Do patterns of establishment support invasive status of five aquatic plants in New Zealand?

摘要

In order to improve management of invasive aquatic plants, a Weed Risk Assessment Model (WRAM) on aquatic plant species in New Zealand was introduced in 2000. The model ranks different attributes such as habitat versatility, competitive ability, reproductive output, dispersal mechanisms, range of potential impacts, potential distribution, and resistance to management activities. The overall objective of this study was to determine to what extent relative growth rate, photosynthetic rate, light use efficiency, allocation of biomass, and bicarbonate use efficiency during establishment could explain the rank assigned to 5 species in the WRAM: Hydrilla verticillata (Linn.f.) Royle, Ceratophyllum demersum L., Egeria densa Planchon, Lagarosiphon major (Ridley) Moss, and Elodea canadensis Michaux. Overall, our results indicate that the parameters measured for 5 invasive species do not support the rank assigned to these same species in the WRAM. Our study investigated only the growth performance of shootsduring establishment and thus only a small part of a plant's life cycle. Although a high rate of establishment might result in a high local abundance, as well as a high regional distribution, our study illustrates that this is a single component to determining overall invasive status of the plants. Consequently, this indicates that other parts of the life cycle and ecology also contribute to high rate of invasion by the highly ranked species H. verticillata and C. demersum.