Subduction zones represent more than half of the total plate boundaries length (38,000 over 64,000km) and cause fast geographic changes by a range of geological processes occurring at local to regional scales such as crustal deformation, volcanism, or dynamic topography (Ruff and Kanamori, 1980). The associated transient changes in land-sea distributions influence the migration, genetic drift, adaptation, speciation, and endemism of the terrestrial biosphere that conquered emerged landmasses (Meert, 2012). Today, archipelagos located along subduction zones host one-third of the biodiversity hotspots in the world (Myers et al., 2000). The phylogeny of extant organisms can track the influence of paleogeographic changes on evolutionary processes like speciation and migration. Understanding how the patterns and mechanisms of biological evolution result from paleogeographic change is an exciting interdisciplinary research field that is still in its infancy (Hedges et al., 2015, Ali and Hedges 2021; Fontenelle et al; 2021) and requires a joint analysis of the geological and biological records. With this proposal, we aim at combining geological and biological data to unravel the links between paleogeographic change induced by subduction dynamics, and the assembly of biotic life using the Caribbean biodiversity hotspot as a case study. This short and dynamic intra-oceanic subduction zone is ideally situated between two giant continents (the Americas) and two equally giant oceans (Atlantic and Pacific) that provide rather static boundary conditions, while land bridges and oceanic gateways directly result from subduction-related geological change. We specifically hypothesize that emergence of land masses in the Lesser Antilles facilitated the arrival of terrestrial lineages (and/or intolerant to salt water, when considering aquatic taxa) into the Antilles (dispersal). In addition, we hypothesize a phylogenetic split between sister species on Hispaniola and Cuba reflecting the history of fragmentation and rejoining of paleo-archipelagos (vicariance i.e. speciation due to geographic isolation). Finally, we predict that speciation times and areagrams will match the chronosequence of land emergence or subsidence. Alternative scenarios of species assemblage in the Caribbean: dispersion, vicariance, and in situ speciation will also be tested. To unravel the role of the southern Lesser Antilles in the dynamics of Caribbean biodiversity, we will perform paleogeographic reconstructions over the last 30 Ma as we identify a gap of knowledge between our understanding of the paleogeography (Cornée et al., in press) and the observed biological speciation and colonization events (Figure 1).
Phylogenetic trees of endemic species intolerant to sea water providing dispersion and speciation ages, together with areagrams showing the distribution of taxa through time, will be combined as two approaches to identify key periods of times of isolation or contact among biological taxa that will shed light on the chronology and spatial extent of biologically relevant Caribbean paleogeographic changes (WP1). Geological mapping and dating of emersion surfaces (biostratigraphic or absolute dating), quantification of erosion rates and surface uplift (by the means of thermochronology or constraining fault motion rates) will provide a consolidated chronology for land emergence and drowning through time (WP2). Numerical modeling of regional and plate-scale vertical motions that control the land-sea mask will bring a better understanding of the triggers, amplitude and wavelength of the evidenced emersion or drowning events (WP3). We will then match the distribution and phylogenetic reconstruction of extant endemic insular species with these paleogeographic reconstructions (WP4), which will allow us to test for alternative scenarios of the temporal dispersion and evolution of life in this highly dynamic hotspot region for both biodiversity and tectonic activity (WP4). The implementation of comparative biogeographical modeling provides here a powerful tool to reveal a natural classification of biogeographic areas, i.e. bio regionalization, and identification of vicariant events (WP1). The paleogeography (WP2) constrained by biological data (WP1) and numerical models (WP3) will later be integrated into the GEN3SIS code (WP4) and the consistency of the output results will be compared with the inferred temporal dispersion from phylogenetic analyses of extant endemic species (WP1). The joint analysis of the geological and biological records will thus provide a novel macro-ecological framework for biodiversity dynamics over subduction zones.

Figure 1 (below): Paleogeographic reconstruction of the eastern part of the Caribbean plate in the Eocene- Oligocene and Oligocene-Miocene transitions (from Boschman et al., 2014) and the current tectonic map showing the distribution areas of the Hutias and Anolis spp. (simplified from Fabre et al., 2014 and Poe et al., 2017). Emerged lands belonging to the GAARlandia (Greater Antilles Aves Ridges land, Itturalde-Vinente and McPhee, 1999) and GrANoLA are shown in pink and green, respectively (modified from Philippon et al., 2020a; Montheil, 2023), the dashed areas are those with geological constraints still missing. The age of colonization of the neotropical flora (after Roncal et al., 2020) and the phylogenetic trees of Anolis lizards (after Poes et al., 2017) and hutias (rodents) (after Fabre et al., 2014) are compared and show that since the Oligocene, species divergences have only occurred after the existence of the supposed GAARlandia (indicated by the green bar).
A trans-disciplinary approach will be conducted in parallel and in close collaborations by four working packages (WP)(Figure 2). WP1. Comparative biogeographical analysis based on phylogenetic data of extant taxa and their related biogeographical areas, key periods of isolation and how it correlates with the known paleogeography, working hand in hand with WP2. Reconstruction of the paleogeography over key intervals determined by the phylogenetic divergence of key taxa by the means of geosciences (structural mapping, dating of faults and erosion, and paleo-environmental reconstructions). WP3 will provide a better understanding of the large-scale geological processes responsible for vertical motion through numerical modeling, and WP4 is the integrative task. In order to carry out these tasks, a consolidation of synergies within the international academic community is necessary between geosciences and evolutionary biology, two disciplines that remain quite disconnected, as well as a strengthening and accretion of existing skills in the field of tropical island ecology.