Ants invading deserts: Non-native species in arid Moroccan oases

Abstract

The oases of Morocco, located between the Mediterranean and the Sahara ecoregions, constitute the main defence system of the temperate region against desert encroachment. This study aims to determine species richness and distribution of native and non-native ants in the oases of southern Morocco. Survey campaigns were conducted in 11 oases between March and May 2017. Thirty-four ant species belonging to 13 genera and three subfamilies were collected. The regional catalogue of Formicidae is enriched by 27 new species (total 44 species) and five were listed as non-native species (11.4% of diversity). The most frequent species is Pheidole pallidula and the richest oasis is Allogoum (containing 11 species of which two are exotic and three are native and exclusively detected here). Of the 11 studied oases, only four were free from non-native ant species. Regression-based methods indicated that species diversity of non-native ants is related to water availability and total flow rate of sources, and only total flow rate of sources for all species combined. All correlations become non-significant when non-native species are removed from analyses, suggesting a recent colonisation and early invasion. Water availability is necessary to maintain local myrmecological diversity. This study sets the basis for future identification of the impacts of non-native ants on the ecological integrity of oasis ecosystem and to establish conservation measures.