Tag Archives: Andrea Schraven

Tasmanian devil (Sarcophilus harrisii) gene flow and source-sink dynamics

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Type: Journal Article

Reference: Schraven, A. L., Hogg, C. J., & Grueber, C. E. (2024). Tasmanian devil (Sarcophilus harrisii) gene flow and source-sink dynamics. Global Ecology and Conservation, 52, e02960. https://doi.org/10.1016/j.gecco.2024.e02960

Abstract

Increased access to genetic data has substantially improved how we manage threatened species. The Tasmanian devil (Sarcophilus harrisii) is listed as endangered due to the ongoing threat of a highly contagious cancer, devil facial tumour disease (DFTD), causing more than 80% population reductions. To assist future management interventions (e.g. releases into wild sites) we expanded upon previous studies of gene flow for the devil by assessing more recent and broad-scale patterns. We use genome-wide single nucleotide polymorphisms generated via DArTSeq across 21 devil sites to delineate source-sink dynamics across the species’ range. Our findings revealed gene flow is stronger on the northeast and central regions of Tasmania, with high rates of bidirectional gene flow among central sites. The northwest exhibits weaker connectivity relative to other regions of Tasmania, while gene flow appears to be non-existent between the southwest and other areas. Northeast coastal sites tend to serve as ‘sources’ for inland central sites, whereas gene flow appears restricted to the coastline in the northwest. These results are consistent with genetic structure of devil sites and spatial spread of DFTD, which has yet to arrive in the southwest region of Tasmania. Southwest isolation is probably due to mountain ranges and lack of roadways. Interestingly, some waterbodies did not appear to restrict devil movement among sites. Conversely, areas of high elevation act as apparent barriers, as evidenced by limited gene flow observed between eastern and western sites. Integrating source-sink dynamics into conservation management planning will be crucial in developing effective strategies to safeguard the Tasmanian devil and other threatened species facing similar threats (i.e. disease, habitat loss).

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IT’S MOVING DAY: Threatened Species Edition

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by Andrea Schraven (PhD Student)

Moving house, city, or country always has its challenges, from adapting to a new environment to establishing connections with unfamiliar neighbours. For threatened species, the concept of moving from one area to another is no less daunting.

However, in the realm of conservation management, ‘moving day’ can be the difference between survival and extinction of endangered animals. Translocations are defined as the “intentional movement of living organisms from one are to another” by the International Union for Conservation of Nature (IUCN), and they represent a strategic effort to give struggling species a fighting chance.

Translocations come in many forms, each serving a unique purpose in species conservation management:

  • Re-introduction involves moving individuals back in areas where they use to exist but have disappeared, thereby giving them a second chance to thrive in their historical habitat.
  • Reinforcements help already existing populations of a species that are currently struggling by moving in additional individuals from another population to boost their chances of persisting.

Assisted Colonisations will introduce a species to a new and suitable habitat where they can establish themselves, often occurring when a species is unable to survive in its original habitat.

Releasing Tasmanian Devil on Maria Island, Australia. © Luke Silver

Deciding on where to move a species to is more than just merely picking the best house in the neighbourhood. Managers of a species must carefully consider numerous factors when choosing their new home. This includes evaluating the availability of resources, identifying potential threats that may jeopardize long term sustainability, and understanding behavioural dynamics such as competition among individuals.

Moreover, determining the effectiveness of translocations necessitates continued monitoring and assessment after the release. Population viability in the long term requires documenting a translocated individual’s ability to acclimate to their new environment and monitoring their survival. Additionally, managers need to monitor the reproductive output and analyse population growth trends to determine if the population is sustainable, or if continued interventions are required.

So next time you here about a species being relocated or released into the wild, remember – it’s not just a new home, but a translocation that could be a potential lifeline for the survival of an entire species.

Author

Andrea Schraven (PhD Student; co-supervised with Dr Catherine Grueber) is projecting the long-term impacts of supplementation to improve the status of wild Tasmanian devil populations with the ongoing threat of DFTD. By evaluating population genetic and fitness data before and after translocations, she is comparing how populations change over a few generations, and then feeding the data into computational models to simulate “evolutionary time”. The results will directly inform conservation management decisions for the species long-term recovery.

Andrea_Schraven

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“It’s an iterative process” – lessons learnt during the first year of my PhD

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by Andrea Schraven (PhD Student)

I began my PhD in July 2021, and in May 2022 I sat down with my panel to confirm my candidature. Although I found the lead up to my confirmation unnecessarily daunting, I am glad I have ticked this major milestone off. Now fully immersed into my research project, I want to share a couple of the big lessons I’ve learnt over the past year.

Read. I came in with no prior knowledge of population genetics, which is an integral part of my project. So having the first four months stuck at home in a COVID lockdown had some perks, it allowed me to buckle down and start reading. I read everything, from theoretical concepts to current literature, I stalked experts in the field on google scholar and sought out the publications of my other lab members (a MUST DO when starting in a new lab), and within a month I had filled an entire notebook. Reading the current literature is a constant practise and I have slowly learnt to be more systematic about it to save time, this is important as other tasks continuously pile up.

Record everything. I like to draw out my ideas and process them on paper, leaving the more stringent writing for my laptop. But whether you prefer the “old school” way of pen and paper or use only the computer, get it down. When I got further along with my research, I found the most essential part of developing my project (with reminders from my supervisors), was not the writing up of the experimental design, codes, or analyses I was using but recording the decisions I was making along the way. This has saved me so much headache in the long run, especially when I’m asked why I chose to go in a certain direction.

Sometimes doing nothing at all is progress. One of the best pieces of advice my supervisors gave me early on was to take what I have learnt from my readings and with the broad objectives of my project go and sit quietly to think. I started to implement this by stepping away from computer, and with just my pen and paper I’d spend hours thinking of how I could apply these grand concepts to my project. Sometimes the better half of a day would go by with the feeling that I hadn’t accomplished anything. This is when I’d take whatever ideas I had back to my supervisors to discuss and flesh out actionable steps, and sometimes those ideas never panned out or weren’t feasible, whereas others really caught on and I am currently implementing them.

Admin chores. Finally, those pesky administrative tasks and online modules that everyone hates doing, rip the band aid off from the beginning and get them over and done with.

Author:

Andrea Schraven (PhD Student; co-supervised with Dr Catherine Grueber) is projecting the long-term impacts of supplementation to improve the status of wild Tasmanian devil populations with the ongoing threat of DFTD. By evaluating population genetic and fitness data before and after translocations, she is comparing how populations change over a few generations, and then feeding the data into computational models to simulate “evolutionary time”. The results will directly inform conservation management decisions for the species long-term recovery.

@andrea_schraven