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Predation on the Invasive Copepod, Pseudodiaptomus forbesi, and Native Zooplankton in the Lower Columbia River: An Experimental Approach to Quantify Differences in Prey-Specific Feeding Rates.

Adams JB, Bollens SM, Bishop JG - PLoS ONE (2015)

Bottom Line: In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi.On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi.Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

View Article: PubMed Central - PubMed

Affiliation: School of the Environment, Washington State University, Vancouver, Washington, United States of America.

ABSTRACT
Invasive planktonic crustaceans have become a prominent feature of aquatic communities worldwide, yet their effects on food webs are not well known. The Asian calanoid copepod, Pseudodiaptomus forbesi, introduced to the Columbia River Estuary approximately 15 years ago, now dominates the late-summer zooplankton community, but its use by native aquatic predators is unknown. We investigated whether three species of planktivorous fishes (chinook salmon, three-spined stickleback, and northern pikeminnow) and one species of mysid exhibited higher feeding rates on native copepods and cladocerans relative to P. forbesi by conducting `single-prey' feeding experiments and, additionally, examined selectivity for prey types with `two-prey' feeding experiments. In single-prey experiments individual predator species showed no difference in feeding rates on native cyclopoid copepods (Cyclopidae spp.) relative to invasive P. forbesi, though wild-collected predators exhibited higher feeding rates on cyclopoids when considered in aggregate. In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi. On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi. Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

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Mean and standard error of Pseudodiaptomus forbesi and native prey consumed by four different predator types in two-prey experiments.(A) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray squares represent native cladocerans, Daphnia retrocurva. (B) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.
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pone.0144095.g002: Mean and standard error of Pseudodiaptomus forbesi and native prey consumed by four different predator types in two-prey experiments.(A) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray squares represent native cladocerans, Daphnia retrocurva. (B) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.

Mentions: Predators offered a choice between the native cladoceran Daphnia retrocurva and the non-native copepod P. forbesi overwhelmingly selected D. retrocurva in two-prey experiments; however, only chinook salmon and northern pikeminnow were tested. Chinook salmon had higher feeding rates on D. retrocurva relative to P. forbesi (t = 3.7, df = 9, P = 0.005) and showed strong positive selection for D. retrocurva (Fig 2A; β = 0.28, t = 11.8, df = 9, P<0.005; S3 and S5 Tables). Likewise, northern pikeminnow feeding rates were higher on D. retrocurva (t = 7.1, df = 9, P<0.0001), which translated into very strong positive selection for D. retrocurva versus P. forbesi (β = 0.14, t = 4.1, df = 9, P<0.0001; Fig 2A, S3 and S5 Tables). In addition, northern pikeminnow exhibited significantly higher feeding rates on the native copepods over P. forbesi (t = 2.4, df = 9, P = 0.04), resulting in positive selection for native copepods over P. forbesi (β = 0.39), though the departure from neutrality was only marginally significant (t = 2.0, df = 9, P = 0.08; Fig 2B, S3 and S5 Tables). Chinook salmon was the only predator to show some tendency for selection of P. forbesi over the native cyclopoid copepods, but because of high variance in β among fish, this trend was not significant (β = 0.67, t = 1.8, df = 9, P = 0.10). There was no evidence for differences in feeding rate or selection between native cyclopoid copepods and P. forbesi for the other predators tested individually (Neomysis β = 0.44, p = 0.14; sticklebackβ = 0.46, p = 0.6), nor in the model including all 4 predators or the 3 wild-caught predators. Finally, there was no relationship between predator length and the selectivity index β (linear regression, P > 0.20 for all cases), again reflecting low within-species variation in length.


Predation on the Invasive Copepod, Pseudodiaptomus forbesi, and Native Zooplankton in the Lower Columbia River: An Experimental Approach to Quantify Differences in Prey-Specific Feeding Rates.

Adams JB, Bollens SM, Bishop JG - PLoS ONE (2015)

Mean and standard error of Pseudodiaptomus forbesi and native prey consumed by four different predator types in two-prey experiments.(A) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray squares represent native cladocerans, Daphnia retrocurva. (B) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664400&req=5

pone.0144095.g002: Mean and standard error of Pseudodiaptomus forbesi and native prey consumed by four different predator types in two-prey experiments.(A) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray squares represent native cladocerans, Daphnia retrocurva. (B) Black triangles represent the invasive copepod, Pseudodiaptomus forbesi, and gray circles represent native copepods, Cyclopidae spp.
Mentions: Predators offered a choice between the native cladoceran Daphnia retrocurva and the non-native copepod P. forbesi overwhelmingly selected D. retrocurva in two-prey experiments; however, only chinook salmon and northern pikeminnow were tested. Chinook salmon had higher feeding rates on D. retrocurva relative to P. forbesi (t = 3.7, df = 9, P = 0.005) and showed strong positive selection for D. retrocurva (Fig 2A; β = 0.28, t = 11.8, df = 9, P<0.005; S3 and S5 Tables). Likewise, northern pikeminnow feeding rates were higher on D. retrocurva (t = 7.1, df = 9, P<0.0001), which translated into very strong positive selection for D. retrocurva versus P. forbesi (β = 0.14, t = 4.1, df = 9, P<0.0001; Fig 2A, S3 and S5 Tables). In addition, northern pikeminnow exhibited significantly higher feeding rates on the native copepods over P. forbesi (t = 2.4, df = 9, P = 0.04), resulting in positive selection for native copepods over P. forbesi (β = 0.39), though the departure from neutrality was only marginally significant (t = 2.0, df = 9, P = 0.08; Fig 2B, S3 and S5 Tables). Chinook salmon was the only predator to show some tendency for selection of P. forbesi over the native cyclopoid copepods, but because of high variance in β among fish, this trend was not significant (β = 0.67, t = 1.8, df = 9, P = 0.10). There was no evidence for differences in feeding rate or selection between native cyclopoid copepods and P. forbesi for the other predators tested individually (Neomysis β = 0.44, p = 0.14; sticklebackβ = 0.46, p = 0.6), nor in the model including all 4 predators or the 3 wild-caught predators. Finally, there was no relationship between predator length and the selectivity index β (linear regression, P > 0.20 for all cases), again reflecting low within-species variation in length.

Bottom Line: In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi.On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi.Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

View Article: PubMed Central - PubMed

Affiliation: School of the Environment, Washington State University, Vancouver, Washington, United States of America.

ABSTRACT
Invasive planktonic crustaceans have become a prominent feature of aquatic communities worldwide, yet their effects on food webs are not well known. The Asian calanoid copepod, Pseudodiaptomus forbesi, introduced to the Columbia River Estuary approximately 15 years ago, now dominates the late-summer zooplankton community, but its use by native aquatic predators is unknown. We investigated whether three species of planktivorous fishes (chinook salmon, three-spined stickleback, and northern pikeminnow) and one species of mysid exhibited higher feeding rates on native copepods and cladocerans relative to P. forbesi by conducting `single-prey' feeding experiments and, additionally, examined selectivity for prey types with `two-prey' feeding experiments. In single-prey experiments individual predator species showed no difference in feeding rates on native cyclopoid copepods (Cyclopidae spp.) relative to invasive P. forbesi, though wild-collected predators exhibited higher feeding rates on cyclopoids when considered in aggregate. In two-prey experiments, chinook salmon and northern pikeminnow both strongly selected native cladocerans (Daphnia retrocurva) over P. forbesi, and moreover, northern pikeminnow selected native Cyclopidae spp. over P. forbesi. On the other hand, in two-prey experiments, chinook salmon, three-spined stickleback and mysids were non- selective with respect to feeding on native cyclopoid copepods versus P. forbesi. Our results indicate that all four native predators in the Columbia River Estuary can consume the invasive copepod, P. forbesi, but that some predators select for native zooplankton over P. forbesi, most likely due to one (or both) of two possible underlying casual mechanisms: 1) differential taxon-specific prey motility and escape responses (calanoids > cyclopoids > daphnids) or 2) the invasive status of the zooplankton prey resulting in naivety, and thus lower feeding rates, of native predators feeding on invasive prey.

Show MeSH
Related in: MedlinePlus