title: Can maternally transmitted endosymbionts facilitate the evolution of haplodiploidy?
abstract: Whilst many invertebrate taxa are haplodiploid, the factors underlying the evolution of haplodiploidy remain unresolved. We investigate theoretically whether haplodiploidy might evolve as an outcome of the co-evolution between maternally inherited endosymbionts and their hosts. First, we substantially extend a recently developed model that involves maternally inherited endosymbionts that kill male offspring by eliminating the paternal genome. We also put forward a new hypothesis and develop a model that involves bacteria that induce cytoplasmic incompatibility (CI). Based on these models, we explore the co-evolutionary events that might occur between hosts and symbionts. We find that both with male-killers and CI-inducing endosymbionts, the hosts are likely to develop increased viability of haploid males, which can be considered a preadaptation to haplodiploidy. In addition, populations with haploidizing male-killers can in some cases evolve directly towards a genetic system of paternal genome elimination, a special form of haplodiploidy. These results are combined with consideration of mechanism and ecology to appraise the likelihood of male-killers and CI inducing bacteria being involved in the evolution of haplodiploidy.
authors.affiliation: Department of Biology, UCL, London NW1 2HE, UK. j.engelstaedter@ucl.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Engelstädter
authors.forename: G D D
authors.initials: GD
authors.lastname: Hurst
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005260:Female; D007448:Invertebrates / Q000235:genetics* / Q000382:microbiology*; D008297:Male; D008954:Models, Biological; D011003:Ploidies; D012744:Sex Ratio; D013559:Symbiosis; D020577:Wolbachia / Q000502:physiology