The fate of a suppressed X-linked meiotic driver: experimental evolution in Drosophila simulans

International audienceSex-ratio (SR) meiotic drivers are X-linked selfish genetic elements that promote their own transmission by preventing the production of Y-bearing sperm, which usually lowers male fertility. The spread of SR drivers in populations is expected to trigger the evolution of unlinked drive suppressors, a theoretically predicted co-evolution that has been observed in nature. Once completely suppressed, the drivers are expected either to decline if they still affect the fitness of their carriers, or to evolve randomly and possibly get fixed if the suppressors eliminate their deleterious effects. To explore this issue, we used the Paris sex-ratio system of Drosophila simulans in which drive results from the joint effect of two elements on the X chromosome: a segmental duplication and a deficient allele of the HP1D2 gene. We set up six experimental populations starting with 2/3 of X chromosomes carrying both elements (XSR) in a fully suppressing background. We let them evolve independently during almost a hundred generations under strong sexual competition, a condition known to cause the rapid disappearance of unsuppressed Paris XSR in previous experimental populations. In our study, the fate of XSR chromosomes varied among populations, from extinction to their maintenance at a frequency close to the starting one. While the reasons for these variable outcomes are still to be explored, our results show that complete suppression can prevent the demise of an otherwise deleterious XSR chromosome, turning a genetic conflict into cooperation between unlinked loci. Observations in natural populations suggest a contrasting fate of the two elements: disappearance of the duplication and maintenance of deficient HP1D2 alleles

Evolution of assortative mating following selective introgression of pigmentation genes between two Drosophila species

International audienc

CEBA: A Data Lake for Data Sharing and Environmental Monitoring

International audienceThis article presents a platform for environmental data named “Environmental Cloud for the Benefit of Agriculture” (CEBA). The CEBA should fill the gap of a regional institutional platform to share, search, store and visualize heterogeneous scientific data related to the environment and agricultural researches. One of the main features of this tool is its ease of use and the accessibility of all types of data. To answer the question of data description, a scientific consensus has been established around the qualification of data with at least the information “when” (time), “where” (geographical coordinates) and “what” (metadata). The development of an on-premise solution using the data lake concept to provide a cloud service for end-users with institutional authentication and for open data access has been completed. Compared to other platforms, CEBA fully supports the management of geographic coordinates at every stage of data management. A comprehensive JavaScript Objet Notation (JSON) architecture has been designed, among other things, to facilitate multi-stage data enrichment. Data from the wireless network are queried and accessed in near real-time, using a distributed JSON-based search engine

Algt_CG33181

Alignment for the CG33181 marke

DNA barcode discovers two cryptic species and two geographical radiations in the invasive drosophilid Zaprionus indianus

Comparing introduced to ancestral populations within a phylogeographical context is crucial in any study aiming to understand the ecological genetics of an invasive species. Zaprionus indianus is a cosmopolitan drosophilid that has recently succeeded to expand its geographical range upon three continents (Africa, Asia and the Americas). We studied the distribution of mitochondrial DNA (mtDNA) haplotypes for two genes (CO-I and CO-II) among 23 geographical populations. mtDNA revealed the presence of two well-supported phylogenetic lineages (phylads), with bootstrap value of 100%. Phylad I included three African populations, reinforcing the African-origin hypothesis of the species. Within phylad II, a distinct phylogeographical pattern was discovered: Atlantic populations (from the Americas and Madeira) were closer to the ancestral African populations than to Eastern ones (from Madagascar, Middle East and India). This means that during its passage from endemism to cosmopolitanism, Z. indianus exhibited two independent radiations, the older (the Eastern) to the East, and the younger (the Atlantic) to the West. Discriminant function analysis using 13 morphometrical characters was also able to discriminate between the two molecular phylads (93.34 +/- 1.67%), although detailed morphological analysis of male genitalia using scanning electron microscopy showed no significant differences. Finally, crossing experiments revealed the presence of reproductive barrier between populations from the two phylads, and further between populations within phylad I. Hence, a bona species status was assigned to two new, cryptic species: Zaprionus africanus and Zaprionus gabonicus, and both were encompassed along with Z. indianus and Zaprionus megalorchis into the indianus complex. The ecology of these two species reveals that they are forest dwellers, which explains their restricted endemic distribution, in contrast to their relative cosmopolitan Z. indianus, known to be a human-commensal. Our results reconfirm the great utility of mtDNA at both inter- and intraspecific analyses within the frame of an integrated taxonomical project

Algt_vermilion

Alignment for the vermilion marke

The Evolutionary History of Drosophila simulans Y Chromosomes Reveals Molecular Signatures of Resistance to Sex Ratio Meiotic Drive

The recent evolutionary history of the Y chromosome in Drosophila simulans, a worldwide species of Afrotropical origin, is closely linked to that of X-linked meiotic drivers (Paris system). The spread of the Paris drivers in natural populations has elicited the selection of drive-resistant Y chromosomes. To infer the evolutionary history of the Y chromosome in relation to the Paris drive, we sequenced 21 iso-Y lines, each carrying a Y chromosome from a different location. Among them, 13 lines carry a Y chromosome that is able to counteract the effect of the drivers. Despite their very different geographical origins, all sensitive Y's are highly similar, suggesting that they share a recent common ancestor. The resistant Y chromosomes are more divergent and segregate in four distinct clusters. The phylogeny of the Y chromosome confirms that the resistant lineage predates the emergence of Paris drive. The ancestry of the resistant lineage is further supported by the examination of Y-linked sequences in the sister species of D. simulans, Drosophila sechellia and Drosophila mauritiana. We also characterized the variation in repeat content among Y chromosomes and identified multiple simple satellites associated with resistance. Altogether, the molecular polymorphism allows us to infer the demographic and evolutionary history of the Y chromosome and provides new insights on the genetic basis of resistance

Organization of the sex-ratio Meiotic Drive Region in Drosophila simulans

Sex-ratio meiotic drive is the preferential transmission of the X chromosome by XY males, which occurs in several Drosophila species and results in female-biased progeny. Although the trait has long been known to exist, its molecular basis remains completely unknown. Here we report a fine-mapping experiment designed to characterize the major drive locus on a sex-ratio X chromosome of Drosophila simulans originating from the Seychelles (X(SR6)). This primary locus was found to contain two interacting elements at least, both of which are required for drive expression. One of them was genetically tracked to a tandem duplication containing six annotated genes (Trf2, CG32712, CG12125, CG1440, CG12123, org-1), and the other to a candidate region located ∼110 kb away and spanning seven annotated genes. RT–PCR showed that all but two of these genes were expressed in the testis of both sex-ratio and standard males. In situ hybridization to polytene chromosomes revealed a complete association of the duplication with the sex-ratio trait in random samples of X chromosomes from Madagascar and Reunion

Algt_Trf2

Alignment for the Trf2 marke