PARENT SESSION
Oral Session # 9: Invasive Species I: Theory and Modeling.
Presiding: E Rykiel
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 201.
Cultivation counters the long-odds on plant naturalizations by mitigating environmental stochasticity.
Minton, Mark*,1, Mack, Richard1, 1 Washington State University, Pullman, Washington, USA
ABSTRACT- Immigrant plant populations may be especially vulnerable to environmental stochasticity; they are often small and cannot withstand the repeated reductions in population size that result from random environmental events in a new range. Cultivation (e.g. irrigation, protection from parasites, predators and grazers) buffers a founder population from a wide array of abiotic and biotic threats; it could provide a prolonged opportunity for population growth, dispersal, and eventual persistence in a new range. Using a series of factorial experiments, we investigated the effects of different regimes of cultivation on the persistence of the founder populations of four alien species. The cultivation removed vertebrate and insect seed predators and grazers and provided different levels of irrigation. Treatments also examined the role of size and density of the founder populations in influencing persistence. The fate of founder populations within and across the three years of experimentation was highly variable and underscored the precarious environment in which plants become established. Irrigation and the exclusion of vertebrate seed predators and grazers resulted in a highly significant (P < 0.001) increase in germination and survival. These forms of cultivation produced a corresponding highly significant (P < 0.001) increase in R0, although the magnitude of R0 varied significantly among the species. The size of the founder population significantly increased R0 (P < 0.001) in most years for all species. Cultivation significantly increased the probability of naturalization; however, the minimum level of cultivation for R0 ≥ 1 varied across years and species. These results underscore the importance of environmental stochasticity in determining the fate of founder populations and the potential of cultivation in countering these long odds against naturalization.
Key words: cultivation, prediction, naturalization, environmental stochasticity