[Coral-List] Diversity, Biogeography and Origins of Indian Ocean Reef-Building Corals

David Obura dobura at cordioea.net
Thu Sep 20 18:20:13 EDT 2012

Dear Listers,

For those interested in Indian Ocean biogeography and an old thread of thought identifying a distinct evolutionary origin to shallow marine species in the IO that is distinct from the dominant Indo-Pacific reef fauna, the following two papers have just been published. One is just out in PLOS ONE, the other was in the ICRS proceedings. They have some implications for conservation planning as well, so hopefully will prove useful for practical conservation too.

The papers can be downloaded from their primary sources, below, or accessed at http://cordioea.net/wio-core/


David Obura

Link: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0045013
Obura D (2012) The Diversity and Biogeography of Western Indian Ocean Reef-Building Corals. PLoS ONE 7(9): e45013. doi:10.1371/ journal.pone.0045013

This study assesses the biogeographic classification of the Western Indian Ocean (WIO) on the basis of the species diversity and distribution of reef-building corals. Twenty one locations were sampled between 2002 and 2011. Presence/absence of scleractinian corals was noted on SCUBA, with the aid of underwater digital photographs and reference publications for species identification. Sampling effort varied from 7 to 37 samples per location, with 15 to 45 minutes per dive allocated to species observations, depending on the logistics on each trip. Species presence/absence was analyzed using the Bray-Curtis similarity coefficient, followed by cluster analysis and multi-dimensional scaling. Total (asymptotic) species number per location was estimated using the Michaelis-Menten equation. Three hundred and sixty nine coral species were named with stable identifications and used for analysis. At the location level, estimated maximum species richness ranged from 297 (Nacala, Mozambique) to 174 (Farquhar, Seychelles). Locations in the northern Mozambique Channel had the highest diversity and similarity, forming a core region defined by its unique oceanography of variable meso-scale eddies that confer high connectivity within this region. A distinction between mainland and island fauna was not found; instead, diversity decreased radially from the northern Mozambique Channel. The Chagos archipelago was closely related to the northern Mozambique Channel region, and analysis of hard coral data in the IUCN Red List found Chagos to be more closely related to the WIO than to the Maldives, India and Sri Lanka. Diversity patterns were consistent with primary oceanographic drivers in the WIO, reflecting inflow of the South Equatorial Current, maintenance of high diversity in the northern Mozambique Channel, and export from this central region to the north and south, and to the Seychelles and Mascarene islands.

Link: c  or http://www.icrs2012.com/Proceedings.htm
Evolutionary mechanisms and diversity in a western Indian Ocean center of diversity. Proceedings of the 12th International Coral Reef Symposium, Cairns, Australia, 9-13 July 2012 3A Evolution, biogeography and taxonomy
David O. Obura

The biogeography and evolutionary history of the shallow marine fauna in the western Indian Ocean (WIO) is poorly known, as are the consequences of ancient and recent biodiversity-generating processes. In- water surveys of scleractinian corals show maximum diversity in a core region centered on the northern Mozambique Channel. Maximum species richness is at ≈300 with a threshold of ≈250 that differentiates this core region from lower-diversity zones in northern Tanzania and Kenya, the Seychelles and small islands in the Mozambique channel, and the Mascarene islands. Species distributions show significant clustering of sites within this high diversity core region, distinguished from peripheral regions. A heritage of ancient Tethyan lineages is suggested by the distinctive WIO endemic fauna of monospecific genera, basal Acropora clades, and cryptic phylogenetic patterns in Stylophora and Siderastrea. Their presence in the WIO is likely associated with the closure of the Tethys Sea in the Miocene and little radiation subsequently. The dominance (90%) of Indo- West Pacific species in the extant WIO coral fauna reflects invasion during the Mio-Pliocene of the younger and more diversified fauna from the West Pacific during the same period. Various lines of evidence suggest the northern Mozambique Channel may have been a refuge for shallow tropical species throughout its history, particularly during the Cenozoic. This deep evolutionary history suggests a unique biodiversity across multiple taxonomic levels in this second peak of tropical marine biodiversity.

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