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Reporting period: 2019-01-07 to 2021-01-06

Environmental stressors such as predation risk and intraspecific competition have important effects on the ecological and evolutionary trajectory of populations through their effects on individual life history, and large-scale demographic processes. The physiological effects of stress-exposure have the potential for significant effects on offspring via maternal effects. For example, maternal stress exposes offspring to elevated maternal glucocorticoids (hormones released in response to stressors) which can feedback to the offspring’s own endocrine physiology, with profound consequences for offspring behaviour, metabolism, and other processes. While the short-term phenotypic outcomes of maternal stress are increasingly well studied in vertebrates, ecologists have only recently begun to explore the effects of maternal stress in wild animals. Furthermore, few studies have demonstrated long-term effects of maternal stress on fitness in ecologically-relevant conditions nor have they explored how these outcomes may vary across ecological contexts. Therefore, we are currently ill equipped to judge the extent to which these transgenerational effects can contribute to the evolutionary process, as well as how environmental stressors (such as climate change and other anthropogenic effects) will influence species persistence. To address these shortcomings and assess the potential evolutionary significance of maternal stress effects, it is necessary to consider the context in which maternal effects occur. A factor that is likely to be important in determining the outcome of maternal effects, and maternal stress specifically, is the post-natal social environment – whether offspring remain with their mother/parents, or not. 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 are:
• (WP1) To experimentally test whether maternal stress effects depend on the post-natal social environment and the consequences of these effects for offspring fitness.
• (WP2) To identify possible physiological mechanisms for phenotypic differences between offspring from stressed and non-stressed mothers under different social conditions;
• (WP3) To test the long-term consequences of phenotypic differences arising as a result of differences in post-natal sociality and developmental stress for fitness-related traits in a wild population using long-term monitoring data;
• (WP4) To test the generality of patterns of environmental-dependence of maternal stress effects across species using a meta-analytical framework.
The project started on January 7, 2019. Meta-analysis and systematic review training, as well as initiation of the associated work package (WP 4) took place between months 2 – 9. This included the literature search and review, and data collection. Fieldwork in Tasmania associated with work packages 1-3 took place between months 9 -15. This period also included key laboratory analysis of blood samples collected. Tissue samples (brain tissue) were also collected and will be analysed in 2021. Data analysis and manuscript preparation for WP 4 and associated deliverables took place between months 15 and 24 – this work package is now close to completion.

This meta-analysis shows that viviparous vertebrates (i.e. those that give birth to live young) are more susceptible to maternal (prenatal) stress effects 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, and will form the basis of my future research.

All critical deliverables and milestones have been achieved as anticipated in months 1 - 24 (but see technical report section 5.1 for minor deviations, and how this will be addressed). Deliverables and milestones for months 24 – 36 are also on track. I anticipate a minimum of 4 scientific articles from WP 1 – 4, two of which are already in preparation and will be published in 2021 as planned.

Deliverables achieved (more details in technical report, see 1.2):
• D1.1 Corticosterone dose treatment protocol for L. whitii
• D2.1 Hormone analysis protocol for hatchling L. whitii
• D3.1 Hormone analysis protocol for adult L. whitii
Two manuscripts are currently in preparation (D1.2 D4.2).

The following milestones were achieved (more details in technical report, see 1.2):
• Study animal collection completed
• Refinement of hormone dose treatment protocol
• Maternal experimental treatment completed
• All experimental data collection completed
• Blood and tissue sample collection completed
• Validation of hormone analysis protocol
• Hormone analysis completed
• Blood sample collection (phase 1)
• Hormone analysis (phase 1)
• Meta-analysis training course completed
• Meta-analysis data collection and analysis complete
In the coming year (months 24 - 36) I expect to publish at least 2 scientific articles directly related to the work packages detailed above. Two manuscripts are in preparation: one from the meta-analysis (WP 4), and one from the experimental fieldwork conducted in Tasmania (WP 1). I will also incorporate a gene expression study, using tissue samples already collected as part of WP 1-2. This brings in new cutting edge research elements to the proposed project, and further expands the collaborative network this project has brought together. This will contribute a further 1 scientific article (minimum) which will likely be published shortly after the completion of the project.

This research will illuminate the potential for variation in an important species trait (post-natal care/sociality) to influence the outcomes of a maternal effect, and therefore its potential to contribute to evolutionary change across species. Second, this work will also help to elucidate the potential role of maternal stress in natural systems, a subject of focus in evolution and ecology. Few studies have tested links between maternal stress and effects on offspring fitness, as this project does. In addition, there has recently been a call for more research integrating stress physiology in an ecological context: my project combines these 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. This study is therefore likely to contribute substantially to the fields of evolutionary biology, comparative endocrinology, and ecology. More broadly, this work specifically tests the potential for a key axis of between-species variation (whether offspring remain with their mothers after birth) and how this changes the outcomes of maternal stress. This therefore has the potential to reveal patterns in how species will be affected by anthropogenic stressors like climate change, providing insight into species of particular conservation concern.
K MacLeod catching female lizards for experimental work
Lizard with offspring in experimental housing