Metabarcoding assessment of the diet of an introduced continental lizard to an oceanic island reveals dietary niche conservatism

Invasive species can have devastating effects when introduced into remote island ecosystems, and a fundamental aspect of this concerns the diet of these exotic taxa. Here we employed a DNA metabarcoding approach to determine the diet of the lizard Agama picticauda on Reunion Island, where it was introduced in 1995. Two separate markers were used to identify animal and plant components. The arthropod aspect was notably conservative, with the agama continuing to predominantly consume ants, as they do in their native range. A variety of other invertebrates were also preyed upon, the vast majority being introduced species. For plants again a wide variety were detected, and while most could not be identified fully, it seems that agamas are deliberately consuming many species, rather than accidentally intaking them along with targeted invertebrates. Agamas may play a role in seed dispersal of invasive plant species. We also detected some nematode groups, although with limited comparative sequences these could not be identified to the species level. Several records of invertebrates appear to be new records for Reunion Island, highlighting how reptiles can be considered as excellent biodiversity samplers, with barcoding diet studies providing novel data for poorly known invertebrate groups. The minimal identifications of endemic prey items may reflect that the agamas are still predominantly occupying anthropogenically disturbed parts of the island. Our study therefore provides baseline data that can be used to determine the impact of this introduced lizard as it spreads through the ecosystem.