Search results for "Sexual Reproduction"
showing 10 items of 95 documents
Nuclear rDNA instability in in vitro-generated plants is amplified after sexual reproduction with conspecific wild individuals
2016
Using micropropagation through tissue culture has become the most used approach worldwide for mass production for the conservation of endangered species. However, the screening of somaclonal variations generated using in vitro culture is usually restricted to the first generation of micropropagated plants, when they have not yet been released in the field. Accordingly, the fate of genetically modified regenerants after sexual reproduction is usually not assessed and changes in the genetic structures of species are unknown. In this work, we assess the cytogenetic stability of two rDNA gene families in the offspring of experimental crosses between accessions generated after in vitro culture a…
Life-cycle switching and coexistence of species with no niche differentiation.
2011
The increasing evidence of coexistence of cryptic species with no recognized niche differentiation has called attention to mechanisms reducing competition that are not based on niche-differentiation. Only sex-based mechanisms have been shown to create the negative feedback needed for stable coexistence of competitors with completely overlapping niches. Here we show that density-dependent sexual and diapause investment can mediate coexistence of facultative sexual species having identical niches. We modelled the dynamics of two competing cyclical parthenogens with species-specific density-dependent sexual and diapause investment and either equal or different competitive abilities. We show th…
Sperm depletion, male mating behaviour and reproductive ‘time-out' in Gammarus pulex (Crustacea, Amphipoda).
2009
6 pages; International audience; In Gammarus pulex, male–male competition is generally intense because the operational sex ratio (OSR) is strongly biased towards males; however, studies have shown possible fluctuation in this intrasexual competition, which could be caused by sperm depletion, a phenomenon recently found in gammarids. Sperm depletion may also affect male mating behaviour. We therefore tested the influence of sperm depletion on the OSR in G. pulex. Two sets of experiments were conducted: first, to find out the number of sperm in the testis before and after mating events (sperm depletion), and second, to test the implications of sperm depletion for the mating behaviour of male …
Linking present environment and the segregation of reproductive modes (geographical parthenogenesis) in Eucypris virens (Crustacea: Ostracoda)
2013
Aim Geographical parthenogenesis – in which parthenogenetic populations are more widely distributed than sexually reproducing populations – is observed in many plant and animal species. Many hypotheses have been proposed to account for this biogeographical pattern, and these often invoke historical processes such as the influence of glaciation. However, there are relatively few empirical studies of the contemporary factors associated with geographical parthenogenesis. The aim of this study was to understand its causes by linking contemporary environmental gradients with reproductive modes in the freshwater ostracod Eucypris virens. Location Europe and North Africa. Methods We sampled popula…
Modes, mechanisms and evidence of bet hedging in rotifer diapause traits
2016
In this contribution, we review our knowledge on bet-hedging strategies associated with rotifer diapause. First, we describe the ecological scenario under which bet hedging is likely to have evolved in three diapause-related traits in monogonont rotifer populations: (1) the timing of sex (because diapausing eggs are produced via sexual reproduction), (2) the sexual reproduction ratio (i.e. the fraction of sexually reproducing females) and (3) the timing of diapausing egg hatching. Then, we describe how to discriminate among bet-hedging modes and discuss which modes and mechanisms better fit the variability observed in these traits in rotifers. Finally, we evaluate the strength of the empiri…
Population and reproductive dynamics of the polychaete Pygospio elegans in a boreal estuary complex
2016
Pygospio elegans is an opportunistic, wide-spread spionid polychaete that reproduces asexually via fragmentation and can produce benthic and pelagic larvae, hence combining different developmental modes in one species. We documented the density, size distribution, and reproductive activity of P. elegans at four sites in the Danish Isefjord-Roskilde Fjord estuary complex, where all modes of reproduction were reported. We compared population dynamics of this species to environmental parameters such as salinity, temperature, and sediment characteristics (grain size, sorting, porosity, water content, organic content, C/N). We observed that new cohorts—resulting either from sexual or asexual rep…
The Reproductive Strategy as an Important Trait for the Distribution of Lower-Trunk Epiphytic Lichens in Old-Growth vs. Non-Old Growth Forests
2021
(1) Research Highlights: The work studied the beta diversity patterns of epiphytic lichens as a function of their reproductive strategies in old-growth and non-old growth forests from the Mediterranean area. (2) Background and Objectives: The reproductive strategies of lichens can drive the dispersal and distribution of species assemblages in forest ecosystems. To further investigate this issue, we analyzed data on epiphytic lichen diversity collected from old-growth and non-old growth forest sites (36 plots) located in Cilento National Park (South Italy). Our working hypothesis was that the dispersal abilities due to the different reproductive strategies drove species beta diversity depend…
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…
Review paper: Seasonal variation as a determinant of population structure in rotifers reproducing by cyclical parthenogenesis
1998
Monogonont rotifers live in habitats that display extensively variation in both biotic and abiotic components. Much of this variation is seasonal and therefore predictable for a given pond or lake. In 1972, King proposed one physiological and two genetic models presenting alternative modes of adaptation to this temporal variation. Our purpose in the present paper is to review and evaluate how our knowledge of the seasonal structure of rotifer populations has changed in the past 25 years. Seasonal changes in clone frequencies have been reported from three studies of natural populations using electrophoretic analysis of isozymes. In one of these studies there was evidence for substantial temp…
Pythium segnitiumsp. nov., isolated from the Canary Islands â its taxonomy, ITS region of rDNA, and comparison with related species
2002
Pythium segnitium (CI-44) was isolated from some soil samples taken in the Canary Islands (Spain). This new species is a slow-growing fungus and is perfectly adapted to terrestrial habitat. It belongs to the group of Pythium that have smooth-walled oogonia, mostly hypogynous antheridia, and plerotic oospores. The fungus lacks sporangia, zoospores, and hyphal bodies are rarely formed. Thus the asexual reproduction, which is so common for fungi and especially for the aquatic ones, is completely lacking in this case. However the fungus reproduces sexually by the formation of oogonia, antheridia and oospores plentifully. The taxonomic description of this fungus, the nucleotide sequence of the i…