Predicting the impact of an invasive seaweed on the fitness of native fauna

Blackwell Publishing
Publication Type:
Journal Article
Journal of Applied Ecology, 2008, 45 (5), pp. 1540 - 1549
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1. Understanding the impacts of invasive species on natural ecosystems is an important component of developing management strategies. Habitat-forming invasive plants and sessile invertebrates often support a high diversity and abundance of native fauna, suggesting some benefits of invasion. However, the fitness responses of these native fauna, and thus the net benefit from their association with habitat-forming invasive species, are not well understood. 2. We determined how fitness-related life-history traits, patterns of resource allocation among life-history traits, and survivorship of an abundant bivalve, Anadara trapezia, responded to invasion by the habitat-forming seaweed, Caulerpa taxifolia, by transplanting A. trapezia into invaded and uninvaded habitats over a 12-month period. 3. Although A. trapezia recruits into C taxifolia in high numbers, adult growth, body condition, shell condition, female reproduction and survivorship were all significantly lower in C taxifolia compared to unvegetated sediment. Notably, we observed high mortality in C taxifolia after heavy rainfall events, highlighting a potential link between sublethal effects on condition, stochastic environmental perturbation and survivorship. 4. In addition to the overall reduction in fitness, there were changes in scaling relationships between reproduction and body size following invasion. Female A. trapezia in C taxifolia habitat allocated proportionally more resources to reproduction (including reproductive tissue and number of eggs per follicle) than those in unvegetated sediment despite their poor condition. Maximizing reproduction following invasion may impose a further cost to already stressed A. trapezia and contribute to the higher mortality observed when living in C. taxifolia.
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