Abstract:

Established invasive plant species have more diverse gene pools than single populations in their home range. This genetic and often phenotypic variation allows for natural selection to act and produce rapid adaptations as an invasive species interacts with other members of the community. For an invasive flowering plant, interactions with pollinators may lead to adaptations to a heterogeneous pollinator community. The variation in the pollinator community in the invaded range is similar to variation in the native range, suggesting that adaptations may mirror patterns seen in the home range. In this study, we investigated variation in flower size in Cytisus scoparius, an invasive leguminous shrub, along an elevation gradient.

This study took place in the Capitol State Forest in Washington State. We measured flower widths and the proportion of visited flowers, using 10 plants per field site. Sites were located along an elevation gradient and were visited three times to measure phenological variation on a per-plant basis.

We saw positive selection for flower size, albeit without a distinct pattern of higher selection at higher elevations. The pattern of natural selection could be seen both in terms of pollinator visitation rates and in seed production. We also found that the largest contributor to changes in seed production was not elevation or flower size but management practices.

Key words: invasive, pollinator, evolution, Cytisus, elevation