Problem Statement: Introduced (alien) species sometimes become invasive, causing biodiversity loss and inflicting major economic and / or ecological damage. As control of invasive species typically involves high and ongoing costs, significant savings can be realised by monitoring introduced species and starting control programmes only if and when a species shows signs of becoming invasive. In the Galapagos Island Archipiélago de Colón Biosphere Reserve, three species of the family Gekkonidae (Phyllodactylus reissi, Gonatodes caudiscutatus and Lepidactylus lugubris) are found, representing the only introduced reptiles which have established reproductive populations in Galapagos. These species were identified as most suitable in order to illustrate a very basic management question when dealing with introduced species, i.e. whether they were potentially invasive and a threat to the survival of the native fauna and hence whether they needed to be controlled or eradicated.

Methods: A monitoring study of the Gekkonidae of the Galapagos Islands was undertaken in which samples were taken from the villages and surrounding rural areas of Puerto Ayora (Santa Cruz), Puerto Baquerizo Moreno (San Cristobal) and Puerto Villamil (Isabela). The distribution patterns of the introduced geckos suggest that they were introduced unintentionally via boats, because they only occur in inhabited islands.

Outcomes and Impacts: The study suggests that introduced and endemic genera have different habitat requirements. Only P. reissi shows the habitat preference of endemic geckos for arid coastal areas, and needs to be considered as a potential threat to the native fauna. Preventing unnecessary control programmes has allowed saving of significant costs, and those funds have rather been invested in the setting up of monitoring programmes, which rely heavily on taxonomic expertise and para-taxonomic skills.

Lessons: Alien species do not necessarily have to be invasive, as they can become integrated into an ecosystem in a non-harmful way. Despite the fact that negative human impact on the Galapagos Islands needs to be prevented and reduced, selected experiences such as that described here would seem to suggest that the influx of alien species introduced incidentally or intentionally can be tolerated, as long as the taxonomic expertise and tools to enable an efficient and effective monitoring system are in place.