A central question in evolutionary biology concerns how adaptive combinations of traits can be maintained. Supergenes offer one solution to this problem: they are clusters of genes that are inherited as a unit and can thus maintain favorable trait combinations. But suppression of recombination at supergenes also comes at the cost of increased accumulation of harmful mutations, which might affect their long-term maintenance. This project aims to improve our understanding of supergene origins and evolution by studies of a classic supergene that governs the balanced floral polymorphism of distyly.
Distyly is an iconic floral polymorphism that ensures outcrossing and efficient pollen transfer to compatible plants. Distyly signifies the presence of two floral morphs, where flowers of different individuals differ reciprocally in the placement of male and female reproductive organs. Distyly has arisen independently many times in different evolutionary lineages, and is a textbook example of convergent evolution. It has been known for a long time that distyly is governed by a supergene, but until recently, the molecular makeup or evolution of distyly supergenes had not been studied in detail.
In this project, we aim to make full use of the latest advances in genomics to elucidate the evolution of a classic supergene that governs distyly in Linum, wild flaxseed species. This system is ideal for this purpose due to the dynamic nature of distyly in Linum. We will establish a genomic framework for studies of the evolution and loss of distyly in wild Linum by generating high-quality contiguous genome assemblies of six Linum species. We will then use these assemblies as a basis for identifying the characterizing the supergene that underlies distyly, and investigate supergene evolution at the genetic and regulatory level. Finally, we will investigate how and when distyly has been lost, and what the population genomic effects are.
The high-quality genomes produced in this project will pave the way for further studies to elucidate the molecular genetics of distyly, an adaptive floral polymorphism studied already by Darwin. The results are of general importance for an improved understanding of the evolution of coadapted gene complexes, and will shed new light on the fascinating phenomenon of supergenes.
