Search results for " Asexual"
showing 10 items of 16 documents
Karyotype variability and inter-population genomic differences in freshwater ostracods (Crustacea) showing geographical parthenogenesis
2018
Transitions from sexual to asexual reproduction are often associated with polyploidy and increased chromosomal plasticity in asexuals. We investigated chromosomes in the freshwater ostracod species Eucypris virens (Jurine, 1820), where sexual, asexual and mixed populations can be found. Our initial karyotyping of multiple populations from Europe and North Africa, both sexual and asexual, revealed a striking variability in chromosome numbers. This would suggest that chromosomal changes are likely to be accelerated in asexuals because the constraints of meiosis are removed. Hence, we employed comparative genomic hybridization (CGH) within and among sexual and asexual populations to get insigh…
Virus epidemics can lead to a population-wide spread of intragenomic parasites in a previously parasite-free asexual population
2014
Sexual reproduction is problematic to explain due to its costs, most notably the twofold cost of sex. Yet, sex has been suggested to be favourable in the presence of proliferating intragenomic parasites given that sexual recombination provides a mechanism to confine the accumulation of deleterious mutations. Kraaijeveld et al. compared recently the accumulation of transposons in sexually and asexually reproducing lines of the same species, the parasitoid wasp Leptopilina clavipes. They discovered that within asexually reproducing wasps, the number of gypsy-like retrotransposons was increased fourfold, whereas other retrotransposons were not. Interestingly, gypsy-like retrotransposons are cl…
Molecular markers linked to breeding system differences in segregating and natural populations of the cereal aphid Rhopalosiphum padi L.
1999
The aphid Rhopalosiphum padi shows coexistence of sexual and asexual populations, providing an opportunity to study the evolution of breeding system variation in the context of theories on the origin and maintenance of sex. However, assessments of the distribution of sexual and asexual lineages of this aphid are complicated by the difficulties in rapidly characterizing their breeding system. To facilitate this task and to gain insight into the genetic relatedness between sexual and asexual genotypes, molecular markers linked to breeding system differences were recently developed. In this study, we have successfully converted a random amplified polymorphic DNA (RAPD) marker associated with l…
The asexual enchytraeid worm Cognettia sphagnetorum (Oligochaeta) has increased Cu resistance in polluted soil
2001
We studied Cu resistance in the asexual (reproduction through fragmentation) enchytraeid worms (Cognettia sphagnetorum, Oligochaeta) originating from two sites: one uncontaminated, and another contaminated by heavy metals. Adult worms were smaller and population density was lower at the polluted site. However, adults from the contaminated site had better survival in Cu-contaminated soil, but lower survival as juveniles (fragments). As we do not know the genetic basis of Cu resistance of the worms, it may have been reached by acclimatization via induced Cu regulation. Because fragmentation is the only mode of reproduction, all phenotypic properties (including resistance) of a parental genera…
Phylogenetic evidence for hybrid origins of asexual lineages in an aphid species
2003
International audience; Understanding the mode of origin of asexuality is central to ongoing debates concerning the evolution and maintenance of sexual reproduction in eukaryotes. This is because it has profound consequences for patterns of genetic diversity and ecological adaptability of asexual lineages, hence on the outcome of competition with sexual relatives both in short and longer terms. Among the possible routes to asexuality, hybridization is a very common mechanism in animals and plants. Aphids present frequent transitions from their ancestral reproductive mode (cyclical parthenogenesis) to permanent asexuality, but the mode of origin of asexual lineages is generally not known bec…
Settlement dynamics and recruitment responses of Mediterranean gorgonians larvae to different crustose coralline algae species
2020
International audience; Sessile marine species such as Anthozoans act as ecosystem engineers due to their three-dimensional structure. Gorgonians, in particular, can form dense underwater forests that give shelter to other species increasing local biodiversity. In the last decades, several Mediterranean gorgonian populations have been affected by natural and anthropogenic impacts which drastically reduced their size. However, some species showed unexpected resilience, mainly due to the supply of new individuals. To understand the mechanisms underlying recovery processes, studies on the first life history stages (i.e. larval dispersal, settlement and recruitment) are needed. In tropical cora…
Soil fungi invest into asexual sporulation under resource scarcity, but trait spaces of individual isolates are unique
2022
During the last few decades, a plethora of sequencing studies provided insight into fungal community composition under various environmental conditions. Still, the mechanisms of species assembly and fungal spread in soil remain largely unknown. While mycelial growth patterns are studied extensively, the abundant formation of asexual spores is often overlooked, though representing a substantial part of the fungal life cycle relevant for survival and dispersal. Here, we explore asexual sporulation (spore abundance, size and shape) in 32 co-occurring soil fungal isolates under varying resource conditions, to answer the question whether resource limitation triggers or inhibits fungal investment…
Sex in an uncertain world: environmental stochasticity helps restore competitive balance between sexually and asexually reproducing populations
2014
Like many organisms, individuals of the freshwater ostracod species Eucypris virens exhibit either obligate sexual or asexual reproductive modes. Both types of individual routinely co-occur, including in the same temporary freshwater pond (their natural habitat in which they undergo seasonal diapause). Given the well-known two-fold cost of sex, this begs the question of how sexually reproducing individuals are able to coexist with their asexual counterparts in spite of such overwhelming costs. Environmental stochasticity in the form of 'false dawn' inundations (where the first hydration is ephemeral and causes loss of early hatching individuals) may provide an advantage to the sexual subpop…
Polymorphism in Developmental Mode and Its Effect on Population Genetic Structure of a Spionid Polychaete, Pygospio elegans
2012
Population genetic structure of sedentary marine species is expected to be shaped mainly by the dispersal ability of their larvae. Long-lived planktonic larvae can connect populations through migration and gene flow, whereas species with nondispersive benthic or direct-developing larvae are expected to have genetically differentiated populations. Poecilogonous species producing different larval types are ideal when studying the effect of developmental mode on population genetic structure and connectivity. In the spionid polychaete Pygospio elegans, different larval types have been observed between, and sometimes also within, populations. We used microsatellite markers to study population st…
Differential competitive ability between sexes in the dioecious Antennaria dioica (Asteraceae)
2012
† Background and Aims Differences in competitive ability between the sexes of dioecious plants are expected as a result of allocation trade-offs associated with sex-differential reproductive costs. However, the available data on competitive ability in dioecious plants are scarce and contradictory. In this study sexual competition was eval- uated using the dioecious plant Antennaria dioica in a common garden transplantation experiment. † Methods Male and female plants were grown for 3 years either in isolation, or in competition with a plant of the same sex or the opposite sex. Flowering phenology, sexual and asexual reproduction, plant growth, nutrient content and arbuscular mycorrhizal col…