Objectif de ce groupe de travail est d’étudier l’influence qu’ont pu avoir les mouvements tectoniques sur la genèse et la préservation de la biodiversité dans les Caraïbes. Pour tester le rôle des différents facteurs biotiques et abiotiques nous allons mettre en place une méta-analyse qui utilisera des données phylogéniques et des données paléogéographiques (données anciennes ou acquises dans le cadre de GAARAnti).
This task aims at answering the following question: How was Caribbean biodiversity generated and maintained, and how geological changes affect(ed) this biodiversity? The objective of this work package aims at teasing apart the contribution of each potential driver in shaping the Caribbean biodiversity; namely we will test for the role of different biotic and abiotic (physical) factors. We will specifically study the underlying processes responsible for the generation and maintenance of the biodiversity pattern in the region. For this purpose, we will set up and conduct a meta-analysis making use of the biological data generated in the form of dated phylogenies combined with the paleogeographic data both generated during GAARAnti.
PIs: F Condamine-ISEM & Ph Münch-GM
Méthodologie : nous utiliserons des approches macro-évolutionnaires (en 3 étapes) basées sur un cadre de maximum de vraisemblance (Figure 8 en annexe), pour extraire les tendances générales.
Methodology – We will use macroevolutionary approaches based on a maximum likelihood framework (Figure 8 in appendix), comprising three steps, to unravel the general evolutionary trends.
Step 1 consists of a synthesis of biological and paleontological data (taxonomy, phylogeny and ecology) on one hand and of onshore/offshore geological data on the other hand. All available data will be geo-referenced in a single GIS-based project allowing drawing palinspastic and biogeographical maps at different time-slices (collab. B. Vrielynck) (e.g. Barrier & Vrielynck, 2008).
Step 2 consists in using/developing birth-death models. This step will be the main focus of the postdoc fellow. This step will aim at testing the:
– Role of global and abrupt historical events. We will infer the main periods of diversification and test their potential relation to past environmental changes using episodic birth-death models following the TreePar approach (Stadler, 2011). The diversification dynamics within the Caribbean Islands will be interpreted under three main macroevolutionary models: (1) ‘cradle of diversity’ hypothesis, (2) ‘museum of diversity’ hypothesis, (3) ‘turnover’ hypothesis. Contrasting these three hypotheses for many groups will contribute to a better understanding of the macroevolutionary trend governing Caribbean biodiversity through time.
– Effects of past climatic (temperature and eustatic) changes. To gain further insight into the role of past climatic fluctuations, we will estimate the clade-specific responses to past environmental changes using a continuous birth-death diversification model (Condamine et al. 2013). This model estimates whether speciation and/or extinction responded positively or negatively to warming (and cooling) events, and to what extent. However, the global climate profile (Zachos et al., 2008) may have differed at regional scales. The generation of sea-water temperature estimations from the Task 1 will be used as a better proxy for the Caribbean climate variations over the Cenozoic. We will compare the fit and performance of the two climate profiles (global and regional). This will allow understanding the role of climate fluctuations on the Caribbean island system where species diversity is high and the level of endemism highly elevated.
– Role of the land area size over time. We will investigate diversification dynamics allowing the incorporation of new geological data into the diversification model as already stated for temperature and eustatic change variables (Condamine et al. 2013). In this case, we will make use of the estimated land surface (area size, in km.) that was above water, and thus available for terrestrial organisms over the course of the Cenozoic (Tasks 1 and 3). In applying this model to Caribbean clades, we aim at (1) testing whether speciation and/or extinction rates were linked to the surface area available, (2) testing the theory of island biogeography that states the « island » species-area relationships (MacArthur and Wilson, 1967), and (3) extending the species-area theory that is mostly (if not entirely) based on ecological studies to geological timescales.
– Estimation of geographic range evolution. To infer the evolution of geographic ranges we will rely on probabilistic approaches based on the Dispersal-Extinction-Cladogenesis (DEC) model (Ree and Smith, 2008), notably with the use of the recently developed DECX model (Beeravolu and Condamine under revision). The DEC/DECX approach allows the comparison of alternative biogeographical models using maximum likelihood to select the key processes that have shaped the clade’s biogeography. In using our refined paleogeographic scenarii, we will create a time-stratified framework that will represent the appearance/disappearance of islands. We will explain the ancestral origin and the colonization routes of our focal clades by comparing a set of biogeographical models with parameters mirroring cladogenetic and/or anagenetic processes. This could potentially highlight the role of now sunken islands (i.e. paleo-islands), as it has been evidenced in other regions (e.g. Canary: Mairal et al., 2015; New Caledonia: Condamine et al. 2017).
Step 3: The third step of the task will have the main objective at developing a new type of birthdeath model that aims at integrating several potential factors simultaneously. F Condamine will handle this part with H. Morlon (authors of RPANDA; Morlon et al., 2016) as an external expert of birth-death models and with the help of the post-doc fellow. We will set up a model testing approach in which the diversification can be correlated to each variable individually or correlated to multiple variables simultaneously. The explanatory power of the different models will be assessed using the corrected Akaike Information Criterion and Akaike weights. Comparing the fit of each model, we could select the best-fitting one. Doing so, one can assess whether a single factor (abiotic or biotic) or both abiotic and biotic factors triggered the past diversification.
Deliverables: Palinspastic and biogeographical maps will be a first deliverable of this Task. The constructed database will also be an open access deliverable. It will lead to the inference of macroevolutionary processes (speciation and extinction) that shaped Caribbean evolutionary radiations for the focal groups. We aim at identifying general trends on the key determinants, may they be ecological or historical, that have contributed to the origin and maintenance of the regional biodiversity. We also hope to unveil the role past environmental changes played on the clades’ diversification.
Risk assessment: This task is intimately linked to the previous tasks, which will provide the solid grounds for the phylogenetic data, and climatic/geological models. Time-calibrated phylogenies are a prerequisite to realize the objectives of this task. Indeed estimation of diversification rates requires a robust and fully resolved topology and accurate estimates of branch lengths and species divergence times. However, the proposed team (Task 2) is a world-leading group on the phylogeny and fossil record of Neotropical mammals, and has already accumulated genetic and fossil data for all the groups under survey. The climatic and geological data are also a key component to achieve the objectives of this task. Furthermore, geological and climatic data are in hands of the team, even if they require a specific treatment and compilation to be efficiently used.
Formal partner members: S. Adnet (paleoenvironmental reconstruction), P.-O. Antoine (paleo-biogeography), J.-J. Cornée (paleogeography), F. Delsuc (biogeography), P.-H. Fabre (biogeography and paleo-biogeography), J.L. Léticée (paleogeography), L. Marivaux (paleo-biogeography), B. Mercier de Lepinay (paleogeography), G. Merzeraud (paleogeography); M. Philippon (geodynamic reconstruction, G-Plate modeling) and a requested 18-months post-doc fellow (ANR funding).
External collaborators (Experts): H. Morlon (ENS Paris, UMR 8197; mathematics applied to ecology), B. Vrielynck (Istep, UPMC & Commission de la Carte Géologique du Monde; palinspastic and paleotectonic maps)