Population genetics, demography and population viability of little penguins (Eudyptula minor) in Australia

Abstract

One of Australia’s most iconic native bird species, the little penguin (Eudyptula minor), is in decline at numerous locations due to manifold anthropogenic impacts including predation by introduced predators, habitat destruction and modification, effects of fishing activity and climate change. The fundamental aim of this thesis was to combine genetic and demographic data about the penguins to forecast likely population changes under a range of possible scenarios, including evaluation of anthropogenic threats. To target this aim, four separate studies were undertaken. The first collated demographic data on population size and survival rates in New South Wales (NSW), using data from existing databases and new surveys. Non-invasive techniques were trialled to estimate population size and survival rates, with the latter resulting in estimates consistent with mark-recapture based approaches. The second study investigated size and connectivity of little penguin populations in Australia using traditional measures of genetic structure and diversity. Smaller colonies were genetically not less diverse than larger ones and differentiation was limited among colonies in NSW. Isolation by distance was not observed within NSW and weak at longer distances between different states. Complex interactions between the influence of oceanic currents and demography were furthermore suggested by contrasting dispersal patterns at different scales and using different genetic markers. The third study was based on an adaptive genetic marker of the immune system (Major Histocompatibility Complex, MHC) to complement the aforementioned population genetic study that was based on neutral genes. Genetic diversity at the MHC locus largely mirrors diversity at neutral loci, indicating a strong effect of stochasticity. Nevertheless, selective pressures are acting on the MHC. The lowest rates of parasite infestation were suspected for individuals of intermediate MHC diversity, and penguins showed differential mortality or inbreeding avoidance at the MHC locus. Results from the first two studies were incorporated into a population viability analysis model to evaluate outcomes of different scenarios and management strategies in the fourth and last study conducted as part of this thesis. All models based on current estimates predicted severe population declines in NSW and Western Australia, and forecasts were particularly sensitive to changes of mortality estimates.