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Reporting period: 2021-01-07 to 2022-01-06

Environmental stressors have important influences on the ecological and evolutionary trajectory of populations through their effects on individual physiology, behaviour, and survival. Stress exposure can additionally have significant effects on offspring via "maternal effects", where the environment of the mother influences the traits and success of her offspring. For example, maternal stress exposes offspring to elevated maternal glucocorticoids (hormones released in response to stress). Elevated glucocorticoids during development can impact the offspring’s own endocrine physiology, with profound consequences for offspring behaviour, metabolism, and other processes. Ecologists have only recently begun to explore the effects of maternal stress in wild animals, but few studies have explored how these outcomes may vary across ecological contexts (for example, across different ecosystems, or in solitary versus group-living animals). A factor that is likely to be important in determining the outcome of maternal stress, is the post-natal social environment – whether offspring remain with their mother/parents, or not. This is because the social environment during early life can itself have substantial effects on offspring traits, with the potential to mitigate the outcomes of prenatal stress/exposure to glucocorticoids. However, the importance of the post-natal social environment in determining the outcomes of maternal stress remains unknown - this question forms the basis of project EGERNIALIZARDS.

How environmental stressors affect animal populations is an increasingly important question for society. Urbanisation, habitat loss, and human-induced climate change all pose significant stressors to wildlife. Better understanding how such stressors affect individuals, and what factors influence the outcomes of stress-exposure across generations, will aid us in better implementing and targeting effective conservation strategies. A better understanding of the outcomes of maternal effects across generations is also a key goal for evolutionary biologists in determining the relative role of genes versus the environment. We are currently ill-equipped to judge the extent to which these cross-generational effects can contribute to evolution (by influencing phenotypic diversity and/or differential survival in the offspring generation), as well as how environmental stressors (such as climate change and other anthropogenic effects) will influence species persistence. The extent of post-natal association with parents is a key source of variation between species; so, testing this question has the potential to reveal important large-scale patterns in the evolutionary importance of maternal effects, and species resilience in a changing world.

The overall objectives of the project EGERNIALIZARDS were to:
• experimentally test how the post-natal social environment influence the consequences of maternal stress for offspring, and identity potential physiological mechanisms;
• test the generality of maternal stress effects across species using a meta-analytical framework.
The EGERNIALIZARDS project started in January of 2019. There were two major strands to the project: the systematic review/meta-analysis, which began immediately; and work packages associated with experimental work in Tasmania, which began in month 9.

The meta-analysis component aimed to uncover broad patterns in the strength and pattern of maternal stress effects mediated by prenatal glucocorticoid exposure. Training, literature review, data collection and analysis, and preparation of the association manuscript were completed by December 2020 (month 24). The completed meta-analysis, which was published after peer review in Ecology & Evolution, shows that viviparous vertebrates (i.e. those that give birth to live young) suffer stronger effects of maternal (prenatal) stress relative to egg-laying vertebrates. This is an important step in understanding the likely variation in the future consequences of anthropogenic stressors such as climate change.

Experimental work in Tasmania used a facultatively social, live-bearing lizard, Liopholis whitii, to test whether mother-offspring association after birth changes the behavioural and physiological effects of prenatal glucocorticoid treatment on offspring. All field and experimental work took place between months 9 -20. This period also included key laboratory analysis of blood samples; tissue samples were also collected and will be analysed in 2022 (this work was delayed unavoidably due to COVID-19). Analysis of data, including behaviour assays and social network data, is complete and shows promising results, specifically that the interaction of prenatal stress and post-natal sociality significantly changes key behavioural traits such as habitat use (use of shelters), movement (home range and dispersal) and sociality. This portion of the project will be published soon.

Aside from peer-reviewed publications, the results of this work have been disseminated through a number of invited seminars and conference presentations, and science media (including podcasts). For more detail see technical report.
Project EGERNIALIZARDS combines novel research questions with innovative and integrative methods, combining advanced endocrine methodology and meta-analytical techniques with field experiments that place these tools firmly in an ecological framework. The results provide an important advance in our understanding of the contribution of maternal effects in the evolutionary process (i.e. evidence that maternal stress effects in live-bearing species may contribute more), and our understanding of the importance of social context in offspring resilience to environmental stressors (i.e. mother-offspring associations after birth alter the behavioural outcomes of prenatal stress). These advances represent significant progress beyond the state of the art, contributing to the fields of evolutionary biology, comparative endocrinology, and ecology.

In order to maximise societal impact, these results will be disseminated as widely as possible. In addition to the already-published article, a further two manuscripts are in preparation. A number of follow-up projects are also planned, drawing on the collaborative network this project has brought together. I plan to further disseminate my results to conservation practitioners such as the Amphibian and Reptile Conservation Trust (UK) as these results may inform their conservation strategies and priorities.
K MacLeod catching female lizards for experimental work
Lizard with offspring in experimental housing