Late-acting inbreeding depression in both male and female function of echium vulgare (Boraginaceae)

We present data on late-acting inbreeding depression in pollen performance, siring success and seed production in Echium vulgare. Pollen viability and rate of pollen-tube growth were both lower for pollen from plants derived from selfing than for pollen from plants derived from outcrossing. Pollen tube numbers within the styles did not differ for pollen from plants derived from selfing or outcrossing. A pollination experiment with two mixtures of pollen from plants derived from selfing or outcrossing, revealed a significant decline of 55% in siring success for pollen from plants derived from selfing. A second experiment with a complete diallel design revealed inbreeding depression for both siring success of the offspring (32.8%) and a decline in seed production of the offspring (34.8%-40.6%). In addition, results indicated a heritable component for seed number per flower. Offspring fitness, measured as seed production and siring ability, can be severely affected by late-acting inbreeding depression. Inbreeding depression values for male and female functions were not correlated. Both functions must therefore be considered when calculating inbreeding depression.