Evolution de la spécificité des relations entre les bruches et leurs plantes-hôtes en relation avec leur capacité à devenir des ravageurs des denrées stockées

Avec près de 1300 espèces (Borowiec, 1987), les bruches constituent un groupe assez peu diversifié au regard des 135000 espèces connues de coléoptères phytophages (Lawrence, 1982). Depuis le milieu du 19ème siècle, ce groupe d’insecte a été traditionnellement considéré comme constituant une famille à part entière (Coleoptera : Bruchidae). Un tournant important eu lieu vers la fin des années 1990, période où la question du rang taxonomique du groupe fit l’objet d’un débat intense entre systématiciens (Kingsolver, 1995; Reid, 1996; Verma & Saxena, 1996; Duckett, 1997; Lingafelter & Pakaluk, 1997; Schmitt, 1998), en particulier en raison de l’apparentement supposé des Sagrinae (Chrysomelidae) avec les Bruchidae (Borowiec, 1987; Reid, 1995; Silvain & Delobel, 1998). Par la suite, un nombre croissant d’études moléculaires (e.g. Duckett et al., 2003; Farrell & Sequeira, 2004; Gomez-Zurita et al., 2007) vinrent soutenir cette hypothèse et mirent en évidence une position phylogénétique relativement dérivée des bruches au sein de représentants de la famille des Chrysomelidae. En conséquence, et en accord avec les principes utilisés dans les classifications modernes (Lecointre & Le Guyader, 2001), la plupart des études récentes portant sur le groupe traitent dorénavant les bruches comme une sous-famille de Chrysomelidae (Coleoptera : Chrysomelidae : Bruchinae). Bien que cette question du rang taxonomique à accorder aux bruches puisse sembler triviale aux yeux du non-spécialiste, elle demeure néanmoins fondamentale pour quiconque souhaite effectuer des recherches bibliographiques sur le groupe

Most diverse, most neglected: weevils (Coleoptera: Curculionoidea) are ubiquitous specialized brood-site pollinators of tropical flora

In tropical environments, and especially tropical rainforests, a major part of pollination services is provided by diverse insect lineages. Unbeknownst to most, beetles, and more specifically hyperdiverse weevils (Coleoptera: Curculionoidea), play a substantial role there as specialized mutualist brood pollinators. The latter contrasts with a common view where they are only regarded as plant antagonists. This study aims to provide a comprehensive understanding of what is known about plant-weevil brood-site mutualistic interactions, through a review of the known behavioral, morphological and physiological features found in these systems, and the identification of potential knowledge gaps. To date, plant-weevil associations have been described or indicated in no less than 600 instances. Representatives of major plant lineages are involved in these interactions, which have emerged independently at least a dozen times. Strikingly, these mutualistic interactions are associated with a range of convergent traits in plants and weevils. Plants engaged in weevil-mediated pollination are generally of typical cantharophilous type exhibiting large, white and fragrant flowers or inflorescences and they also show specific structures to host the larval stages of their specialist pollinators. Another characteristic feature is that flowers often perform thermogenesis and exhibit a range of strategies to separate sexual phases, either spatially or temporally. Conversely, lineages of brood-site weevil pollinators present numerous shared behavioral and physiological traits, and often form multispecific assemblages of closely related species on a single host; recent studies also revealed that they generally display a high degree of phylogenetic niche conservatism. This pollination mutualism occurs in all tropical regions, and the contrasts between the known and expected diversity of these systems suggests that a wide range of interactions remain to be described globally. Our early estimates of the species richness of the corresponding weevil clades and the marked pattern of phylogenetic niche conservatism of host use further suggest that weevil-based pollination far exceeds the diversity of other brood-site mutualistic systems, which are generally restricted to one or a few groups of plants. As such, weevil pollinators constitute a relevant model to explore the emergence and evolution of specialized brood-site pollination systems in the tropics

Spodoptera frugiperda (Lepidoptera: Noctuidae) host-plant variants: two host strains or two distinct species?

International audienceThe moth Spodoptera frugiperda is a well-known pest of crops throughout the Americas, which consists of two strains adapted to different host-plants: the first feeds preferentially on corn, cotton and sorghum whereas the second is more associated with rice and several pasture grasses. Though morphologically indistinguishable, they exhibit differences in their mating behavior, pheromone compositions, and show development variability according to the host-plant. Though the latter suggest that both strains are different species, this issue is still highly controversial because hybrids naturally occur in the wild, not to mention the discrepancies among published results concerning mating success between the two strains. In order to clarify the status of the two host-plant strains of S. frugiperda, we analyze features that possibly reflect the level of post-zygotic isolation: (1) first generation (F1) hybrid lethality and sterility; (2) patterns of meiotic segregation of hybrids in reciprocal second generation (F2), as compared to the meiosis of the two parental strains. We found a significant reduction of mating success in F1 in one direction of the cross and a high level of microsatellite markers showing transmission ratio distortion in the F2 progeny. Our results support the existence of post-zygotic reproductive isolation between the two laboratory strains and are in accordance with the marked level of genetic differentiation that was recovered between individuals of the two strains collected from the field. Altogether these results provide additional evidence in favor of a sibling species status for the two strains

Genetic data from the extinct giant rat from Tenerife (Canary Islands) points to a recent divergence from mainland relatives

Evolution of vertebrate endemics in oceanic islands follows a predictable pattern, known as the island rule, according to which gigantism arises in originally small-sized species and dwarfism in large ones. Species of extinct insular giant rodents are known from all over the world. In the Canary Islands, two examples of giant rats, †Canariomys bravoi and †Canariomys tamarani, endemic to Tenerife and Gran Canaria, respectively, disappeared soon after human settlement. The highly derived morphological features of these insular endemic rodents hamper the reconstruction of their evolutionary histories. We have retrieved partial nuclear and mitochondrial data from †C. bravoi and used this information to explore its evolutionary affinities. The resulting dated phylogeny confidently places †C. bravoi within the African grass rat clade (Arvicanthis niloticus). The estimated divergence time, 650 000 years ago (95% higher posterior densities: 373 000-944 000), points toward an island colonization during the Günz-Mindel interglacial stage. †Canariomys bravoi ancestors would have reached the island via passive rafting and then underwent a yearly increase of mean body mass calculated between 0.0015 g and 0.0023 g; this corresponds to fast evolutionary rates (in darwins (d), ranging from 7.09 d to 2.78 d) that are well above those observed for non-insular mammals.For technical support, we thank the research service facilities of IJC and IGTP, the Crystallization Facility of the Max Planck Institute of Biochemistry, the ICTS NMR facility from the Scientific and Technological Centres of the University of Barcelona and Biophysics Core Facility of BMC-LMU. I.G. was a fellow of the Marie Skłodowska Curie Training network ‘ChroMe’ (H2020-MSCA-ITN-2015-675610, awarded to M.B. and A.G.L.). The project was further supported by national grants (nos. RTI2018-094005-B-I00 and BFU2015-66559-P from FEDER/Ministerio de Ciencia e Innovación—Agencia Estatal de Investigación to M.B.). Research in the participating labs was further supported by the following grants: the Marie Skłodowska Curie Training network ‘INTERCEPT-MDS’ no. H2020-MSCA-ITN-2020-953407 (to M.B.), MINECO-ISCIII no. PIE16/00011 (to M.B.); the Deutsche José Carreras Leukämie Stiftung DJCLS (no. 14R/2018 to M.B.), AGAUR (no. 2017-SGR-305 to M.B.), Fundació La Marató de TV3 (no. 257/C/2019 to M.B.), German Research Foundation Project (ID 213249687—SFB 1064 and Project ID 325871075—SFB 1309 to A.G.L.), the Spanish Ministry of Science (PID2019-110183RB-C21 to A.R.M.), Community of Madrid (P2018/BAA-4343-ALIBIRD2020-CM to A.R.M), Ramón Areces Foundation (to A.R.M.), National Science Foundation (EF-1921402 to J.M.E.L.), 2015 International Doctoral Fellowship La Caixa-Severo Ochoa (to M.F.V.), Marie Skłodowska-Curie Individual Fellowship (no. 747789 to M.M.L.), Juan de la Cierva-Incorporación (IJC2018-036657-I to M.M.L., ERC-2012-CoG-616960 to I.R.T.), MINECO (BFU2017-90114-P to I.R.T.), AGAUR (2017-SGR-324 to X.S.) and MINECO (BIO2015-70092-R and ERC-2014-CoG-648201 to X.S.). Research at the IJC is supported by the ‘La Caixa’ Foundation, Fundació Internacional Josep Carreras, Celgene Spain and the CERCA Programme/Generalitat de Catalunya

Integrative taxonomy of New Caledonian beetles: species delimitation and definition of the [i]Uloma isoceroides[/i] species group (Coleoptera, Tenebrionidae, Ulomini), with the description of four new species

New Caledonia is an important biodiversity hotspot with much undocumented biodiversity, especially in many insect groups. Here we used an integrative approach to explore species diversity in the tenebrionid genus Uloma (Coleoptera, Tenebrionidae, Ulomini), which encompasses about 150 species, of which 22 are known from New Caledonia. To do so, we focused on a morphologically homogeneous group by comparing museum specimens with material collected during several recent field trips. We also conducted molecular phylogenetic analyses based on a concatenated matrix of four mitochondrial and three nuclear genes for 46 specimens. The morphological study allowed us to discover and describe four new species that belong to the group of interest, the Uloma isoceroides group. Molecular analyses confirmed the species boundaries of several of the previously described species and established the validity of the four new species. The phylogenetic analyses also provided additional information on the evolutionary history of the group, highlighting that a species that was thought to be unrelated to the group was in fact a member of the same evolutionary lineage. Molecular species delimitation confirmed the status of the sampled species of the group and also suggested some hidden (cryptic) biodiversity for at least two species of the group. Altogether this integrative taxonomic approach has allowed us to better define the boundaries of the Uloma isoceroides species group, which comprises at least 10 species: Uloma isoceroides (Fauvel, 1904), Uloma opacipennis (Fauvel, 1904), Uloma caledonica Kaszab, 1982, Uloma paniei Kaszab, 1982, Uloma monteithi Kaszab, 1986, Uloma robusta Kaszab, 1986, Uloma clamensae sp. n., Uloma condaminei sp. n., Uloma jourdani sp. n., and Uloma kergoati sp. n. We advocate more studies on other New Caledonian groups, as we expect that much undocumented biodiversity can be unveiled through the use of similar approache

Using macroevolutionary approaches to study evolutionary trajectories of insect communities

National audienc

Les changements environnementaux passés impactent des communautés d’insectes phytophages.

Site INRA - Les départements INRA - Santédes plantes et environnement - ActualitésUne équipe de chercheurs américains et français ont mené une étude sur la réponse aux changements environnementaux sur des temps longs chez un groupe de noctuelles foreuses de graminées et leurs plantes-hôtes. Parmi les principaux résultats publiés le 30 novembre 2018 dans la revue Nature Communications, l’équipe de recherche internationale montre que les noctuelles et les graminées étudiées ont eu des dynamiques adaptatives opposées, en lien direct avec les changements de température