Parasite and gut-microbiota dynamics in the experimental translocation of an endangered lizard

Author: Bonnie Derne

Derne, Bonnie, 2021 Parasite and gut-microbiota dynamics in the experimental translocation of an endangered lizard, Flinders University, College of Science and Engineering

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In this thesis, I aim to inform parasite risk assessment for the translocation of an endangered skink. Translocations are potentially useful wildlife conservation strategies, but entail parasite-related risks, such as loss of host fitness and population decline, but also loss of ecosystem function if parasites are unnecessarily eliminated. Novel host-symbiont associations may arise from translocations, and existing relationships may play out differently in new abiotic and biotic environments, where hosts are likely to be stressed and immunocompromised. Predicting and minimising parasite-related costs to the hosts and the ecosystem for translocation risk assessment requires a knowledge of parasite diversity, of host-parasite relationships, and how this may change under translocation conditions. Despite this need, much of the world’s estimated parasite diversity remains undescribed, and the biology of most wildlife parasites poorly understood. This thesis helps address these knowledge gaps for the endangered pygmy bluetongue lizard (Tiliqua adelaidensis) and its parasites and other symbionts; the mite Ophiomegistus michaeli, the nematode Pharyngodon wandillahensis, and its gut bacterial communities. Specifically, I examine the dynamics of parasites and gut microbiota, and the effect on resident and translocated host fitness following an experimental population augmentation of T. adelaidensis in a wild setting.

This thesis furthers our understanding of a wildlife host-parasite system by accompanying the taxonomic description of the parasitic mite Ophiomegistus michaeli sp. nov. with the first observations on the ecology of this mite and its relationship with T. adelaidensis. With its only known host being endangered, this parasite may be at risk of co-extinction. I examined inter-population genetic variation in parasite biota in this system, with implications for local adaptation and variable host-outcomes in a multi-population translocation context. Use of single nucleotide polymorphisms in mites and nematodes revealed genetic structure among isolated host populations. I used these genetic differences to identify transmission of allopatric parasites among lizards of three different population origins sharing habitat following translocation. These transmission events were few and occurred several months after translocation, suggesting slow and host-driven parasite dispersal. Transmission mechanisms were investigated but remain unclear. Gut microbiota in T. adelaidensis were also examined over the course of the translocation as likely influences of host health. No clear differences in detected bacterial species were found among hosts from different populations, nor did communities or strains clearly change in the two years following translocation. Finally, in models based on mark-recapture data, no difference was found between the survival probabilities of translocated and resident T. adelaidensis individuals post-translocation. The lack of macroparasite spread, absence of microbial change, and unaffected survival probabilities together suggest that translocation is a relatively safe conservation intervention to undertake for the species in this respect.

This work has furthered knowledge on the host-parasite relationships in T. adelaidensis in a translocation context, and my findings suggest that parasite effects are not likely to threaten the viability of population augmentation as a conservation strategy for this species. Future research should be directed towards elucidating parasite lifecycles and transmission mechanisms, testing host fitness effects more precisely, and identifying functional roles of gut microbiota.

Keywords: Wildlife conservation, translocation, wildlife parasites, Tiliqua adelaidensis, skink, microbiota

Subject: Biodiversity and Conservation thesis

Thesis type: Doctor of Philosophy
Completed: 2021
School: College of Science and Engineering
Supervisor: A/Prof Michael Gardner