Populations at the edge: range dynamics and conservation of the Great Crested Newt under global change.

Apply here by February 1st, 2023 – Informal enquiries welcome!

Under anthropogenic exploitation and rapid environmental changes, many species are challenged with novel conditions, some are shifting their ranges moving to new suitable areas, and many are now threatened or extinct1,2. Populations at the edges of species’ range are key and often the most vulnerable3: they are small, fragmented and less connected; harbour low genetic diversity and occupy suboptimal habitat; often face multiple anthropogenic stressors such as habitat loss and deterioration. However, populations that are at the range leading margin (the edge towards the direction of climate change) are key for successful species’ range shifting: they already occupy locations where suitability will improve and thus could potentially readily expand, and might possess unique and locally favourable genetic variants. Understanding how these populations will respond to environmental change, both ecologically and evolutionarily, whether they will be able to persist under multiple natural and anthropogenic stressors, and how better we can assist them in this process, is crucial for effective species’ conservation under global change.

Predictive process-based models, that integrate the fundamental processes shaping species’ ecology and adaptive responses, such as genetic variation, demography and dispersal, together with assessing impacts of multiple environmental stressors, are a powerful tool to both better understanding species’ range dynamics and making better predictions of likely species’ responses to future environmental change4-6. These models are being developed, and they are now ripe for testing and for applications of conservation relevance.

Amphibians are declining globally and are a high priority for biodiversity conservation7,8. They are particularly vulnerable to multiple stressors as they rely on wetlands, an ecosystem particularly challenged by climate change and habitat loss, and are threatened by invasive species, diseases and pollution.

The great crested newt Triturus cristatus is a declining species in Europe. In Britain it is an important wetland flagship species and has shown the highest rate of decline in recent years amongst native amphibians9-11. In Scotland, T. cristatus is uncommon, with a restricted and fragmented range and, importantly, Scotland represents the north-west range of the species’ world range. Critically, the species has a disjoint distribution in Scotland with an 80 km gap between the most northerly site in Fife and the most southerly Highland site10,12. Much suitable unoccupied habitat has been identified and more is predicted to become suitable with climate change, creating potential for these edge populations to expand their range11-13. However, multiple threats such has increasing habitat fragmentation, due to urbanization, agricultural changes and industrial developments, increasing drought, reduced genetic diversity, and increasing risk of predation from non-native species, make it extremely uncertain whether this expansion and persistence will be at all possible9,11. T. cristatus is thus an excellent and important species for investigating ecological and adaptive responses to environmental changes of populations at the warming range margins, and for applying new integrated process-based modelling to predict these responses and guide conservation interventions.

The overall aim of this project is to understand and predict the persistence of T. cristatus under ongoing climate change and multiple stressors, and its potential expansion from marginal populations, to inform conservation management, moving towards a pro-active, rather than reactive, management14 of declining amphibians under global change.

Although there is ample scope for the students to shape the project, some specific objectives are:

1. Characterise patterns of adaptive genetic variation across T. cristatus climatic gradients, and to assess inbreeding risk and amount of genetic variation for the Highland populations.

2. Forecast responses of T. cristatus Scottish populations to multiple natural and anthropogenic stressors with integrated process-based modelling.

3. Test the effectiveness of alternative management interventions designed to improve persistence of T. cristatus under environmental change.

1IPBES 2019; 2Urban 2015 Science 348:571; 3Nadeau & Urban 2019 Ecography 42:1280; 4Urban et al. 2022 BioScience 72:91-104; 5Urban et al. 2016 Science 353:aad8466; 6Briscoe et al. 2019 Ecol Lett 22:1940; 7Nori et al. 2015 Biol Cons 191:367; 8Araújo et al. 2006 J Biogeog 33:1712; 9McInerny 2018 doi:10.5772/intechopen.74949; 10O’Brien et al. 2015 Eur J Wildl Res 61:27; 11Miró et al. 2017 Hydrobiologia 792:169; 12O’Brien & Hall 2012 Herpetol Bull 119:9; 13 O’Brien et al. 2021 J Nat Conserv 64:126077; 14Sterrett et al. 2019 Biol Cons 236:404;

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