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The impact of parasites during range expansion of an invasive gecko
- Louise K. Barnett, Ben L. Phillips, Allen C. G. Heath, Andrew Coates, Conrad J. Hoskin
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- Journal:
- Parasitology / Volume 145 / Issue 11 / September 2018
- Published online by Cambridge University Press:
- 14 February 2018, pp. 1400-1409
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- Article
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Host–parasite dynamics can play a fundamental role in both the establishment success of invasive species and their impact on native wildlife. The net impact of parasites depends on their capacity to switch effectively between native and invasive hosts. Here we explore host-switching, spatial patterns and simple fitness measures in a slow-expanding invasion: the invasion of Asian house geckos (Hemidactylus frenatus) from urban areas into bushland in Northeast Australia. In bushland close to urban edges, H. frenatus co-occurs with, and at many sites now greatly out-numbers, native geckos. We measured prevalence and intensity of Geckobia mites (introduced with H. frenatus), and Waddycephalus (a native pentastome). We recorded a new invasive mite species, and several new host associations for native mites and geckos, but we found no evidence of mite transmission between native and invasive geckos. In contrast, native Waddycephalus nymphs were commonly present in H. frenatus, demonstrating this parasite's capacity to utilize H. frenatus as a novel host. Prevalence of mites on H. frenatus decreased with distance from the urban edge, suggesting parasite release towards the invasion front; however, we found no evidence that mites affect H. frenatus body condition or lifespan. Waddycephalus was present at low prevalence in bushland sites and, although its presence did not affect host body condition, our data suggest that it may reduce host survival. The high relative density of H. frenatus at our sites, and their capacity to harbour Waddycephalus, suggests that there may be impacts on native geckos and snakes through parasite spillback.
Chapter 21 - Austral amphibians – Gondwanan relicts in peril
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- By Jean-Marc Hero, Griffith University,, J. Dale Roberts, University of Western Australia, Conrad J. Hoskin, James Cook University, Katrin Lowe, Griffith University, Edward J. Narayan, Griffith University, Phillip J. Bishop, University of Otago
- Edited by Adam Stow, Macquarie University, Sydney, Norman Maclean, University of Southampton, Gregory I. Holwell, University of Auckland
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- Book:
- Austral Ark
- Published online:
- 05 November 2014
- Print publication:
- 22 December 2014, pp 440-466
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Summary
Summary
Over 30% of Australasian amphibians are currently threatened with extinction. While habitat loss, introduced species and disease have been identified as major threats, the impacts of climate change are understudied. Threatened frogs fall into distinct biogeographical and ecological groupings that can be linked to specific threats (e.g. mountain- top endemics and climate change; stream-dwelling wet forest frogs and disease; and small island endemics and feral pests). The impacts of gradual climate change over millions of years has isolated specific species into climatic refugia (resulting in restricted geographic ranges), which combined with the ecological traits of these species (e.g. small clutch-size) dramatically increases extinction risk. Australasian frogs demonstrate intrinsic links between biogeographic history, species ecology and conservation status. The solutions to most threats are clear at a broad level, stop land clearing, reduce CO2 emissions and control feral animals; however, declines linked to the disease chytridiomycosis are not easily resolved. Chytridiomycosis is not a universal threat and understanding the causes of variation in impact is critically important. While the threats of land clearing, disease and introduced species are regional and/or species specific, the impacts of climate change must be examined carefully as all species are likely to affected. Here we cover these issues for Australasian frogs, presenting regional examples that highlight threats and avenues for future research and management.
Phylogenetic and biogeographic history
Over 30% of amphibian species are threatened with extinction globally making them the most threatened of the vertebrate groups (Wake and Vredenburg 2008). There are multiple threats to Austral frogs: e.g. disease – critically chytrid fungus for species with more aquatic lifestyles; small clutch size and limited range associated with higher decline or extinction risk; introduced species (Gambusia and trout in Australia, Gillespie and Hero, 1999; Murray et al., 2011; Rattus in New Zealand, Thurley and Bell, 1994; and mongoose in the Pacific Islands, Pernetta and Watling, 1979) and less specific threats, identified in both Austral and global analyses of amphibian declines: e.g. climate change (Hero et al., 2006, 2008; Hof et al., 2011) and habitat loss and fragmentation (Hero et al., 2008). These factors pose serious threats in many other regions of the world (Stuart, 2008) and their impacts vary among species and genera, depending on their current distribution and habitat use (Table 21.1).