Alexander Brandt
Every semester, EES organise a seminar series, which takes place on Mondays at 16:00 at Biozentrum, Lecture Hall B 01.019
Winter Semester 2025/26
Alexander Brandt
Universität Lausanne - Switzerland
Evolution of alternative reproductive modes and regulatory novelty in hybrids: insights from Bacillus stick insects
Abstract: Many organisms reproduce through non-canonical modes such as parthenogenesis or hybridogenesis (clonal transmission of one parent’s chromosomes), but whether these arise abruptly or stepwise from each other remains unclear. We address this in the stick-insect genus Bacillus, which harbors several hybrid lineages with diverse reproductive modes. From haplotype-resolved phylogenies of >500 wild-caught individuals, we infer a single, recent (~8,000 years) origin of all hybrids. The ancestral hybrid reproduced via hybridogenesis, which subsequently diversified into parthenogenesis and, twice independently, into triploid lineages. Laboratory crosses recapitulate this trajectory, where each step facilitated the next. These findings reveal how a single genomic perturbation can act as a catalyst for evolutionary innovation, turning the loss of sex into a driver of diversification rather than a dead end. The sequence of hybridization events in Bacillus likely generated regulatory novelties e.g. expression levels, expression patterns, and splicing variants that differ from those observed in the parents. These may have aided their adaptive potential despite the loss of sex. I introduce Bacillus stick insects as a new system to elucidate how hybridization generates regulatory novelty and how regulatory novelty evolves in natural populations, with and without the genetic reshuffling through sex, and under different ploidy levels. Addressing these novel questions in a single study system promises to yield a comprehensive and detailed picture of how regulatory evolution in hybrids contributes to shaping life's diversity.
Host: Natascha Turetzek
Previous and future talks in the EES seminar series