Effects of supplementary feeding on growth and reproduction of three carnivorous plant species in a subarctic environment

Abstract

1. The effect of supplementary feeding on growth and reproduction of three carnivorous plants species was investigated over a 6-year period. Pinguicula alpina, P. villosa and P. vulgaris populations growing at two altitudes in a subarctic environment were fed with fruit flies (Drosophila melanogaster). 2. Fed plants increased in size relative to control plants during the first years. Subsequently a stable size difference between feeding levels was established. The weight of the over-wintering part was higher in fed plants than in control plants. 3. The flowering frequency (i.e. proportion of plants in a population carrying flowers) was also higher in the fed plants. The proportion of flowering plants increased in the feeding treatment compared to control plants during more-or-less the whole experimental feeding period (5-6 years). Seed production also increased slowly in response to feeding. 4. No feeding effect on nitrogen and phosphorus concentrations in seeds and overwintering parts was found. 5. In most characteristics the high-altitude populations were less responsive than populations growing at low altitude. In the high-altitude population reproduction failed repeatedly, suggesting that seed output may be more dependent on abiotic factors than on resource availability in cold environments. 6. Pinguicula villosa and P. vulgaris used the new resources the same summer for increased leaf rosette growth and current reproduction, showing these species to be income breeders, while the third species (P. alpina) allocated a larger proportion to storage and future reproduction, characteristic of a capital breeder.