Land crabs as key drivers in tropical coastal forest recruitment |
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Authors: | Erin Stewart Lindquist Ken W. Krauss Peter T. Green Dennis J. O'Dowd Peter M. Sherman and Thomas J. Smith III |
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Affiliation: | Meredith College, Department of Biological Sciences,;3800 Hillsborough Street, Raleigh, North Carolina 27607, USA U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Boulevard, Lafayette, Louisiana,;70506, USA Department of Botany, La Trobe University, Bundoora, Victoria;3086, Australia Australian Centre for Biodiversity, School of Biological Sciences, Monash University, Victoria;3800, Australia University of Redlands, Department of Environmental Studies,;1200 East Colton Avenue, P.O. Box 3080, Redlands, California 92373, USA U.S. Geological Survey, Florida Integrated Science Center,;600 Fourth Street, South, St. Petersburg, Florida, 33701, USA |
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Abstract: | Plant populations are regulated by a diverse assortment of abiotic and biotic factors that influence seed dispersal and viability, and seedling establishment and growth at the microsite. Rarely does one animal guild exert as significant an influence on different plant assemblages as land crabs. We review three tropical coastal ecosystems–mangroves, island maritime forests, and mainland coastal terrestrial forests–where land crabs directly influence forest composition by limiting tree establishment and recruitment. Land crabs differentially prey on seeds, propagules and seedlings along nutrient, chemical and physical environmental gradients. In all of these ecosystems, but especially mangroves, abiotic gradients are well studied, strong and influence plant species distributions. However, we suggest that crab predation has primacy over many of these environmental factors by acting as the first limiting factor of tropical tree recruitment to drive the potential structural and compositional organisation of coastal forests. We show that the influence of crabs varies relative to tidal gradient, shoreline distance, canopy position, time, season, tree species and fruiting periodicity. Crabs also facilitate forest growth and development through such activities as excavation of burrows, creation of soil mounds, aeration of soils, removal of leaf litter into burrows and creation of carbon-rich soil microhabitats. For all three systems, land crabs influence the distribution, density and size-class structure of tree populations. Indeed, crabs are among the major drivers of tree recruitment in tropical coastal forest ecosystems, and their conservation should be included in management plans of these forests. |
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Keywords: | biotic control ecological filter environmental gradient environmental engineer mangrove island maritime forest predation seed seedling terrestrial mainland forest tree |
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