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Browsing EG - Artigos by Subject "Caenorhabditis elegans"
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- Evolution of Outcrossing in Experimental Populations of Caenorhabditis elegansPublication . Teotonio, Henrique; Carvalho, Sara; Manoel, Diogo; Roque, Miguel; Chelo, Ivo M.Caenorhabditis elegans can reproduce exclusively by self-fertilization. Yet, males can be maintained in laboratory populations, a phenomenon that continues to puzzle biologists. In this study we evaluated the role of males in facilitating adaptation to novel environments. For this, we contrasted the evolution of a fitness component exclusive to outcrossing in experimental populations of different mating systems. We introgressed a modifier of outcrossing into a hybrid population derived from several wild isolates to transform the wild-type androdioecious mating system into a dioecious mating system. By genotyping 375 single-nucleotide polymorphisms we show that the two populations had similar standing genetic diversity available for adaptation, despite the occurrence of selection during their derivation. We then performed replicated experimental evolution under the two mating systems from starting conditions of either high or low levels of diversity, under defined environmental conditions of discrete non-overlapping generations, constant density at high population sizes (N = 10(4)), no obvious spatial structure and abundant food resources. During 100 generations measurements of sex ratios and male competitive performance showed: 1) adaptation to the novel environment; 2) directional selection on male frequency under androdioecy; 3) optimal outcrossing rates of 0.5 under androdioecy; 4) the existence of initial inbreeding depression; and finally 5) that the strength of directional selection on male competitive performance does not depend on male frequencies. Taken together, these results suggest that androdioecious males are maintained at intermediate frequencies because outcrossing is adaptive.
- Genetic variation for outcrossing among Caenorhabditis elegans isolatesPublication . Teotónio, H; Manoel, D; Phillips, PCThe evolution of breeding systems results from the existence of genetic variation and selective forces favoring different outcrossing rates. In this study we determine the extent of genetic variation for characters directly related to outcrossing, such as male frequency, male mating ability, and male reproductive success, in several wild isolates of the nematode Caenorhabditis elegans. This species is characterized by an androdioecious breeding system in which males occur with hermaphrodites that can either self-fertilize or outcross with males. We find genetic variation for all characters measured, but also find that environmental variation is a large fraction of the total phenotypic variance. We further determine the existence of substantial genetic variation for population competitive performance in several laboratory environments. However, these measures are uncorrelated with outcrossing characters. The data presented here contribute to an understanding of male maintenance in natural populations through their role in outcrossing.
- Reproductive assurance drives transitions to self-fertilization in experimental Caenorhabditis elegansPublication . Theologidis, Ioannis; Chelo, Ivo M; Goy, Christine; Teotónio, HenriqueEvolutionary transitions from outcrossing between individuals to selfing are partly responsible for the great diversity of animal and plant reproduction systems. The hypothesis of 'reproductive assurance' suggests that transitions to selfing occur because selfers that are able to reproduce on their own ensure the persistence of populations in environments where mates or pollination agents are unavailable. Here we test this hypothesis by performing experimental evolution in Caenorhabditis elegans.
- Selection against males in Caenorhabditis elegans under two mutational treatmentsPublication . Manoel, D; Carvalho, S; Phillips, PC; Teotónio, HWithin populations with mixed mating systems, selfing is expected to be favoured over outcrossing unless a countervailing process such as severe inbreeding depression is present. In this study, we consider the relationship between the expression of deleterious alleles and the maintenance of outcrossing in the nematode species, Caenorhabditis elegans. This species is characterized by an androdioecious breeding system composed of males at low frequency and self-fertilizing hermaphrodites that can only outcross via males. Here, we find that experimentally increasing the mutational load in four different isogenic wild isolates using 10 generations of Ethylmethane sulphonate (EMS) and UV irradiation mutagenesis significantly diminishes the cost of males. Males are maintained at higher frequencies in mutagenized versus non-mutagenized populations. Nevertheless, males still tend to be driven to low frequencies within isolates that are known to be prone to lose males. Further, we determine the viability effects of a single round of mutagen exposure and find that, for EMS, outcrossing overcomes the almost completely recessive and nearly lethal effects generated. We briefly interpret our results in light of current evolutionary theory of outcrossing rates.