Maternal care as a provider of adaptive behavioural, neural, and morphological diversity

Adaptive evolution is often described as a process whereby variation is targeted by natural selection to cause genetic change over time. Variation is therefore fundamental and required for selection to have an effect. While we often assume variation to have a heritable genetic basis this could represent an oversimplification1.

Variation can arise from a range of mechanisms, however this project will focus on the contribution of maternal influences on offspring, and how this contributes toward the variation found in a major adaptive radiation. Specifically, this project will use the exemplar adaptive radiation of African cichlids from Lake Malawi as a model to test the impacts of maternal care on behavioural, neural, and morphological diversity. Over 500 species of Malawi cichlids are known to exist, representing the largest extant example of an adaptive radiation. Cichlids are renown for the large amounts of phenotypic variation they display in craniofacial traits, and brain anatomy2,3. The vast majority of these species use mouthbrooding, whereby females incubate eggs and care for larvae within their buccal cavity. This is a reproductive tactic that is thought to increase survivorship as offspring can avoid predation, and emerge at a far more developed state than would be possible through other modes of fish parental care.

However, our preliminary data suggests that cichlid offspring phenotypes depend on differences among mothers in the mouthbrooding tactic. This includes influences on behaviour, morphology, and brain development. In this system, we can experimentally manipulate the duration of parental care, and hence investigate its role in determining offspring phenotype. Therefore, using a range of Malawi cichlid species the successful candidate will aim to assess the following questions:

1) What impact does mouthbrooding incur on social behaviours in cichlids, and does this reflect species differences?
2) How strongly can morphological variation be impacted by mouthbrooding across species and does this impact the function of trophic morphology?
3) What are the impacts of mouthbrooding on brain development and gene expression, and do these impacts last throughout ontogeny to adulthood?

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Image Captions

A Malawi cichlid performing maternal care through mouthbrooding


The successful candidate will learn a range of approaches that will provide them with a set of exciting modern tools that will be used within a cutting-edge context. This project will include the use of breeding stocks of Malawi cichlids currently housed at Glasgow. This currently includes over ten species that encompass a wide range of phenotypic variation.

The student will conduct experiments on these fish that will alter the duration of mouthbrooding and conduct behavioural assays. This will include the use of advanced tracking software to quantify the degree of movement and association with conspecifics.

Evolutionary developmental biology will form a key component of this project and the student will take advantage of the well characterized developmental series for cichlids. This will allow them to identify key stages of brain and craniofacial development. The student will learn morphometric techniques to characterize variation in craniofacial shape, and determine the functional consequences of differential parental care using assessments of kinematic performance including the use of high-speed video image analysis.

Finally, the student will take advantage of a range of histological and genomic techniques to characterize the impact of parental care on gene expression and neural development.

Project Timeline

Year 1

– exposure to fish husbandry and experimental manipulation of parental care begins
– initiation of behavioural assays and training in data analysis
– collection of brain material for the extraction of RNA for comparisons of gene expression
– writing of the first chapter focused on behavioural assays
– attend a national conference related to their project.

Year 2

– collect material for morphological analysis
– receive training in morphometrics and statistical analyses of shape data, as well as assessments of functional morphology
– perform functional tests using high-speed video methods
– begin writing up results from this project
– preparation of material for gene expression (RNAseq)
– attend an international conference

Year 3

– perform histological techniques to examine neurological variation
– obtain and analyze gene expression data
– completion of data analysis across all chapters

Year 3.5

– writing and final editing of chapters

& Skills

The candidate will learn a broad range of transferable skills that will enhance their prospects and prepare them for a career in academia or industry. These skills include experimental design, genomic sequencing, tissue sampling, histology, fish husbandry, high-speed video analysis, statistics, data management and manipulation, molecular and developmental biology. In addition, the lab component will provide the experience of working across two labs and the interaction with teams in Glasgow and Newcastle. We will take advantage of the close proximity of the supervisors to ensure frequent meetings, and the candidate will also profit from exposure to the extended networks of the collaborating team.

References & further reading

1. Skulason, Parsons et al. 2019. A way forward with eco evo devo: an extended theory of resource polymorphism with postglacial fishes as model systems. Biological reviews 94, 1786-1808. https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12534
2. McWhinnie et al. 2022. Assessing the levels of functional adaptation: finite element analysis reveals species, hybrid, and sexual variation in the biomechanics of African cichlid mandibles. Evolutionary Biology 49, 205-220. https://link.springer.com/article/10.1007/s11692-022-09566-0
3. Sylvester et al. 2010. Brain diversity evolves via differences in patterning. PNAS 107, 9718-9723. https://www.pnas.org/doi/abs/10.1073/pnas.1000395107
4. https://www.youtube.com/watch?v=c2dPUInKZQ4

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