The mechanical evolution from biting-chewing to piercing-sucking in insects

Informations projet

MECH-EVO-INSECT

N° de convention de subvention: 754290

DOI

10.3030/754290

Projet clôturé

Date de signature de la CE 28 Septembre 2017

Date de début 1 Février 2018

Date de fin 30 Septembre 2023

Financé au titre de

• EXCELLENT SCIENCE - European Research Council (ERC)

Coût total

€ 1 499 891,00

Contribution de l’UE

€ 1 499 891,00

Coordonné par

RHEINISCHE FRIEDRICH-WILHELMS-UNIVERSITAT BONN
Germany

Periodic Reporting for period 4 - MECH-EVO-INSECT (The mechanical evolution from biting-chewing to piercing-sucking in insects)

Période du rapport: 2022-03-01 au 2023-09-30

Résumé du contexte et des objectifs généraux du projet

Insects evolved an astonishing diversity of different mouthpart and head capsule types optimally adapted to ingest their particular food recourses. Among early winged insects, mayflies (Ephemeroptera), dragonflies (Odonata), and Polyneoptera (including grasshoppers, cockroaches and allies) show biting-chewing mouthparts, while bark and true lice (Psocodea) possess "intermediate" mouthparts commonly known as a 'mortar-pestle type'. Thrips (Thysanoptera) and true bugs (Hemiptera) show piercing-sucking mouthparts, together they are known as Condylognatha, the most speciose insect group after Holometabola. How the transition from one mouthpart type to the other could have happened is unclear. The ultimate goal of this project was to explain and quantify to mechanical transition from chewing-biting to piercing-sucking mouthparts in "basal" winged insects taking into account recent as well as fossil species.
The project faced considerable delays due to COVID19. The project began in 2018 so that we had to cope with all COVID19 measures taken by governments around the world. I estimate that, in summary, this lead to a delay of at least one year concerning all project steps and we had to deviate from our original plans by analysing other taxa and/or using other methodological approaches.
Therefore, the core question of this research project - the evolutionary and mechanical pathway from biting-chewing to pericing-sucking mouthparts - has not been answered, yet, mainly due to the COVID related delays. Nevertheless, we have already landmarked 95% of the relevant specimens so that I estimate that we are able to publish papers about the core research questions within 24 months after this report and also after that time. At the time of this report (November 2023) we were able to publish our research in 17 peer-reviewed journals. We have published ten papers regarding different aspects of head shape morphology and evolution in arthropods with a particular focus on insects. Two papers were published regarding methodological developments, while we published two other papers about the head and gill biomechanics of fishes. These two papers are indeed follow-up studies stemming from our core research agenda about insect head and mouthpart biomechanics. Finally, we participated in another three papers about different aspects of insect biomechanics and phylogeny.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

The project achieved to scan ~3000 insect heads and other organ structures using high resolution µCT carried out at three different synchrotron accelerators in Germany and Switzerland. We visited all major collections in Europe to obtain a phylogenetically informed sampling of taxa which, at the same time, was chosen to maximize head shape disparity across non-holometabolan insects. In parallel, we (i) developed an experimental setup to measure bite forces in insects, (ii) developed an R package to analyse bite force curves, (iii) developed workflows for semiautomatic µCT data curation and initial data analysis. The methodological aspects of this project are all published except for one data paper about the µCT scans which is currently under internal review. We were already able to publish several analyses using the µCT data and our group participated in a number of follow-up analyses which are based on our µCT activities. At the time of this report (November 2023) we were able to publish our research in 17 peer-reviewed journals.
However, the project also faced considerable delays due to COVID19. The project began in 2018 so that we had to cope with all COVID19 measures taken by governments around the world. I estimate that, in summary, this lead to a delay of at least one year concerning all project steps and we had to deviate from our original plans by analysing other taxa and/or using other methodological approaches.
Essentially, the core question of this research project - the evolutionary pathway from biting-chewing to pericing-sucking mouthparts has not been answered, yet. This will be done after the financial closing of the project due to the COVID related delays. We have already landmarked 95% of the relevant specimens so that I estimate that we are able to publish papers about the core research questions within 24 months after this report and also after that time.
We have published ten papers regarding different aspects of head shape morphology and evolution in arthropods with a particular focus on insects. Two papers were published regarding the methodological developments mentioned above, while we published two other papers about the head and gill biomechanics of fishes which indeed are follow-up studies stemming from our core research agenda about insect head and mouthpart biomechanics. Finally, we participated in another three papers about different aspects of insect biomechanics and phylogeny.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

This project is unique in its scope. The PI does not know of any other project with such a large database of insect head capsule scans. This database is needed because insects show a diversity which is several orders of magnitude higher than in all other animal groups. If we want to learn about the drivers of insect head shape variation and how mouthpart transitions in insects could have happened, we need data from several thousand species. Therefore data collection needed more time compared to other projects which is the reason why a five year financial support was needed. Now data collection is completed and the first core papers regarding methodology, data curation, and scientific results are published. At the time of this report (November 2023) we were able to publish our research in 17 peer-reviewed journals. For example, one study dealt with the head morphology of several groups of Polyneoptera in order to learn more about which ecological factors affect head shape variation in these taxa. We also developed a setup to measure bite forces in insects and other small organisms and programmed an R package to analyse the data from this setup. Our bespoke bite force sensor setup allows taking bite force measurements in a wide array of scenarios ranging from field studies to lab based setups. The setup allows workgroups with a tight budget in developing countries to advance the field and analyse data. We already got several email requests from those countries. Another study dealt with a detailed analysis of bite forces in insects with an unprecedented taxon sampling of 654 species (more than all vertebrate studies combined) including basic ecological, and morphometric data, as well as the largest phylogeny of insects to date. A third study will cover the head shape variation and biomechanics of all Polyneoptea and Psocodea, i.e. all non-holometabolous biting-chewing lineages. This study will be complemented by another study with a focus on the non-holometabolan piercing-sucking lineages. A fourth study, which is almost finished, will focus on a detailed investigation of the lever mechanics of the mandibles in biting chewing insects while a fifth study will investigate how mandible and head shape variation are influenced by wing configuration.

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