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APPENDIX 1. Recommendations from invasion biologists
SUSAN WILLIAMS, Bodega Marine Laboratory, University of California, Davis
Monitoring program for answering a prominent question in invasion biology
Management of invasive species has made strides but remains diffuse, uncoordinated, and terrestrial habitats remain the priority.
NERR monitoring would be a huge advance, especially in combination with ongoing ballast water monitoring authorized under the National Invasive Species Act (NISA).
Why monitor?
- To address basic questions on invasive species ecology (examples listed below)?
A national system provides a model to tease apart hypotheses re. relative importance of
community resistance vs. disturbance because it might be possible to control for bias in sources of invaders. Could also lead to an increased capacity to distinguish dynamics of non-native vs. invasive spp. during lag period of establishment.
Survey for all non-native species
For reserve stewardship (to preserve ecological integrity of NERR for research)?
Requires early detection of species with track records, then eradicate. Requires an a priori management commitment/strategy. Early detection monitoring will be intensive and expensive.
Target known invasive species (example: CA Dept. of Food & Agriculture's semi-quantitative mapping for star thistle)
- To develop monitoring methodology- to establish sensitivity of detection, refine methods?
Requires comparison of methods and then adaptive monitoring. Development/ testing of methodology might be one of the most useful contributions that NERR could make to invasive spp. biology.
Questions: We are developing a sense of general attributes of good invaders. Much less is known about the relative importance of invader attributes vs. community vulnerability. Little is known about ecological/economic impacts of invaders; this is required for risk assessment.
- What are the ecosystem attributes that influence invasibility and ecological impacts?
- What is the relative importance of community resistance vs. disturbance in invasibility and ecological impacts?
- How do invasive species rank with other environmental problems in estuaries?
- How does nutrient loading interact with estuarine plant invasions?
- A current hypothesis is that the distribution of invasive species in several small populations leads to faster spread vs. a single large population (Moody & Mack. 1988. J. Appl. Ecol. 25:1009).
National monitoring system might provide a way to control for bias in sources of invaders.
How data from monitoring program would have been/would be useful: in evaluation of the correlation between disturbance and invasibility.
There is evidence that ‘healthy’ unfragmented seagrass beds are more resistant to a diverse group of invasive species (listed below). In native habitats, some co-exist without overrunning the angiosperm community. A NERR monitoring program including invasive spp. and environmental parameters would have been important to assessing the strength of this correlation.
- Asian mussel Musculista senhousia (so. CA, Reusch & Williams, 1998, Oecologia 113:428,1999, Oikos 84:398; Japan, SLW pers. obs.); Bunodeopsis sp. (Williams & Heck, 2001. In Bertness et al. (eds.), Marine Community Ecology, p. 317-337);
- Caulerpa taxifolia- invaded very unnatural degraded habitats in so. CA; evidence from Mediterranean (Chishom et al. 1997, Mar. Poll. Bull. 34:78; Ceccherelli & Cinelli 1997, JEMBE 217:165, 1999, JEMBE 240:19)
- Anecdotal accounts suggest that invasive Codium fragile ssp. tomentosoides invades after kelp or eelgrass are disturbed (Trowbridge, 1998, Ann. Rev. Oceanogr. Mar. Biol.).
- Don Strong and colleagues's work in San Francisco Bay suggest that the invasive hybrid of Spartina alterniflora and S. foliosa are rare in established S. foliosa marshes, suggesting a role of disturbance in providing safe sites for hybrid seeds (Ayers et al. 2000, Mole. Biol. 8).
- NERR system is probably large enough for multivariate analysis of environmental parameters, disturbance history, community changes, and invader dynamics. Multivariate analysis of zebra mussel invasions in Europe has lead to a good predictive understanding of which US waterbodies were and will be invaded (Ramchran et al. 1992, Can. J. Fish. Aquat. Sci. 49:1).
- Matter of time before Musculista invades Gulf and Atlantic coasts
Monitoring Program:
- Need to involve quantitative/statistical ecologists
- Program must be flexible and undergo periodic review (example: FL Keys Marine Sanctuary monitoring program)
- Beyond mapping- need to have abundance data on wetland plant communities, which are the 'foundation' communities in many NERRs. Monitoring needs to address changes in density; by the time coverage is lost, it is too late to manage.
- Density: estimation can be labor-intensive
Braun-Blanquet (http://www.eri.nau.edu/applications/lesson 111400.htm): Rapid visual assessment method that estimates abundance using relative categories. Developed/used extensively in Europe and also successfully in assessing decline/recovery of Florida Bay seagrasses.
- Grid-based permanent plots (example: enabled detection of decline in native Elodea sp. with increase in non-native Elodea sp., Mack, RN in Mooney & Hobbs, Invasive Species in a Changing World)
- Teams of experts- experts are tired!
- Herbarium specimens- can extract DNA
- Monitoring to detect impact is a useful objective because impact will carry program funding
- CRIMP (Centre for Research on Introduced Marine Pests, AU) models (stratified systematic sampling)
Devil’s advocate position: Byers & Goldwasser (2001, Ecol. 82:1330) modeled impact of non-native on native snail species and the impact would not have been evident for at least 20 years of monitoring. The impacts of the Asian mussel on eelgrass would not have been evident without manipulative experiments. We need national monitoring program, but will it get us farther faster than strategic experimentation? The potential impact of the species is what carries the message to policy makers and provides information for risk assessments.
Other Needs/Questions:
- Genetic analyses: genetic composition might be critical to invasive plant success. Evidence exists for Spartina and is suggested for Caulerpa.
- Increased capacity to distinguish dynamics of non-native vs. invasive species during the lag period
- What is the role of physiological stress in limiting invasions in estuaries?
- Estuaries are particularly prone to effects of climate change; programs need to address these effects, including sea level changes.
Economic data should be collected if possible- involving social scientists is important.
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