Project Details
Projekt
The genomic basis of extreme sexual dimorphism in fireflies.
Applicants
Dr. Ana Catalan, Ph.D.; Dr. Sebastian Höhna
Subject Area
Evolution, Anthropology
General Genetics and Functional Genome Biology
General Genetics and Functional Genome Biology
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 503346030
Fireflies are well known for their charismatic lighted mating signals. Less known, fireflies exhibit a fascinating variation in sexual dimorphism: some species show very mild sexual dimorphism whereas other species exhibit extreme sexual dimorphism. In species where extreme sexual dimorphism is present, females remain in a neotenic state with wing pads instead of fully developed wings. In some species the light organ is also sexually dimorphic, where males do not have a light organ but neotenic females do. Most importantly, this sexual dimorphism has evolved repeatedly across the firefly phylogeny. A considerable proportion of strong trait variation, including sexually dimorphic traits, must be caused by underlying gene expression variation. However, there is very little known about which type of evolutionary forces act on sex-biased gene expression and if the same sex-biased genes are shared across the phylogeny. Furthermore, gene expression is most likely regulated by open chromatin accessibility. Nevertheless, the correlation between sex-biased open chromatin accessibility and sex-biased gene expression is still unclear. In this project, we will identify the evolutionary forces (e.g. neutral drift, stabilizing or directional selection) acting on gene expression using a phylogenetic framework. Only within a phylogenetic framework we can distinguish between all scenarios of gene expression evolution, for example, distinguishing directional selection from relaxed stabilizing selection. To address our questions, we will develop new methods and theory for the statistical analysis (Brownian Motion and Ornstein-Uhlenbeck), specifically focusing on utilizing within-species variance in sex-biased gene expression. Our novel methods will allow us to study the evolutionary forces acting on sex-biased gene expression, and if sex-biased gene expression is linked to extreme sexual dimorphism through repeated evolution. To investigate the genetic basis of extreme sexual dimorphism we will sequence whole transcriptomes of 15 firefly species from 5 divergent genera, with multiple individuals per species and separated by body parts. Additionally, by generating ATAC-seq data, we will produce novel insights into the correlation between gene expression evolution and chromatin accessibility evolution on a phylogenetic scale. Taken together, our project will (a) generate a new comprehensive transcriptomic and chromatin accessibility dataset, (b) develop novel methods to study gene expression and chromatin accessibility evolution for multiple species and individuals across a phylogeny and (c) advance our understanding of genome evolution with regards to the molecular mechanism underlying sexual dimorphism. Finally, our project will uncover which genomic elements are driving innovations in insects, such as neoteny.
DFG Programme
Priority Programmes
