Corals, sponges, algae and seagrass beds make up our underwater coastal landscapes, where organisms fixed to the substrate or sedentary in their adult state (molluscs, crustaceans and coastal fish) live side by side. During their first stage of life, most of these marine species disperse. In the form of propagules (eggs, larvae, seeds, etc.), they are transported by ocean currents over great distances. Connectivity, the process that characterises these spatial exchanges of individuals and their genes, is crucial to the spatial structure, demographic dynamics and genetic diversity of these marine populations. In the current context of biodiversity loss, we need to understand how genetic material is transmitted in space from one population to another, but also in time from one generation to another.
A team of scientists from MIO and IMBE (see inset), used a biophysical model to obtain a realistic representation of transport due to currents by simulating ocean circulation. Coupled with tools derived from graph theory, the team defined probabilities of genetic connections resulting from successive dispersal events (Fig. 1a, b). Filial connectivity (the probability that one population is related to another) was distinguished from coalescent connectivity (the probability that two populations share common 'ancestors'). These innovative models were used to reconstruct the gene flow of species representative of the biodiversity of the Mediterranean coastal ecosystem, which was then compared with pre-existing observations of genetic differentiation.
By reconstructing the family trees of marine populations, the newly defined coalescent connectivity provides better gene flow predictions than previous models (Fig. 2). The speed of gene flow is faster than previously thought (around ten to one hundred kilometres per generation), suggesting that the capacity of marine populations to adapt to climate change may be faster than previously thought. The genetic structures observed on a small scale would therefore not be due to transport barriers but rather to adaptation to abrupt environmental contrasts, suggesting a possible plasticity of genetic diversity within a few generations of dispersal. This model offers a flexible and cost-effective numerical solution for understanding and possibly predicting the future spatial reorganisation of biodiversity due to global change, thereby helping to improve the management and protection of ecosystems.
CNRS laboratories involved
Mediterranean Institute of Oceanology ( MIO - OSU Pythéas)
Supervisory bodies: CNRS / AMU / IRD / Univ. Toulon
Mediterranean Institute of Biodiversity and Marine and Continental Ecology (IMBE)
Supervisory bodies: CNRS / IRD / AMU / Univ. Avignon
To find out more
Legrand, T., Chenuil, A., Ser-Giacomi, E. et al. Spatial coalescent connectivity through multi-generation dispersal modelling predicts gene flow across marine phyla. Nat Commun 13, 5861 (2022).
Contact
Vincent Rossi
CNRS researcher at the Mediterranean Institute of Oceanology ( MIO )
04 86 09 06 28
vincent.rossi@mio.osupytheas.fr
Térence Legrand
Aix Marseille University doctoral student at the Mediterranean Institute of Oceanology (MIO)
legrandterence@gmail.com