Blanc SVSE 7 - Blanc - SVSE 7 - Biodiversité, évolution, écologie et agronomie

Eco-evolutionary dynamics in deep time – ECODEV

Eco-evolutionary dynamics in deep time

Dynamic of ancient marine ecosystem structuration (-385 My), or how a major environmental crisis can modify ecosystems ?

Understand the eco-evolutionay dynamic of an ancient ecosystem after a major crisis

The aim of the projekt is to understand the impact of global environmental changes on the structuration and evolution of marine diversity. The interest of ancient times is to provide a dynamic overall view of intercations between the actors of the ecosystem and their environment, interactions at the origin of the construction of an ecosystem in evolution.

The project is based on a pluridisciplinary approach. (1) paleontology, with a sampling in details of sections covering the period of interest. (2) Geochemistry, to characterise environments and trophic levels. (3) Morphometry, to quantify the evolution of organisms. (4) Evo-Devo on living models to propose mecanisms related to the eco-evolutionary response.

(1) Two outcrops allow to document in the same samples, environmental changes and morphological variations of organisms
(2) Calibration of a new geochemical method (calcium isotopes) to characterise trophic levels, validated on living sharks was applied to ancient marine assemblages
(3) The Investigation of skeletogenesis on extant chondrichtyans is in progress and wiil be used in the broader context of gnathostome skeletal evolution

Analyses in progress:
- Comparison of the two studied sections in order to test the globality of results.
- analyses of the morphological variations of fossil organisms in both sections, development of statistical methods for the analyses of data.
- Confrontation between the morphology of the organisms and the environmental changes to define possible relationships
- Biomechanical analyses of dental structures based on 3D imaging
- Evaluation on a living model of the plastic response to food consistency : towards a comprehension of the mechanisms of morphological response.

The analysis of trophic level structure with calcium isotopes was validated on living sharks: Martin, Tacail, Adnet, Girard, Balter, 2015 Chemical Geology
Skeletic evolution of gnathostomes is analysed studying the skeletic develoment of extand sharks (Enault, S., Adnet, S., Debiais-Thibaud, M. 2015. MorphoMuseuM)
- New multivariate analyses have been applied on morphometric data, and the structure of intragroup variance has been studied : Renaud, Dufour, Hardouin, Ledevin, Auffray. i2015 PLoS ONE.

The ongoing global change is on the verge of triggering an unprecedented biodiversity crisis. This stimulated numerous studies about eco-evolutionary interactions conditioning the faunal response to environmental changes. As the past can be a key to the present, the present can be a key to the past. Revisiting past crises at the light of the concepts derived from studies on modern perturbations has the potential to provide an original view of past processes, and together to enlighten the dynamics that lead to modern biodiversity. By mobilizing multi-disciplinary expertises (paleobiology, ecology, evolution, developmental biology, evo-devo, paleoenvironments), the ECODEV project aims at renewing the understanding of an ancient period (the Late Devonian) characterized by one of the five major mass extinctions of Earth History. The project focuses on few model organisms (foraminifers, conodonts, cartilaginous and bony fishes), chosen for their abundance in sediments allowing the use of quantitative methods. (1) Three sections sampling all the Late Devonian period have been identified in France, Germany and Algeria. A detailed sampling will be performed during field trips and the fossil remains will be picked in order to deliver material for the other tasks. (2) Using geochemical proxies, environmental trends will be characterized and the trophic position of the groups of interest will be clarified. These analyses will be based on relevant well-known markers (oxygen isotopes for temperature; Rare Earth Elements for productivity). This task will also includes methodological developments. Benefiting from experimental data on fishes bred in controlled conditions, methods based on calcium isotopes will be developed to estimate temperatures as well as the trophic position of organisms. (3) The eco-evolutionary dynamics will be analyzed using geometric morphometrics. For each fossil group, these methods will deliver estimates of morphological diversity (disparity). This information will be interpreted in terms of occupation of the ecological space and resource exploitation, because the form of conodont and fish teeth is under obvious selective pressures related to nutrients, and form of foraminifers is related to subtract exploitation. Furthermore, evolutionary patterns will be documented. They constitute an important component of the adjustment of organisms to their environment. The interpretation of morphological variations in these ancient fossils will be supported by comparison with a modern model. Developments regarding multivariate data analyses will allow improvements in the exploitation of an exceptional data set including several parallel records (morphometrics of each group, geochemical proxies). (4) The project will be completed by an experimental approach on the lesser-spotted dogfish (Scyliorhinus canicula). Breeding in aquaria with different sea-water temperatures, and with diets of different consistencies and trophic positions (mackerel, soft and secondary consumer; shrimp, hard and primary consumer) will allow a calibration of geochemical developments, and an evaluation of the plastic sources of morphological variations. An exploratory study of fish teeth within and among populations will provide data about the relative importance of intra-individual (position along the jaw), intra-population and inter-population variations. These data based on modern material will be crucial to support the interpretations proposed in the fossil record.
The original combination of quantitative morphometric analyses on several actors of a former ecosystem, of paleoenvironmental analyses in the same samples, of experimental data obtained on a modern model, has the potential to deliver a original view of the network of interactions between actors and with the environment of the former ecosystem. This is the key to understand the dynamics of construction of an ecosystem itself in evolution in this deep time.

Project coordinator

Madame Catherine GIRARD (Institut des Sciences de l'Evolution de Montpellier)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LGLTPE Laboratoire de Géologie de Lyon, Terre, Planètes et Environnement
ISE-M Institut des Sciences de l'Evolution de Montpellier
LBBE Laboratoire de Biométrie et Biologie Evolutive

Help of the ANR 278,012 euros
Beginning and duration of the scientific project: December 2013 - 42 Months

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