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International audience; Temperate grasslands provide both habitats and flower resources for pollinators in agricultural landscapes. Plant-pollinator networks change according to local and landscape variables, which are important to identify to help conserve pollinators in grasslands. We analysed plant-pollinator networks in 18 grasslands on experimental dairy farms located in three French regions contrasting by their climate, altitude, landscape or management. We combined visual surveys and pollen DNA barcoding. Our objectives were to determine which environmental factors influence pollinator taxa abundance and diversity and differences among the visual plant-pollinator networks in the three farming regions. Flower-visiting insects were trapped in six grasslands per farm during three sessions from mid-April to mid-July along fixed 400 m2 transects. Insects were identified individually to the lowest taxonomic rank possible. Pollen carried by insects was identified using nuclear ribosomal ITS2 sequences belonging to the NCBI nucleotide database. The size and diversity of plant-pollinator networks were much larger and higher in permanent grasslands at the two farms located in lowlands (Mirecourt) and mountains (Marcenat) than those at the farm with temporary grasslands and a crop landscape (Lusignan), but the degree of specialisation (H2′) was relatively similar and low (mean of 0.46). Diptera, especially Empididae and Syrphidae, represented most plant-pollinator interactions in Mirecourt and Marcenat, while Hymenoptera were more abundant at Lusignan. The percentage of semi-natural habitats in 500 m buffers and vegetation height explained 23% of the variance in pollinator abundance. Ranunculus sp. Knautia arvensis, Centaurea jacea and Trifolium repens were key plant species in the networks. DNA metabarcoding of pollen loads identified 114 genera in addition to those identified by visual observations (+34–42 per site), reflecting insects’ floral pathways and differences in the immediate landscape among farms. This study highlighted the importance of Diptera in plant-pollinator networks and the need to conserve permanent grassland diversity to conserve pollinators.

Oilseed rape (Brassica napus L.) was formed ~7500 years ago by hybridization between B. rapa and B. oleracea, followed by chromosome doubling, a process known as allopolyploidy. Together with more ancient polyploidizations, this conferred an aggregate 72× genome multiplication since the origin of angiosperms and high gene content. We examined the B. napus genome and the consequences of its recent duplication. The constituent An and Cn subgenomes are engaged in subtle structural, functional, and epigenetic cross-talk, with abundant homeologous exchanges. Incipient gene loss and expression divergence have begun. Selection in B. napus oilseed types has accelerated the loss of glucosinolate genes, while preserving expansion of oil biosynthesis genes. These processes provide insights into allopolyploid evolution and its relationship with crop domestication and improvement.

Second-strand cDNA priming is a central problem for full-length characterization of transcripts. A new strategy using bacteriophage T4 DNA ligase and partially degenerate adapters is proposed for grafting a sequence tag to the end of polyribonucleotides. Based on this RNA tagging system and previously described protocols, a new method for full-length cDNA production has been implemented. Validation of the method is shown in Arabidopsis thaliana by the construction of a full-length cDNA library and the analysis of 154 clones and by 5′-RACE–PCR run on a documented experimental system.

The 14 species of Ficus of the subgenus Sycomorus (Moraceae) are invariably pollinated by Ceratosolen species (Hym. Chalcidoidea), which in turn reproduce in the fig florets. They are distributed mostly in continental Africa, Madagascar, and the Mascarene and Comoro Islands, but 1 species extends its geographical range all over the Oriental region. Fig–pollinator relationships are usually strictly species specific, but exceptions to the ‘one-to-one’ rule occur within the group we studied. In order to understand both the biogeographical history of the Ceratosolen species associated with Ficus of the subgenus Sycomorus and the origins of the specificity breakdown cases, we have used cytochrome b sequences to reconstruct a phylogeny of the fig wasps. The results show that the pollinators from the Malagasy region and those from continental Africa form two distinct clades, which probably diverged after the crossing of the Mozambique Channel by an ancestral population. The Oriental wasp species show strong affinities with the African species. The two species-specificity exceptions are due to different evolutionary events. The occurrence of the two West African pollinators associated with F. sur can be explained by successive speciation events of the mutualistic partner without plant radiation. In contrast, we hypothesize that C. galili shifted by horizontal transfer from an unknown, presumably extinct, Ficus species to F. sycomorus after this native Malagasy fig species colonized Africa.

According to the present classification, the family Agaonidae contains all fig pollinators as well as five subfamilies of non-pollinating fig wasps. The molecular phylogeny of the family was reconstructed using partial sequences of the 28S rRNA (D1 and D2 domains). Our results show that the family Agaonidae is not monophyletic. As a consequence, we restrict the famiy to the pollinator clade, and assign the non-pollinating subfamilies to various chalcid families. Sycoecinae, Otitesellinae and Sycoryctinae are included in Pteromalidae, whereas Sycophaginae and Epichrysomallinae are left unclassified and will require more in-depth morphological studies. Moreover, we proved that the fig pollination syndrome evolved only once, early in group history. The resource due to the fig-pollinator mutualism has secondarily been colonized independently by different Chalcid lineages.

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