Genetic data can also be used to infer invasion pathways, including the source(s) of invasion, extent and direction of migration, and the dispersal capacity of a particular species 7, 11. Since then, using genetic data for defining eradication units has become an effective strategy for invasive species management on islands, evidenced by its many applications and recommendations 5, 9, 10. An early application involved population genetic analysis of invasive Norway rats ( Rattus norvegicus) across 18 islands representing five archipelagos off the coast of France, where microsatellite genotypic data were used to determine eradication units (i.e., islands with sufficient gene flow to be considered single populations) and highlight the importance of conducting pre-eradication genetic surveys to minimize eradication failure 8. Genetic and genomic tools have a proven history and promising future for informing invasive mammal management 6, 7. As such, there is a need for quantitative tools to assist managers in the decision-making process before, during, and after management operations to increase chances of successful ecological restoration, while also minimizing the costs associated with eradication failure. Eradication failures, particularly those resulting from rapid recolonization, are often due to knowledge gaps of key population parameters, including population connectivity and dispersal capacity 5. Yet, efforts to remove such species are costly and subject to failure for example, mammal eradication attempts on islands throughout the world have resulted in a ~15% failure rate 4. The control and eradication of invasive mammals have become increasingly common tools used on islands globally 2, leading to substantial conservation gains in the form of ecological restoration and endemic species recovery 1, 3. Invasive mammalian species are the primary cause of animal extinction on islands and represent one of the most significant threats to insular biodiversity 1. Thus, limiting eradications to isolated islands combined with controlled culling and enhanced biosecurity may be the most effective strategies for achieving ecological restoration goals. As a result, the archipelago itself should be considered the primary eradication unit, with the exception of geographically isolated islands like S Gang Gwaay. Here we use restriction-site associated DNA sequencing (12,947 SNPs) to investigate connectivity and gene flow of invasive deer ( n = 181) across 15 islands, revealing little structure throughout Haida Gwaii and identifying the large, central island of Moresby (>2600 km 2) as the greatest source of migrants. Previous eradication attempts demonstrate forest regeneration upon deer removal, but reinvasion reverses conservation gains. Over-browsing by invasive Sitka black-tailed deer ( Odocoileus hemionus sitkensis) is causing severe ecological and cultural impacts across the Haida Gwaii archipelago (Canada). Invasive mammals represent a critical threat to island biodiversity eradications can result in ecological restoration yet may fail in the absence of key population parameters.

Genodive genetic kinship