Worldwide invasion by the little fire ant: routes of introduction and eco‐evolutionary pathways

Abstract

Biological invasions are generally thought to occur after human aided migration to a new range. However, human activities prior to migration may also play a role. We studied here the evolutionary genetics of introduced populations of the invasive ant Wasmannia auropunctata at a worldwide scale. Using microsatellite markers, we reconstructed the main routes of introduction of the species. We found three main routes of introduction, each of them strongly associated to human history and trading routes. We also demonstrate the overwhelming occurrence of male and female clonality in introduced populations of W. auropunctata, and suggest that this particular reproduction system is under selection in human-modified habitats. Together with previous researches focused on native populations, our results suggest that invasive clonal populations may have evolved within human modified habitats in the native range, and spread further from there. The evolutionarily most parsimonious scenario for the emergence of invasive populations of the little fire ant might thus be a two-step process. The W. auropunctata case illustrates the central role of humans in biological change, not only due to changes in migration patterns, but also in selective pressures over species.

Androgenesis is a maternal trait in the invasive antWasmannia auropunctata

“…Second, this mechanism maintains high levels of heterozygosity and/or beneficial genetic combinations over time in the sexually produced worker offspring. In agreement with this, Foucaud et al [16,27] found that heterozygosity, in workers from clonal populations, is on average higher than that in sexual 107 (5) 40 (5) 31 (4) type of crosses rspb.royalsocietypublishing.org Proc R Soc B 280: 20131181…”

Experimental evolution in fluctuating environments: tolerance measurements at constant temperatures incorrectly predict the ability to tolerate fluctuating temperatures

“…In addition to theoretical expectations (Lee and Gelembiuk 2008), the high invasion success of invaders from disturbed environments has been shown in recent empirical studies (Foucaud et al 2010). Findings from plant invasion studies (Burke andGrime 1996, Davis et al 2000) and microbial invasions (Liu et al 2012, Li andStevens 2012) support the theories of high invasibility of disturbed environments (Elton 1958, Davis 2009).…”

At the brink of supercoloniality: genetic, behavioral, and chemical assessments of population structure of the desert ant Cataglyphis niger

“…Unicoloniality is also typified by the lack of aggression, even between very distant nests e.g., Linepithema humilis (Giraud et al, 2002;Brandt et al, 2009b;Blight et al, 2012), Wasmannia auropunctata (Errard et al, 2005;Vonshak et al, 2009;Foucaud et al, 2010) or Pheidole megacephala (Fournier et al, 2009). This is attributed to the relaxation or complete loss of nestmate recognition in these population, the mechanism of which is postulated to be either "genetic cleansing" following introduction (Giraud et al, 2002) or a "bottleneck" phenomenon (Suarez et al, 2008).…”