Evidence for an epigenetic role in inbreeding depression

Abstract

Inbreeding depression (i.e. negative fitness effects of inbreeding) is central in evolutionary biology, affecting numerous aspects of population dynamics and demography, such as the evolution of mating systems, dispersal behaviour and the genetics of quantitative traits. Inbreeding depression is commonly observed in animals and plants. Here, we demonstrate that, in addition to genetic processes, epigenetic processes may play an important role in causing inbreeding effects. We compared epigenetic markers of outbred and inbred offspring of the perennial plant Scabiosa columbaria and found that inbreeding increases DNA methylation. Moreover, we found that inbreeding depression disappears when epigenetic variation is modified by treatment with a demethylation agent, linking inbreeding depression firmly to epigenetic variation. Our results suggest an as yet unknown mechanism for inbreeding effects and demonstrate the importance of evaluating the role of epigenetic processes in inbreeding depression.

Figure 1.

Epigenetic variation in outbred and inbred plants. Percentage of DNA methylation (mean ± s.e.m.), estimated by the percentage of methylated fragments in 198 MSAP-fragments.

Figure 2.

Effects of demethylation on different plant traits. Photosynthetic efficiency (solid lines), biomass (dashed lines), leaf number (square-dotted lines), and bolting time (long-dashed-dotted lines) of outbred (circles with grey lines) and inbred (triangles with black lines) plants treated with and without 5-azacytidine (mean ± s.e.m.). For statistical results, see table 2.