Galapagos land iguanas as ecosystem engineers

Area of Science:

• Ecology
• Conservation Biology
• Island Biogeography

Background:

• Large-bodied herbivorous reptiles are declining globally.
• Their impact on ecosystem function, particularly on tropical islands, is poorly understood.
• Reptiles are key herbivores on many tropical islands, making their role in ecosystem engineering critical.

Purpose of the Study:

• To investigate the ecosystem-level effects of Galapagos land iguanas (Conolophus subcristatus) on plant communities.
• To assess the role of large-bodied herbivores in shaping terrestrial ecosystems.
• To inform restoration strategies for tropical island ecosystems.

Main Methods:

• A quasi-experimental approach comparing two adjacent Galapagos islands, one with and one without land iguanas.
• High-resolution aerial imagery (<1 cm²) to map plant associations and delineate plant extents.
• Individual plant counts to quantify community structure.

Main Results:

• Islands with land iguanas exhibited significantly reduced woody plant cover.
• Areas with iguanas showed increased seasonal grass coverage.
• Cacti were less abundant and more clumped in the presence of iguanas.

Conclusions:

• Galapagos land iguanas are significant engineers of terrestrial plant community structure.
• Restoration of large-bodied reptilian herbivores, including land iguanas and giant tortoises, is crucial for ecosystem recovery.
• Conservation efforts should prioritize the reintroduction of extirpated reptilian herbivores on tropical islands.