Pollination and Plant Reproductive Success in Restored Urban Landscapes

Lomov, B; Keith, DA; Hochuli, DF Pollination and plant reproductive success in restored urban landscapes dominated by a pervasive exotic pollinator LANDSCAPE AND URBAN PLANNING, 96 (4): 232-239 JUN 30 2010

Pollinators may be essential to the long-term persistence of restored sites, nonetheless the positive feedbacks between plants and pollinators has rarely been addressed. This paper focuses on native and invasive (European honeybee) bee pollination services to an endemic plant species situated within an urban landscape. While visitation rates by bees were similar in both remnant (forest) versus restored (open) habitats, the target plant species had differing flower phenology and rates of seed initiation, though, interestingly, not seed set. Pollinators may be more robust across landscape types, but local environmental factors may exert strong influence over vegetation. Native bees visited plants more consistently over their bloom period whereas honeybees visited when resources were at a peak- thus native bees may be more reliant on local-scale resources.

This paper begins the process of filling a key gap in the literature by examining trophic interactions in restored sites. However, the authors make the assumption that pollination is a necessary element in restored sites, yet the threshold at which pollination services contribute to community and/or individual persistence remains unclear. I am wary of the author’s conclusion that utilization of dominant long-flowering plant species is necessary to attract pollinators to restored sites as their study did not focus on this question explicitly as there were no sites with only “sub-dominant” species present. Nor was there sufficient replication due to lack of independence among potential study sites. Many other studies (e.g. Potts et al. 2005) have found that a diverse community of annual forbs is the most significant factor determining community diversity (which often leads to robustness). Nonetheless, this paper remains on the cutting edge of integrating ecological interactions of both native and non-native species into evaluations of restoration success.

Photo: H. Sardiñas Xylocopa tabaniformis (CA carpenter bee) and Streptanthus sp. (Jewelflower)