AP Biology class blog for discussing current research in Biology

Tag: ants

Stop Thinking Food Webs are so Simple!!

We have all learned about food chains and food webs: the producers perform photosynthesis to create their own food (autotrophs), the primary consumers eat the producers for energy (herbivores), the secondary consumers eat the primary consumers for energy (carnivores) and the tertiary consumers eat the secondary consumers for energy (carnivores). We also know that animals can often fit into multiple categories in a food web.

However, it is not quite as often that people explore the effects that just one population change of any part of a food web can have on the rest of the food web; that is to say that a producer decreasing in population would indirectly hurt a tertiary consumer’s population. That is the case because producers are how the food chain gets all its energy in the first place, so with less producers, less energy is in the food chain. Furthermore, as we learned in AP Bio class, each trophic level is merely 10% energy efficient in consuming the trophic level below; thus, each higher trophic level has less energy than the last. Not only is this lack of energy efficiency why there are only a few trophic levels in each food web, but that is why it is so vital for there to be enough (energy) producers in the food web. Additionally, with energy so scarce, any organism’s population size changing can have a dramatic effect on the other populations in its food web.

In the African savanna, Jake Goheen and his colleagues at the University of Wyoming and the Ol Pejeta Conservancy in Laikipia, Kenya, have taken investigating food web relationships to another level. They have spent about 15 years examining how acacia ants (genus Crematogaster) impact a food chain that they are not even a part of consumer wise. They have found that acacia ants protect whistling thorn trees from elephants, which would rip the trees apart: the ants, abundant in the savanna area, consistently protect the trees by swarming in the elephants’ nostrils and biting them from the inside out.

Whistling thorn acacia in Masai Mara

However, with the arrival of a new invasive species theorized to have arrived along with the shipping of human goods, called big-headed ants (Pheidole megacephala), acacia ants have been massively killed off in certain areas. Although the acacia ants are not part of the food chain consumption wise with the whistling thorn trees, the loss of the protection for the trees allows elephants to eat them. Then, much more grassland is opened up. According to Goheen and his colleagues, this open land, with approximately 2.67 times higher visibility than the land typically has (according to a separate study they did), hurts the diet of a higher trophic level predator, lions:

Goheen and his colleagues found that higher visibility in land with less whistling thorn trees helped one of the lions’ main prey sources, zebras, more than it helped them: their chance of taking down a zebra dropped from 62% to only 22% in areas with big-headed ants and thus minimal whistling thorn trees, according to Goheen’s study. Thus, lions pivoted to eating buffalos, which became 42% of their diet. Eating buffalos instead of zebras hurts lions because buffalos are more likely to injure them than zebras are, but buffalos and zebras are still both primary consumers, meaning they both have 10% of the energy of the producers that they eat; that is to say, although buffalos are more dangerous than zebras to lions, lions do not lose energy with their diet swap.

Regardless, more lion deaths from lions having to kill buffalos suggests that the invasive species of big-headed ants that killed off the acacia ants truly caused massive indirect changes in a food web that it and what it killed had nothing to do with consumer wise: to me, it seems apparent that there is much more to food webs than the basic, linear way people usually think about them.

What other ways do you think food webs are affected that we do not realize?

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!


Ants Play Dead?

Ants are known for their amazing survival strategies, from building complex colonies to working together to gather food. However, researchers have discovered a new survival strategy used by ants on Kangaroo Island in Australia: playing dead. In a recent study, published in the journal Ecology, researchers found that ants on Kangaroo Island would freeze and stop moving when they sensed a predator nearby, effectively playing dead to avoid being attacked. This strategy, known as thanatosis or “playing dead,” has been observed in other insects, but this is the first time it has been documented in ants. The researchers studied two species of ants on Kangaroo Island: the meat ant (Iridomyrmex purpureus) and the bull ant (Myrmecia pyriformis). They found that when the ants were exposed to potential predators, such as spiders or lizards, they would freeze and remain motionless for up to 15 minutes. This behavior appeared to be a successful defense mechanism, as the predators did not attack the ants while they were in this state. The researchers also discovered that the ants used chemical signals to communicate with one another during this process. When a predator was detected, the ants would release a chemical signal that alerted other ants to play dead as well. This allowed the entire colony to effectively avoid being attacked by predators. This discovery sheds light on the complex and sophisticated survival strategies of ants, and raises questions about how other species may have evolved similar behaviors to avoid being preyed upon.

Portrait of an ant, profile view

While the behavior of “playing dead” may be new to ants, it is not uncommon in other species. Many animals have evolved this strategy as a way to avoid predators. Here are a few examples: Opossums are well-known for their ability to play dead. When they sense danger, they will fall to the ground and remain motionless, with their tongue hanging out and their eyes closed. This behavior can last for several minutes, fooling predators into thinking they are dead and leaving them alone.  Some species of snakes, such as the hognose snake, will play dead when threatened. They will roll onto their back, open their mouth, and emit a foul-smelling odor. This behavior can deter predators from attacking them. Some species of fish, such as the threespine stickleback, will “play dead” by floating upside down when they sense danger. This can make them appear unappetizing to predators, and increase their chances of survival. Species may evolve to play dead as a survival strategy to avoid being preyed upon by predators. By appearing lifeless, an animal may fool a predator into thinking that it is not worth attacking, or that it has already been killed. This can provide the animal with an opportunity to escape, or to wait until the predator moves on before resuming its normal activities. Playing dead can be particularly effective when an animal is confronted by a predator that relies on movement or other cues to detect prey. By remaining still and appearing lifeless, the animal may be able to avoid being detected altogether. In addition, playing dead can be a low-cost defense mechanism that does not require the animal to expend a lot of energy or risk injury in a fight with a predator. The evolution of the “playing dead” strategy is likely a response to the pressure of predation and has allowed many species to survive in environments where they might otherwise be vulnerable to attack.

The discovery of ants “playing dead” on Kangaroo Island is a fascinating insight into the survival strategies of these insects. It highlights the complexity and sophistication of ant behavior and raises questions about how other species may have evolved similar strategies to avoid predators. As we continue to study the behavior of animals, we may uncover even more surprising and innovative survival strategies.

Zombie Apocalypse? Yes, it’s happening right now.

Most of us would think that a zombie apocalypse is simply a fantasy seen in scary movies. However, in Brazil, this freaky fantasy has rapidly turned into reality for some unfortunate carpenter ants. In the Brazilian rainforests, one could find carpenter ants whose jaws are forever locked onto a leaf, with a fungus growing right through the dead ant’s face. This is a result of the deadly zombie-like fungi that is brutally murdering ants, otherwise known as Ophiocordyceps unilateralis. 

Ophiocordyceps unilateralis initially infects its victims through spores that are launched from other zombie-ant fungi. The fungus initially penetrates the ant’s exoskeleton as singular cells, but eventually begins multiplying rapidly to form an inviolable fungal network.  This network engulfs the ant’s nervous system and muscles, and eventually the ant capitulates to the parasitic fungi. The ant slowly begins to deteriorate, beginning with simple actions like leaving its colony, to eventually losing full control of its body and dying. However, before the horrible death that the ant suffers, lots of actions take place within the ant’s body. After leaving its colony, the fungi commands the ant to move to a height of approximately 10 inches above the ground. This is done because it is the ideal height for the humidity that the fungi needs to proliferate and flourish inside the ant’s body. Next, the fungi commands the ant use its jaws to permanently form a death grip into a twig or leaf, so it will never move its body ever again. After inevitably killing the ant, the fungi proceeds to grow right through the face of the ant, where it will consequently release more spores to be spread to other ants. Over time, the fungi will spread quickly, and zombify entire colonies of ants.

It’s seriously wild to think that fungi in Brazilian jungles are brutally murdering and zombifying ants by taking over their entire bodies! Moreover, it is crazy that something as simple as a single celled fungi that enters an ant’s blood flow is powerful enough to expeditiously wipe away an ant’s entire life. With over 400 different species of this fungi in the wild, we can expect the ant zombie apocalypse to continue in the jungles of Brazil.




60 Million Year Old Farmers

Microbial ecologist Cameron Currie of the University of Wisconsin-Madison has made an intriguing discovery about the lives of some South American leaf-cutter ants. He found that long before humans cultivated fruits and vegetables for food ancient leaf cutter ants where cultivating fungus. The ants farm the fungus as a food source, but there are pathogenic bacteria that can kill the fungus. To thwart these malicious bacteria, the ants have formed a symbiotic relationship with a different bacteria known as actinobacteria. These actinobacteria fight off the pathogenic bacteria and protect the fungus.

File:Leafcutter ant.jpg

Leaf Cutter Ant

But how could we possibly know if fungal-farming ants existed millions of years ago?

File:Baltic amber inclusions - Ant (Hymenoptera, Formicidae)10.JPG

Ant Trapped In Amber

Well, I am glad you asked. Curries research focused on a 20-million-year-old sample of amber that had a few of these green-thumbed ants trapped inside. The ants had specialized pockets in their heads called crypts where the ants store these actinobacteria. These leaf cutter ants are walking pharmaceutical factories.

It is intriguing that some of the smallest insects on the planet where farming and cultivating food millions of years before we even thought of it. Not only that, but they have been using anti-biotics for millions of years whereas humans have only started using them 60 or 70 years ago.

What lessons do you think humans today can take away from these ants? Could they be the key to our anti-biotic overuse crisis?

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