Bioassay design and length of time in the laboratory affect intercolonial interactions of the Formosan subterranean termite (Isoptera, Rhinotermitidae)

This study examined the effect of diet, experimental design, and length of time in the laboratory on intercolonial agonism among Formosan subterranean termite, Coptotermes formosanus Shiraki, colonies. In pairings of 12 C. formosanus Shiraki colonies collected in an urban forest, there was no significant reduction in survival of termites in 30 out of 59 colony pairs compared to colony controls, but there was <50% survival in 18 colony pairs and <10% survival in six colony pairs. There was no correlation between the level of aggressive behavior and the laboratory diet of the termites. Effect of bioassay design and length of time in the laboratory was evaluated in three colony pairs where tests were first conducted on the day of field collection, then colony pairs were retested every 7 days. Aggressive behavior decreased over time in both bioassays, but it tended to decrease more rapidly in the Petri dish tests. The rapid loss of agonism in groups of termites kept in the laboratory demonstrates that changes in environmental factors affect intercolonial agonism

Genetic analysis of the breeding system of an invasive subterranean termite, Reticulitermes santonensis, in urban and natural habitats.

Reticulitermes santonensis is a subterranean termite that invades urban areas in France and elsewhere where it causes damage to human-built structures. We investigated the breeding system, colony and population genetic structure, and mode of dispersal of two French populations of R. santonensis. Termite workers were sampled from 43 and 31 collection points, respectively, from a natural population in west-central France (in and around the island of Oleron) and an urban population (Paris). Ten to 20 workers per collection point were genotyped at nine variable microsatellite loci to determine colony identity and to infer colony breeding structure. There was a total of 26 colonies, some of which were spatially expansive, extending up to 320 linear metres. Altogether, the analysis of genotype distribution, F-statistics and relatedness coefficients suggested that all colonies were extended families headed by numerous neotenics (nonwinged precocious reproductives) probably descended from pairs of primary (winged) reproductives. Isolation by distance among collection points within two large colonies from both populations suggested spatially separated reproductive centres with restricted movement of workers and neotenics. There was a moderate level of genetic differentiation (F(ST) = 0.10) between the Oleron and Paris populations, and the number of alleles was significantly higher in Oleron than in Paris, as expected if the Paris population went through bottlenecks when it was introduced from western France. We hypothesize that the diverse and flexible breeding systems found in subterranean termites pre-adapt them to invade new or marginal habitats. Considering that R. santonensis may be an introduced population of the North American species R. flavipes, a breeding system consisting primarily of extended family colonies containing many neotenic reproductives may facilitate human-mediated spread and establishment of R. santonensis in urban areas with harsh climates

Invasions biologiques : le rôle des microorganismes symbiotiques

National audienceUne des principales causes de perte de biodiversité à l'échelle planétaire est l'introduction par l'homme, volontaire ou non, d'espèces animales et végétales en dehors de leur aire de répartition naturelle. Les individus introduits peuvent parfois fonder une population qui s'installe durablement dans le nouvel environnement, voire qui l'envahisse. Certains biologistes ont récemment suggéré que les microorganismes symbiotiques vivant en association avec les envahisseurs pourraient jouer un rôle clé dans les invasions biologiques. Le projet Xylobiotic, financé par la Région Centre Val-de-Loire et conduit par des chercheurs affiliés à quatre unités de recherche de cette Région, aborde la question du rôle des symbiotes mutualistes dans le succès invasif de plusieurs insectes xylophages introduits en France, afin d'améliorer les méthodes de lutte contre les insectes invasifs

Disentangling the effects of recombination, selection, and demography on the genetic variation at a major histocompatibility complex class II gene in the alpine chamois.

The major histocompatibility complex (MHC) harbours some of the most polymorphic loci in vertebrate genomes. MHC genes are thought to be subject to some form of balancing selection, most likely pathogen-mediated selection. Hence, MHC genes are excellent candidates for exploring adaptive processes. In this study, we investigated the genetic variation at exon 2 of the DRB class II MHC locus in 191 alpine chamois (Rupicapra rupicapra) from 10 populations in the eastern Alps of Italy. In particular, we were interested in distinguishing and estimating the relative impact of selective and demographic factors, while taking into account the confounding effect of recombination. The extremely high d(n)/d(s) ratio and the presence of trans-species polymorphisms suggest that a strong long-term balancing selection effect has been operating at this locus throughout the evolutionary history of this species. We analysed patterns of genetic variation within and between populations, and the mitochondrial D-loop polymorphism patterns were analysed to provide a baseline indicator of the effects of demographic processes. These analyses showed that (i) the chamois experienced a demographic decline in the last 5000-30 000 years, most likely related to the postglacial elevation in temperature; (ii) this demographic process can explain the results of neutrality tests applied to MHC variation within populations, but cannot justify the much weaker divergence between populations implied by MHC as opposed to mitochondrial DNA; (iii) similar sets of divergent alleles are probably maintained with similar frequencies by balancing selection in different populations, and this mechanism is also operating in small isolated populations, which are strongly affected by drift

Disentangling the effects of recombination, selection and demography on the genetic variation at a major histocompatibility complex class II gene in the alpine chamois

The major histocompatibility complex (MHC) harbours some of the most polymorphic loci in vertebrate genomes. MHC genes are thought to be subject to some form of balancing selection, most likely pathogen-mediated selection. Hence, MHC genes are excellent candidates for exploring adaptive processes. In this study, we investigated the genetic variation at exon 2 of the DRB class II MHC locus in 191 alpine chamois (Rupicapra rupicapra) from 10 populations in the eastern Alps of Italy. In particular, we were interested in distinguishing and estimating the relative impact of selective and demographic factors, while taking into account the confounding effect of recombination. The extremely high dn/ds ratio and the presence of trans-species polymorphisms suggest that a strong long-term balancing selection effect has been operating at this locus throughout the evolutionary history of this species. We analysed patterns of genetic variation within and between populations, and the mitochondrial D-loop polymorphism patterns were analysed to provide a baseline indicator of the effects of demographic processes. These analyses showed that (i) the chamois experienced a demographic decline in the last 5000–30 000 years, most likely related to the postglacial elevation in temperature; (ii) this demographic process can explain the results of neutrality tests applied to MHC variation within populations, but cannot justify the much weaker divergence between populations implied by MHC as opposed to mitochondrial DNA; (iii) similar sets of divergent alleles are probably maintained with similar frequencies by balancing selection in different populations, and this mechanism is also operating in small isolated populations, which are strongly affected by drif

Biosystematics of Reticulitermes termites in Europe: morphological, chemical and molecular data

In Europe the most abundant naturally residing termite is the subterranean genus Reticulitermes (Rhinotermitidae). Six phenotypes of Reticulitermes have been identified on the basis of morphological, chemical (cuticular hydrocarbons and soldier defensive secretions), and molecular (enzymatic alleles and mitochondrial ND1 sequence) features. They are R. santonensis in western France, R. grassei in southwestern France, northwestern and southern Spain and Portugal, R. banyulensis in northeastern Spain, central area of the Iberian Peninsula and southwestern France, R. lucifugus in Italy and southeastern France, R. balkanensis in the Balkans and R. sp. nov., a recently identified urban phenotype resembling R. balkanensis, in northern Italy and southeastern France. R. santonensis is close kin to the American species R. flavipes. R. grassei, R. banyulensis and R. lucifugus belong to the same species complex. R. balkanensis and the new phenotype R. sp. nov. are close to R. santonensis regarding cuticular hydrocarbons, to the lucifugus complex regarding DNA and to R. clypeatus from Israel regarding morphology. The species status of these genotypes has been confirmed by the mechanisms of species isolation. Prevention of hybridization depends on the method of colony formation in each species. Swarming dates, differences in pheromones, and infertility prevent hybridization by sexual alates. Interspecific aggression between workers prevents hybridization by necotenics. Behavioral and molecular studies have provided many data on the genetic structure of nests, which varies according to species and location. All colonies of R. santonensis are open all year. The colonies of R. grassei in southern areas and all colonies of R. banyulensis are closed families with generally a single reproductive couple. The colonies of R. grassei in northern areas and the colonies of R. lucifugus are open in the summer and closed in the winter. Based on the here presented data, the taxonomy and the speciation of the Reticulitermes genus in Europe are discussed