Unraveling the origin and evolutionary history of male chimerism in yellow crazy ants

• Applicant: Hugo Darras, Ph.D.
• Subject Area: Evolution, Anthropology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 538242487

Multicellular organisms typically develop from a single cell into a collection of clonal cells. However, in a recent study on the invasive yellow crazy ant, Anoplolepis gracilipes, we made a remarkable discovery. Males of this species are all chimeras of two divergent lineages, R and W. Unlike other known chimeras in the animal, plant, and fungi kingdoms that originate from cells of different individuals, chimerism in A. gracilipes arises from a single fertilization event. Instead of fusing, the parental nuclei skip syngamy and divide separately within a single egg, resulting in chimeras with haploid R and W parental genomes in distinct cells of their bodies. When syngamy does occur, the resulting egg develops into a queen if fertilized by R sperm or a worker if fertilized by W sperm. Genetic analyses suggest that this intriguing mode of reproduction may stem from a genetic tug-of-war between the R and W lineages. The proposed project seeks to understand the intricacies of male chimerism in A. gracilipes. We will investigate the phylogeographic distribution of chimerism across the putative native range of the species in Thailand and determine the phylogenetic origin of this reproductive strategy. Next, we will delve into the genetic factors leading to chimerism and assess the roles of the R and W lineages in creating these chimeras. For this, we intend to conduct crossbreeding experiments and compare the genomes and transcriptomes of the R and W lineages. Finally, we will examine the unique cellular processes allowing two distinct genetic lineages to divide and coexist within a single individual. Exploring chimerism in the yellow crazy ant will offer insights into the evolution of cell cooperation and competition, the impact of sexual and caste antagonistic selection on insect societies, and the crucial mechanisms controlling early developmental stages.

• DFG Programme: Research Grants