Species introductions
Species introductions are one of the largest threats to biodiversity globally. Though not all non-native species are detrimental, those that do become invasive have strong negative effects on local community structure and ecosystem function.
Crayfish are an integral part of stream ecosystems: they link aquatic and terrestrial food webs and influence sediment transport and nutrient cycling. They are also one of the most widespread aquatic invaders globally, causing declines in fish and invertebrate populations and alterations in stream morphology. Crayfish are introduced to new habitats via anglers who use non-native crayfish as bait, schools that free their study organisms, or aquarium hobbyists who release pets. Their success is dependent on their ability to outcompete native species for resources in order to survive, grow, and reproduce in their new habitat.
Ringed crayfish (Orconectes neglectus, above left) are native to the Ozark region of the United States and were discovered in Oregon’s Willamette River drainage in 2015. Though they have the potential to displace native signal crayfish (Pacifastacus leniusculus, above right) and have been found in other river systems in Oregon, interactions between the two species are largely unknown.
Wendy Saepharn (bottom left), as part of her Summer Undergraduate Research Experience project, tested the competitive abilities of the two crayfish species for limited food and space. Contrary to her hypotheses, she found that introduced ringed crayfish did not outcompete native signal crayfish for food or space in a laboratory setting.
I also conducted a field experiment to see how the two crayfish species affect invertebrate community composition and leaf processing rates. I am currently working with a group of highly motivated undergraduate research assistants (self titled "Bug Brigade") to process field samples.