Trait variation within species: environmental drivers and ecological consequences
Species traits are widely understood to influence the roles of organisms in communities and ecosystems. Substantial variation in traits also occurs within species, but this variation is typically not considered by ecologists. Human activities are rapidly altering the traits within species at a global scale. Therefore, it is critical to determine whether intraspecific variation is important for community and ecosystem processes.
Behavioral traits, in particular, respond rapidly to environmental change and vary considerably both within and among populations. Past research in our lab has demonstrated substantial variation in behavioral traits including activity and boldness across the geographic range of different species of freshwater crayfish. These changes in traits alter the ecological impacts of the crayfish population, which affects important freshwater ecosystem functions like leaf litter decomposition and nutrient cycling.
Currently, we are examining how freshwater invertebrate behavioral traits change in response to environmental drivers like land use change, whether these behaviors are heritable and persist in populations, and how behavioral traits influence the ecological impacts of different freshwater invertebrate taxa.
Trait variation within species: environmental drivers and ecological consequences
Species traits are widely understood to influence the roles of organisms in communities and ecosystems. Substantial variation in traits also occurs within species, but this variation is typically not considered by ecologists. Human activities are rapidly altering the traits within species at a global scale. Therefore, it is critical to determine whether intraspecific variation is important for community and ecosystem processes.
Behavioral traits, in particular, respond rapidly to environmental change and vary considerably both within and among populations. Past research in our lab has demonstrated substantial variation in behavioral traits including activity and boldness across the geographic range of different species of freshwater crayfish. These changes in traits alter the ecological impacts of the crayfish population, which affects important freshwater ecosystem functions like leaf litter decomposition and nutrient cycling.
Currently, we are examining how freshwater invertebrate behavioral traits change in response to environmental drivers like land use change, whether these behaviors are heritable and persist in populations, and how behavioral traits influence the ecological impacts of different freshwater invertebrate taxa.
(A) Experimental arena used to test crayfish shelter use and competition (B) Measuring benthic and water column metabolism in a stream
Invasive species and their parasites
Invasive species are a major threat to freshwater biodiversity due to the isolated nature of freshwater habitats, which intensifies invasive species impacts. One of the main research aims of our lab is to expand our understanding of the causes and consequences of biological invasions in fresh water. Much of this work has focused on the role of parasites in invasions.
Research in our lab has enhanced our understanding of the role of parasites in invasions, especially how parasites affect the ecological impacts of invasive species. For example, we have used mesocosm experiments (artificial ponds) to test the effects of parasites on invasive crayfish impacts. Some parasites (a trematode in the genus Microphallus) enhance crayfish impacts by increasing crayfish boldness, while others (a microsporidian in the genus Nosema) reduce impacts by reducing crayfish activity levels. Both of these are examples of trait-mediated effects of parasites, which have received little attention compared to density-mediated effects (i.e., effects on host mortality or fecundity).
Invasive species may also influence parasite communities by acting as a reservoir for native parasites or introducing parasites to a new region, which may be a critical part of the risk they pose to native species. Our research examines how invasive species alter parasite dynamics. For example, we have demonstrated that native crayfish are infected with different parasite taxa when a lake has been invaded by rusty crayfish. Further, by examining parasites in native and invasive crayfish, we have identified many new crustacean parasites that may be relevant for conservation or invasive species control.
Mesocosms at Trout Lake Research Station to test the effects of trematode parasites on freshwater communites
(A) Crayfish surveys in northern Wisconsin (B) A trematode metacercaria in a virile crayfish hepatopancreas (digestive organ) (C) A microsporidian infection in rusty crayfish abdominal muscle
Crayfish conservation and invasions
Freshwater crayfish are a diverse group that contains many species of conservation concern with limited distributions as well as numerous invasive species and have recently undergone dramatic range expansions. Crayfish often play a central role in freshwater ecosystems, where they are typically dominant consumers of leaf litter, periphyton, and benthic invertebrates. Crayfish are also a critical food resource for many recreationally and economically important centrarchid fishes. Because of their central role in freshwater ecosystems, crayfish additions, losses, or species replacements often have large ecological impacts.
We are currently partnering with scientists at the Florida Fish and Wildlife Conservation Commission to investigate the causes and consequences of the invasion of the white tubercled crayfish into the Black Creek drainage in Florida. This drainage contains an imperiled crayfish species, the black creek crayfish. The white tubercled crayfish has already replaced the black creek crayfish throughout most of its range.
Crayfish conservation and invasions
Freshwater crayfish are a diverse group that contains many species of conservation concern with limited distributions as well as numerous invasive species and have recently undergone dramatic range expansions. Crayfish often play a central role in freshwater ecosystems, where they are typically dominant consumers of leaf litter, periphyton, and benthic invertebrates. Crayfish are also a critical food resource for many recreationally and economically important centrarchid fishes. Because of their central role in freshwater ecosystems, crayfish additions, losses, or species replacements often have large ecological impacts.
We are currently partnering with scientists at the Florida Fish and Wildlife Conservation Commission to investigate the causes and consequences of the invasion of the white tubercled crayfish into the Black Creek drainage in Florida. This drainage contains an imperiled crayfish species, the black creek crayfish. The white tubercled crayfish has already replaced the black creek crayfish throughout most of its range.
Benthic invertebrate community ecology
Benthic macroinvertebrates are commonly used as indicators of water quality, and they are critical for energy flow through food webs and nutrient cycling in freshwater ecosystems. Therefore, part of the research in our lab focuses on benthic invertebrate abundance, diversity, and community composition to examine how human impacts and environmental change alter freshwater ecosystems.
For example, we have examined whether benthic invertebrate communities in urban stormwater ponds are influenced by human management (vegetation control). Stormwater ponds are commonly constructed to control pollution, flooding and erosion caused by human development, but they also support freshwater organisms. Understanding how management of these ponds affects benthic invertebrate communities may help managers maintain biodiversity in urban landscapes.
In addition, we are interested in the effects of prescribed fire on wetland ecosystems. While prescribed fire is instrumental in managing forest ecosystems in the southeastern USA, our knowledge of its impacts on freshwater ecosystems is severely limited. Research in the lab will continue to examine benthic invertebrate communities to assess environmental impacts, and this approach can be adapted to new questions and freshwater ecosystems of interest.
(A) Dragonfly larvae from an urban stormwater pond (B) A stormwater pond in Gainesville, FL (C) A wetland in a landscape managed by prescribed fire