Western Indian Ocean marine fish biogeography and phylogeography

R/V. Dr. Fridtjof Nansen in port, Mauritius Processing a collection in Shimoni, Kenya Lutjanus bohar specimens at market in Zanzibar
Malindi landing site, Zanzibar Identifying a specimen, Dabaso Creek, Kenya Landing site, Matemwe, Zanzibar

Although ongoing surveys and taxonomic studies are advancing our knowledge of the biodiversity of the Western Indian Ocean (WIO), our understanding of the origins of this diversity and of regional faunas, the relationship of these to the wider Indo-Pacific and of the historical and contemporary processes responsible for the distributions of diversity remains poor. This research programme aims to investigate, using genetic data and considering multiple, predominantly reef fish species, patterns of differentiation and relationships over varying spatial and temporal scales in the WIO with a view to understanding connectivity, phylogeographic and biogeographic patterns and the influence of physical features and oceanographic processes in the region.

The programme comprises complementary projects funded by the African Coelacanth Ecosystem Programme (ACEP) and the Western Indian Ocean Marine Science Association’s Marine Science for Management (WIOMSA-MASMA) directorate.

The programme is being led by the the core team of SAIAB researchers (Drs Gavin Gouws, Monica Mwale and Ofer Gon), Prof. Paulette Bloomer and her team in the Molecular Ecology and Evolution Programme (University of Pretoria), Drs Jerome Bourjea and Delphine Muths of IFREMER-Reunion, and a extensive network of co-investigators and collaborators.

In the research component conducted at SAIAB, DNA sequence data from both mitochondrial and nuclear genes will be analysed under a phylogenetic framework to determine broad-scale patterns of differentiation, connectivity and relationships among the regions of the WIO, elucidating the biogeographic history of the region over evolutionary time and the region’s relationship to marginal areas and the Indo-Pacific.

Two competing biogeographic hypotheses are being evaluated: whether regional reef-fish faunas have originated from dispersal from a centre of origin in the Indo-West Pacific, or whether these faunal assemblages arose due to in situ speciation following the vicariant isolation of different regions as a result of geological or oceanographic changes. More than 18 species from the families Apogonidae (cardinalfish), Ballistidae (triggerfish), Labridae (wrasses), Lethrinidae (emperors), Lutjanidae (snappers), Pomacentridae (damselfish) and Scaridae (parrotfish) are being examined to determine the extent to which phylogeographic breaks are congruent; whether a unified biogeographic hypothesis would be applicable to the WIO; or whether species-specific histories exist which are dictated by biology or life-history strategies. This component will also assess the taxonomic status of several widespread species, determining whether conspecificity is a reality or whether these species harbour cryptic diversity.

The components led by our research partners will consider population genetics and phylogeography at a much finer spatial scale and consider contemporary patterns of connectivity. These are particularly important in a conservation context, evaluating the efficacy of the existing Marine Protected Area network, and aiding in the identification of suitable areas for future reserves.

Funding
ACEP and WIOMSA-MASMA

Duration
2008 – 2011

Additional co-investigators and collaborators
Dr. Augustine Mwandya, Sokoine University of Agriculture, Tanzania
James Mwaluma, Kenya Marine and Fisheries Research Institute, Kenya
Dr. Blandina Lugendo, University of Dar es Salaam, Tanzania
Dr. Gerry Allen, Conservation International, Australia
Dr. Daniel Golani, Hebrew University, Israel

SAIAB-based students:
Moqebelo Morallana