An evolutionary correlate of genome size change in plethodontid salamanders

Variation in the amount of nuclear DNA, the C-value, does not correlate with differences in morphological complexity. There are two classes of explanations for this observation, which is known as the 'C-value paradox'. The quantity of DNA may serve a 'nucleotypic' function that is positively selected. Alternatively, large genomes may consist of junk DNA, which increases until it negatively affects fitness. Attempts to resolve the C-value paradox focus on the link between genome size and fitness. This link is usually sought in life history traits, particularly developmental rates. I examined the relationship among two life history traits, egg size and embryonic developmental time and genome size, in 15 species of plethodontid salamanders. Surprisingly, there is no correlation between egg size and developmental time, a relationship included in models of life history evolution. However, genome size is positively correlated with embryonic developmental time, a result that is robust with respect to many sources of variation in the data. Without information on the targets of natural selection it is not possible with these data to distinguish between nucleotypic and junk DNA explanations for the C-value paradox.