My project centers on exploring the evolution of reproductive isolation through genomic barriers, such as chromosomal rearrangements or hybrid incompatibility mutations, with a specific focus on the evolution of haploid sex chromosomes.
Understanding the genetic foundations of speciation, the process of new species formation, has remained a fundamental quest within evolutionary biology and genomics but many questions remain, especially when it comes to elucidate the molecular underpinnings of species formation.
My model system is the filamentous brown algae Ectocarpus (Phaeophyceae), comprising 16 cryptic species (Montecinos et al., 2017).
Ectocarpus offers an excellent opportunity to study the role of UV sex chromosomes in speciation. Notably, there has been a limited exploration of the role of haploid sex chromosomes in speciation, despite their significant advantages, including the absence of a dominance effect, equivalent reduction in effective population size for both sex chromosomes compared to autosomes, and the direct accessibility of recombinant progeny through a single cross involving the F1 haploid gametophyte.
Furthermore, these Ectocarpus species exhibit varying degrees of pre- and post-zygotic incompatibilities and asymmetries in hybrid viability in reciprocal crosses, adding to their appeal as a subject for study in the context of speciation.
Ectocarpus exhibits a haploid-diploid life cycle (typical of seaweed species), where sexual reproduction happens during a haploid gametophyte phase and the sexes are determined by the haploid U (female) and V (male) sex chromosomes.
Throughout this project, I aim to adress three of the long-standing questions in speciation research:
1) What constitutes the genetic architecture of reproductive barriers?
2) To what extent do chromosomal rearrangements contribute to speciation?
3) What roles do haploid sex chromosomes play in the evolution of reproductive isolation?
Leveraging a cutting-edge linked-read sequencing method known as haplotagging, I strategically exploited existing data to generate genomic information from hundreds of individuals in hybridization regions across Europe and Chile. This approach was decisive in overcoming the challenge of understanding how and when introgression occurred in both species.
Here is the poster I presented during the PopGroup57 meeting with a specific focus on how mitochondrial genomes reconstructed with our data, helped us to identify potential errors in the species identifications.
While some Ectocarpus species have been sequenced, the success of my project hinges on generating high-quality chromosome-level genomic assemblies for all species. Given the critical role of taxon sampling in species delineation, I participated in a sampling campaign in Japan in April 2023 to enrich our understanding of Ectocarpus diversity.
During the year 2024, thanks to the Salto exchange programme, I will initialte a collaboration with Thomas Broquet at the Station Biologique de Roscoff.
In this framwork, I am organizing a workshop on the 11th of April 2024 on Speciation and sex chromosome evolution.