BIOLOGY 23

Plenary session I – Elena Conti

Comparative Genomics elucidates the convergent origins of floral heteromorphism

Convergent evolution is one of the most fundamental yet contentious issues in evolutionary biology. The rapid accumulation of high-quality reference genomes and transcriptomes now enables us to re-examine evolutionary convergence and parallelism in a new framework: Does convergence at the phenotypic level correspond to convergence or deep homology at the genotypic level? Do the same genes and genetic architectures underlie convergent traits, or can different genes be recruited to achieve the same phenotypic outcome? I will discuss these questions focusing on heterostyly in Primulaceae but within the broader framework of flowering plants. Heterostyly evolved three times independently in Primulaceae, namely in Primula, Hottonia, and Androsace. Heterostylous taxa of Primulaceae typically comprise two different types of plants with distinct floral morphs characterized by reciprocally placed sexual organs and a heteromorphic incompatibility system that blocks self- or intra-morph fertilization. Heterostyly thus promotes cross-fertilization while preventing the harmful effects of self-fertilization, and it evolved at least 14 times in angiosperms. A supergene known as the S locus operates the genetic control of heterostyly. Despite the numerous genetic, morphological, and reproductive studies on heterostyly over the past 150 years, the molecular nature and evolutionary origins of the S locus remained unknown until recently. What are the genes and genetic architectures of the S locus? Are they the same in independent origins of heterostyly? Did the S locus evolve through a single, large duplication followed by loss of intervening genes or through multiple, asynchronous gene duplications followed by translocations? We addressed these questions by generating highly contiguous, chromosome-scale, haplotype-phased assemblies of heterostylous and homostylous genomes of Primulaceae and performing comparative genomic analyses across Ericales, the order that includes Primulaceae. Primulaceae thus represent an ideal system to study evolution on repeat in the genomics era, clarifying the connections and disconnections of evolutionary convergence from the genotypic to the phenotypic level and back.

Chair: Yamama Naciri

45min

A300

Plenary session II – Laurent Excoffier

Demographic inference from ancient human genomes

Reconstructing the demographic history of our species is important not only for satisfying a legitimate curiosity about our origins, but also because it can allow us to better infer past episodes of selection and correctly interpret observed patterns of genomic diversity. In the last 10 years, ancient DNA has revolutionized the way we can reconstruct the settlement history of modern humans, as it gives us direct access to the genomic identity of the first colonizers of different regions of the world. However, most ancient genomes are only partially sequenced, which limits their use for demographic inference as the retrieved information suffers from ascertainment bias. However, investing in good quality ancient genomes allows one to use sophisticated inference methods developed for the analysis of modern genomes. These ancient genomes can thus be used as anchor points in the analysis of modern genomes, or be analyzed on their own to provide new insights about past settlement processes. I will illustrate this point by showing how they have allowed us to provide new insights about the exit of modern humans out of Africa, the settlement of northeastern Siberia and the relationships between early farmers and hunter gatherers from western Eurasia.

Chair: Estella Poloni

45min

A300

Darwin Talk – Sonya Clegg

Tales of the South Pacific: the evolutionary ecology of island colonising birds

Chair: Alice Cibois

45

Le Bateau Genève