Geography and island geomorphology shape fish assemblage structure on isolated coral reef systems

Bennett, Scott, Halford, Andrew R., Choat, J. Howard, Hobbs, Jean-Paul A., Santana-Garcon, Julia, Ayling, Anthony, Harvey, Euan S., and Newman, Stephen J. (2018) Geography and island geomorphology shape fish assemblage structure on isolated coral reef systems. Ecology and Evolution, 8 (12). pp. 6242-6252.

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We quantify the relative importance of multi-scale drivers of reef fish assemblage structure on isolated coral reefs at the intersection of the Indian and Indo-Pacific biogeographical provinces. Large (>30 cm), functionally-important and commonly targeted species of fish, were surveyed on the outer reef crest/front at 38 coral reef sites spread across three oceanic coral reef systems (i.e. Christmas Island, Cocos (Keeling) Islands and the Rowley Shoals), in the tropical Indian Ocean (c. 1.126x106km(2)). The effects of coral cover, exposure, fishing pressure, lagoon size and geographical context, on observed patterns of fish assemblage structure were modelled using Multivariate Regression Trees. Reef fish assemblages were clearly separated in space with geographical location explaining similar to 53 % of the observed variation. Lagoon size, within each isolated reef system was an equally effective proxy for explaining fish assemblage structure. Among local-scale variables, 'distance from port', a proxy for the influence of fishing, explained 5.2% of total variation and separated the four most isolated reefs from Cocos (Keeling) Island, from reefs with closer boating access. Other factors were not significant. Major divisions in assemblage structure were driven by sister taxa that displayed little geographical overlap between reef systems and low abundances of several species on Christmas Island corresponding to small lagoon habitats. Exclusion of geographical context from the analysis resulted in local processes explaining 47.3% of the variation, highlighting the importance of controlling for spatial correlation to understand the drivers of fish assemblage structure. Our results suggest reef fish assemblage structure on remote coral reef systems in the tropical eastern Indian Ocean reflects a biogeographical legacy of isolation between Indian and Pacific fish faunas and geomorphological variation within the region, more than local fishing pressure or reef condition. Our findings re-emphasise the importance that historical processes play in structuring contemporary biotic communities.

Item ID: 54602
Item Type: Article (Research - C1)
ISSN: 2045-7758
Keywords: Christmas Island, Cocos Islands, endemism, island biogeography, multiscale drivers, range edge, reef fish communities, Rowley Shoals
Copyright Information: © 2018 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Funders: H2020 Marie Skłodowska-Curie Actions, Department of Infrastructure and Regional Development, Australian Government
Projects and Grants: H2020 Grant/Award Number 659246
Date Deposited: 18 Jul 2018 07:59
FoR Codes: 31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310402 Biogeography and phylogeography @ 50%
31 BIOLOGICAL SCIENCES > 3104 Evolutionary biology > 310410 Phylogeny and comparative analysis @ 50%
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