This past week in PNAS (Proceedings of the National Academy of Science) a new paper by Tim Doherty et al., was published on the global impact of invasive mammalian predators. After conducting a global meta-analysis, the authors found that these invasive predators are responsible for 58% of extinctions of birds, mammals, and reptiles that have occurred since 1500 AD. Nearly half of which are attributable to cats and rodents alone! Unfortunately, the most affected groups of species are those that are most “evolutionarily distinct,” or unique compared to many other species. This underscores the critical need to manage these invasive predators to preserve global biodiversity.
Andria Kroner, Ph.D. student in Biology
Sweden’s recent push to ban American Lobsters from the EU highlights issues concerning the categorization and management of invasive species. Several individuals were discovered in the wild which drummed up fear that they would become established and begin to wreak havoc on native species. This problem is mirrored by the lifted ban on monk parakeets in New Hampshire. The species is a pest in warmer climates but has yet to successfully establish in the wild wherever winters can be harsh. The policy paradigm resultantly switched from blacklisting banned species to whitelisting acceptable species. This places the burden onto potential importers so that they must prove that a species will not turn invasive if released. This also lightens the load on the bureaucracy in light of difficulties such as the complexity of predicting invasiveness and that invasions can be ‘natural’ in the face of a changing world. Article by David Brooks in the Concord Monitor.
Shane Tripp, Master's student in Geography
The Asian Hornet has been spotted in Britain for the first time (BBC NEWS), sending the Department for Environment, Food, and Rural Affairs on a quest to find and eliminate their nests. The invasive hornet doesn't pose a direct threat to humans, but it does to the native honey bees. Honey bees are responsible for plant pollination, which helps to provide a critical food source for humans. If honey bee colonies decline, so does the ecosystem services it provides. This invasive species could alter ecosystems causing a cascading effects, by changing honey bee populations and plant communities. Queens of the Asian hornets' nests are being targeted so that this invasive colony dies out and isn't able to establish.
Samantha Klein, Undergraduate student in Biology
European frog bit: don’t let the name fool you, as America’s lakes are in for more than a “bit” of trouble. On paper it looks like more than your typical lily pad—green, round, and likely a favorite of the creature that serves as its namesake. However, in America, it’s a bit of a different story. Without consumers and diseases to keep the plant in check, frog bit goes wild: the result is thick mats of light-blocking vegetation that even impede the movement of boats and other recreational/commercial activity. It’s a two-for-one series of bad tidings for affected waterways, however. When the plants eventually die back en masse, the sheer amount of rotting material can turn healthy lakes hypoxic, tipping the balance of lake ecosystems for the worse. For now, the plant has only been spotted in the Fisk and Reeds Lakes in Michigan, but as one researcher notes, “As aquatic invasive species go, frog-bit is near the top regarding concern.” More concerning still is the lack of a plan to eradicate it, although it is known that the plant is already too established to pull by hand. Article by Jan Holst in mLive.
Isaiah J. Barker, Master’s student in Geography @chitincladheart
An article in the Daily Cardinal is informing the public about a ‘tiny in size but large in impact’ invasive species, the Asian jumping worm - Amynthas agrestis. Jiangxiao Qiu, from the University of Wisconsin, Madison published a paper on the ecological impacts of this invader in Biological Invasions. The Asian Jumping Worm can consume up to 95 percent of the leaf litter in an area in approximately four months! This is because where present, they occur in high densities -numbering upwards of 150 worms per square meter. This barely allows the plants themselves to absorb the nutrients that the leaves would normally provide to the trees and soil and accelerates the timing of nutrients being released into the surrounding soil. Without being absorbed, these nutrients may be flushed into sources of ground water. The high concentrations of nutrients in the soil provide potential habitats for new invasive species to germinate, while making it a poor environment for many native plants. Humans may provide some helpful controls on the worms by putting down fertilizers and treatments made especially for them. In all, the article is an important read for those living in Wisconsin and surrounding states, as the Asian Jumping Worm can be moved in the soil of nursery plants and can cause turmoil if given the opportunity to establish.
Brooke Florio, Senior Undergraduate in Biology
Zebra and quagga mussels are two of the most notorious invasive species in the Great Lakes. Despite numerous introductions, these mussels have failed to establish in Lake Superior. In this article, fishery research biologist Don Schloesser explains that Superior’s cold temperatures, scarcity of phytoplankton, and low calcium levels contribute to the lake being an inhospitable environment for zebra and quagga mussels. However, this does not mean Lake Superior is safe from these invasive mussels. At first, Lake Michigan also seemed immune to these invaders, but they are now found at the lake bottom in high densities. Time will tell if the molluscs can adapt and conquer the final Great Lake.
Sheila Moore, Master’s student in Biology
Do invaders always have negative impacts? Although they certainly have a bad reputation, the answer is no! Impacts on communities and ecosystems depend on the traits of interacting native and invasive species, and the outcomes of complicated interactions among species in the context of their environment. This important point was highlighted in a nice study lead by Catherine Searle from Purdue published in The American Naturalist. The team predicted that an invasive water flea Daphnia lumholtzi would likely increase disease transmission of a fungal pathogen because its susceptibility to the pathogen was relatively higher than a native species. However, in experiments in miniature artificial ecosystems, they found that the presence of the invader decreased disease presence! The story was just not as simple as disease patterns relying on the relative susceptibility of these species. Rather the outcome of competitive interactions on the population dynamics of these species ultimately influenced patterns of disease – which was unexpectedly lower in the presence of the invader.
Kirsten Prior, Assistant Professor in Biology