Thierry Backeljau emeritus occasional assignment

Research Thierry Backeljau

Research team

Expertise

My research focusses on taxonomy, phylogeny and population genetics of animals, and in particular of molluscs. Yet, other taxa, such as flatworms (Platyhelminthes), ring worms (Annelida) and millipedes (Diplopoda) are equally dealt with. The geographic areas of my research include Belgium and Europe, Macaronesia (Azores, Canary Islands, Madeira and Cape Verde Islands), Thailand, Vietnam, Nepal, Cuba and Benin. My research is based on a combination of morphological and molecular techniques. My interest goes particularly to the problem of speciation in general and more specifically to that in hermaphrodites. In addition, I hane a strong interest in the practical aspects of taxonomy (e.g. zoological nomenclature) and evolutionary thinking. As such I defend the essential societal relevance of taxonomy and I'm active with respect to the “evolution vs creationism” problem. I regularly give seminars and publish papers in this latter domain. Next to all this, I'm also very interested in the problem of introduced and invasive animal species, with a particular focus on land snails. In this context, I'm editor for the “EASIN – European Alien Species Information Network” program and I lead a species identification team that, upon request, identifies specimens and organismal fragments (see: A barcoding facility for organisms and tissues of policy concern http://bopco.myspecies.info/). Linked to my function at the Royal Belgian Institute of Natural Sciences, my research is strongly connected to natural history collections.

The role of microbial symbionts in host plant use and spectrum in oligophagous cucurbit feeding fruit flies (Tephritidae). 01/11/2020 - 31/10/2024

Abstract

Herbivorous insects are among the most species-rich groups of animals. Although it is not clear how this large diversity arose, one major factor is thought to be the evolutionary interaction between plants and insects. The wide variety of toxins in plants and of specialized detoxifying mechanisms in insects resulted in co-evolution and insect radiations. Nevertheless, different groups of specialized insects are sometimes observed in novel host plants. This might result in a series of host-plant shifts which might eventually result in speciation. The underlying mechanisms are largely unknown but it has been suggested that microbes could play a major role (the microbial facilitation hypothesis). There is increasing evidence that multicellular organisms are intimately associated with microbes, which can have a big impact on their phenotype. This project aims to investigate the microbial facilitation hypothesis by focusing on specialized frugivorous tephritid flies feeding on Cucurbitaceae plants that were recently observed on unconventional host plants. In a first phase, we will assess whether different cucurbit feeding fruit flies have similar microbiota and metabolic responses to cucurbits. Second, we will explore how the flies own metabolic machinery and their microbiota respond to novel host plants. In the last experiment, we will investigate how disrupting their microbiota affects insect fitness.

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  • Research Project

The role of microbial symbionts in host plant use and spectrum in oligophagous cucurbit feeding fruit flies (Tephritidae). 01/11/2019 - 31/10/2020

Abstract

Herbivorous insects are the most diverse group of animals. Although it is not clear how this large diversity arose, one major factor is thought to be the co-evolution between plants and insects . The wide variety of defensive toxins in plants and presence of specialized detoxifying mechanisms in insects resulted in the formation of several species. Nevertheless, different groups of specialized insects are sometimes observed in novel host plants. So we get a chronology of diet range expansion followed by specialization on different plant species. The underlying mechanisms are largely unknown but it has been suggested that microbes could play a role in this process (the microbial facilitation hypothesis). Recently, it has become clear that multicellular organisms are intimately associated with microbes that live inside/on their bodies and can have a big impact on the animal. This project aims to address these questions by focusing on specialized frugivorous flies feeding on Cucurbitaceae plants that were recently observed on atypical host plants (Solanaceae). In a first phase, we will assess whether different cucurbit feeding fruit flies have similar microbiota and metabolic responses to cucurbits. Second, we will explore how the flies own metabolic machinery and their microbiota respond to novel host plants. In the last experiment, we will investigate how impairing their microbiota affects the capacity of the flies to attack plants.

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Poneroid Ants of Ecuador (Formicidae, Agroecomyrmicinae, Amblyoponinae, Ponerinae, Proceratiinae, Paraponerinae). 01/01/2015 - 31/12/2016

Abstract

Our general objective is to set up an information structure about the Poneroid ants existing in Ecuador. To achieve our objective we will combine the Ecuadorian and Belgian competences to investigate the specific status of as many Ecuadorian Poneroid species as possible.

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Belgian network for DNA barcoding. 01/01/2011 - 31/12/2015

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This is a fundamental research project financed by the Research Foundation - Flanders (FWO). The project was subsidized after selection by the FWO-expert panel.

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FWO-Visiting Postdoctoral Fellowship (Heike KAPPES, Germany) 01/05/2008 - 30/04/2009

Abstract

The primary project airns at relating neutral genetic divergence to quantitative genetic divergence within a metapopulation framework caused by habitat fragmentation. The model organisms for this study are wolf spiders (Lycosidae: Pardosa). Although these animals show several interesting features for this kind of work, the picture they may provide on the etfrts of habitat fraginentation wifl be biased towards organisros that are characterised by (1) relatively high dispersal capabilities (running, ballooning), (2) obligate outcrossing, (3) differential sex ratios (affecting, for example, effèctive population sizes), and (4) possible resource limitations due to variable prey abundance. The present proposal for a visiting postdoctoral fellowship therefore aims at expanding the scope and picture of the primary project by focusing on a number of terrestrial gastropods. Slugs and snails can indeed be regarded as 'complementary' to wolf spiders because on the one hand they are ground-dwelling orgarnisms that belong to the same macroscopic size category as wolf spiders, while on the other hand (1) they have more limited dispersal capacities, (2) they are hermaphrodites that may be not obligatory outcrossers, (3) they have no differential sex ratios, and (4) they are probably much less limited by food supplies. Consequently, the research conducted during the visiting postdoctoral fellowship will strengthen the primary project because the comparison of spatial structuring in 'neutral' vs. quantitative genetic variation in wolfspiders and terrestrial gastropods will provide a more general picture of the effects of habitat fragmentation by contrasting a wider array of interfering, ecologically relevant factors, It should be emphasised that hitherto very few studies have addressed the effects of habitat fragmentation in terrestrial gastropods, so that the fellowship is expected to provide much needed basic data on this issue. Hence the comparative work on wolf spiders and terrestrial gastropods is expected to lead to novel insights in the effects of habitat fragmentation in abundant, speciose and ecologically important taxa, that unfortunately still all too often are neglected in landscape management and conservation biology.

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Determinants of the rate and degree of phenotypic evolution: Podarcis sicula as model system. 01/10/2006 - 30/09/2007

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Island populations as a study model for fast evolution. 01/01/2006 - 31/12/2009

Abstract

From the very start (e.g. Darwin 1845, Wallace 1859), the faunas of island groups have played a special role in the growth of our understanding of evolutionary changes and speciation - and they continue to do so (e.g. Losos et al. 1997, 2004). Islands in archipelagos constitute repeated, discrete and relatively simple entities and therefore function as 'natura/laboratories' that can be used to test general theories (Whittaker 1998). The (often prominent) differences in phenotype (morphology, behaviour, ecology, life history) among island populations or between island and mainland populations are almost invariably attributed to genetic divergence, but it is often unclear which evolutionary processes (founder effect, genetic drift, natural selection, introgression, ...) induce these differences (Barton 1989, Clarke & Grant 1996). The alternative explanation, that the differences arise from phenotypic plasticity, is often not considered (Losos et al. 2000). In this project, we intend to take advantage of an exceptional opportunity to unravel the causes of fenotypic divergence among (island) populations.

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Sexual conflicts and sexual selection in a hermaphroditic slug: The effects of body size on sex allocation and sperm competition. 01/01/2006 - 31/12/2006

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Sexual selection in hermaphroditic animals: an example of the land snail Succinea putris (Mollusca, Pulmonata, Gastropoda). 01/05/2005 - 30/04/2009

Abstract

This project uses the land snail Succinea putris to test several recent hypotheses on sexual selection and sperm-trading in hermaphroditic animals: 1) individuals assess the quality of their partner even during copulation, 2) individuals change the physiology of their partner to enhance their fertilization chances, 3) individuals allocate more to male structures at higher population densities and 4) reciprocal sperm-transfer not necessarily implements reciprocal fertilization.

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Effects of environmental stress on the genetic structure of natural populations of intertidal invertebrates. 01/10/2004 - 16/08/2007

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    Pyrethroid resistance in malaria vectors: KDR genvariation and detection. 01/10/2004 - 30/09/2006

    Abstract

    Malaria vector control is primarly based on the use of bed nets impregnated with pyrethroid insecticides. The appearance of insecticide resistance in a mosquito population can nullify the positive effect of the vector control. Appropriate monitoring of resistance to insecticides is an integral component of planning and evaluation of insecticide uses in malaria control programmes. The usual means of detecting insecticide resistance is a bioassay where a relative large number of insects has to be exposed, for a defined period of time, to an insecticide-impregnated paper. However, these bioassays are difficult to implement in field conditions. The main problems are the collection of an appropriate number of mosquitoes and the fact that a bioassay can be biased by fluctuations in temperature and age. Molecular detection systems for insecticide resistance can be usefull if the molecular resistance mechanism is known. Pyrethroids and DDT block the nerve-impuls conduction by preventing the para-type sodium channel from returning to their closed-gated configuration after an action potential. An important resistance mechanism, known as knockdown resistance or kdr, is due to a substitution in the S6 segment of domain II of the para-type sodium channel. Point mutations in the para-type sodium channel gene have been linked to kdr in several insects, including the African malaria vector An.gambiae. For An.gambiae, diagnostic PCR test have been developed for the detection of the kdr mutation. For this vector, the frequency of the kdr allele in a population was strongly correlated with the reduced mortality observed in a bioassay. The aim of this thesis is to develop diagnostic tests to detect the knockdown resistance in field populations of the African (An.arabiensis and An.funestus) and Southeast Asian (An.sundaicus, An.minimus, An.dirus, An.vagus and An.sinensis) malaria vectors. The diagnostic tests will be used to determine the kdr frequency in these vectors. Later, the developed tests will be used by the Malaria Control Programmes of Africa, Laos, Cambodia and Vietnam.

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    Pyrethroid resistance in malaria vectors: KDR gene variation and detection. 01/10/2002 - 30/09/2004

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    Population genetics of European periwinkles (Mollusca, Gastropoda: Littorinidae). 01/05/2002 - 30/04/2004

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    Phylogeography of hermaphroditc terrestrial snails in Europe (Mollusca, Gastropoda). 01/05/2002 - 30/04/2004

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    Life history responses to time constraints and ecological constraints during the larval period in the damselfly Lestes viridis. 01/01/2002 - 31/12/2003

    Abstract

    When environments within the range of a species vary, it is unlikely that any single phenotype will confer high fitness in all situations. As a result most genotypes may express life history traits differently across environments. Moreover genotypes may also differ in reaction norms. The aim is to study life history responses to a combination of time constraints and ecological constraints imposed on larvae of Lestes viridis by using both the optimality and genetic approach.

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    Genetic differentiation in uniparental terrestrial slugs (Stylommatophora) 01/01/2002 - 31/12/2003

    Abstract

    In this project, I will investigate the taxonomy of two land gastropod species complexes, Carinarion spp. and Arion intermedius and study the evolutionary significance of the interaction between self- and cross-fertilization in the colonizing capacity, the phylogenetic and phylogeographic relationships among populations and genetic strains, the genetic differentiation and the genetical/morphological diversity in both complexes.

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    Systematics, phylogeography and population genetics of introduced and autochtonous populations of the hermaphroditic land slug Arion subfuscus (Mollusca: Gastropoda: Pulmonata). 01/01/2001 - 31/12/2002

    Abstract

    The hermaphroditic land slug Arion subfuscus is a complex of several taxa, some of which are serious pest species. This project aims at delimiting the systematic status of, and assessing the phylogenetic relationships among, these entities using molecular and morphometric techniques. This species has also been introduced by men into Central-Asia, North-America and Venezuela. These introductions are well documented and offer opportunities to study fundamental evolutionary processes such as speciation and adaptive radiation.

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      Ecological and genetical determinants of phally-polymorfism in land gastropods 01/05/2000 - 30/04/2002

      Abstract

      Hermaphroditic animals are able to rperoduce by outcrossing as well as uniparentally. The evolutionary meaning of several reproductive methods is far from clear although the reproductive mode has a strong influence on how genetic variation is created, maintained and structured. In this project we investigate the evolutionary meaning of differrent reproductive methods in a pulmonate, hermaphroditic land gastropod.

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        Life history responses to time constraints and ecological constraints during the larval period in the damselfly Lestes viridis. 01/01/2000 - 31/12/2001

        Abstract

        When environments within the range of a species vary, it is unlikely that any single phenotype will confer high fitness in all situations. As a result most genotypes may express life history traits differently across environments. Moreover genotypes may also differ in reaction norms. The aim is to study life history responses to a combination of time constraints and ecological constraints imposed on larvae of Lestes viridis by using both the optimality and genetic approach.

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          • Research Project

          Genetic differentiation in uniparental terrestrial slugs (Stylommatophora) 01/01/2000 - 31/12/2001

          Abstract

          In this project, I will investigate the taxonomy of two land gastropod species complexes, Carinarion spp. and Arion intermedius and study the evolutionary significance of the interaction between self- and cross-fertilization in the colonizing capacity, the phylogenetic and phylogeographic relationships among populations and genetic strains, the genetic differentiation and the genetical/morphological diversity in both complexes.

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            The genetical and environmental determination of phally polymorphism in hermaphroditic land gastropods (Stylommatophora). 01/10/1999 - 30/09/2000

            Abstract

            The evolution and maintenance of sexual polymorphisms is well-studied in plants but studies on animals are scarce. In this project, I investigate the evolution and maintenance of a polymorphism in the male genitalia (phally polymorphism) in hermaphroditic land snails using genetic markers (allozymes, random amplified polymorphic DNA, DNA-sequencing) and behavioural experiments.

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              Genetic differentiation in uniparental terrestrial slugs (Stylommatophora). 01/10/1999 - 31/12/1999

              Abstract

              In this project, I will investigate the taxonomy of two land gastropod species complexes, Carinarion spp. and Arion intermedius and study the evolutionary significance of the interaction between self- and cross-fertilization in the colonizing capacity, the phylogenetic and phylogeographic relationships among populations and genetic strains, the genetic differentiation and the genetical/morphological diversity in both complexes.

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                Phenotypic plasticity in development of the damselfly Lestes viridis in a heterogeneous environment. 01/01/1999 - 31/12/1999

                Abstract

                In environments that widely vary on a spacial and temporal scale, it is unlikely that any single phenotype will confer high fitness in all situations. In such case, phenotypic plasticity can provide increased environmental tolerance and is thus one solution to the problem of adaptation to heterogeneous environments. The aim of the study is to investigate phenotypic plasticity in development of Lestes viridis in both permanent and temporary ponds.

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                  01/10/1998 - 30/09/2001

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                    The influence of plant-genotype on the interactions between grasses and insect herbivores. 01/05/1998 - 30/04/1999

                    Abstract

                    In this project the impact of genetic variation on the interactions between grasses and their insect herbivores is assessed. Therefore common garden experiments are carried out under controlled conditions in climatic rooms. Differences in resistance and/or tolerance between different host plant clones are recorded. The plant tissues are analysed to establish the resistance/tolerance mechanisms.

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