Biology subjects

Cornette, R.

Publications and source records attributed to Cornette, R..

12 recordsLinked to original sources

bioRxiv2026

Decoupled wing evolution reveals trait-specific links between morphology, geography, and diversification in Ithomiini butterflies.

Understanding when species diversification and phenotypic evolution are coupled remains a central challenge in macroevolution. Such coupling may depend on the traits considered, phenotypic integration, or the geographic context in which diversification occurs. Here, we investigate these relationships in Ithomiini, a diverse Neotropical butterfly tribe whose diversification is strongly associated with the Andes-Amazonia system. We quantified forewing and hindwing size and shape for 1,618 individuals representing 291 species using geometric morphometrics, and combined these data with phylogenetic comparative methods, diversification-rate estimates, and spatial analyses of species distributions. Evolutionary rate shifts were largely trait- and wing-specific, indicating limited coupling between forewing and hindwing evolution. Across the phylogeny, wing size evolution and extant wing size were not associated with species diversification, nor was hindwing shape evolution. By contrast, forewing shape evolutionary rates showed a positive association with diversification. Spatial analyses revealed that this coupling was geographically concentrated in the Andes, where high diversification rates coincided with elevated forewing size and shape diversity and increased forewing evolutionary rates. Hindwing diversity, by contrast, more closely tracked phylogenetic diversity and showed weaker or opposing relationships with diversification. Our results show that diversification and phenotypic evolution in Ithomiini are neither generally coupled nor fully independent, but linked in trait-specific and geographically structured ways. More broadly, they highlight the need to decompose complex phenotypes and integrate spatial context when testing macroevolutionary coupling.

ecology↗

bioRxiv2022

Armed to the teeth: the underestimated diversity in tooth shape in snakes and its relationship to feeding constraints

Teeth are one of the most studied hard tissues in vertebrates. Their structure, composition and shape are related to dietary specialization in many species. At first glance, snake teeth all look similar; conical, sharp, curved. Yet, snakes, like other vertebrates, have very diverse diets that may have affected their shape. We compared the morphology of the teeth of 63 species that cover both the phylogenetic and dietary diversity of snakes. We predicted that prey properties play a role in shaping snakes teeth along with their feeding behavior. Limblessness combined to the peculiar feeding behavior of snakes impose strong functional constraints on their teeth, especially during arboreal or aquatic feeding. Our results show that prey hardness, foraging substrate and the main feeding constraint are drivers of tooth shape, size, and curvature. We highlight two main morphotypes: long, slender, curved with a thin layer of hard tissue for snakes that need a good grip on their prey and short, stout, less curved teeth in snakes that eat hard or long prey. Our study demonstrates the diversity of tooth morphology in snakes and the need to investigate the underlying functional implications to better understand the evolution of teeth in vertebrates.

evolutionary biology↗

bioRxiv2022

Femora from an exceptionally large population of coeval ornithomimosaurs yield evidence of sexual dimorphism in extinct theropod dinosaurs

Sexual dimorphism is challenging to detect among fossils, due to a lack of statistical representativeness. The Angeac-Charente Lagerstatte (France) represents a remarkable "snapshot" from a Berriasian (Early Cretaceous) ecosystem and offers a unique opportunity to study intraspecific variation among a herd of at least 61 coeval ornithomimosaurs. Herein, we investigated the hindlimb variation across the best-preserved specimens from the herd through 3D Geometric Morphometrics and Gaussian Mixture Modelling. Our results based on complete and fragmented femora evidenced a dimorphism characterized by variations in the shaft curvature and the distal epiphysis width. Since the same features vary between sexes among modern avian dinosaurs, crocodilians, and more distant amniotes, we attributed this bimodal variation to sexual dimorphism based on the extant phylogenetic bracketing approach. Documenting sexual dimorphism in fossil dinosaurs allows a better characterization and accounting of intraspecific variations, which is particularly relevant to address ongoing taxonomical and ecological questions relative to dinosaur evolution.

paleontology↗

bioRxiv2022

The draft genome sequence of Japanese rhinoceros beetle Trypoxylus dichotomus

Beetles are the largest insect order and one of the most successful animal groups in terms of number of species. The Japanese rhinoceros beetle Trypoxylus dichotomus (Coleoptera, Scarabaeidae, Dynastini) is a giant beetle with distinctive exaggerated horns present on the head and prothoracic regions of the male. T. dichotomus has been used as research model in various fields such as evolutionary developmental biology, ecology, ethology, biomimetics, and drug discovery. In this study, de novo assembly of 615 Mb, representing 80% of the genome estimated by flow cytometry, was obtained using the 10x Chromium platform. The scaffold N50 length of the genome assembly was 8.02 Mb, with repetitive elements predicted to comprise 49.5% of the assembly. In total, 23,987 protein-coding genes were predicted in the genome. In addition, de novo assembly of the mitochondrial genome yielded a contig of 20,217 bp. We also analyzed the transcriptome by generating 16 RNA-seq libraries from a variety of tissues of both sexes and developmental stages, which allowed us to identify 13 co-expressed gene modules. The detailed genomic and transcriptomic information of T. dichotomus is the most comprehensive among those reported for any species of Dynastinae. This genomic information will be an excellent resource for further functional and evolutionary analyses, including the evolutionary origin and genetic regulation of beetle horns and the molecular mechanisms underlying sexual dimorphism.

genomics↗

bioRxiv2020

Analysis Of Polycerate Mutants Reveals The Evolutionary Co-Option Of HOXD1 To Determine The Number And Topology Of Horns In Bovidae

In the course of evolution, pecorans (i.e. higher ruminants) developed a remarkable diversity of osseous cranial appendages, collectively referred to as headgear, which likely share the same origin and genetic basis. However, the nature and function of the genetic determinants underlying their number and position remain elusive. Jacob and other rare populations of sheep and goats, are characterized by polyceraty, the presence of more than two horns. Here, we characterize distinct POLYCERATE alleles in each species, both associated with defective HOXD1 function. We show that haploinsufficiency at this locus results in the splitting of horn bud primordia, likely following the abnormal extension of an initial morphogenetic field. These results highlight the key role played by this gene in headgear patterning and illustrate the evolutionary co-option of a gene involved in the early development of bilateria to properly fix the position and number of these distinctive organs of Bovidae.

genomics↗

bioRxiv2020

Cas9-mediated Genome Editing Reveals a Significant Contribution of Calcium Signaling Pathways to Anhydrobiosis in Pv11

Pv11 is an insect cell line established from the midge Polypedilum vanderplanki that exhibits an extreme desiccation tolerance known as anhydrobiosis. Pv11 has also an anhydrobiotic ability which is induced by trehalose treatment. Here we report the successful construction of the genome editing system for Pv11 cells and its application for identifying the signaling pathways in the anhydrobiosis. Using the Cas9-mediated gene knock-in system, we established GCaMP3-stably expressing Pv11 cells to monitor intracellular Ca2+ mobilization. Intriguingly, trehalose treatment evoked a transient increase of cytosolic Ca2+ concentration, and further experiments indicated the contribution of the calmodulin - calcineurin - NFAT pathway to the tolerance for trehalose treatment as well as the desiccation tolerance, while the calmodulin - calmodulin Kinase - CREB pathway conferred only the desiccation tolerance on Pv11 cells. Thus, our results show the critical contribution of the trehalose-induced Ca2+ surge to the anhydrobiosis and the temporal different roles of each signaling pathway.

molecular biology↗

bioRxiv2020

Population genomics of two closely related anhydrobiotic midges reveals differences in adaptation to extreme desiccation

The sleeping chironomid Polypedilum vanderplanki is capable of anhydrobiosis, a striking example of adaptation to extreme desiccation. Tolerance to complete desiccation in this species is associated with the emergence of multiple paralogs of protective genes. One of the gene families highly expressed under anhydrobiosis and involved in this process are protein-L-isoaspartate (D-aspartate) O-methyltransferases (PIMTs). Recently, a closely related anhydrobiotic midge from Malawi, P. pembai, showing the ability to tolerate complete desiccation similar to that of P. vanderplanki, but experiences more frequent desiccation-rehydration cycles due to differences in ecology, was discovered. Here, we sequenced and assembled the genome of P. pembai and performed a population genomics analysis of several populations of P. vanderplanki and a population of P. pembai. We observe positive selection and radical changes in the genetic architecture of the PIMT locus between the two species, including multiple duplication events in the P. pembai lineage. In particular, PIMT-4, the most highly expressed of these PIMTs, is present in six copies in the P. pembai; these copies differ in expression profiles, suggesting possible sub- or neofunctionalization. The nucleotide diversity ({pi}) of the genomic region carrying these new genes is decreased in P. pembai, but not in the orthologous region carrying the ancestral gene in P. vanderplanki, providing evidence for a selective sweep associated with post-duplication adaptation in the former. Overall, our results suggest an extensive recent and likely ongoing, adaptation of the mechanisms of anhydrobiosis.

evolutionary biology↗

bioRxiv2020

Development of a Tet-On inducible expression system for the anhydrobiotic cell line, Pv11

The Pv11 cell line established from an African chironomid, Polypedilum vanderplanki, is the only cell line tolerant to complete desiccation. In Pv11 cells, a constitutive expression system for Pv11 cells was previously exploited and several reporter genes were successfully expressed. Here we report the identification of an effective minimal promoter for Pv11 cells and its application to the Tet-On inducible expression system. First, using a luciferase reporter assay, we showed that a 202 bp deletion fragment derived from the constitutively active 121-promoter functions in Pv11 cells as an appropriate minimal promoter with the Tet-On inducible expression system. The AcGFP1 protein was also successfully expressed in Pv11 cells using the inducible system. In addition to these reporter genes, avian myeloblastosis virus reverse transcriptase subunit (AMV RT), which is one of the most widely commercially available RNA-dependent DNA polymerases, was successfully expressed through the inducible expression system and its catalytic activity was verified. These results demonstrate the establishment of an inducible expression system in cells that can be preserved in the dry state and highlight a possible application to the production of large and complex proteins. HighlightsO_LIA 202 bp-deletion fragment derived from a constitutively active promoter was identified as a minimal promoter in Pv11 cells. C_LIO_LIA Tet-On inducible expression system was developed for Pv11 cells using the minimal promoter. C_LIO_LITypical reporter genes (GFP and luciferase) and an enzyme with complex structure, i.e. a viral reverse transcriptase, were successfully and inducibly expressed in Pv11 cells using the Tet-On system. C_LI

bioengineering↗

bioRxiv2020

Exploring the functional meaning of head shape disparity in aquatic snakes.

Phenotypic diversity, or disparity, can be explained by simple genetic drift or, if functional constraints are strong, by selection for ecologically relevant phenotypes. We here studied phenotypic disparity in head shape in aquatic snakes. We investigated whether conflicting selective pressures related to different functions have driven shape diversity and explore whether similar phenotypes may give rise to the same functional output (i.e. many-to-one mapping of form to function). We focused on the head shape of aquatically foraging snakes as they fulfil several fitness-relevant functions and show a large amount of morphological variability. We used 3D surface scanning and 3D geometric-morphometrics to compare the head shape of 62 species in a phylogenetic context. We first tested whether diet specialization and size are drivers of head shape diversification. Next, we tested for many-to-one mapping by comparing the hydrodynamic efficiency of head shapes characteristic of the main axis of variation in the dataset. We 3D printed these shapes and measured the forces at play during a frontal strike. Our results show that diet and size explain only a small amount of shape variation. Shapes did not functionally converge as more specialized aquatic species evolved a more efficient head shape than others. The shape disparity observed could thus reflect a process of niche specialization under a stabilizing selective regime.

evolutionary biology↗

bioRxiv2019

Limited thermal plasticity and geographic divergence in the ovipositor of Drosophila suzukii

Phenotypic plasticity has been repeatedly suggested to facilitate adaptation to new environmental conditions, as in invasions. Here we investigate this possibility by focusing on the worldwide invasion of Drosophila suzukii: an invasive species that has rapidly colonized all continents over the last decade. This species is characterized by a highly developed ovipositor, allowing females to lay eggs through the skin of ripe fruits. Using a novel approach based on the combined use of SEM and photogrammetry, we quantified the ovipositor size and 3D shape, contrasting invasive and native populations raised at three different developmental temperatures. We found a small but significant effect of temperature and geographic origin on the ovipositor shape, showing the occurrence of both geographic differentiation and plasticity to temperature. The shape reaction norms are in turn strikingly similar among populations, suggesting very little difference in shape plasticity among invasive and native populations, and therefore rejecting the hypothesis of a particular role for plasticity of the ovipositor in the invasion success. Overall, the ovipositor shape seems to be a fairly robust trait, indicative of stabilizing selection. The large performance spectrum rather than the flexibility of the ovipositor would thus contribute to the success of D. suzukii worldwide invasion.

developmental biology↗

bioRxiv2018

Transcriptome analysis of Pv11 cells infers the mechanism of desiccation tolerance and recovery

The larvae of the African midge, Polypedilum vanderplanki, can enter an ametabolic state called anhydrobiosis to conquer fatal desiccation stress. The Pv11 cell line, derived from embryos of the midge, shows desiccation tolerance by pretreatment with trehalose before desiccation; they can resume proliferation after rehydration. To address the underlying molecular mechanisms, we desiccated Pv11 cells after pretreatment with the medium containing trehalose and induced proliferation by rehydration. We collected the cells at each before and after desiccation and rehydration step and performed CAGE-seq of mRNA of those cells. By analysing differentially expressed genes (DEGs) among the results of CAGE-seq, we detected 384 DEGs after trehalose treatment and 14 DEGs after rehydration. Hierarchical clustering of the identified DEGs indicated that rehydration returns their expression pattern to that in the control culture state. DEGs involved in various stress responses, detoxification of harmful chemicals, and regulation of oxidoreduction were upregulated by trehalose treatment. DEGs for rehydration supported that DNA repair is one of the potential mechanisms involves recovery. This study provided initial insight into the molecular mechanisms underlying the extreme desiccation tolerance of Pv11 cells with a potential for proliferation following rehydration.

genomics↗

bioRxiv2017

Towards Water-Free Biobanks: Long-Term Dry-Preservation At Room Temperature Of Desiccation-Sensitive Enzyme Luciferase In Air-Dried Insect Cells

Desiccation-tolerant cultured cells Pv11 derived from the anhydrobiotic Polypedilum vanderplanki embryo endure complete desiccation because of their ametabolic state and resume their metabolism after rehydration. These features led us to develop a novel dry preservation technology for enzymes as it was still unclear whether Pv11 cells preserved an exogenous enzyme in the dry state. This study shows that Pv11 cells protect an exogenous desiccation-sensitive enzyme, luciferase, preserving the enzymatic activity even after dry storage for 372 days at room temperature. A process including pre-incubation with trehalose, dehydration, storage, and rehydration allowed Pv11 (Pvll-Luc) cells stably expressing luciferase to survive desiccation and still emit luminescence caused by luciferase after rehydration. Luminescence produced by luciferase in Pvll-Luc cells after rehydration did not significantly decrease in presence of a translation inhibitor, showing that the activity did not derive from de novo enzyme synthesis following the resumption of cell metabolism. These findings indicate that the surviving Pv11 cells almost completely protect luciferase during desiccation. Lacking of the preincubation step resulted in the loss of luciferase activity after rehydration. We showed that preincubation with trehalose associated to induction of desiccation-tolerant related genes in Pv11 cells allowed effective in vivo preservation of enzymes in the dry state.

biochemistry↗