Reproductive ecology of the three Nordic Pinguicula species (Lentibulariaceae)

Reproductive ecology (pollination biology, breeding systems, and reproductive effort and success) of the three Nordic species of Pinguicula, P. alpina, P. villosa , and P. vulgaris (Lentibulariaceae), was investigated in a subarctic-subalpine area at Abisko, N Swedish Lapland. Additional studies were carried out at Latnjajaure Field Station, a subarctic-alpine tundra site in the Abisko mountains ( P. alpina, P. vulgaris ), and in W Greenland ( P. vulgaris ). At Abisko the species are sympatric and large populations of all three were found within a 50 × 50 m area. The three species are reproduc-tively isolated by internal barriers by occupying different ploidy levels. Pinguicula alpina and P. vulgaris thrive in base-rich habitats, whereas P. villosa is restricted to nutrient-poor Sphagnum bogs, but habitat separation alone is probably not sufficient to prevent illegitimate pollen flow among the species. However, results showed that there are large and consistent differences in pollination biology, flowering phenology, and breeding systems, and these factors interact to create a highly efficient reproductive isolation at all levels, pre-zygotic as well as post-zygotic. Pinguicula alpina is an early-flowering outbreeder, P. vulgaris is an opportunistic late-flowering inbreeder, and P. villosa is quite intermediate between the two extremes. The phenology-based life history strategies of the Pinguicula species were in accordance with a general model developed for arctic flowering plants, predicting maximized fitness through pollen or seed in early- and late-flowering species, respectively.