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Temperature and nutrient interactions in aquatic ectotherms: individuals, populations and communities at latitudinal edges

Interações entre temperatura e nutrientes em ectotérmicos aquáticos: indivíduos, populações e comunidades em extremos latitudinais

Reference
PTDC/BIA-BMA/1893/2020
Project Start Date
2021-09-17
Project End Date
2025-09-16
Principal Investigator
Coinvestigator
Scientific Area
Natural sciences
Funding Program
Concurso para Financiamento de Projetos de Investigação Científica e Desenvolvimento Tecnológico em Todos os Domínios Científicos - 2020

Abstract

Climate change produced a new surge of interest for the effects of temperature, especially in ectotherms. Although temperature governs many physiological processes, its effects on nutrient acquisition have only recently started to unfold. Understanding temperature and nutrient interactions across levels of biological organization is critical to develop realistic predictions of the ecological responses to the ongoing global changes [1], especially in ectotherm-dominated ecosystems (e.g. freshwaters). Recent studies suggest that temperature modulates nutrient acquisition in ectotherms [2,3]. Compelling evidence shows low temperatures to promote carnivory and herbivory to increase with temperature in a multitude of taxa [4-13]. Temperature-induced dietary shifts likely arise from an active influence of temperature on feeding preferences, prompting ectotherms to optimize energetic intake by feeding selectively [14], together with a passive temperature effect on nutrient assimilation efficiency that changes the protein:carbohydrate assimilation ratio [15]. Reported experimentally, these dietary shifts agree with large-scale latitudinal surveys showing higher temperatures to increase the prevalence of herbivory in fish communities, potentially by alleviating the thermal constraints on gut microbiota helping in the digestion of plant matter [16]. Ranking among the first contributions to the topic worldwide, the previous work by the project team identified temperature-induced dietary shifts in several ectotherms (anuran larvae, crayfish and freshwater snails) [6,9,12]. With implications for the assessment of direct and indirect effects of climate change on species and ecosystems, the discovery of this biological phenomenon raised new questions. While successful in demonstrating the occurrence of temperature-induced dietary shifts, studies failed to explain the mechanisms underlying this response, its adaptive value and the potential role of gut microbiota. These studies focused mainly on carbon (C) and nitrogen (N), but a meaningful comprehension of temperature and nutrient interactions must examine other important nutrients such as phosphorus (P), and go beyond the individual level. Furthermore, including the climatic conditions under which populations and species evolve will be key towards a general conceptualization. To this end, the project team gathered complementary expertise on life-history traits, stable isotopes, metagenomics and food webs, presenting an ambitious proposal that integrates local climatic adaptation. Structured in three experimental tasks and a field task, the project will study trophic plasticity in populations and communities at the edges of a 2500 km latitudinal gradient. We aim to develop a comprehensive study of temperature and nutrient interactions on individual fitness (Task 1), to flesh out the physiological pathways involved in temperature-induced dietary shifts (Task 2), assessing the potential contribution of gut microbiota (Task 3), and to examine the impacts on communities (Task 4). In the laboratory, we will conduct experiments on aquatic ectotherms with a wide distribution range, contrasting populations from Southern Portugal (38° N) and Southern Sweden (56º N). The taxonomic broadness of the responses will be assessed using two model species from different phyla (a larval anuran and a freshwater snail). Individuals will be reared at one of four temperatures (16, 20, 24 and 28ºC) and offered P-depleted (C:P=500) or P-rich diets (C:P=200), with one of 4 different C:N ratios (4:1, 12:1, 20:1, 28:1) or allowed to choose between 4:1 and 28:1 C:N ratio diets. In the field, we will compare omnivory in pond communities at the edges of the same latitudinal gradient. Targeting species and communities from habitats priority for conservation, the research plan fits within the Sustainable Development goals of the 2030 Agenda. With far-reaching implications for ecology, well-beyond its focal species and systems, the project will contribute towards a general conceptualization of temperature and nutrient interactions on ectotherms. The new aspects of ectotherm physiology revealed will increase the predictive power over the ecological responses to climate change and inform on the vulnerability of freshwaters. We predict that local climatic adaptation may influence the extent and the adaptive value of temperature-induced dietary shifts in the two populations of the model species. Higher temperatures will increase the relative demand for C over N and P and lessen the negative effects of P-depletion, stronger in the vertebrate species. Dietary shifts should arise mainly through changes in feeding preference, but changes in nutrient assimilation efficiency and in gut microbiota can also play a significant role. The trophic level of omnivorous ectotherms should be lower and the diversity of gut microbiota should be higher in low-latitude pond communities.

Institutions

Main Institutions

  • FCiênciasID Associação para a Investigação e Desenvolvimento de Ciências (Fciências.ID)
  • Universidade de Lisboa Centro de Ecologia Evolução e Alterações Ambientais (CE3C/FC/ULisboa)

Other Institutions

  • FCiênciasID Associação para a Investigação e Desenvolvimento de Ciências (Fciências.ID)
  • Universidade de Lisboa Instituto Superior de Agronomia (ISA/ULisboa)
  • Universidade de Lisboa Centro de Estudos Florestais (CEF)
  • School of Biological and Chemical Sciences, Queen Mary University of London (SBCS, QM)
  • Evolutionary Biology Centre from Uppsala University (EBC/UU)

Funding 249.851,13 €

Fundação para a Ciência e a Tecnologia (FCT) - Portugal

249.851,13 €