Abstract
Coral reefs are degrading globally leading to a catastrophic loss of biodiversity. While shifts in the species composition of communities have been well documented associated with habitat change, the mechanisms that underlie change are often poorly understood. Our study experimentally examines the effects of coral degradation on the trait-mediated effects of predators on the morphology, behaviour and performance of a juvenile coral reef fish. Juvenile damselfish were exposed to predators or controls (omnivore or nothing) in seawater that had flowed over either live or dead-degraded coral over a 45d period. No interaction between water source and predator exposure was found. However, fish exposed to degraded water had larger false eyespots relative to the size of their true eyes, and were more active, both of which may lead to a survival advantage. Non-consumptive effects of predators on prey occurred regardless of water source and included longer and deeper bodies, large false eyespots that may distract predator strikes away from the vulnerable head region, and shorter latencies in their response to a simulated predator strike. Research underscores that phenotypic plasticity may assist fishes in coping with habitat degradation and promote greater resilience to habitat change than may otherwise be predicted.
Highlights
Coral reefs are degrading globally leading to a catastrophic loss of biodiversity
At the start of the experiment, there was a significant difference in the length of damselfish between water sources (F1,125 = 5.78, P = 0.02, ηp2 = 0.04), with fish in the live coral water treatment being slightly longer than those exposed to dead-degraded seawater
Body depth of experimental P. amboinensis differed among treatments (F2,126 = 4.07, P = 0.019, ηp2 = 0.06; Fig. 1b), though not between water sources, and there was no interaction between treatment and water source (P > 0.05)
Summary
Coral reefs are degrading globally leading to a catastrophic loss of biodiversity. While shifts in the species composition of communities have been well documented associated with habitat change, the mechanisms that underlie change are often poorly understood. Studies of aquatic organisms have found that the sight or smell of a predator can lead to changes in life history traits (e.g., developmental rates and hatching times21;), behaviour (e.g., development of neophobic phenotypes22;) and alter body morphology[23] to forms that are best suited to surviving in a location where the threat of predation is high Landmark examples of this are the deepening of the body in crucian carp (Carassius carassius) to the smell of predatory pike (Esox lucius)[24], and the increase in the relative size of the false eyespot in damselfish (Pomacentrus amboinensis) prey, believed to attract predator strikes to the less vulnerable tail region[23]. While studies have shown that prey survival is compromised in degraded habitats due to uninformed decisions[30,31], it is unknown whether the degradation of habitats such as coral reefs alters the action of trait-mediated antipredator solutions
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