From Heartbeats to Habitat Shifts: The Physiology, Phenology, and Biogeography of Ecosystem Engineers under Climate Change

ORCID

Abstract

Climate warming is restructuring marine ecosystems, yet the pathways connecting organismal physiology, reproductive phenology, and large-scale range dynamics remain poorly resolved. In this thesis, I use limpets of the genus Patella - abundant grazers and ecosystem engineers of northeastern Atlantic rocky shores, as a model system to examine how environmental temperature filters ecological responses across scales, spanning the thermal performance of individuals, the reproductive phenology of populations, and the biogeographic shifts that reshape ecosystems.First, the use of a common-garden thermal ramping experiment revealed differences in physiological performance among Patella vulgata (boreal), P. depressa and P. ulyssiponensis (both Lusitanian) collected from two contrasting environmental contexts reflecting change in latitudinal position. This study provided a step change in traditional approaches for assessing physiological performance using thermal ramping, by simultaneous measurement of oxygen consumption and heart rate. I demonstrate not only feasibility but added value of considering a cardio-respiratory response over a single indicator that reveals cold stress induced reversible metabolic suppression and heat stress imposed absolute ceilings, which exposes asymmetric thermal sensitivities across species and latitudes.Second, a unique long-term data series (1972-2016) of reproductive cues from five regions spanning northeastern England to southern Portugal was used to demonstrate that reproductive phenology has shifted unevenly among species under long-term warming trends. Specifically, P. vulgata was shown to have advanced its peak reproductive timing and increased total reproductive investment (shown via the area under the curve: AUC) at poleward sites, while P. ulyssiponensis exhibited delayed peaks and synchrony breakdowns toward its equatorward range edge (but not elsewhere), and P. depressa showed consistent declines in reproductive investment across all regions. Reproductive seasons contracted sharply toward equatorward limits but either extended or stabilised toward the poleward range, highlighting how thermal affinity linked to latitude determines ‘local’ reproductive phenology and wider demographic resilience in these species.Finally, I used species distribution modelling (Maximum Entropy - MaxEnt) to test how future climate change is likely to reshape the geographic distributions and functional diversity patterns of these study species. While previous modelling efforts have projected future changes in habitat suitability, here we incorporate annual range (min-max) predictors (sea-surface temperature, salinity, and primary productivity) to better capture the environmental variability and extremes that define species’ physiological limits and shape real-world distribution boundaries, under present and future emission scenarios (SSP2-4.5 and SSP5-8.5). Models revealed consistent habitat gains in the high Arctic, persistent losses in the southern North Sea, and relative stability along western Iberia, but with species-specific nuances. A novel mapping of multi-species richness across space suggests functional losses across latitude and highlighted areas of elevated risk for ecological functioning where these key grazers are predicted to become locally extirpated.By investigating temperature across three ecological pillars - physiology, phenology, and biogeography - this thesis demonstrates that temperature acts as a pervasive ecological filter, linking organismal limits to population persistence and biogeographic restructuring. It contributes to knowledge by showing clearly that multi-scale approaches can expose both resilience and vulnerability in ecosystem engineers and provides a transferable framework for forecasting ecological futures in dynamic coastal systems.

Awarding Institution(s)

University of Plymouth

Supervisor

David T. Bilton, Antony M. Knights, Louise B. Firth

Keywords

Climate Change, Species Distribution Modelling, Ecophysiology, Biogeography, Patella vulgata, Thermal Biology, Reproduction, Phenology, Limpets, Patella depressa, Patella ulyssiponensis

Document Type

Thesis

Publication Date

2026

Embargo Period

2027-03-28

Deposit Date

March 2026

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

This document is currently not available here.

This item is under embargo until 28 March 2027

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