Karyotypes of twenty-one ant species (Hymenoptera; formicidae), with reviews of the known ant karyotypes.

Abstract

Six dolichoderine species have haploid numbers: 9 (Iridomyrmex pilifer, I. sp. nr. pilifer, Dorymyrmex ?thoracicus, D. ?pulchellus), 13 (D. bicolor) and 16 (Forelius foetidus). Robertsonian changes could account for the differences between the Dorymyrmex numbers. The Iridomyrmex species, both Neotropical, have a different karyotype from Australian 9-chromosome Iridomyrmex. The species with numbers 13 and 16 have relatively more acrocentrics per karyotype than those with lower numbers. Five formicine species have haploid numbers: 8 (Oecophylla smaragdina), 9 (Brachymyrmex sp.), 15 (Lasius nearcticus), 21 (Polyrhachis rastellata), and 26 (Camponotus (Colobopsis) sp. (impressus gp.)). Although thelytoky has been reported for Oecophylla spp., a queenless greenhouse colony died out after producing an all-male brood; further work is suggested on Oecophylla populations where thelytoky has been reported. The 8- and 9-chromosome formicines have all chromosomes metacentric, while acrocentrics predominate in the higher-numbered species. The ponerine Proceratium silaceum has n = 18. Nine myrmicine species have haploid numbers: 10 (Pheidole dentata, P. dentigula), 11 Solenopsis molesta, Monomorium minimum, M. viridum, Meranoplus sp. (hirsutus gp.)), 12 (Leptothorax longispinosus), and 16 (Solenopsis aurea, S. geminata). Monomorium karyotypes have a small acrocentric, while all 11-chromosome Solenopsis chromosomes are metacentric. Reviewing the 92 known ant karyotypes supports some present taxonomic schemes but not others. Imai's (1966) suggestions, that polyploidy occurred in formicine evolution and that high numbers occur more frequently at 'high' latitudes, are not supported by present evidence.