An overview of grey mullet (Mugilidae) global occurrence and species-rich ecoregions, with indications of possible past dispersal routes within the family

Abstract

This review examines the published literature on the distribution and species richness of the family Mugilidae around six continents as well as their phylogenetic relationships in a time-calibrated tree. Three mugilid species-rich regions were identified globally, namely the Coral Triangle, southern Asia and southern Africa, all of which have between 16 and 18 morphologically recognized species. Two of the species hotspots are tropical, and only southern Africa incorporates temperate waters. The centre of mugilid evolution and then global dispersion appears to be located in the tropical waters of the Indo-Pacific. Speciation within the family was promoted mainly by plate tectonics, eustatic sea-level changes, tropical climate and high habitat diversity within this region. The number of these tropical species that radiated out to the coastal waters of Africa and America was clearly less than the number that remained in the central Indo-Pacific region. Nonetheless, access by tropical mugilid species was greater to Africa than the Americas because of the direct tropical and subtropical coastal connectivity to the former continent. This enabled more tropical mugilids to reach Africa than America, with the latter probably relying on Palaeocene "island hopping" or "rafting" to move eastwards across the Pacific Ocean. In addition, tropical mugilids were able to access warm western and central African coastal waters from the Pacific prior to the closure of the Tethys Sea gap in the eastern Mediterranean and prior to the development of the cool Benguela Current upwelling off the southwest African coast, and from America through at least two transatlantic rafting events.

Keywords: biogeography; distribution; evolution; hotspots; mugilids.