Changes in the native fauna of the Galápagos Islands following invasion by the little red fire ant, Wasmannia auropunctata



The little fire ant, Wasmannia auropunctata, occurs on five islands in the Galápagos archipelago. It is still in the process of expanding its range on at least two of these islands (Santa Cruz and San Salvador). At least 17 of the remaining 28 ant taxa currently known from the Galápagos are affected by the presence of Wasmannia. On Santa Cruz and San Salvador few other species of ants co-occurred with Wasmannia, except at the edges of its distribution or in areas which it had only recently invaded. Wasmannia was also found to reduce population densities, or eliminate altogether, three species of arachnids (a scorpion and two theridiid spiders) as well as reducing the overall abundance and species diversity of flying and arboricolous insects at two sites on San Salvador. The mechanisms by which these species are displaced are currently being investigated.

Certain arthropods may escape the detrimental influences of Wasmannia through non-overlap of habitat and food requirements (as documented in the case of certain hypogeic ants), while others may actually benefit from the presence of Wasmannia, as appears to be the case for some coccids.