GAARlandia land-bridge vs Lesser Antilles dispersal pathways – Coupling subduction dynamics and evolutionary processes in the Caribbean domain. – GAARAnti

The purpose of the GAARAnti project is to unravel couplings between deep Earth dynamics and evolutionary processes through an innovative and original multi-disciplinary study combining Earth and Life sciences. This innovative approach will reconcile biological and geological clocks and timeframes through the combined use of radiochronological methods, biostratigraphy and phylogenetic inferences, to constrain the Cenozoic paleo-biogeography of the Antillean arc. The GAARAnti project will generate novel collaborative works between geologists/marine geophysicists and biologists/paleontologists and new results by constraining the pattern, timing, and dynamics of biodiversity in Lesser Antilles at the Cenozoic scale. This will in turn allow untangling biotic and geological constraints that forced such history. In the frame of the ongoing debate about the Tertiary origin of terrestrial organisms of the Greater Antilles, GAARAnti will focus on the role of subduction dynamics onto the evolution of emergent areas as a promoter or an antagonist of the terrestrial faunas dispersal. Altough it is now widely admitted that most components of Antillean terrestrial communities originated from South and Central America, the mechanisms (dispersal vs vicariance) responsible for the observed evolution and its precise timing are still highly debated. Previous studies have mainly addressed this question through Earth sciences or Life sciences separately. We are confident and deeply believe that our innovative and original multi-disciplinary approach within the GAARAnti project will generate major advances in the knowledge of Cenozoic Antillean biodiversity dynamics.

To be efficient, the project is organized in five strongly-interconnected scientific tasks and a supplementary management task including annual meetings (Task 0). Task 1 will quantify past emergent areas through Cenozoic times, and to estimate the timing and duration of land emersion periods (amplitude and rate of vertical motions) both being key constraints for paleo-geographic and paleo-environmental reconstructions. Task 2 will estimate divergence times among living, recently extinct, and fossil mammals from the Lesser Antilles. We will then clarify the pattern and timing of mammalian dispersals into the Caribbean and proposing paleo-biogeographic models. Task 3 will refine the knowledge of the poorly known structure of both the Aves Ridge and the Lesser Antilles back-arc domains, i.e. the most probable dispersal pathways. This task is connected to the GARANTI marine cruise project, taking place in May-June 2017 and aiming at acquiring a large dataset of Wide Angle Seismic and Multi-Channel Seismic lines and dredged/cored samples. Onshore-Offshore correlations will be realized to establish paleogeographic reconstructions at the scale of the Eastern Caribbeans. In Task 4, we will perform 2D/3D numerical and analog models of subduction in order to simulate the surface response (topographic variations) to deep processes and to propose a global framework for the geodynamic evolution of the Lesser Antilles arc during the Cenozoic. Task 5 is a central and federative task in the project aiming at 1) establishing palinspastic reconstructions, 2) testing the influence of abiotic (temperature, eustasy, continental domain surfaces) vs biotic variables (species diversity, clade diversity, clade-specific shifts) based on birth-death models and 3) develop new mixed models to test the link between abiotic and biotic variables (to be assembled during the project) and the macro-evolutionary dynamics of studied groups in the Antilles.

Beyond the novel expected scientific outcomes, the GAARAnti project will promote the preservation of both the geological and paleontological patrimony of the Antilles, to disseminate the results through local institutions of scientific popularization that are associated to the projects and through collaborations with local primary and high schools and Guadeloupe ESPE.