The elusive alien fauna of soil and leaf litter of Socorro Island, Revillagigedo Archipelago, México

Global trade and migration have facilitated the arrival of alien species within new ecosystems. Alien species that become invasive constitute a major driver of biodiversity loss. On Socorro Island, alien species in the soil have not been sistematically searched where their arrival is possibly associated with introduced plant species and the movement of various goods. We searched for alien and invasive fauna in the soil and leaf litter of Socorro Island and compared their present distribution with historical records. We recorded for the first time four earthworm species, 10 new ant species, and a fossorial snake. Snakes and earthworms were detected in areas where alien tree species were introduced several decades ago, suggesting a parallel invasion. Native and alien ant species were found across all sampling sites; nonetheless, invasive ant species were found solely around the naval base, the area with the highest human disturbance. Alien and invasive species represent a threat to soil structure and composition, and interactions with other species could facilitate their spread and establishment. Our findings highlight the need for immediate conservation actions to avert damage to soil communities on Socorro Island.