Ocean circulation allows us to reconstruct the family tree of marine populations

Corals, sponges, algae and sea grass beds constitute our underwater littoral landscapes where organisms fixed to the substrate or sedentary in their adult state (mollusks, crustaceans and coastal fish) cohabit. During their first stage of life, the majority of these marine species disperse. In the form of propagules (eggs, larvae, seeds, etc.), they are transported by ocean currents over great distances. Connectivity, a process that characterizes these exchanges of individuals and their genes in space, is crucial in the spatial structure, population 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 box), used a biophysical model to obtain a realistic representation of the transport due to currents through simulations of ocean circulation. Coupled with tools 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 allowed the reconstruction of the gene flow of representative species of the Mediterranean coastal ecosystem biodiversity, which was then compared to pre-existing observations of genetic differentiation.  

By reconstructing the family trees of marine populations, the newly defined coalescent connectivity shows better gene flow predictions compared to previous models (Fig. 2). The rate of gene flow is faster than previously thought (about 10-100 km per generation) suggesting that the ability 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 economical numerical solution to understand and possibly predict the future spatial reorganization of biodiversity due to global change, thus contributing to improved management and protection of ecosystems.

CNRS laboratories involved

Mediterranean Institute of Oceanology ( MIO - OSU Pythéas)

Supervision: CNRS / AMU / IRD / Univ. Toulon

Mediterranean Institute of Biodiversity and Marine and Continental Ecology (IMBE)

Supervisors: CNRS / IRD / AMU / Univ. Avignon

For more information

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
Doctoral student at Aix Marseille University, Mediterranean Institute of Oceanology (MIO)
legrandterence@gmail.com