Demography and life history of Daucus carota L. populations in the Netherlands

Abstract

In nature so-called ‘biennial’ plants often delay their life cycle, flowering in the third or fourth year, or even later. Life-history theory predicts that high rosette survival is associated with longer life histories. We test this in wild carrot (Daucus carota) populations along disturbed roadsides in the Netherlands, covering a range from unfertile to highly fertile soils. Only 24.2% of the plants behaved as biennial or monocarpic perennial. Most plants were winter (38.9%) or summer annual (36.8%). There was no significant association between life history and habitat, despite differences in mortality and soil fertility between the populations. Annual rosette survival was between 19% and 80%, indicating a high turnover of populations. As predicted by life history theory, the fraction summer annuals (the shortest life-cycle) decreased significantly with rosette survival. In five populations the fraction plants flowering increased with plant size in a similar manner, but in the North Holland dune population plants had a higher threshold size. The annual behaviour of the carrots is quite different from their monocarpic perennial life cycle described in other studies. Carrot cultivars may cross with wild carrots and in this way generation time of the offspring can be affected. We discuss how this may affect plant fitness in the wild.