AP Biology class blog for discussing current research in Biology

Tag: invasive species

Alien Earthworms Invade! North American Ecosystems are Threatened

The invasion of non-native earth worms poses a complex ecological threat to North America. Earthworms are an integral part of agriculture, aerating and letting water and other nutrients penetrate the soil with the underground tunnels made, and fertilizer from their waste products.  Earthworms also produce net decrease of CO2. As a result of the services earthworms provide, people looking to capitalize off of them have brought earthworms from all over the world to North America.

Lumbricus rubellus HC1

The non-native species have successfully enhanced the agricultural economy in some places, however there are other cases where the alien earthworms have dramatic impacts on ecosystems. The alien earthworms are more likely to consume above ground leaf litter which harms the plants, amphibians, and insects.  “Leaf litter provides many nutrients for the plants and animals” on the lower ends of the food chain, like primary and secondary consumers.  These earthworms can also change the microbiomes of the soil, which can cause serious harm to the plants in the area and indirectly affect other animals.  Microbiome changes appear in pH shifts, nutrients, and even texture, all leading to poorer plant quality and health.  Without the main players, producers, functioning at peak performance, the ecosystem can begin to waver.

To make things even worse, some female alien earthworms can reproduce without fertilization from a male. Faster reproduction, independent of males, contributes to better ecological fitness.  Different species of earthworms exhibit varying levels of fitness. This is not due to their gym habits, but rather because they have evolved to survive and reproduce more effectively than others. Additionally, as a byproduct of climate change, there is new inhabitable land ripe for the alien earthworms to dig their way into.

“Despite all this, only a limited number of studies have documented alien earthworms’ spread, and none have covered colonization dynamics over a large spatial scale or a large number of species.” A new database using records from 1891 to 2021 of native vs. alien earthworms, was used in tandem with another database of U.S. border interceptions of alien earthworms between 1945 and 1975. The new technology powered by ‘machine learning’ aimed at finding the non-native earthworm introduction and spread. Researchers have found that in Canada the alien earth worm population is three times greater than the native population, and in the US and Mexico there are 2 native earthworms for every non-native earth worm.

In AP Biology, we have explored ecology, including concepts such as trophic levels, food webs, and ecological fitness. Trophic levels and food webs directly related to the Alien earthworm threat because a dip in low trophic levels, especially producers, have catastrophic effects on the ecosystem of a certain place.  For context, a trophic level of an organism is the number of steps away from producers it is, ex a primary consumer in NYC are crickets because they only eat grass a producer, and a food web consists of all the food chains of an ecosystem.  An important thing to note with food webs and trophic levels is each trophic level only can gain ten percent of the energy of the last trophic level.  So, if an ecosystem lost significant plant growth or biomass, the trophic levels above it would have less energy and the population sizes of the organisms living in the ecosystem would shrink.  The harmful alien earthworms damage ecosystems by targeting plant mass and soil nutrients which gives each trophic level less energy, effectively shrinking the entire ecosystem.

This topic intrigued me because of how closely related it is to what I have been learning in class.  I also enjoyed learning and writing about how such a seemingly small change in an ecosystem can have impacts much larger than themselves.  I also find human impacts on ecosystems interesting to learn about.  I found this one to be especially interesting because of course something like the industrial revolution had huge long term impacts on the ecology of the world, but you wouldn’t immediately think something trivial like earthworms would have much of an impact on anything, or be so different from one another that they can change the pH of the soil!  What do you think: are alien earthworms worth paying attention to? Is there anything to do against the spread of these alien earthworms? Why does Canada have so many more alien worms than the United States and Mexico?



The Ant Who Stole the Lion’s Dinner

In the African savanna ants are changing the diet of lions, but how? The introduction of an invasive ant has disrupted what seemed to be an insignificant mutual relationship within the intricate web of life in the savanna.

The invaders of the savannah are the big headed ants, and the native ants are the acacia ants. The big headed ants overpower and kill of the native ants. The acacia ants protect the whistling thorn trees from the elephants. The ants protect these trees by biting the elephant when it gets close. The acacia ants biting the elephant prevent the elephant from  uprooting the tree. When the elephants do this there is less cover for the lions to hunt for their preferred meal, the zebra. As a consequence, lions shift their focus to hunting buffalo instead. How would you feel if you were no longer to have your favorite food?

African Sunrise, Amboseli National Park (30385097358)

Elephants in African Ecosystem

The relationship between the acacia ants and the whistling thorn tree is mutualistic, where both species benefit from the interaction. Imagine it as you are each other’s best friends. The tree provides shelter and sustenance to the ants through specialized structures called domatia and extrafloral nectaries, while the ants protect the tree from herbivores like the elephant, as well as competing plants by aggressively defending it against potential threats.

Acacia drepanolobium-- Whistling Thorn (25396927222)

Whistling Thorn Tree

Scientists tracked the activity and kills of lionesses in a conservancy in kenya, while also conducting experiments on big-headed ants and those under the influence of the native ants. The invasion of big-headed ants, believed to have been introduced from imported produce.

The researchers did not have the budget to use drones or satellite imagery. So the researchers measured tree cover by tracking lions and the visibility near their kills. The results stated that areas with big-headed ants exhibited significantly higher visibility. This allows for lions to see their prey better but also the prey can see the lions allowing them to escape.

“Over the three years of the study, zebra dinners decreased from 67 percent to 42 percent of lion kills” “Buffalo kills increased from zero to 42 percent of kills over the study period” By lions switching to buffalo is more risky for the lion since the  buffalo are more likely to be injure the lion over the zebra.

This study in relation to AP Bio relates to the topic of ecology. If you had to guess what one of the most important things to take away form this study is? You are right if you said the disruption of mutualism can have cascading effects on other species in a community. The ants were able to change the food web of the whole ecosystem. It is important to keep the food web in balance because an imbalance will create major effects on the populations of some species. As seen in the study, the population of zebras in crease while the population of buffalo and lions decrease. Symbiotic pairs are able to keep ecosystems in check when one organism has the other to rely on. The loss of one partner could trigger cascading effects, reshaping entire ecosystems. The study of the lions change in diet offers valuable insights into the delicate balance of nature.

King of the Jungle no more? How an unlikely species have halted Lions in the wild

Everybody has known lions as the ‘Kings of the Jungles.’ For years, they’ve dominated the African Wild and easily maintained their status as most dominant in the African Wild and Jungles. However, recently, a somewhat new and indirect foe has halted the Kings of the Jungle quest. In a recent ScienceNews article, it was discovered that the invasive species Pheidole megacephala, more commonly known as big-headed ants, has indirectly made Lions switch their prey from the preferred zebras to buffalos.

Lions - Sharing a Meal

The big-headed ants, seemingly originally imported on produce, prey on the native acacia ants. Although it may seem like a slight difference in an ecosystem, it starts a big chain event. Without acacia ants, who live near whistling thorn trees, elephants can graze on the trees freely. Usually, when acacia ant populations are normal, they stop elephants from grazing on the trees and keep the grassland covered. However, without them, the lions are forced to switch from their primary prey, zebra, to buffalo. Although the lions are still able to successfully hunt, being tertiary consumers, it can potentially be detrimental to their ability to survive. Lions are tertiary consumers, meaning they are at the top of the tropic levels. This indicates that for lions, it’s super hard to get the energy necessary to survive due to the loss of power when transferring from one tropic level to another. Basically, the lions have a super-low availability of energy, and losing the ability to hunt zebras makes this even lower, putting them in even greater danger of going extinct.

Herd of Zebras in Serengeti

For Lions, whose wildlife numbers have dwindled 75% in the past 5 decades, losing a crucial prey could have immense effect. Right now, the impact the introduction of invasive ants will have on Lions is unknown, but since most invasive species come from human trading or shipping, We should feel responsible for helping lions and animals we have exposed to invasive species due to our actions. If you know any other examples of invasive species messing up an ecosystem or how humans impact the introduction of invasive species, let us know in the comments!


The Silent Extinction: How an invasive species is likely to destroy the Ash Tree

There is a mass extinction occurring right now all across North America that millions of people have never hear of. First discovered in North America in 2002, the Emerald Ash Borer, an invasive species native to Mongolia and northern China, has destroyed tens of millions of Ash Trees across North America; and it is likely to destroy millions more.

The Emerald Ash Borer does its damage as larvae. They burrow into the bark of Ash Trees to protect against the cold and in the process of this, cut off the nutrients and water the Ash Tree needs. Scientist suspect that the Emerald Ash Borer has been in North America at least ten years before it was detected.

The devastating effects of the Ash Borer go far beyond losing a tree on your property or favorite hiking trail. The destruction of Ash trees could have a chain effect that leads to the endangerment of numerous plant and animal species. The removal of the canopy that the Ash Trees create leads to sunlight hitting spots of the forest floor that it previously did not. This could lead to invasive species of thickets and bushes covering the forest floor, preventing native plants from growing. Which, in turn, would lead to animals that inhabit the forest going without some of their primary food sources.

In the past, invasive insects have been fought by a combination of insecticides, awareness, and felling of infected trees. This proved fairly successful with the Asian long-horned Beetle in Chicago, but the Emerald Ash Borer presents a different set of challenges. Firstly, the Emerald Ash Borer is march harder to spot than the more distinctive Asian Asian long-horned Beetle. Secondly, it is much easier to deal with an invasive species when it is still localized. While the long-horned beetle was still mostly confined to Illinois, the Ash Borer has spread all across the Upper Midwest.

All factors considered, it may seem that there is nothing that can be done. However, with increased awareness, improved insecticides, and new containment techniques there is hope. The fate of millions of Ash Trees depend on that hope.

For more information click here




Tree Lobsters Are Back!

Image result for Stick insects Tree lobsters Lord Howe

Lord Howe Tree Lobster

Tree Lobsters are actually not lobsters at all. Nor are they crustaceans.  They are actually just insects with a similarly shaped exoskeleton. But that’s not what makes them interesting. What does, is that Tree Lobsters have seemingly come back from extinction.

The Species, originally from the Lord Howe Island in the Tasman Sea between Australia and New Zealand, went extinct during the 1920’s due to becoming the main food source for an invasive rat species that came onto the island. The Tree Lobsters were only formally declared extinct in 1960 though. Since then scientist had pretty much forgotten about them.

Image result for Stick insects Tree lobsters Lord Howe

Ball’s Pyramid Stick Insect

Thus, when scientists found a small group of stick insects similar to Lord Howe Tree Lobster’s on Ball’s Pyramid, a volcanic stack 12 miles away from Lord Howe Island, in 2001, they were quite surprised. The Ball’s Pyramid stick insects were skinnier and darker but scientists were still hopeful the newly discovered insects were, in fact, the same species as the extinct Lord Howe Tree Lobsters. Scientists tested the genes of the stick bugs from Ball’s Pyramid with genes extracted from preserved Lord Howe Tree Lobsters and found out that despite some morphological variance, they are still the same species. They speculate that diet, age, and environment had caused the Ball’s Pyramid Stick Insects to look a little different. How the species got to the volcanic stack is still a mystery as the insects cannot swim but they infer that they had been carried over by birds.

The newly discovered Tree Lobsters are now being bred at the Melbourne Zoo and elsewhere in an attempt to reintroduce the species to Lord Howe Island. However, the invasive rat species on Lord Howe Island still remains a problem as it threatens the lives of over 70 different native species. In order to successfully reintroduce the Tree Lobsters back to Lord Howe, the rat problem needs to be taken care of first.

Invasive Troubles

In the 2000’s a container ship carrying Asian toads arrived in Madagascar. Invasive species have a reputation have a reputation for causing an imbalance in local ecosystems. However, what has happened with the Asian toads in Madagascar since then?

File:Asian Common Toad (Duttaphrynus melanostictus).jpg

Photograph of Asian Toad taken in Thailand

A new report says that the eradication of the species from Madagascar is “not currently feasible.” Estimates place their current population at around 4 million. Each female toad can lay an average of 20,000 eggs each year. Although most don’t survive, their population is not going down anytime soon. Scientists estimate that keeping the population stable would require 1.5 million toads killed each year while eradicating the population would require 2.5 million toads killed per year. It wouldn’t be very expensive, but no one knows where to look for these toads, let alone kill over 60% of its population.

As a result of being a new introduction into the ecosystem, predators do not have any way of dealing with this toad. Since the Asian toad is also poisonous, predator populations can decline. This can have profound effects on the ecosystem, one of which the further decline of the snake population. Snakes are also predators for rodents. If their population is allowed to skyrocket, diseases can run rampant. Industries and commercial items can be overrun. Toads can also directly affect the human population if humans decide to try and eat them.

If nothing is done, which is probably the most likely case, the toad population will go past the point of recovery similar to the case of the introduction of cane toads to Australia. Madagascar’s only choice is to attempt to adapt to this invasion.

Original Article

Invaders or Saviors: The Truth Behind “Invasive” Species


With a name such as “invasive” its hard for an emerging species in a new biome to establish a good reputation.  An “invasive species” can be defined as an organism establishing a presence in a newly introduced area not native to it whether by accidental or intentional means.  For the most part, as stated by the New York Times, it has been the general opinion of conservation organizations to either eradicate or eliminate the invasive species.  However, a large number of scientists including Dov Sax and Ken Thompson, both professors of Ecology at Brown University and the University of Sheffield respectively, are beginning to dispute this idea.  Dr. Thompson claims that species have been moving around for centuries and that humans play a large role in their movement.  In a modern era of globalization, it is getting increasingly harder to stop the spread of “invasive” species and climate change is multiplying the number of species considered “invasive” drastically.  Although Thompson’s theory has a large following, it is not universal.  Some “invasive” species are undeniably harmful such as the fungus that causes chestnut blight which decimated thousands of trees across America in the 1900s or more recently the Zika virus spreading rapidly through mosquitoes drawn north by the warmer climates.  It has been discovered that islands and mountaintops are even more susceptible to these species due to their isolation and indigenous population’s lack of evolutionary defenses.  For example the the accidental transport of the brown tree snake to Guam has nearly eliminated the bird population.  However, this general trend has given many nonnative species a bad representation.  For example, monarch butterflies of California prefer to live in the eucalyptus tree which was brought there 150 years ago.  Or the nonnative crayfish pictured above which feeds the migratory wetland birds of Spain.  In fact the term “invasive species” was coined in Charles Elton’s 1958 book The Ecology of Invasions by Plants and Animals drawing from the heightened tensions caused by World War 2.  This term did not gain its modern weight until the 1990s when the field of Invasive Biology began to grow popular.  Despite findings such as the ones by Thompson and Sax, this is still a much highly debated topic in the field of biology.

original article:




Invasive Rabbitfish

A team of researchers, lead by Dr. Adriana Vergés and Dr. Fiona Tomas, has recently discovered a species of tropical fish that “poses a major threat to the entire Mediterranean basin.” The species, called a rabbitfish has greatly harmed the algal forests in the Mediterranean Sea, primarily the eastern portion. The rabbitfish arrived in the waters of the Mediterranean through the Suez Canal. The rabbitfish are not indigenous to the Mediterranean waters, which makes them so dangerous to the ecosystem. This phenomenon has also been observed in lionfish, snakehead fish, and other organisms that are not indigenous to the location that they are harming. The rabbitfish have been eating seaweed and other ocean plants, which provide shelter and food for other species.


The scientists conducted their study by examining 1000 kilometers of coastline in the eastern Mediterranean specifically Turkey and Greece. Both places two separate species of rabbitfish have come to inhabit. The two areas focused upon were warm and cold regions. In the warmer regions the rabbitfish were present while in the colder regions they were not. The warmer regions filled with rabbitfish had a much lower abundance of seaweeds, and were mostly barren rocky bottoms. On the other hand the colder climates had a thriving ecosystem. There was a 60% reduction in algae and invertebrates and 40% reduction in overall species present in the warm rabbitfish filled environment. After filming rabbitfish as well as indigenous species scientists realized that rabbitfish didn’t actually eat more algae than other fish. However, the distinction was that rabbitfish ate both young and adult algae while indigenous species only ate adults. Eating the young and growing algae before it has a chance for reproduction quickly reduces the overall population.

This topic interested me not only because of my love for marine biology, but also because marine sustainability is extremely important to humans. Without oceans there would be no human life on Earth. The abundance of water is what separates a lush green planet like Earth from the rest of the planets in our solar system. In addition the marine ecosystems are very important, and there have become more and more invasive species due to changes in the environment. Fish such as the rabbitfish threaten whole ecosystems as well as hundreds or even thousands of species that rely on those ecosystems.

Should humans attempt to stop this infestation of rabbitfish? If so, what should be done?



Bacteria to become a new environmentally safe way to control invasive species?



zebra mussels attached to a dock

Zebra mussels have, since 1991, become a huge problem in the hudson river. They devour the phytoplankton and disrupt the ecosystem, and, being an invasive species and having no natural predators in the americas, their population has soared uncontrollably. Until recently, Dr. Daniel Malloy has discovered a species of bacteria that is deadly to the shellfish, and to his knowledge, not to any other organism in the ecosystem. This solution might be just what the Hudson river ecosystem needs, a way to eradicate the aggressive zebra mussel without using chemicals that are harmful to the rest of the river’s inhabitants. This idea sprang from the use of the natural pesticide BTI (Bacillus thuringiensis israelensis) to control blackflies. Malloy has discovered a species of  Pseudomonas fluorescens called “Strain CL145A” that had the desired affect on zebra mussels. When ingested, the dead cells of the bacteria, emit a toxin that destroys the digestive tracts of mussels, the live cells, outside of the digestive system have little to no effect. Malloy and his team are working on finding a fresh water strain of the bacteria to start to eradicate invasive mussels in other bodies of water.


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