My research focuses on the evolution of communication modalities and habitats in crickets, and the causal relationships that may exist between these two variables of the biology of species. They are based on observations of non-model species in the natural environment, and use a phylogenetic framework to test evolutionary hypotheses about the origin and changes in species attributes. They involve a significant amount of taxonomy and inventory, since targeted studies in the natural environment lead to the sampling of an often unknown part of the diversity of the clade. Evolutionary hypotheses are tested at the scale of Ensifera, crickets (Grylloidea), or particular cricket clades, depending on the questions.
For the next two years, I will concentrate on the following projects :
1. Molecular phylogeny of crickets :
We built the first molecular phylogeny of crickets (Chintauan-Marquier et al. 2016) using 205 taxa and seven molecular markers : This analysis allowed for the first time to test the few more or less formal morphological studies proposed up now for crickets (Gorochov 1986, Desutter 1987), and to revise the upper taxonomy of crickets. The results supported two superfamilies and six families, ie Gryllotalpidae and Myrmecophilidae (ant-crickets) within Gryllotalpoidea, and Mogoplistidae, Trigonidiidae, Phalangopsidae and Gryllidae within Grylloidea.
This hypothesis will be improved using several complementary sets of data :
- Morphological characters will be examined, especially wing venation and general morphology, in order to incorporate fossil taxa in the reconstruction matrix.
- New extant taxa will be incorporated in the data matrix, in particular to test the relationships and definitions of the subfamilies within Phalangopsidae and Gryllidae.
- New molecular markers will be added to the molecular matrix, i.e. original markers (Chintauan-Marquier, pers. comm.), and mitochondrial genomes (studies in progress 2017-2018). Transcriptomic and genomic developments are currently performed (Post-doc LabEx, Ioana Chintauan-Marquier) to define ultraconserved DNA regions.
Phylogeny of crickets based on 205 terminals and seven DNA markers in Bayesian inference, and derived classification of crickets. The current position of each terminal species in the subfamilies used by the OSF is indicated on the right of the tree. From Chintauan-Marquier et al. 2016. Cladistics 32, Figure 7.
2. Insect wing evolution (collaboration with André nel) :
X-ray tomography has been used for the first time to study insect wings, especially their very bases, in order to identify the basivenal sclerites and the emergence points of the veins (Desutter-Grandcolas et al. 2017) : these studies allowed to test the various patterns of venation proposed at present and in the past for the clade, and to check vein homologies. For Ensifera, our results show that the stridulatory files present in crickets, mole crickets, katydids and prophalangopsids are not homologous : in crickets and katydids, the stridulatory file is carried by the first anal vein, whereas it is found on different branches of the posterior cubital in molecrickets and prophalangopsids. The resonant surfaces of the elytra also differ according to the clade. These results support a hypothesis of multiple convergence for acoustic evolution in Ensifera.
I am currently checking the venation patterns of all the terminal taxa used in the phylogeny of Chintauan-Marquier et al. (2016), to check for putative apomorphies of cricket families / subfamilies. This will also help to reconsider the many fossil species described as "crickets", and possibly incorporate them in the next future in a global phylogenetic analysis of the Gryllidea, to date the divergence events of the clade.
Similar studies have been performed on Odonata (Jacquelin et al., submit.) and Phasmatodea (Chintauan-Marquier et al., submit.).
3. Evolution of habitats in Phalangopsidae crickets, with a focus on the South West Indian Ocean and the Neotropical Region.
The Neotropical Region is particularly rich and diverse for crickets. I began my PhD work there, analyzing in parallel the phylogenetic relationships of taxa and their ecological specialization throughout a succession of forests (Desutter-Grandcolas 1992). This work has resulted in many taxonomic papers, with the descriptions of several dozen of taxa. I resumed this work via collaborations (Desutter-Grandcolas et al., 2014, 2017, Souza-Dias et al., 2014, 2015), but also focusing on the French Guiana (among other opportunities, the "Planète revisitée" Mitaraka Expedition in 2015) and the French West Indies, where an inventory of Orthoptera is underway in collaboration with Sylvain Hugel (Desutter-Grandcolas & Hugel 2016, in prep.). These data are presently analysed in a phylogenetic frame to test the diversification patterns of phalangopsid crickets in the Neotropical Region, and the emergence of convergent ecological syndromes.
In parallel, the Phalangopsidae distributed in the Indian Ocean have been sampled and revised (Desutter-Grandcolas 2015, Desutter-Grandcolas & Felix 2012, Desutter-Grandcolas & Jaiswara 2012), in collaboration with Sylvain Hugel and Ranjana Jaiswara. The taxonomic revision of the Phalangopsidae from the Seychelles, extensively sampled by Sylvain Hugel, and the Comoros are in progress. The analysis of their distributions will be done in 2017 (collaboration with Ben Warren).
4. Origin and diversity of Nemobiinae crickets in New Caledonia (Trigonidiidae)
The Neocaledonian fauna is highly endemic and dysharmonic (Grandcolas et al., 2008, Nattier et al., 2012), and it hosts a very rich assemblage of original crickets (Grylloidea). 40 genera, 180 species were recorded in 2016 (Desutter-Grandcolas et al., 2016), including 19 genera and more than 90% endemic species in the Territory.
The Nemobiinae (Trigonidiidae) is the most diverse clade in this assemblage, with 11 known genera, nine of which endemic to the Grande Terre. Several genera are strictly straminicolous, while others have more original ecologies, such as Thetella, the “marine” cricket, or Paniella, which lives in mosses on tree trunks. Most species present original morphological characteristics, as Orintia bicornata and its two long parallel horns on the face (Desutter-Grandcolas et al., 2016).
The phylogeny of Chintauan-Marquier et al. (2016), which includes only a part of the Neocalcedonian Nemobiinae, supports two successive colonizations of the island, and at least one episode of subsequent diversification. A more complete phylogeny is currently under reconstruction, to date the successive episodes of colonization of New Caledonia by the Nemobiinae, determine their origin, and analyze the changes of ecological specializations that have occurred during their evolution on the territory.