Dead foundation species create coral rubble habitat that benefits a resilient pest species.

ABSTRACT

Critical loss of habitat is the greatest threat to biodiversity, yet some species are inherently plastic to and may even benefit from changes in ecosystem states. The crown-of-thorns sea star (CoTS; Acanthaster spp.) may be one such organism. CoTS are large corallivores native to the tropical Indo-Pacific and in unexplained high densities, can adversely affect entire coral reefs. Proximal causes of CoTS outbreaks remain elusive, so this phenomenon remains a daunting and costly challenge for reef conservation and management. Amplifying anthropogenic impacts and new empirical data point to the degraded reef hypothesis to explain the episodic nature of CoTS population outbreaks. We posit that loss of live coral paradoxically benefits CoTS juveniles, which accumulate in their rubble nursery habitat before conditions trigger their pulsed emergence as coral-eaters. We review trait plasticity across the CoTS life cycle and present the degraded reef hypothesis in an integrative understanding of their propensity to outbreak.