Content area
Full text
ABSTRACT The hermaphroditic nematode Caenorhabditis elegáns has been one of the primary model systems in biology since the 1970s, but only within the last two decades has this nematode also become a useful model for experimental evolution. Here, we outline the goals and major foci of experimental evolution with C. elegáns and related species, such as C. briggsae and C. remanei, by discussing the principles of experimental design, and highlighting the strengths and limitations of Caenorhabditis as model systems. We then review three exemplars of Caenorhabditis experimental evolution studies, underlining representative evolution experiments that have addressed the: (1) maintenance of genetic variation; (2) role of natural selection during transitions from outcrossing to selflng, as well as the maintenance of mixed breeding modes during evolution; and (3) evolution of phenotypic plasticity and its role in adaptation to variable environments, including host-pathogen coevolution. We conclude by suggesting some future directions for which experimental evolution with Caenorhabditis would be particularly informative.
KEYWORDS adaptation; C. briggsae; C. elegans; C. remanei; domestication; experimental design; laboratory selection experiments; self-fertilization; reproduction systems; mutation accumulation; standing genetic variation; WormBook
"With them, many important questions will be accessible to patient observers who do not fear long-term experiments." - Emile Maupas (1900)
OVER a century ago, Emile Maupas introduced the nematode Caenorhabditis elegáns to the scientific community with his report on a failed experiment aimed at testing the hypothesis that continual self-fertilization (selfing) should lead to population extinction (Maupas 1900). This goal was ultimately thwarted, as after nearly 50 generations of selfing, Maupas' C. elegáns culture collapsed due to an errant spike in temperature that led to abnormalities in development and reproduction independently of inbreeding effects. Maupas' experimental evolution study was inspired by an ongoing debate about the long-term sustainability of selfing as a reproductive strategy (Darwin 1876), and provides a particularly telling introduction to experimental evolution: the expected outcome (extinction) was achieved, but for the "wrong" reason, as it was not a result of selfing.
Experimental Evolution (EE) has long been used as the gold standard for testing evolutionary hypotheses about natural selection and genetic drift, estimating theoretical parameters regarding standing genetic variation, such as mutation and recombination rates, and, more recently, as a means for gene discovery. The main organismal models to...