Unraveling lionfish invasion: Is Pterois volitans truly a morphologically novel predator in the Caribbean?

The harmful effects of lionfish (Pterois volitans) invasion on ecosystems already affected by overfishing, pollution and climate change in the western Atlantic are widely known. However, despite the detrimental consequences, it is also a unique opportunity to explore differences between invasive and resident species that may have led to the success of the invader. Using a functional morphology approach, we evaluated whether lionfish has novel traits and how they influenced the theoretical ecological space of some of the main small Caribbean reef predators. Additionally, we assessed if the native community generated biological resistance on the density of the invader. Lionfish and 12 native Caribbean small reef predators were used in this study. Thirteen characters were used to produce a morpho-functional space that defined the guild. A correlation was made between the total density of predators and that of lionfish. Morphological analyses indicated that the invasive species presents novel morphological traits, in comparison to native species. Additionally, the invader influences the reduction of the theoretical ecological space, suggesting competition with five Caribbean coral reef meso-predators. On the other hand, our data does not support the biological resistance hypothesis of native predators being the phenomenon that controls lionfish density.