科研之友
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摘要
Increasing rates of invasion have led to shifts in dominance, and even replacement, of nonindigenous species. Shifts in invader dominance from the Zebra Mussel (Dreissena polymorpha) to a functionally similar and closely related species, the Quagga Mussel (Dreissena rostriformis bugensis), have occurred in several European and North American water bodies. We tested whether patterns of local dominance of these mussels in the St Lawrence River, a large heterogeneous system, could be explained by interspecific differences in morphological plasticity. We conducted field experiments across sites of contrasting turbidity (an important stressor for sessile filter feeders) to assess whether Zebra and Quagga Mussels grow at different rates, and whether such differences are related to variation in the morphology of their feeding organs (the palp-to-gill area ratio [PGR]) under different turbidity conditions. Turbidity had a small negative influence on the shell growth of both species, but Zebra Mussels were affected more severely. Across all sites, Zebra Mussels sustained reduced growth and greater mortality than Quagga Mussels. Spatial and temporal variation in PGR was observed for both species, but was more pronounced for Zebra Mussels. Reciprocal transplants suggested that these patterns reflect local acclimation rather than selection or genetic differentiation among local populations. Zebra Mussels exhibited significant shifts in PGR both across the growing season and after being transplanted from low- to high-turbidity conditions, whereas Quagga Mussels altered their PGR only while residing at, or after being transplanted to, a low-turbidity site. We propose that interspecific differences in morphological acclimation to low food conditions result in a competitive advantage for Quagga Mussels.
- 出版日期2017-6
- 单位McGill
