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The European BrasExplor project aims to explore the genetic diversity present in two economically important Brassica crop species, Brassica oleracea and B. rapa, for sustainable crop production. This diversity is present in wild populations but also in cultivated landraces and has been shaped by contrasting environments. An international consortium of 11 partners has begun to collect and multiply wild populations extending from the French North Atlantic coast to the southern Algerian desert as well as local cultivars from 6 contributing countries in order to characterize the genetic diversity available over a wide soil-climate gradient. A total of 100 populations has been obtained for each species. Identifying the genetic variation and understanding the basis for it will allow the development of breeding strategies for a better adaptation of turnip (Brassica rapa) and cabbage (Brassica oleracea var. capitata) to climate change. One third of the collection has been already phenotyped for its germination traits of native seeds harvested in 2020 for wild populations or of local landraces provided by farmers and seed banks. In favourable conditions, a high diversity in germination capacity and germination rate was observed independently of seed age. The two species have a different germination profile: some turnip seeds can stand higher temperature and lower water potential than most cabbage seeds. Variation in flowering time has also been documented in these plants.

The circular distribution of the willow warbler Phylloscopus trochilus around the Baltic Sea shares many features with the classic examples of ring species; however, the system is much younger. It has previously been shown that a secondary contact zone is located in central Scandinavia, where there are narrow clines for several morphological traits coincident with a migratory divide. Here we analyse multiple traits and genes from > 1700 males captured on breeding territories at 77 sites spread around the Baltic Sea to test the following hypothesis. If the secondary contact zone in Scandinavia is a result of divergence in two allopatric refuge populations during the last glaciation, we expect to find a similar secondary contact zone somewhere else around the circular distribution. Our results show that the trait clines were wider and displaced from each other along the eastern side of the Baltic Sea. Analyses of 12 microsatellite loci confirmed that the genome is very similar between the terminal forms (F(ST) = 0). Two AFLP-derived markers filtered out from a genomic scan instead appear to be maintained by selection. These markers exhibited steep clines at the secondary contact zone in Scandinavia, but as for the phenotypic traits, had vastly different cline centres east of the Baltic Sea. The trait clines along the ring distribution outside the Scandinavian secondary contact zone thus seem to have been shaped by independent action of selection or drift during the process of postglacial colonization.

Conflicts of interest between mates can lead to the evolution of male traits reducing female fitness and to coevolution between the sexes. The rate of adaptation and counter-adaptation is constrained by the intensity of selection and its efficiency, which depends on drift and genetic variability. This leads to the largely untested prediction that coevolutionary adaptations such as those driven by sexual conflict should evolve faster in large populations where the response to selection is stronger and sexual selection is more intense. We test this using the bruchid beetle Callosobruchus maculatus, a species with well documented male harm. Whilst most experimental evolution studies remove sexual conflicts, we reintroduce sexual conflict in populations where it has been experimentally removed. Both population size and standing genetic variability were manipulated in a factorial experimental design. After 90 generations of relaxed conflict (monogamy), the reintroduction of sexual conflicts for 30 generations favoured males that harmed females and females more resistant to the genital damage inflicted by males. Large population size rather than high initial genetic variation allowed males to evolve faster and become more harmful. Sexual selection thus creates conditions where males benefit from harming females and this selection is more effective in larger populations.

The extent to which mitochondrial DNA (mtDNA) variation 25 is involved in adaptive evolutionary change is currently being reevaluated. In particular, emerging evidence suggests that mtDNA genes coevolve with the nuclear genes with which they interact to form the energy producing enzyme complexes in the mitochondria. This suggests that intergenomic epistasis 30 between mitochondrial and nuclear genes may affect whole-organism metabolic phenotypes. Here, we use crossed combinations of mitochondrial and nuclear lineages of the seed beetle Callosobruchus maculatus and assay metabolic rate under two different temperature regimes. Metabolic rate was affected by an interaction between the mitochondrial and nuclear lineages and 35 the temperature regime. Sequence data suggests that mitochondrial genetic variation has a role in determining the outcome of this interaction. Our genetic dissection of metabolic rate reveals a high level of complexity, encompassing genetic interactions over two genomes, and genotype × genotype × environment interactions. The evolutionary implications of these results are 40 twofold. First, because metabolic rate is at the root of life histories, our results provide insights into the complexity of life history evolution in general, and thermal adaptation in particular. Second, our results suggest a mechanism that could contribute to the maintenance of non-neutral mtDNA polymorphism. Evolution Page 2 of 37