Abstract
Parasites are the most biodiverse organisms on the planet, but they are given little attention when it comes to conservation. Captivity and translocation are two of the most common and important conservation management strategies for conserving host species, but they represent a potentially drastic change in environment that may impact parasites and thus, paradoxically, conservation of host species could lead to parasite extinction. However, it is not known how frequently conservation leads to parasite extinction, which aspects are most detrimental for parasites, or which parasites and their life history traits are most at risk. Therefore, this thesis aimed to examine how host captivity and translocation affect parasites.
First, to examine the effect of host captivity on host-parasite interactions, I compared the odds of infection by parasites in captive vs. wild host populations in a meta-analysis. Captivity decreased the odds of infection by helminths, especially those with complex life cycles. Environmentally transmitted parasites (faecal-oral transmission) were also less common in captivity, as were vector-borne protozoa. These results highlight that helminths and vector-borne protozoa were most affected by host captivity, as well as parasites with complex life cycles and environmental transmission.
As a model organism to study the impact of translocation on host-parasite interactions, I focused on the critically endangered Australian marsupial, the woylie (Bettongia pencillata) because they are the most translocated animal in Australia. To determine the host specificity of nematode and coccidia parasites, I compared the parasite communities of the woylie and three other sympatric marsupial species found in south-western Australia: the brushtail possum (Trichosurus vulpecula hypoleucus), chuditch (Dasyurus geoffroii), and quenda (Isoodon fusciventer). By using next generation sequencing (NGS), I was able to determine which parasites were specific to the woylie while also exploring the parasite communities of marsupial species that have not been examined previously for parasites on a fine, molecular scale.
Lastly, I examined how translocation and translocation history affected nematode and coccidia parasites of the woylie. By using NGS, I found that for translocated woylies, the prevalence of specialist nematodes and generalist coccidia decreased. For resident woylies, the prevalence of nematodes increased after translocation and the diversity of nematodes increased at one site. I also found that parasite infracommunities of translocated and resident woylies became more similar after one month. When examining translocation history, I found
that woylies in different sites of translocation had different parasite communities in terms of diversity, infracommunity composition or prevalence. Overall, nematodes were most prevalent diverse in a site closest resembling natural populations, whereas coccidia were most prevalent and diverse in a site founded by captive woylies. Further, nematodes were undetected in one site while coccidia were undetected in a different site.
This thesis uncovers some of the underlaying processed playing a part in conservation-driven parasite extinction and highlights which parasite taxa may be most at risk, and which life history traits may play the most important role in conservation-driven extinction of parasites.