Heritability of nectar production in Echium vulgare.

Heritabilities of nectar production in the wild species Echium vulgare were estimated as realised heritability under controlled and field conditions. The nectar production of offspring from high- and low-nectar-producing parents was significantly different in both controlled and field conditions, indicating that nectar production is in part genetically determined. The present study is the first one to report a genetic component of variation of nectar production in a wild plant species in the field. Heritability estimated under controlled conditions was 0.13 and therewith less than the heritability estimated under field conditions, which amounted to 0.26. Offspring of high-nectar-producing plants produced comparable amounts of nectar in the growth chamber (1.28 microl) and in the field (1.22 microl). In contrast, the nectar production of offspring of low-nectar-producing plants was significantly higher in the growth chamber (0.95 microl) than in the field (0.55 microl), indicating a genotype by environment interaction. The level of heritability of nectar production was dependent on the environment. Under less favourable conditions, like those in the field, heritability of nectar production increased. Nectar production was not correlated with any of the vegetative or reproductive traits measured, and hence no costs of nectar production could be detected. Results obtained stress the importance of field measurements in determining heritabilities.