Abstract:
Due to their geographic isolation, biotas of oceanic islands are likely influenced by
episodic long distance dispersal events, but such observations are scarce. In June 2012,
fishermen from Réunion Island caught an unknown specimen of grouper, identified as dusky
grouper Epinephelus marginatus (Lowe, 1834). This was highly unexpected considering the
large distance of its closest verified occurrence (South Africa, ~2500 km). To identify the origin
of this specimen and the mechanisms driving this potential long distance colonization, we
combined genetic analyses and hydrodynamic connectivity modeling approaches. Molecular
markers and samples from various locations across the distribution range resulted in the
identification of three putative source populations. The Réunion specimen clustered genetically
with South Africa. The estimated spawning period in relation to the connectivity modeling of
larvae showed no possible direct connection between South Africa and Réunion. However,
connectivity was predicted through intermediate stepping stone populations likely located around
the southern tip of Madagascar, where the occurrence of the species has yet to be verified. The
results further highlight the potential role of the cyclone Bingiza (February 2011) in the
connection between Madagascar and Réunion. This shows that cyclones may be an important
driver in long distance colonization of oceanic islands.
