Molecular Ecology Resources (2008) 8, 919–922 doi: 10.1111/j.1755-0998.2008.02116.x © 2008 The Authors Journal compilation © 2008 Blackwell Publishing Ltd Blackwell Publishing Ltd PERMANENT GENETIC RESOURCES Isolation and characterization of microsatellite loci from the invasive ant Pheidole megacephala DENIS FOURNIER, DAMIEN DUBOIS and SERGE ARON Behavioural and Evolutionary Ecology CP 160/12, Université Libre de Bruxelles, Avenue F.D. Roosevelt, 50, B-1050 Brussels, Belgium Abstract We report the characterization of eight microsatellite markers in the big-headed ant Pheidole megacephala, a pest ant registered in the list of ‘100 of the world’s worst invasive alien species’. An enrichment protocol was used to isolate microsatellite loci, and polymorphism was explored with 36 individuals collected in an invasive population from Australia and 20 individuals collected in a population from the native mainland location in South Africa. These primers showed a number of alleles per locus ranging from two to 10, and expected heterozygosities ranging from 0.083 to 0.826. Moreover, results of cross-species amplifica- tion are reported in five other Pheidole species and in seven other ants of the subfamily Myrmicinae. Keywords: big-headed ant, colony structure, invasive species, microsatellite, Pheidole megacephala, population structure Received 24 October 2007; revision accepted 19 December 2007 Ants are popular organisms to address a variety of questions in ethology, genetics, ecology, evolution or conservation biology. Among the family Formicidae, Pheidole is one of the most speciose and widespread genera: 898 described species are distributed over the eight zoogeographical regions where ant fauna are found (Neotropical, Nearctic, Palearctic, Afrotropical, Malagasy, Oriental, Indo-Australian and Australasian) (Hölldobler & Wilson 1990; Bolton 1995). In the New World, species of the genus Pheidole are the most abundant and diverse ants, and range from the northern USA to Argentina (Wilson 2003). Pheidole species have been studied for various aspects of their biology, including the ecological correlates of their temporal and physical castes and the associated division of labour (e.g. P. dentata, Calabi & Traniello 1987; P. morrisi, Brown & Traniello 1998); their highly biased colony sex ratio (P. desertorum, Helms 1999; P. pallidula, Fournier et al. 2003); their foraging strategies and territorial behaviour (e.g. P. pallidula, Passera et al. 1996; P. xerophylla (previously P. tucsonica) and P. gilvescens, Langen et al. 2000; Tripet et al. 2006); and their impact on biodiversity (e.g. P. megacephala, Passera 1994 and references therein; Wetterer 2007; P. fervens and P. moerens, Garrison 1996). The big-headed ant P. megacephala is well known as a household and agricultural pest, and its negative ecological impact on biodiversity may be greater than any other invasive ant (Wetterer 2007). The species is nominated as one of the 100 of the world’s worst invaders by the IUCN Species Survival Commission Invasive Species Specialist Group (Lowe et al. 2001). However, despite its ecological and economical impacts, no genetic studies have been conducted to decipher the evolutionary processes associated with the invasion of the big-headed ant. Here, we describe the development of eight microsatellite loci for this invasive species and their application to individuals from Africa, the supposed native range of the species (Wilson & Taylor 1967), and Australia. Samples were collected in March 2005 from four Australian populations and stored in ethanol at –80 °C. Total genomic DNA was isolated using a standard phenol–chloroform extraction protocol (Sambrook & Russell 2001). An enriched library was made by ecogenics GmbH from size-selected genomic DNA ligated into SAULA/SAULB-linker (Armour et al. 1994) and enriched by magnetic bead selection with biotin-labelled (CT) 13 , (GT) 13 (GTAT) 7 and (GATA) 7 oligo- nucleotide repeats (Gautschi et al . 2000a, b). Of 374 recombinant colonies screened, 163 gave a positive signal after hybridiza- tion. Plasmids from 64 positive clones were sequenced and primers were designed for 16 microsatellite inserts. Correspondence: Denis Fournier, Fax: +32 (0)2 650.24.45; E-mail: Denis.Fournier@ulb.ac.be