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Papers by William McDowell

Research paper thumbnail of Identity, reproductive potential, distribution, ecology and management of invasive Pomacea maculata in the southern United States

Established populations of introduced Pomacea maculata, a highly fecund, large species of apple s... more Established populations of introduced Pomacea maculata, a highly fecund, large species of apple snail native to South America, now occur throughout southeast Asia, in Spain and extensively across the southern United States. Substantial research on nonnative apple snails takes place in Southeast Asia and has frequently identified apple snails as P. canaliculata. That these Asian populations represent at least two Pomacea species, P. canaliculata and P. maculata, has been confirmed through anatomical and genetic evidence. However, the two species are often still confused because of their similar shell morphologies and life history traits. This contribution reviews the distribution, life history, ecology and management of P. maculata introduced to the southern USA. So

Research paper thumbnail of High abundance of an invasive species gives it an outsized ecological role

Freshwater Biology, 2019

1. Many communities are shifting composition, with losses of native species and increases of non-... more 1. Many communities are shifting composition, with losses of native species and increases of non-indigenous species (NIS). At its extreme, such alteration of ecological guilds can result in simplification with a single NIS performing an ecological role once carried out by a suite of natives. This alteration has occurred in many rivers of the southeastern U.S.A., where the invasive filter-feeding freshwater clam Corbicula fluminea has proliferated following the nearly complete extirpation of native mussels.

Research paper thumbnail of Mass mortality of a dominant invasive species in response to an extreme climate event: Implications for ecosystem function

Limnology and Oceanography, 2016

Research paper thumbnail of Effects of Mass Mortality of an Abundant Invasive Species on Ecosystem Function

Research paper thumbnail of Climate and pH Predict the Potential Range of the Invasive Apple Snail (Pomacea insularum) in the Southeastern United States

Research paper thumbnail of Climate controls the distribution of a widespread invasive species: implications for future range expansion

Research paper thumbnail of Mass Mortality Events of Invasive Freshwater Bivalves: Current Understanding and Potential Directions for Future Research

Frontiers in Ecology and Evolution, 2019

Mass mortality events, the rapid, catastrophic die-off of organisms, have recently been recognize... more Mass mortality events, the rapid, catastrophic die-off of organisms, have recently been recognized as important events in controlling population size, but are difficult to quantify given their infrequency. These events can lead to large inputs of animal carcasses into aquatic ecosystems, which can have ecosystem scale impacts. Invasive freshwater bivalves such as the Asian clam Corbicula fluminea, the zebra mussel Dreissena polymorpha, the golden mussel Limnoperna fortunei, and the Chinese pond mussel Sinanodonta woodiana can attain high densities and biomass and play important roles in aquatic ecosystems through filtration, bioturbation, and excretion. Invasive bivalve species can best be described as R-selected species and appear not to have the same tolerance to abiotic stressors as native species, causing them to be prone to mass mortality events in their invasive range. In contrast to their ecological effects while alive, the frequency and impacts of mass mortality events of invasive freshwater bivalves are not well-understood. Here we review the causes and impacts of mass mortality events, as well as identify important questions for future research. Extreme abiotic conditions, including both drought and flooding, as well as high and low temperatures were the primary drivers of mass mortality events. Short-term impacts of mass mortality events include large pulses of nitrogen and increased oxygen stress due to large amounts of soft tissue decomposition, while shells can impact habitat availability and nutrient cycling for decades. Impacts on biological communities (bacteria, fungi, and macroinvertebrates) are less studied but some examples exist concerning C. fluminea. Better documentation of mass mortality events, particularly their magnitude and frequency, is needed to fully understand the impacts invasive bivalve species have on ecosystems, especially as climate change may make mass mortality events more frequent and/or have a larger magnitude.

Research paper thumbnail of Identity, reproductive potential, distribution, ecology and management of invasive Pomacea maculata in the southern United States

Established populations of introduced Pomacea maculata, a highly fecund, large species of apple s... more Established populations of introduced Pomacea maculata, a highly fecund, large species of apple snail native to South America, now occur throughout southeast Asia, in Spain and extensively across the southern United States. Substantial research on nonnative apple snails takes place in Southeast Asia and has frequently identified apple snails as P. canaliculata. That these Asian populations represent at least two Pomacea species, P. canaliculata and P. maculata, has been confirmed through anatomical and genetic evidence. However, the two species are often still confused because of their similar shell morphologies and life history traits. This contribution reviews the distribution, life history, ecology and management of P. maculata introduced to the southern USA. So

Research paper thumbnail of High abundance of an invasive species gives it an outsized ecological role

Freshwater Biology, 2019

1. Many communities are shifting composition, with losses of native species and increases of non-... more 1. Many communities are shifting composition, with losses of native species and increases of non-indigenous species (NIS). At its extreme, such alteration of ecological guilds can result in simplification with a single NIS performing an ecological role once carried out by a suite of natives. This alteration has occurred in many rivers of the southeastern U.S.A., where the invasive filter-feeding freshwater clam Corbicula fluminea has proliferated following the nearly complete extirpation of native mussels.

Research paper thumbnail of Mass mortality of a dominant invasive species in response to an extreme climate event: Implications for ecosystem function

Limnology and Oceanography, 2016

Research paper thumbnail of Effects of Mass Mortality of an Abundant Invasive Species on Ecosystem Function

Research paper thumbnail of Climate and pH Predict the Potential Range of the Invasive Apple Snail (Pomacea insularum) in the Southeastern United States

Research paper thumbnail of Climate controls the distribution of a widespread invasive species: implications for future range expansion

Research paper thumbnail of Mass Mortality Events of Invasive Freshwater Bivalves: Current Understanding and Potential Directions for Future Research

Frontiers in Ecology and Evolution, 2019

Mass mortality events, the rapid, catastrophic die-off of organisms, have recently been recognize... more Mass mortality events, the rapid, catastrophic die-off of organisms, have recently been recognized as important events in controlling population size, but are difficult to quantify given their infrequency. These events can lead to large inputs of animal carcasses into aquatic ecosystems, which can have ecosystem scale impacts. Invasive freshwater bivalves such as the Asian clam Corbicula fluminea, the zebra mussel Dreissena polymorpha, the golden mussel Limnoperna fortunei, and the Chinese pond mussel Sinanodonta woodiana can attain high densities and biomass and play important roles in aquatic ecosystems through filtration, bioturbation, and excretion. Invasive bivalve species can best be described as R-selected species and appear not to have the same tolerance to abiotic stressors as native species, causing them to be prone to mass mortality events in their invasive range. In contrast to their ecological effects while alive, the frequency and impacts of mass mortality events of invasive freshwater bivalves are not well-understood. Here we review the causes and impacts of mass mortality events, as well as identify important questions for future research. Extreme abiotic conditions, including both drought and flooding, as well as high and low temperatures were the primary drivers of mass mortality events. Short-term impacts of mass mortality events include large pulses of nitrogen and increased oxygen stress due to large amounts of soft tissue decomposition, while shells can impact habitat availability and nutrient cycling for decades. Impacts on biological communities (bacteria, fungi, and macroinvertebrates) are less studied but some examples exist concerning C. fluminea. Better documentation of mass mortality events, particularly their magnitude and frequency, is needed to fully understand the impacts invasive bivalve species have on ecosystems, especially as climate change may make mass mortality events more frequent and/or have a larger magnitude.