Ma. Coutellec-vreto et al., Inbreeding and fitness in the freshwater snail Lymnaea peregra: An evaluation over two generations of self-fertilization, EVOLUTION, 52(6), 1998, pp. 1635-1647
Inbreeding depression was estimated from an outbreeding population of the f
reshwater snail Lymnaea peregra, on the basis of two successive generations
of enforced selfing and outcrossing, and 70 maternal lineages. Outcrossing
was analyzed under two treatments, groups of two and five individuals. The
fitness parameters measured included fecundity, growth, and survival. In t
he first generation, we contrasted three treatments (selfers vs, paired out
crossers and group outcrossers). Very similar results were obtained between
the two outcrossing treatments, A strong self-fertilization depression (wh
ich includes parental fecundity and progeny fitness) was detected in the se
lfing treatment (about 90%). In the second generation, there was again mark
ed evidence for self-fertilization depression, with the highest contributio
ns coming from parental fecundity and progeny hatching rate. Our results su
ggest that the decreased parental fecundity is a consequence of the mating
system in the previous generation, although the role of partial self-incomp
atibility and the copulation behavior could not be ruled out. Hatching rate
and early survival data are suggestive of purging of lethal mutations. Sig
nificant variation in fitness among selfing lineages was found for most fit
ness traits. Our experimental design also allowed to test for interactions
among fitness loci. Only one trait of the nine studied behaved as expected
under synergistic interactions. However we cannot rule out some purging dur
ing the experiment, which could have biased results towards linearity. Inbr
eeding depression was also inferred from the change of inbreeding level acr
oss generations in the same population. We obtained a Value similar to the
experimental estimate.