The worldwide expansion of the Argentine ant

Abstract

Aim The aim of this study was to determine the number of successful establishments of the invasive Argentine ant outside native range and to see whether introduced supercolonies have resulted from single or multiple introductions. We also compared the genetic diversity of native versus introduced supercolonies to assess the size of the propagules (i.e. the number of founding individuals) at the origin of the introduced supercolonies.Location Global.Methods We used mitochondrial DNA (mtDNA) markers and microsatellite loci to study 39 supercolonies of the Argentine ant Linepithema humile covering both the native (n = 25) and introduced range (n = 14).Results Data from three mitochondrial genes and 13 nuclear microsatellites suggest that the introduced supercolonies studied originated from at least seven founding events out of the native area in Argentina (primary introductions). The distribution of mtDNA haplotypes also suggests that supercolonies in the introduced range each derive from a single source supercolony and that one of these source supercolonies has been particularly successful, being the basis of many introduced populations spread across the world. Comparison of the genetic diversity of supercolonies based on the five most diverse loci also revealed that native and introduced supercolonies have greatly overlapping ranges of diversity, although the genetic diversity is on average less in introduced than in native supercolonies.Main conclusions Both primary introductions (from the native range) and secondary introductions (from sites with established invasive supercolonies) were important in the global expansion of the Argentine ant. In combination with the similar social organization of colonies in the native and introduced range, this indicates that invasiveness did not evolve recently as a unique and historically contingent event (e.g. reduction of genetic diversity) in this species. Rather, native L. humile supercolonies have characteristics that make them pre‐adapted to invade new – and in particular disturbed – habitats when given the opportunity. These results have important implications with regard to possible strategies to be used to control invasive ants.

Relative roles of climatic suitability and anthropogenic influence in determining the pattern of spread in a global invader

“…Jump dispersal from the native range (i.e., the primary source) played a major role at the initial stage of the expansion of the Argentine ant (16), but now the dispersion of propagules from secondary sources (i.e., established populations in the introduced range) accounts for much of the spread of the species worldwide (15,16). Further information on dispersal pathways (sensu ref.…”

“…Many studies have examined the distribution and dispersal pathways of this invasive ant (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) and described the range limits at regional and global scales (20,(23)(24)(25)(26)(27)(28). However, most of these studies relied on simple environmental niche models or described the current distribution of the species using only partial records.…”

The widespread collapse of an invasive species: Argentine ants ( Linepithema humile ) in New Zealand

“…However, population genetics predicts that invasive species might collapse owing to inbreeding depression or an inability to adapt to their new environment [12]. Previous genetic studies have revealed that the New Zealand population of Argentine ants has among the lowest recorded genetic diversity of any introduced Argentine ant population worldwide, indicative of the entire supercolony having arisen from an incursion of just one nest [7,12]. Low genetic diversity, perhaps in combination with pathogens [13] or a depletion of local resources [10], is a candidate mechanism for these collapses.…”

Sib mating without inbreeding in the longhorn crazy ant

“…Therefore, introduction into new habitats may yield consequences similar to those of conventional inbreeding in terms of increasing the frequency of detrimental phenotypes owing to recessive deleterious mutations. For example, all introduced populations of invasive ants studied so far possess fewer alleles than native populations [11,[15][16][17][18][19], and introduced populations of the fire ant Solenopsis invicta [8,15] produce high proportions of diploid males.…”