The ghost sex-life of the paedogenetic beetle Micromalthus debilis.
Genetic and sexual systems can be evolutionarily dynamic within and among clades. However, identifying the processes responsible for switches between, for instance, sexual and asexual reproduction, or cyclic and non-cyclic life histories remains challenging. When animals evolve parthenogenetic reproduction, information about the sexual mating system becomes lost. Here we report an extraordinary case where we have been able to resurrect sexual adults in a species of beetle that reproduces by parthenogenetic paedogenesis, without the production of adults. Via heat treatment, we were able to artificially induce adult beetles of Micromalthus debilis in order to describe its pre-paedogenetic mating system. Adults showed a highly female biased sex ratio, out-breeding behaviour, and sex-role reversal. Paedogenetic larvae of Micromalthus are infected with the endosymbiotic bacteria Rickettsia and Wolbachia. Clear signs of vestigialization in adults are concurrent with the loss of adults. Our data suggest an ancient female sex ratio bias that predates the loss of adults, perhaps associated with endosymbionts. We propose a model for the transition from a haplodiploid cyclical parthenogenetic life history to parthenogenetic paedogenesis. Paedogenetic development induces a new mechanism of sex ratio bias in midges, wasps and beetles.
School of Biological Sciences, University of Reading, Reading, RG6 6AS, UK.
M Alejandra
MA
Perotti
Department of Entomology, 1630 Linden Drive, University of Wisconsin, Madison, WI 53706, USA.
Daniel K
DK
Young
School of Biological Sciences, Bangor University, Bangor, LL57 2UW, UK.
Henk R
HR
Braig
D000818:Animals; D001517:Coleoptera / Q000502:physiology* / Q000528:radiation effects*; D006358:Hot Temperature; D010312:Parthenogenesis / Q000528:radiation effects; D012281:Rickettsia / Q000254:growth & development; D020577:Wolbachia / Q000254:growth & development