Large-area imaging reveals biologically driven non-random spatial patterns of corals at a remote reef
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For sessile organisms such as reef-building corals, differences in the degree of dispersion of individuals across a landscape may result from important differences in life-history strategies or may reflect patterns of habitat availability. Descriptions of spatial patterns can thus be useful not only for the identification of key biological and physical mechanisms structuring an ecosystem, but also by providing the data necessary to generate and test ecological theory. Here, we used an in situ imaging technique to create large-area photomosaics of 16 plots at Palmyra Atoll, central Pacific, each covering 100 m2 of benthic habitat. We mapped the location of 44,008 coral colonies and identified each to the lowest taxonomic level possible. Using metrics of spatial dispersion, we tested for departures from spatial randomness. We also used targeted model fitting to explore candidate processes leading to differences in spatial patterns among taxa. Most taxa were clustered and the degree of clustering varied by taxon. A small number of taxa did not significantly depart from randomness and none revealed evidence of spatial uniformity. Importantly, taxa that readily fragment or tolerate stress through partial mortality were more clustered. With little exception, clustering patterns were consistent with models of fragmentation and dispersal limitation. In some taxa, dispersion was linearly related to abundance, suggesting density dependence of spatial patterning. The spatial patterns of stony corals are non-random and reflect fundamental life-history characteristics of the taxa, suggesting that the reef landscape may, in many cases, have important elements of spatial predictability.
KeywordsCoral reefs Community structure Landscape ecology Spatial dispersion Photomosaics Palmyra Atoll
This work was made possible through funding provided by the Gordon and Betty Moore Foundation, Grant #3420, and the UC San Diego Frontiers of Innovations Scholarship Program. We are grateful to Gideon Butler, Sho Kodera and Tayler Fewell who contributed to image digitization. This is Palmyra Atoll Research Consortium contribution ## PARC-0125. Thank you to The Nature Conservancy and the Palmyra Atoll Research Consortium for logistical support and the United States Fish Wildlife Service for special use permit # 12533-13025 and access to the refuge.
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