Introduced hosts are capable of introducing parasite species and altering the abundance of parasites that are already present in native hosts, but few studies have compared the tolerances of native and invasive hosts to introduced parasites or identified the traits of introduced hosts that make them supershedders of non‐native parasites. Here, we compare the effects of a nematode In the laboratory, infection with Any conservation intervention to reduce the effects of CTFs on native treefrogs would benefit from knowing the traits that contribute to the invasive host being a supershedder of this parasite. Hence, we conducted necropsies on 330 CTFs to determine how host sex and body size affect the abundance of There was a significant linear increase in
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Abstract Aplectana hamatospicula that is native to Cuba but appears to be introduced to Florida on the native Floridian treefrog,Hyla femoralis , and on the Cuban treefrog (CTF),Osteopilus septentrionalis . We were particularly interested in CTFs because their introduction to Florida has led to reported declines of native treefrogs.A. hamatospicula caused a greater loss in body mass ofH. femoralis than CTFs despiteH. femoralis shedding fewer total worms in their faeces than CTFs. Field collections of CTFs,H. femoralis , and another native Floridian treefrog,H .squirella (Squirrel treefrog) from Tampa, FL also showed that CTFs shed more larval worms in their faeces than both native frogs when controlling for body size. Hence, the non‐native CTF is a supershedder of this non‐native parasite that is spilling over to less tolerant native treefrogs.A. hamatospicula , and two other common parasites in this species (acuariid nematodes and trematode metacercariae).A. hamatospicula and encysted acuariids with CTF body size, but there was no detectable relationship between host body size and the intensity of metacercariae. Female CTFs were bigger, lived longer and, on average, had moreA. hamatospicula than male CTFs.Synthesis and applications . These results of the study suggest that there is parasite spillover from the invasive Cuban treefrog (CTF) to native treefrogs in Florida. Additionally, at least some of the adverse effects of CTFs on native treefrogs could be caused by the introduction and amplification of this introduced parasite, and female and larger CTFs seem to be amplifying these infections more than males and smaller CTFs, respectively, suggesting that management could benefit from targeting these individuals. -
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Abstract Global climate change is increasing the frequency of unpredictable weather conditions; however, it remains unclear how species‐level and geographic factors, including body size and latitude, moderate impacts of unusually warm or cool temperatures on disease. Because larger and lower‐latitude hosts generally have slower acclimation times than smaller and higher‐latitude hosts, we hypothesised that their disease susceptibility increases under ‘thermal mismatches’ or differences between baseline climate and the temperature during surveying for disease. Here, we examined how thermal mismatches interact with body size, life stage, habitat, latitude, elevation, phylogeny and International Union for Conservation of Nature (IUCN) conservation status to predict infection prevalence of the chytrid fungus
Batrachochytrium dendrobatidis (Bd ) in a global analysis of 32 291 amphibian hosts. As hypothesised, we found that the susceptibility of larger hosts and hosts from lower latitudes toBd was influenced by thermal mismatches. Furthermore, hosts of conservation concern were more susceptible than others following thermal mismatches, suggesting that thermal mismatches might have contributed to recent amphibian declines. -
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Abstract Complex ecological relationships, such as host–parasite interactions, are often modeled with laboratory experiments. However, some experimental laboratory conditions, such as temperature or infection dose, are regularly chosen based on convenience or convention, and it is unclear how these decisions systematically affect experimental outcomes. Here, we conducted a meta‐analysis of 58 laboratory studies that exposed amphibians to the pathogenic fungus
Batrachochytrium dendrobatidis (Bd) to understand better how laboratory temperature, host life stage, infection dose, and host species affect host mortality. We found that host mortality was driven by thermal mismatches: hosts native to cooler environments experienced greater Bd‐induced mortality at relatively warm experimental temperatures and vice versa. We also found that Bd dose positively predicted Bd‐induced host mortality and that the superfamilies Bufonoidea and Hyloidea were especially susceptible to Bd. Finally, the effect of Bd on host mortality varied across host life stages, with larval amphibians experiencing lower risk of Bd‐induced mortality than adults or metamorphs. Metamorphs were especially susceptible and experienced mortality when inoculated with much smaller Bd doses than the average dose used by researchers. Our results suggest that when designing experiments on species interactions, researchers should carefully consider the experimental temperature, inoculum dose, and life stage, and taxonomy of the host species.
