An exception to the rule: top-down control of a coral reef macroinvertebrate community by a tropical spiny lobster

In temperate habitats, predation by lobsters creates trophic cascades that reverberate through benthic communities. However, the influence of lobsters on tropical benthic communities is thought to be minimal due to higher prey diversity and the mobility and broad diet of lobsters. We hypothesized that this would not be the case for the spotted spiny lobster (Panulirus guttatus Latreille, 1804), an obligate, philopatric dweller of Caribbean coral reefs. Our study took place in the Florida Keys (USA), where we examined the gut contents of wild lobsters, conducted laboratory experiments on lobster prey selection and foraging effectiveness in rubble, and manipulated lobster density on isolated patch reefs to examine the effects of lobster predation on macroinvertebrate prey over a 3-yr period. We found P. guttatus to be a generalist carnivore that consumed a suite of macroinvertebrates, including important reef herbivores (e.g., herbivorous crabs, gastropods, and urchins) that comprised >60% of its diet. Higher densities of P. guttatus exerted strong top-down control over the abundance and composition of macroinvertebrate prey in rubble substrates on patch reefs, but not prey living in substrates dominated by macroalgae. Lobster foraging success in rubble also depended on rubble size; lobsters extracted prey from and overturned rubble more easily when rubble was smaller. The abundance and high site fidelity of predatory P. guttatus appears to provide the necessary conditions for top-down control of prey in coral reef rubble zones, an effect similar to the powerful influence of lobster predation observed in temperate ecosystems.