A study on the interaction among natural selection, mutation and recombination, with Caenorhabditis elegans experimental evolution

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Publications

The role of hermaphrodites in the experimental evolution of increased outcrossing rates in Caenorhabditis elegans

Publication . Carvalho, Sara; Chelo, Ivo M; Goy, Christine; Teotónio, Henrique

Why most organisms reproduce via outcrossing rather than selfing is a central question in evolutionary biology. It has long ago been suggested that outcrossing is favoured when it facilitates adaptation to novel environments. We have previously shown that the experimental evolution of increased outcrossing rates in populations of the male-hermaphrodite nematode Caenorhabditis elegans were correlated with the experimental evolution of increased male fitness. However, it is unknown whether outcrossing led to adaptation, and if so, which fitness components can explain the observed increase in outcrossing rates.

2014-06-02Journal article

Open access

Hermaphrodite life history and the maintenance of partial selfing in experimental populations of Caenorhabditis elegans

Publication . Carvalho, Sara; Phillips, Patrick C; Teotónio, Henrique

Classic population genetics theory predicts that mixed reproductive systems, where self reproduction (selfing) and outcrossing co-exist, should not be as common as they are in nature. One means of reconciling theory with observations is to recognize that sexual conflict between males and hermaphrodites and/or constraints in the allocation of resources towards sex functions in hermaphrodites can balance the fitness components of selfing and outcrossing.

2014-06-02Journal article

Open access

Reproductive assurance drives transitions to self-fertilization in experimental Caenorhabditis elegans

Publication . Theologidis, Ioannis; Chelo, Ivo M; Goy, Christine; Teotónio, Henrique

Evolutionary 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.

2014-11-05Journal article

Open access

Evolution of Outcrossing in Experimental Populations of Caenorhabditis elegans

Publication . 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.

2012-04-23Journal article

Open access

An experimental test on the probability of extinction of new genetic variants

Publication . Chelo, Ivo M.; Nédli, Judit; Gordo, Isabel; Teotónio, Henrique

In 1927, J.B.S. Haldane reasoned that the probability of fixation of new beneficial alleles is twice their fitness effect. This result, later generalized by M. Kimura, has since become the cornerstone of modern population genetics. There is no experimental test of Haldane's insight that new beneficial alleles are lost with high probability. Here we demonstrate that extinction rates decrease with increasing initial numbers of beneficial alleles, as expected, by performing invasion experiments with inbred lines of the nematode Caenorhabditis elegans. We further show that the extinction rates of deleterious alleles are higher than those of beneficial alleles, also as expected. Interestingly, we also find that for these inbred lines, when at intermediate frequencies, the fate of invaders might not result in their ultimate fixation or loss but on their maintenance. Our study confirms the key results from classical population genetics and highlights that the nature of adaptation can be complex.

2013-09-13Journal article

Open access