T Backeljau

Publications (8)28.07 Total impact

• Article: Cryptic diversity and gene flow among three African agricultural pests: Ceratitis rosa, Ceratitis fasciventris and Ceratitis anonae (Diptera, Tephritidae).

  M Virgilio, H Delatte, S Quilici, T Backeljau, M De Meyer
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  ABSTRACT: The 'Ceratitis FAR complex' is a species complex of African fruit flies (Diptera, Tephritidae) including the major agricultural pest Ceratitis rosa and the morphologically similar Ceratitis fasciventris and Ceratitis anonae. To resolve their intra- and interspecific genetic relationships and to estimate gene flow within this complex, we surveyed allelic variation at 16 microsatellite loci in 27 African populations of the three morphospecies. Interpopulation genetic distances and individual Bayesian assignments distinguished five genotypic clusters: two involving C. rosa (R1, R2; that may occur in sympatry), two involving C. fasciventris (F1, F2; with parapatric distributions) and one involving C. anonae (A). Intra- and interspecific patterns of genetic differentiation were not hierarchically structured and genetic differentiation between conspecific clusters (F1-F2 and R1-R2) was higher or comparable with differentiation between heterospecific clusters (e.g. F1-A or R2-A). In some cases, gene flow estimates among morphospecies or among heterospecific genotypic clusters were significantly different from zero, showing the lack of reproductive isolation. Genetic differentiation between genotypic clusters was partly supported by morphological differences observed a posteriori in male secondary sexual characters. These results suggest important revisions to current models of ecological niche requirements and invasion risk of the major agricultural pest C. rosa and provide a basis for a taxonomic re-interpretation of the FAR complex.
  Molecular Ecology 03/2013; · 5.52 Impact Factor
• Article: A quantitative comparison of frugivorous tephritids (Diptera: Tephritidae) in tropical forests and rural areas of the Democratic Republic of Congo.

  M Virgilio, T Backeljau, R Emeleme, J L Juakali, M De Meyer
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  ABSTRACT: Most of the current knowledge about African tephritids originates from studies performed in agricultural areas, while information about their distribution in pristine or moderately disturbed environments is extremely scarce. This study aims at (i) describing levels of spatial variability of frugivorous tephritids in tropical forests and small rural villages of the Congo River basin and (ii) verifying if human-mediated activities, such as small-scale agriculture and trade, can affect their distribution patterns. Four locations were sampled along a 250 km stretch of the Congo River. At each location, pristine and disturbed habitats (i.e. tropical forests and small rural villages, respectively) were sampled, with three replicate sites in each combination of habitat and location. Sampling with modified McPhail traps baited with four different attractants yielded 819 tephritid specimens of 29 species from seven genera (Bactrocera, Carpophthoromyia, Ceratitis, Dacus, Celidodacus, Perilampsis, Trirhithrum). The three most abundant species sampled (Dacus bivittatus, D. punctatifrons, Bactrocera invadens) showed significant variations in abundance across locations and sites and accounted for 98.29% of the overall dissimilarity between habitats. Assemblages differed among locations and sites while they showed significant differences between pristine and disturbed habitats in two out of the four locations. This study shows that frugivorous tephritids in central Congo have remarkably patchy distributions with differences among locations and sites representing the main source of variability. Our data show that, in rural villages of central Democratic Republic of Congo, human activities, such as small-scale agriculture and local commerce, are not always sufficient to promote differences between the tephritid assemblages of villages and those of the surrounding tropical forests.
  Bulletin of entomological research 05/2011; 101(5):591-7. · 1.58 Impact Factor
• Article: Macrogeographic population structuring in the cosmopolitan agricultural pest Bactrocera cucurbitae (Diptera: Tephritidae).

  M Virgilio, H Delatte, T Backeljau, M De Meyer
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  ABSTRACT: The macrogeographic population structure of the agricultural pest Bactrocera cucurbitae (Diptera: Tephritidae) was investigated in order to identify the geographic origin of the species and reconstruct its range expansion. Individuals of B. cucurbitae were collected from 25 worldwide-distributed localities (n = 570) and genotyped at 13 microsatellite loci. The Bayesian clustering reveals that B. cucurbitae can be subdivided into five main groups corresponding to populations from (i) the African continent, (ii) La Réunion, (iii) Central Asia, (iv) East Asia and (v) Hawaii. The proportions of inter-regional assignments and the higher values of genetic diversity in populations from Pakistan, India and Bangladesh suggest that B. cucurbitae originated in Central Asia and expanded its range to East Asia and Hawaii on one hand and to Africa and the islands of the Indian Ocean on the other. A number of outliers (10-19 specimens according to different clustering algorithms) show high levels of admixture (Q > 0.70) with populations from different regions and reveal complex patterns of inter-regional gene flow. Anthropogenic transport is the most plausible promoter of this large-scale dispersal. The introduction of individuals from geographically distant sources did not have a relevant role in the most recent African invasions, which originated from the expansion of local populations. These results could provide a useful background to better evaluate invasion risks and establish priorities for the management of this cosmopolitan agricultural pest.
  Molecular Ecology 07/2010; 19(13):2713-24. · 5.52 Impact Factor
• Article: Phylogeography of the common ragworm Hediste diversicolor (Polychaeta: Nereididae) reveals cryptic diversity and multiple colonization events across its distribution.

  M Virgilio, C Fauvelot, F Costantini, M Abbiati, T Backeljau
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  ABSTRACT: Previous studies on the common ragworm Hediste diversicolor (Polychaeta: Nereididae) revealed a marked genetic fragmentation across its distribution and the occurrence of sibling taxa in the Baltic Sea. These results suggested that the phylogeographic patterns of H. diversicolor could reflect interactions between cryptic differentiation and multiple colonization events. This study aims to describe the large-scale genetic structuring of H. diversicolor and to trace the phylogeographic origins of the genetic types described in the Baltic Sea. Samples of H. diversicolor (2 < n < 28) were collected at 16 locations across the NE Atlantic coasts of Europe and Morocco and in the Mediterranean, Black and Caspian Seas and sequenced at two mitochondrial gene fragments (COI and cytb, 345 and 290 bp, respectively). Bayesian analyses revealed deep phylogeographic splits yielding three main clades corresponding to populations (i) from the NE Atlantic coasts (from Germany to Morocco) and from part of the Western Mediterranean, (ii) from the Mediterranean Sea, and (iii) from the Black and Caspian Seas. These clades are further divided in well-supported subclades including populations from different regions of NE Atlantic and Mediterranean (i.e. Portugal/Morocco, Western Mediterranean, Adriatic Sea). The Baltic Sea comprises three sympatric lineages sharing a common evolutionary history with populations from NE Atlantic, Western Mediterranean and Black/Caspian Seas, respectively. Hence, the current patterns of genetic structuring of H. diversicolor appear as the result of allopatric isolation, multiple colonization events and possible adaptation to local environmental conditions.
  Molecular Ecology 03/2009; 18(9):1980-94. · 5.52 Impact Factor
• Article: African Dacus (Diptera: Tephritidae: Molecular data and host plant associations do not corroborate morphology based classifications

  M. Virgilio, M. De Meyer, I.M. White, T. Backeljau
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  ABSTRACT: The genus Dacus Fabricius includes economically important pest fruit flies distributed in the Afrotropical and Indo-Australian regions. Two recent revisions based on morphological characters proposed new and partially discordant classifications synonymizing/revalidating several subgeneric names and forming species groups. Regardless these efforts, the phylogenetic relationships among Dacus species remained largely unresolved mainly because of the difficulties in assigning homologous character states. Therefore we investigated the phylogeny of African Dacus by sequencing 71 representatives of 32 species at two mitochondrial (COI, 16S) and one nuclear (period) gene fragments. Phylogenetic relationships were inferred through Bayesian and Maximum Parsimony methods and hypotheses about the monophyly of Dacus subgenera were tested by Shimodaira–Hasegawa tests. The congruence tests and the analyses of the single gene fragments revealed that the nuclear gene supports similar conclusions as the two mitochondrial genes. Levels of intra- and inter-specific differentiation of Dacus species were highly variable and, in some cases, largely overlapping. The analyses of the concatenated dataset resolved two major bootstrap-supported groups as well as a number of well-supported clades and subclades that often comprised representatives of different subgenera. Additionally, specimens of Dacus humeralis from Eastern and Western African localities formed separate clades, suggesting cryptic differentiation within this taxon. The comparisons between the molecular phylogeny and the morphological classification revealed a number of discrepancies and, in the vast majority of cases, the molecular data were not compatible with the monophyly of the currently recognised subgenera. Conversely, the molecular data showed that Apocynaceae feeders are a monophyletic sister group of species feeding on both Cucurbitaceae and Passifloraceae (these latter being also monophyletic). These results show a clear association between the molecular phylogeny of African Dacus and the evolution of host plant choice and provide a basis towards a more congruent taxonomy of this genus.
  Molecular Phylogenetics and Evolution 02/2009; · 3.61 Impact Factor
• Source

  Available from: Massimiliano Virgilio

  Article: Molecular evaluation of nominal species in the Ceratitis fasciventris, C. anonae, C. rosa complex (Diptera: Tephritidae).

  M Virgilio, T Backeljau, N Barr, M De Meyer
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  ABSTRACT: Ceratitis fasciventris, C. anonae and C. rosa form a complex of economically important fruit fly pests infesting a variety of crops in African countries. Hitherto only adult males of these species can be distinguished easily by morphological characters. Other stages cannot, and for some taxa the taxonomic interpretation and species boundaries remain unclear. In order to clarify phylogenetic relationships and taxonomic status of these species, sequences of mitochondrial (16S, COI, ND6) and nuclear markers (period, ITS1) were analysed in specimens of the three morphospecies throughout the distribution of the complex. Maximum likelihood trees did not recover monophyletic groups corresponding to the morphospecies. Conversely, ND6 and COI divided West African C. fasciventris specimens in two consistent and bootstrap supported clades, involving specimens from Benin and from Mali/Ivory Coast, while the nuclear gene fragments per and ITS1 recovered a well-supported clade corresponding to C. fasciventris from Kenya/Uganda. Hence, the phylogenetic relationships and taxonomic interpretation of the complex appear more intricate than previously hypothesised. The current molecular data do not allow to identify C. fasciventris, C. anonae and C. rosa as distinct phylogenetic species but rather suggest that the morphospecies C. fasciventris is itself a complex of cryptic taxa.
  Molecular Phylogenetics and Evolution 08/2008; 48(1):270-80. · 3.61 Impact Factor
• Article: Mitochondrial DNA and allozyme patterns of Hediste diversicolor (Polychaeta: Nereididae): The importance of small scale genetic structuring

  M. Virgilio, T. Backeljau, M. Abbiati
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  ABSTRACT: A hierarchical sampling design was used to describe scales of genetic structuring of Hediste diversicolor (Polychaeta: Nereididae) along the North Adriatic coast of Italy and investigate possible relationships with patterns of heavy metal contamination. Analyses of a fragment of the mitochondrial cytochrome oxidase 1 (COI) gene yielded 10 different haplotypes showing that the genetic structuring at this locus is more complex than previously hypothesised. Both COI and allozyme data suggest that most of the total genetic variance is due to genetic differentiation among (1) sites within estuaries and (2) individuals within sites. These results suggest that within estuaries H. diversicolor does not form contiguous panmictic populations, but rather is structured in fragmented populations isolated at small spatial scales. Sediment concentrations of Zn, Cu and Ni in sediments were above effects range-low (ERL) guideline values at several of the investigated sites. Yet, we did not observe any relationship between heavy metal concentrations of metals and either the estimators of genetic diversity in H. diversicolor or the distribution of Aldolase genotypes expected from previous toxicity tests. These results suggest that, within North Adriatic estuaries, populations of H. diversicolor are structured by chaotic genetic patchiness and that stochastic processes (e.g. genetic drift or sweepstake recruitment) have a major role in promoting small scale genetic structuring.
  Marine Ecology Progress Series 01/2006; 326:157-165. · 2.71 Impact Factor
• Article: Ammonicera rota in Norway (Mollusca, Gastropoda: Omalogyridae). --Fauna Norvegica Ser A5, 6-8.

  T. backeljau, M. de Meyer, L. Janssens, R. Proesmans, W. Vader
  Fauna Norvegica Ser. A 5. 01/1984; 5:5-8.