Co-obligate symbioses have repeatedly evolved across aphids, but partner identity and nutritional contributions vary across lineages

Aphids are a large family of phloem-sap feeders. They typically rely on a single bacterial endosymbiont, Buchnera aphidicola, to supply them with essential nutrients lacking in their diet. This association with Buchnera was described in model aphid species from the Aphidinae subfamily and has been assumed to be representative of most aphids. However, in two lineages, Buchnera has lost some essential symbiotic functions and is now complemented by additional symbionts. Though these cases break our view of aphids harbouring a single obligate endosymbiont, we know little about the extent, nature, and evolution of these associations across aphid subfamilies. Here, using metagenomics on 25 aphid species from nine subfamilies, re-assembly and re-annotation of 20 aphid symbionts previously sequenced, and 16S rRNA amplicon sequencing on 223 aphid samples (147 species from 12 subfamilies), we show that dual symbioses have evolved anew at least six times. We also show that these secondary co-obligate symbionts have typically evolved from facultative symbiotic taxa. Genome-based metabolic inference confirms interdependencies between Buchnera and its partners for the production of essential nutrients but shows contributions vary across pairs of co-obligate associates. Fluorescent in situ hybridisation microscopy shows a common bacteriocyte localisation of two newly acquired symbionts. Lastly, patterns of Buchnera genome evolution reveal that small losses affecting a few key genes can be the onset of these dual systems, while large gene losses can occur without any co-obligate symbiont acquisition. Hence, the Buchnera-aphid association, often thought of as exclusive, seems more flexible, with a few metabolic losses having recurrently promoted the establishment of a new co-obligate symbiotic partner

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

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

Documenting tenebrionid diversity: progress on Blaps Fabricius (Coleoptera, Tenebrionidae, Tenebrioninae, Blaptini) systematics, with the description of five new species

With about 250 species, the genus Blaps Fabricius, 1775 is one of the most diverse genera of darkling beetles (Coleoptera: Tenebrionidae: Tenebrioninae: Blaptini: Blaptina). In this study, we provide new insights on the evolutionary relationships of Blaps species using a combined molecular and morphological dataset encompassing 69 distinct Blaps species and subspecies (105 specimens in total, all belonging to the subgenus Blaps), four other representatives of the tribe Blaptini (from the subtribes Gnaptorina, Gnaptorinina and Prosodina) and 12 outgroup species. Five new species of Blaps are also described within the subgenus Blaps: B. effeminata sp. nov. from Libya, B. intermedia sp. nov. from Morocco, B. maldesi sp. nov. from Algeria, B. nitiduloides sp. nov. from Algeria and Tunisia and B. teocchii sp. nov. from Tunisia. The results of the phylogenetic analyses indicate that the genus Blaps is likely paraphyletic; the two highlighted clades are morphologically distinct and correspond to groups previously referred to as sections (I and II) within the subgenus Blaps. This suggests the need for more phylogenetic studies in order to clarify the status of the various genera and subgenera belonging to the tribe Blaptini

On the role of niche specialization in the geographic distribution of aphid asexual lineages: a case study using the leaf-curl plum aphid superclones

Information on sampling is available in the database https://aphiddb.supagro.inrae.frData are available from the Zenodo Digital Repository: https://zenodo.org/records/10924797 (Jousselin and Godefroid 2024)International audienceAsexual lineages often exhibit broad distributions and can thrive in extreme habitats compared to their sexual counterparts. Several hypotheses can be proposed to explain this pattern. Asexual lineages could be versatile genotypes with wide environmental tolerance, enabling their dispersal and persistence across large geographic areas. Alternatively, asexual genotypes could be ecological specialists that thrive in specific environments and outcompete relative colonizing distantly related with similar conditions in the process. Several aphid species feature widespread obligate asexual lineages, commonly known as ‘superclones’. Yet it is often unknown whether these clones are widespread ecological generalists or successful specialists. To explore these hypotheses,we examined climatic niche differentiation among six globally distributed obligateasexual lineages of the cosmopolitan aphid pest, Brachycaudus helichrysi. To ensure that we were investigating the aphid genotype niche and not a by-product of their association with endosymbionts mediating thermal tolerance, we first verified that clones hosted similar endosymbiont communities. Subsequently, we conducted multivariate analyses on clone occurrence data on a worldwide scale. Our results revealed that, despite their global distribution, B. helichrysi superclones occupy different climatic niches. This study represents the first evidence that aphid superclone distribution can be mediated by distinctive ranges of climatic tolerance

The Tenebrionidae (Coleoptera) of Mount Wilhelm and Wanang,with description of a new species and a preliminary phylogeny of Stenochiinae

More than 40 species of Tenebrionidae were collected within the frame of the land workgroup of the Papua New Guinea 2012 expedition “Our Planet Reviewed” (Muséum national d’Histoire naturelle / Institut de Recherche pour le Développement and Pro-Natura International). Pending the identification of all collected material, a preliminary list is given below with the description of a new species, Uloma pascali n. sp., which is thought to be endemic to New Guinea. Some of sampled specimens (from subfamily Stenochiinae) were also used to conduct phylogenetic analyses on a multi marker molecular dataset. The objectives were the following: (i) provide a preliminary phylogenetic framework for the Stenochiinae, thanks to the inclusion of 46 representatives of the two most diverse stenochiine tribes (Cnodalonini and Stenochiini); and (ii) assess and discuss the placement of the sampled New Guinean Stenochiinae representatives. Our analyses support the monophyly of the tribe Stenochiini and the paraphyly of the tribe Cnodalonini. The latter is likely a by-product of the complex taxonomic history of the tribe, which has produced an artificial assemblage of distinctive lineages

Mitochondrial phylogenomics, the origin of swallowtail butterflies, and the impact of the number of clocks in Bayesian molecular dating

International audienceSwallowtail butterflies (Lepidoptera: Papilionidae) have been instrumental in understanding many foundational concepts in biology; despite this, a resolved and robust phylogeny of the group has been a major impediment to elucidating patterns and processes of their ecological and evolutionary history. This study presents a mitogenomic, time-calibrated phylogeny for all swallowtail genera. A shotgun sequencing approach was performed to obtain 32 complete mitogenomes that were added to available butterfly mitogenomes, resulting in a dataset including 142 butterfly taxa (and four outgroups) representing all butterfly families. Phylogenetic analyses were carried out under maximum likelihood (ML) and Bayesian inferences (BIs) with alternative partitioning strategies and the mixture (CAT) model. To test competing hypotheses about the systematics of Papilionidae, such as the enigmatic position of Baronia brevicornis or the status of the tribe Teinopalpini, we estimated the marginal likelihood of alternative topologies and computed Bayes factors. Estimates of divergence times were assessed using a Bayesian relaxed-clock approach calibrated with six fossils while testing for the number of clocks. The results recovered a well-resolved and supported phylogeny confirming that Baroniinae is sister to Parnassiinae + Papilioninae, both recovered as monophyletic. It also laid the foundations for classification at tribe and genus level, suggesting that the tribe Teinopalpini only contains the genus Teinopalpus (Meandrusa being sister to Papilio). The number of molecular clocks in dating analyses had a significant impact on divergence times. A single clock recovered an origin of butterflies in the Cretaceous (98, 66–188 Ma) and also for swallowtails (85, 55–163 Ma), while partitioning the clocks yielded an origin of Papilionoidea in the very Late Cretaceous (71, 64–86 Ma), and all butterfly families originated in the aftermath of the Cretaceous–Paleogene extinction. These results challenge previous studies suggesting that butterflies appeared in the Early Cretaceous, 110 Ma, concurrently with the rise of angiosperms

Diversification patterns and processes of wingless endemic insects in the Mediterranean Basin: historical biogeography of the genus Blaps (Coleoptera: Tenebrionidae)

International audienceAimThe Mediterranean Basin (MB) is a species-rich biogeographical region with many endemic taxa. We analysed the historical patterns of temporal and geographical diversification of Mediterranean Blaps (Tenebrionidae), a diverse group of flightless beetles, estimated their date of origin and colonization of the MB, and tracked temporal changes in diversification rates. LocationMediterranean Basin. MethodsWe reconstructed the phylogenetic relationships of Mediterranean Blaps using four mitochondrial genes and 47 morphological characters. Divergence-time estimates were investigated with a Bayesian relaxed clock approach that was calibrated with both fossil and geological constraints. Biogeographical analyses were performed using the dispersal-extinction-cladogenesis likelihood model associated with a stratified palaeogeographical scenario. Diversification rate analyses allowed the investigation of diversity dynamics through time as well as rate shifts during major Cenozoic climate events. ResultsThe Bayesian relaxed clock analysis suggests that Blaps first appeared in the MB about 28Ma. The most likely scenario is that Mediterranean Blaps originated in the Arabian and north-east African regions and then dispersed progressively westwards and northwards, using temporary land bridges to colonize the northern shores of the MB. Island endemics are more likely to be the products of recent dispersals than of old vicariance events. Birth-death analyses suggest that diversification rates in the Miocene and Pliocene are consistent with a museum model', in which most of the extant diversity is best explained by a steady accumulation of lineages under constant diversification rates. Although major Cenozoic climatic events do not seem to have influenced the diversification of Mediterranean Blaps, a decrease in diversification rates was detected during the Pleistocene. Main conclusionsOur results suggest that Mediterranean Blaps lineages diversified between the Oligocene and the Pliocene, with current distribution patterns mostly accounted for by early vicariance and late dispersal events. Diversification rates were relatively constant through time, but decreased during Pleistocene glaciation cycles. This scenario may be applicable to other Mediterranean terrestrial animal taxa