Nov 20

Friday Feast! November 20, 2015

Eating invasive species news and notes from around the internet!

Nov 13

Friday Feast! November 13, 2015

Eating invasive species news and notes from around the internet!

Oct 09

Friday Feast! 9 October 2015

Eating invasive species news and notes from around the internet!

Sep 28

A future that is hard to predict: Complex forces can drive evolutionary change in invasive lionfish

This contribution if from Ellie Bors, a PhD student in the Joint Program in Oceanography between the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution. Her research topics include rapid range expansion on populations at the genomic level, climate-driven distributional shifts, invasive species, and deep-sea biology. You can learn more about her work and interests on her personal website.


Our contributor, Ellie Bors, a PhD student studying lionfish invasions

Lionfish are being served up hot on tables throughout the Caribbean and farther afield. But are lionfish speared by divers in Florida the same as those filleted in Aruba? This question is complicated. The answer depends on natural selection, random genetic changes (called genetic drift), and ocean currents.

Lionfish (profiled by invasivore here) were reported in Southern Florida in the late 1980s. Around 2000 the population exploded and spread up the US East Coast and then south into the Caribbean Sea and Gulf of Mexico. Along the way, lionfish have decimated native reef fish populations and unfortunately, no native predators seem excited to eat them. You can read more about the invasion online with the NOAA National Ocean Service lionfish fact sheet and check the invasion’s progress on this USGS website. My dissertation research focuses on how the process of invading a new region might alter lionfish genetics.

At the center of any species’ survival toolbox—dictating their ability to live certain places, eat certain prey items, and reproduce—are genes, or segments of DNA in present in every cell that help determine what that individual cell does and how it interacts with other cells in the organism. This is why I and other biologists obsess about genetic diversity, or the full array of genes that can influence species’ traits. Generally, higher levels of diversity allow populations of a given species to adapt to regional differences in environment, or to new and changing environments. For example, if a population has diversity in the genes that make individuals resistant to a disease, some individuals are likely to survive an epidemic, allowing that population to persist into the future. However, if all individuals have the same genes that leave them susceptible to the disease, the whole population could die off. Two of the forces that impact genetic diversity in all species are natural selection and genetic drift.

You’ve probably heard about natural selection—the idea that there are pressures in the environment that cause certain versions of a species (faster vs. slower; shorter vs. taller; seaweed-colored vs. sand-colored) to be more successful. Typically, selection is pushing genetic diversity in a specific direction. A group of scientists in Australia have shown how natural selection during invasion has caused invasive cane toads to have longer legs, move in straighter lines, and invade faster. This supports the idea that the act of invading actually makes toads at the edge of the invasion better at invading—a dangerous feedback loop!

The other side of the evolutionary coin is genetic drift. Genetic drift is the mischievous counterpart to selection. While selection acts to favor a specific gene at any given time, drift is random. Genetic drift happens because no population on the planet is infinite, and so the genetic makeup of that population will, necessarily, have some random fluctuations each generation. Imagine you have a bag of jellybeans with two flavors. If you pick out twenty jellybeans, you probably won’t get exactly ten of each flavor. If you do it again and again, you’re likely to have a slightly different proportion each time. That’s the same as random fluctuations in the genetic makeup of a population caused by drift.

Now put those twenty jelly beans on a table exactly one foot from the bag. Then randomly take ten of the twenty and put those jellybeans another foot away, and then randomly take five of those and put them yet another foot away. Your final jellybean population is now three feet from the bag and you’ve simulated a mini range expansion! It’s possible that the five jellybeans that are three feet from the bag are all the same flavor, showing that you’ve completely eliminated half of the jellybean diversity. That’s a big problem for the jellybean population, especially if it’s your favorite flavor. The same thing happens with an invading species.

So, what if your jellybeans were in the ocean and they were actually lionfish? Everything in the ocean happens in a fluid context. Currents act as conduits for dispersing animals’ eggs and larvae. In the case of an invasion, the currents could launch the invaders quickly between sites. For lionfish, we can see this when juvenile lionfish show up in New England during the summer (photographed preserved in the lab below). These fish do not survive the winter (thankfully!!) but they are carried to the shores of Long Island and Cape Cod in eddies known as warm core rings that pinch off of the Gulf Stream and come into shore. For lionfish, it’s possible that the complex currents of the Caribbean Sea and Gulf of Mexico could diminish some of the signals of genetic drift that we might expect to see. But it’s also possible that these currents could drive stronger genetic drift by connecting some islands and isolating others. On the US East Coast we think we see certain patterns of genetic diversity because of the strong Gulf Stream shooting the invaders up the coast.

Juvenile lionfish from the invasion edge

Juvenile lionfish from the invasion edge

With both natural selection and genetic drift at play, and in a swirling sea of currents, it becomes a tricky job to predict how the invasion will impact the evolution of lionfish. But by looking into the patterns of genetic diversity, we will better understand which of the three forces is the most important in a marine invasion like this one.

So next time you contemplate devouring an invasive lionfish, think about where it came from and the three main forces that have shaped its identity. And stay tuned for the results of ongoing lionfish genetics research!



Sep 18

Friday Feast! September 18, 2015

Eating invasive species news and notes from around the internet!

Aug 28

Friday Feast! August 28, 2015

Eating invasive species news and notes from around the internet.

Aug 14

Friday Feast! August 14, 2015

Eating invasive species news and notes from around the internet!

Jul 13

Tao Orion reflects on her new book, Beyond the War on Invasive Species

We asked Tao Orion, the author of Beyond the War on Invasive Species: A Permaculture Approach to Ecosystem Restoration to tell us a little bit about her new book. We’ll provide our own review in the future, but here’s what she has to say!

Beyond the War on Invasive Species: A Permaculture Approach to Ecosystem Restoration offers a holistic perspective on invasive species and their management. Invasive plant and animal species are considered one of the primary threats to ecological integrity and global biodiversity today, thus many people consider their eradication a top priority. However, though invasive species may appear troublesome, the ecological processes that underlie their proliferation (many of which we are directly responsible for) are much more concerning, but are not necessarily as easily addressed. For example, an invasive plant like salt cedar growing along the Colorado River appears to be displacing native vegetation, but this view focuses on the plant itself as a driver of ecological change, rather than piecing together the complex dynamics of water use and over-allocation on the river. But when you do that analysis, its clear that only a plant like salt cedar would survive there, and that the contemporary lack of native species like willow and cottonwood has more to do with the ways that we have altered the flow and course of the river and less to do with the presence of salt cedar. The so-called ‘war on invasive species’ is one that is narrowly focused on organisms rather than acknowledging changed and changing ecosystems.

Beyond the War
takes a look at invasive species and their management from a permaculture-based perspective. Though permaculture is often thought of as a system of farming or gardening, the ethics and principles at its core are based on in-depth understanding of natural systems. From an ecological perspective, invasive species aren’t necessarily ‘good’ just as they aren’t necessarily ‘bad’ – they are making the best out of the available situation. Native plants also have very desirable qualities, but if they are unable to thrive, and it appears that an invasive species is displacing them, then we have to look at the ecological conditions that are facilitating the invasion, and work from there if we wish to steer the ecosystem toward more productive ends.

My book focuses on use of invasive species in the context of managing their populations, rather than focusing solely on eradicating them. Kudzu, for example, is a highly multi-functional plant. It’s a perennial nitrogen fixer, goats and cows can eat the high protein leaves, the root (also known as arrowroot) is a common ingredient used to thicken soups and gluten-free breads, it’s medicinal, bees relish its prolific flowers, and its massive roots stabilize erosion-prone slopes. These attributes could be put to use – grazing goats and cows on kudzu in the southeastern U.S. rather than feeding them alfalfa grown in California’s deserts would be a great way to start a Permaculture-type restoration plan. In the process, the landscape where kudzu once grew could be replanted to native hardwoods like hickory and black walnut, and the young trees would benefit from the prodigious nitrogen made available by the kudzu roots. If these types of activities—small-scale, locally adapted, and based in holistic concepts—happened on a large enough scale, even the ecosystem where alfalfa grows in southern California could be restored to greater diversity as demand for products from far away places declines.

Restoration can and should be about more than just removing invasive species. We should be looking at the big picture of how our daily needs are met, and question the relative ecological value of those activities. Restoration as a practice tends to focus efforts on certain landscapes and not others – restoration is generally not part of the planning process of planting an 8,000 acre field of soybeans, clear cutting a forest for plywood, planning a housing development, or adding lanes to a highway. However, ecosystem services and the organisms they support are heavily affected by agriculture, forestry, and urban/suburban development, and the way that these activities are carried out deserve at least as much scrutiny for their role in degrading ecological function as do novel species. Beyond the War on Invasive Species offers compelling examples of how to think differently about the ecological functionality of invasive species in the context of creating a more diverse, abundant, and dynamic world.



Jul 03

Friday Feast! July 3, 2015

Eating invasive species news and notes from around the internet!

Jun 24

Managing invasive plants in Knoxville’s Urban Wilderness

This post was contributed by Emily Zefferman, Research Associate in Urban Ecological Restoration at the University of Tennessee, and a 2014 PhD graduate from the University of California Davis Graduate Group in Ecology.

Urban forests and greenways are increasingly-valued oases in cities across the United States and globally. These areas offer recreational opportunities to city dwellers, improve water and air quality, and provide important habitat for native species. However, many such areas suffer from a prevalence of exotic species, due to their high levels of disturbance and close proximity to intentionally introduced species.

Knoxville, Tennessee’s “Urban Wilderness” is no exception. This collection of private and public parks and land easements comprises approximately 1000 acres of forested land along the southern edge of the Tennessee River. While featuring scenic vistas, unique geologic features, shaded trails, and historical landmarks like former mining sites and Civil War-era forts and battlefields, the Urban Wilderness harbors a growing threat to the area’s native habitats: a massive infestation of invasive plant species. Among the worst are privet (Ligustrum spp.), honeysuckle (Lonicera spp.), English ivy (Hedera helix), multiflora rose (Rosa multiflora), and winter creeper (Euonymus fortunei), which cover much of the understory. These invasives displace native plants, cause irritation and injury to hikers (e.g. multiflora rose), and could impact native birds, insects, and other animals that use native plants as food and habitat.

forest of invasives

In many areas of the Urban Wilderness, the understory is dominated by non-native shrubs like honeysuckle (Lonicera spp.), privet (Ligustrum spp.), and multiflora rose (Rosa multiflora). In this photo, taken in early spring, almost everything green is invasive.

While these invasive plant infestations have been well known to local land managers, no one had documented their extent throughout the Urban Wilderness—a crucial initial step for beginning to tackle the problem. Nor had there been a comprehensive effort to document the native biodiversity in the Urban Wilderness, to better understand the areas that need greatest protection. To begin to understand these ecological assets and challenges, a group of regional stakeholders began an effort in spring 2015 to create an “Ecological Inventory” of Knoxville’s Urban Wilderness. This project is led by researchers at the University of Tennessee Knoxville, with the help of a diverse group of partner organizations: the City of Knoxville, Legacy Parks Foundation, Discover Life in America, and the Tennessee Exotic Pest Plant Council. Coordination between stakeholders with different types of experience and expertise will benefit the overall project by allowing resources and knowledge to be shared and put towards a common goal. Cooperation is essential for managing an assemblage of parcels with different owners in a holistic, united way. This is a great model for other multi-stakeholder, grassroots conservation and recreation projects.

citizen science

University of Tennessee students identify winter creeper (Euonymus fortunei) and bush honeysuckle (Lonicera sp.) during a volunteer invasive plant mapping event on March 28, 2015 at River Bluff Park in Knoxville.

The first step of the Ecological Inventory was to map invasive plants throughout the Urban Wilderness. Because there was only a small amount of funding and staff support for this daunting effort, a creative solution was required. Citizen-scientists were recruited to conduct the surveys, using a mapping technique based on the methodology of the Early Detection and Distribution Mapping System. Volunteers who had experience with plant identification led teams of 2-4 University of Tennessee undergraduate students and other participants in mapping patches of invasive species in designated zones of the Urban Wilderness. Over six work days, a total of 85 different volunteers helped map almost 500 acres of land. The data are being entered into a geodatabase that will allow managers to see the spatial extent of different invasive species and begin to plan invasive plant removal and restoration projects. For example, information about where invasive plants occur will be used in planning a volunteer-based “Weed Wrangle” event in Knoxville in 2016. The geodatabase will also allow researchers to answer questions about why certain species may occur in particular areas.

In addition to creating valuable data that will be used to guide management, these citizen science events helped educate students about plant identification, invasive plant impacts, local ecosystems, and ecological survey methods. Many students said they had fun, and came back multiple days. Invasivore editor Sean Hoban attended, and reports, “I learned to identify invasive plants, and can now pass that skill on to others. I also learned firsthand that invasive species’ cover in our urban wilderness is very heterogeneous- some areas are invaded heavily while others are mostly native, and certain invasives do better in some places than others. Surveys like these can be the base for a lot of good invasive plant ecology work. I hope to participate again!”

The Ecological Inventory of Knoxville’s Urban Wilderness is a great example of how readers of this blog can be involved in studying and controlling invasive species. If you are interested to know more, please contact Emily Zefferman at


Knoxville’s Urban Wilderness is a recreational asset for local residents and visitors.


Periwinkle (Vinca sp.) is a beautiful but invasive plant that is prevalent in many areas of the Urban Wilderness. Photo credit: Wes Charlton

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