Table 1.

Major hypotheses tested with experimental evolution in Caenorhabditis.

topic	key question or idea	finding	references
coevolution	is there genetic diversity for pathogen resistance?	found for resistance to S. marsecens, B. thuringensis, P. luminscens	[29,47,60]
	does evolution of resistance to pathogens have trade-offs?	an increase in resistance, but reductions in growth and feeding rate	[29,48]
	does coevolution and local adaptation occur between host and pathogen?	populations showed higher resistance to their own pathogens and genetic diversity between populations increased	[49,50]
	red queen hypothesis	outcrossed sex allowed faster adaptation to parasites	[51–53]
population structure and ecosystems	can ecosystems be constructed?	three species interactions and dependencies	[55]
	is dispersal beneficial in varying environments?	dispersal is beneficial under random extinction, can be regulated by a single gene and can be selected for	[33,42,56,57]
effects and accumulation of mutations	how do traits evolve with mutation accumulation (MA)?	fitness, body size, behaviour, oxidizing state and other traits degrade	[59,61–65]
	does fitness recover after MA?	restoring selection, or greatly increasing mutation rate leads to fitness recovery	[43,66]
	what is the rate and spectrum of new mutations?	many mutations identified after 396 generations of MA by genome sequencing	[22,23,67]
	do mutation properties differ among genetic backgrounds, species or environments?	different strains, species and conditions do or do not have differing mutation profiles	[23,68–71]
mating systems	are males evolutionary relics?	males reduce in frequency under the lack of selection, depending on the strain and genetic background	[16,41,72,73]
	does outcrossing sex promote removal of detrimental mutations?	male frequencies increased under higher mutational loads	[41,44]
	does outcrossing sex accelerate adaptation?	male frequencies increased under directional selection	[42,51,52,74]
	does outcrossing sex help retain heterozygosity?	no difference between reproductive modes, balancing selection dominates	[30]
	do inbreeding and outbreeding depression depend on reproductive mode?	inbreeders showed outbreeding depression and vice versa	[75]
	how does sexual selection by sperm competition evolve?	competition led to larger sperm and restored male sexual function	[34,76,77]
life history	does increased lifespan have pleiotropic costs?	fewer offspring for longer lived worms in one study, but not in another	[78,79]
	is individual vigour linked to lifespan?	selection for good condition worms led to longer lifespans	[20]
	how does selection affect reproductive life-history trade-offs?	selection between faster generation times and offspring number changed the trade-off	[18]