Alain Migeon

Genetic structure of a greenhouse population of the spider mite Tetranychus urticae : spatio-temporal analysis with microsatellite markers

The genetic structure of a greenhouse population of the mite Tetranychus urticae was studied by the analysis of five microsatellite loci. Genetic variation was compared during a crop season between periods of population foundation and rapid population increase and was investigated in two consecutive years. The population displayed significant heterozygote deficiency at all the sampling periods. However, inbreeding tended to decrease with increasing density (FIS coefficient between 0.13 and 0.25). No significant genetic differentiation between samples was found either at a spatial scale within the greenhouse or at a temporal scale between two growing seasons (FST between 0.008 and 0.09). Estimations of the genetic relatedness between pairs of individuals indicated that the distances between pairs of sisters and unrelated mites in the greenhouse were not significantly different, suggesting that mites do not tend to form patches that reside close to the point of birth.

Contrasting effects of Wolbachia on cytoplasmic incompatibility and fecundity in the haplodiploid mite Tetranychus urticae

Recent studies on Wolbachia‐induced incompatibility in haplodiploid insects and mites have revealed a diversity of cytoplasmic incompatibility (CI) patterns among host species. Here, we report intraspecific diversity in CI expression among four strains of the arrhenotokous mite Tetranychus urticae and in T. turkestani. Variability of CI expression within T. urticae ranged from no CI to complete CI, and included either female embryonic mortality or male conversion types of CI. A fecundity cost attributed to the infection with the high‐CI Wolbachia strain was the highest ever recorded for Wolbachia (−80 to −100% decrease). Sequence polymorphism at a 550‐bp‐portion of Wolbachia wsp gene revealed two clusters distant by 21%, one of which included three Wolbachia strains infecting mite populations sampled from the same host‐plant species, but showing distinct CI patterns. These data are discussed in the light of theoretical predictions on the evolutionary pathways followed in this symbiotic interaction.

Microsatellite markers reveal spatial genetic structure of Tetranychus urticae (Acari : Tetranychidae) populations along a latitudinal gradient in Europe

The genetic structure of populations of the two-spotted spider mite Tetranychus urticae was investigated along a south–north European transect spanning from southern France to The Netherlands. Mites were collected on Urtica dioica in 6 sampling zones. Microsatellite variation at 5 loci revealed considerable genetic variation with an average heterozygozity of 0.49. Significant heterozygote deficiency was found in 7 populations out of the 18 samples analyzed and one of them was completely monomorphic. Tetranychus urticae populations show some level of genetic structuring. First, genetic differentiation between localities (FST estimates) was significant for all comparisons. Second, the analysis of molecular variance, AMOVA, indicates that there is an effect, albeit low (9%), of the locality in accounting for allele frequency variance. Geographic distance emerges as a factor responsible for this genetic structure. The results are discussed in relation to the biological features of the species and the known patterns of migration. Related agronomical issues are addressed.

Tomato whole genome transcriptional response to Tetranychus urticae identifies divergence of spider mite-induced responses between tomato and Arabidopsis

The two-spotted spider mite Tetranychus urticae is one of the most significant mite pests in agriculture, feeding on more than 1,100 plant hosts, including model plants Arabidopsis thaliana and tomato, Solanum lycopersicum. Here, we describe timecourse tomato transcriptional responses to spider mite feeding and compare them with Arabidopsis in order to determine conserved and divergent defense responses to this pest. To refine the involvement of jasmonic acid (JA) in mite-induced responses and to improve tomato Gene Ontology annotations, we analyzed transcriptional changes in the tomato JA-signaling mutant defenseless1 (def-1) upon JA treatment and spider mite herbivory. Overlay of differentially expressed genes (DEG) identified in def-1 onto those from the timecourse experiment established that JA controls expression of the majority of genes differentially regulated by herbivory. Comparison of defense responses between tomato and Arabidopsis highlighted 96 orthologous genes (of 2,133 DEG) that were recruited for defense against spider mites in both species. These genes, involved in biosynthesis of JA, phenylpropanoids, flavonoids, and terpenoids, represent the conserved core of induced defenses. The remaining tomato DEG support the establishment of tomato-specific defenses, indicating profound divergence of spider mite-induced responses between tomato and Arabidopsis.

Evidence of co-specificity between Tetranychus evansi and Tetranychus takafujii (Acari: Prostigmata, Tetranychidae): comments on taxonomic and agricultural aspects

ABSTRACT Using a combination of the cytochrome oxidase subunit I gene (COI) and internal transcribed spacer (ITS) sequence information, cross-breeding, and morphological criteria, the taxonomic status of Tetranychus takafujii was reassessed. Described from Japan and very close to Tetranychus evansi, only the male empodium II separated the two species. Six T. evansi samples collected in Brazil, France, Kenya, Spain (including the Canary Islands), Taiwan, and two samples from Japan previously species-identified as T. takafujii, were examined. DNA sequences consistently divide the samples into two groups: group I held the mites from Brazil and France and group II contained the remaining samples of T. evansi together with the two mites collected in Japan. Likewise, cross-breeding experiments detected the same two groups that were reproductively partially incompatible. However, the Japanese samples were completely compatible with the rest of the group II T. evansi samples. The empodium II shape failed to distinguish consistently between the T. evansi and T. takafujii samples, but rather highlighted its variability, questioning its utility for separating these taxa. Congruent results support the co-specificity of the two taxa. It is concluded that T. takafuji is a junior synonym of T. evansi.

Intergenomic interactions affect female reproduction: evidence from introgression and inbreeding depression in a haplodiploid mite

Nuclear and cytoplasmic genomes can coevolve antagonistically or harmoniously to affect fitness. One commonly used test for nuclear–cytoplasmic coadaptation relies on the breakup of coadapted gene complexes by introgression, potentially resulting in an increased frequency of nuclear alleles in deleterious interaction with an alien cytoplasm. We investigated the phenotypic effect of such genes on female reproduction in outbred and inbred introgressed lines of the haplodiploid mite Tetranychus urticae. Introgression changed female lifetime fecundity and increased male production, in ways suggesting a control of fecundity by nuclear genes. Conversely introgression reduced the fertilization rate, possibly due to sperm–egg incompatibility or maternal effects. The intensity of inbreeding depression expressed as a reduction in fecundity was more severe in introgressed females than in nonintrogressed ones, giving evidence for recessive interacting alleles contributing to residual nucleo–cytoplasmic incompatibility. Overall, our data suggest recessive negative interactions between nuclear and cytoplasmic genes. This study is the first report of a contribution of nuclear polymorphism within a population to deleterious interactions with an alien cytoplasmic genome.

Tracking paternal genes with DALP markers in a pseudoarrhenotokous reproductive system: biparental transmission but haplodiploid-like inheritance in the mite Neoseiulus californicus.

The complexity of some sexual reproductive systems in arthropods still leaves both their genetic and epigenetic determinism and their evolutionary significance poorly understood. Pseudoarrhenotoky is characterized by obligate fertilization and differential inactivation and/or elimination of paternal chromosomes in embryos that develop into males. Here, we investigate how the paternal genome is transmitted in a pseudoarrhenotokous mite, Neoseiulus californicus, using codominant genetic markers detected by DALP (direct amplification of length polymorphism). Transmission patterns of parental alleles through one and two generations are reported at four or five loci corresponding to four linkage groups. Our data provide strong evidence for selective elimination of the paternal genome among male tissues. Sperm contained maternal genes exclusively, whereas some male somatic tissues retained most if not all paternal chromosomes. No recombination between parental genomes prior to paternal genome elimination from the embryonic germ line was observed. These data allow a reinterpretation of previous phenotypic and cytogenetic observations in these mites, from which we suggest some relevant mechanistic and evolutionary implications. In addition, this is the first published study using polymorphic codominant loci detected by the recently developed DALP method.

Isolation, characterization and PCR multiplexing of microsatellite loci for a mite crop pest, Tetranychus urticae (Acari: Tetranychidae)

BackgroundTetranychus urticae is a highly polyphagous species with a cosmopolitan distribution that has the status of pest in more than 100 economically significant crops all over the world. Despite a number of previous efforts to isolate genetic markers, only a reduced set of microsatellite loci has been published. Taking advantage of the whole genome sequence of T. urticae that recently became available; we isolated and characterized a new set of microsatellite loci and tested the level of polymorphism across populations originating from a wide geographical area.ResultsA total of 42 microsatellite sequences widespread in the T. urticae genome were identified, the exact position in the genome recorded, and PCR amplification of microsatellite loci tested with primers defined here. Fourteen loci showed unambiguous genotype patterns and were further characterized. Three multiplex polymerase chain reaction sets were optimized in order to genotype a total of 24 polymorphic loci, including 10 previously published Tetranychus-specific loci. The microsatellite kits successfully amplified 686 individuals from 60 field populations for which we assessed the level of genetic diversity. The number of alleles per locus ranged from 3 to 16 and the expected heterozygosity values ranged from 0.12 to 0.81. Most of the loci displayed a significant excess of homozygous and did not model the Hardy–Weinberg equilibrium. This can be explained by the arrhenotokous mode of reproduction of T. urticae.ConclusionsThese primers represent a valuable resource for robust studies on the genetic structure, dispersal and population biology of T. urticae, that can be used in managing this destructive agricultural pest.

Host plant use by two distinct lineages of the tomato red spider mite, Tetranychus evansi , differing in their distribution range

Abstract The tomato red spider mite, Tetranychus evansi, is an emerging pest of solanaceous crops. Two distinct genetic lineages (I and II) have been identified, lineage I having a much wider geographic distribution than lineage II. This has been attributed to differences in cold hardiness that make lineage I better adapted to colonize the coldest parts of the invaded area. However, other factors such as the ability to exploit different hosts may also be involved. In this work, we compared the performance of the Nice (lineage I) and Perpignan (lineage II) strains of T. evansi on two frequent host plants for this species: black nightshade, Solanum nigrum, and cultivated tomato, S. lycopersicum. In general, Nice strain mites performed better (higher fecundity, lower offspring mortality, bigger egg size and lower percentage of males) than Perpignan strain mites when both: (1) they were reared and tested on the same host plant (S. lycopersicum or S. nigrum); and (2) when shifted from S. nigrum to S. lycopersicum and vice versa. Digestive proteases showed also higher expression in Nice strain mites than in Perpignan strain mites, independently of their plant host, potentially reflecting a more efficient proteolytic digestion of plant proteins. However, no differences in detoxification enzyme (P450, esterases and glutathione S-transferases) activities were found when the two strains were compared. In conclusion, our results demonstrate that Nice strain mites exhibited life history traits leading to higher fitness on two different hosts, which may be related with the higher invasive potential and outbreak risks of mites from lineage I.

The Jean Gutierrez spider mite collection

Abstract The family Tetranychidae (spider mites) currently comprises 1,275 species and represents one of the most important agricultural pest families among the Acari with approximately one hundred pest species, ten of which considered major pests. The dataset presented in this document includes all the identified spider mites composing the Jean Gutierrez Collection hosted at the CBGP (Montferrier-sur-Lez, France), gathered from 1963 to 1999 during his career at the Institut de Recherche pour le Développement (IRD). It consists of 5,262 specimens corresponding to 1,564 occurrences (combination species/host plant/date/location) of 175 species. Most specimens were collected in Madagascar and other islands of the Western Indian Ocean, New Caledonia and other islands of the South Pacific and Papuasia. The dataset constitutes today the most important one available on Tetranychidae worldwide.