"Sex is a ubiquitous phenomenon where the reshuffling and mixing of two genomes give rise to the genetic makeup of the next generation, a process that generates novel combinations of alleles and that is central to understanding evolution. Unusual genetic systems involving mating between partners from different lineages or species have evolved multiple times in the animal kingdom. Such systems have recently been reported in several ant genera. Ants, as other Hymenoptera, are haplo-diploid. Males are haploid and develop from unfertilized eggs, whereas queen and worker females are diploid and typically develop from fertilized eggs. ""Double-clonality"" represents a peculiar deviation from this canonical system. Under this system, all workers in the colony are hybrids but reproductive individuals are not. Workers are produced by sexual reproduction, while new reproductive queens are clones of their mother and males are clones of their father. The queen and male genomes therefore evolve as separate non-recombining entities, which only interbreed to produce sterile first-generation hybrid workers. Double-clonality has been reported in four invasive species to date, namely Wasmannia auropunctata, Vollenhovia emeryi, Paratrechina longicornis and Cardiocondyla kagutsuchi and may be discovered in many additional species in the future. No theory has been formulated on genome evolution in the context of these bizarre genetic systems and empirical data are still scarce. Beyond fundamental research, having genomic resources from different localities across the invasive ranges of this widespread species can help understand how this unique reproductive system could have facilitated the spread of these species.
The longhorn crazy ant Paratrechina longicornis is a common pest and one of the most broadly dispersed ants in the world. Recent research showed that colonies from Thailand display a double-clonal mating system. The objective of the H2020 MELCA action was to investigate the consequence of “double clonal” reproduction on genome evolution in Paratrechina longicornis. Our work provides genetic resources from several invasive populations and revealed further details on how the double-clonal reproductive system operates in this species, laying a solid foundation for understanding the interplay between molecular evolution of the genome and mode of sexual reproduction."
