibians, for example in Australia with the invasive cane toad ( Rhinella marina ) and in France with the invasive African clawed frog ( Xenopus laevis ) (Phillips et al ., ; Louppe, Courant & Herrel, ). Similarly, reduced parasite prevalence in range‐edge populations has been demonstrated with the blue striped snapper ( Lutjanus kasmira ) in Hawaii and the common house geckos ( Hemidactylus frenatus ) in Australia (Gaither et al ., ; Coates et al ., ). In both cases there is a clear decrease in parasite prevalence moving from core, intermediate, to range‐edge populations.…”

Habitat type influences parasite load in Algerian Psammodromus (Psammodromus algirus) lizards

“…For instance, it has been found that parasite load varies according to habitat type, as a result of the environmental suitability for the parasite (Bulté et al 2009, Rubio andSimonetti 2009). In this regard, parasitism rate widely oscillates not only between individuals of the same species due to factors related to health condition (i.e., infection susceptibility or ability to defend against infection through immune system) (Folstad and Karter 1992) or behavioral avoidance (Hart 1990), but also between populations due to the differences in environmental conditions where each population inhabits (Coates et al 2017).…”