Speaker
Description
Altica lythri is a hybridogenetic beetle with unique reproduction anomalies that provide an ideal model for understanding how genetic conflicts shape the sex, and thus evolution, of species. Ancient interspecific hybridization and Wolbachia bacterial infections in A. lythri resulted in introgression of mitochondrial (mt) DNA (HT1, HT2, HT3). Depending on a female’s mtDNA haplotype and Wolbachia strain (HT1- wLytA1), the progeny can consist exclusively of daughters. This female bias could, on one hand, be caused by the Wolbachia infection itself, which is known to induce male-killing, feminization of genetic males and parthenogenesis. On the other hand, the female bias could also have its cause in the genetic consequences of hybridization in the form of nuclear-cytoplasmic conflicts between introgressed mtDNA and nuclear genes, which result in the absence of heterogamous males with the mtDNA HT1. To understand the mechanisms that contribute to this sex-specific bias, we have extensively studied the different mechanisms by which Wolbachia can interact with its host to manipulate the sex as well as the Wolbachia infection itself.
We address these issues in A. lythri with genomic and molecular approaches. Using different PCR techniques, we established and applied screening methods for phenotypic and genetic sex determination in the different life stages of Altica lythri. Paternity analyses by a ddRAD approach as well as chromosome spreads of unfertilized eggs enabled us to show that the HT1 females reproduce by gynogenesis.
Our results provide key insights into how sex determination is altered and whether selfish genetic elements and/or reproductive manipulating endosymbionts play the key role in this system.
