Search Results for: projectbiodiversify.org

4.20.21

How milkweed plants defend against monarch butterflies

Anurag looking at a monarch caterpillar on a milkweed plant.

The activities are as follows:

For millions of years, monarch butterflies have been antagonizing milkweed plants. Although adult monarchs drink nectar from flowers, their caterpillars only eat milkweed leaves, which harms the plants. This is an ecological interaction called herbivory. The only food for monarchs is milkweed leaves, meaning they have evolved to be highly specialized, picky eaters. But their food is not a passive victim. Like most other plants, milkweeds fight back with defenses against herbivory.

Monarch butterflies lay their eggs on the underside of milkweed leaves. After eggs hatch, caterpillars start to feed and quickly meet the plant’s first defense. Milkweed leaves are covered in thousands of tiny hairs, called trichomes, that the caterpillar needs to shave off before they can take a bite. The next challenge happens when the caterpillar takes a bite of the leaf. They get a mouthful of latex, which is sticky like Elmer’s glue. The caterpillars have to be very careful in how they feed. They cut the veins in the leaf to drain out the latex before continuing to feed on the leaf. Even after monarch caterpillars make it past the trichomes and latex, there’s another defense they need to overcome. Milkweed leaves have chemical toxins called cardiac glycosides, which are poisonous to most animals. As they feed, monarchs eat some of this poison.

Anurag is a scientist who has long been fascinated by plants and their defenses. He thinks this comes from the fact that his mother was such an avid gardener. She would grow food, such as peppers, squashes, and tomatoes. He looks back and has memories that are associated with garden plants and their defenses. For example, he remembers eating a bitter cucumber as a kid and spitting it out. He also can still recall the bitter aroma on his hand after brushing against the sticky tomato leaves. And plants that are tough and stringy, like kale, are not as tasty to eat. These traits are examples of plant defenses in action, making them harder or less enjoyable to eat, reducing herbivory.

Anurag collecting data on milkweed plants.

Anurag first started studying milkweeds 20 years ago, based on a recommendation from a friend. His friend told him of the bitter, sticky, and furry leaves that were treasured by the monarch butterfly caterpillars. This led him to study the paradox of coevolution. The milkweed and monarch have such a tight relationship that over time, milkweeds have evolved multiple ways to defend themselves against their herbivores. In response, monarchs have evolved to overcome those defenses because they need to eat the milkweed. This arms race may continue to shift back and forth over the course of evolutionary time.

This back-and-forth battle between caterpillar and plant intrigued Anurag. He wanted to know whether milkweed’s defensive traits are still effective against monarchs, or have monarchs evolved in ways that make them unaffected by the defenses? Because each defense trait might be at a different phase in the coevolution process, perhaps some would be effective defenses to herbivory, but others would not be effective. He predicted that monarchs would be harmed by all three milkweed defense traits (trichomes, latex, and cardiac glycosides), but that some would cause more harm than others.

To test his ideas, Anurag and his collaborators grew monarch caterpillars on 24 different North American milkweed species. They put a single newly hatched caterpillar on each plant and had five replicate plants per milkweed species. They recorded each caterpillar’s growth over the course of 5 days to see how healthy it was. They also measured the amount of trichomes, latex, and cardiac glycosides in each plant to determine their level of defense. Once they had their data, they looked for a relationship between caterpillar growth and plant defense traits to determine which made the best plant defenses. The better the defense, the less caterpillars would grow.

Featured scientist: Anurag Agrawal (He/Him/His) from Cornell University

Flesch–Kincaid Reading Grade Level = 8.5

Additional teacher resources related to this Data Nugget include:

  • Anurag has other examples, data, and related stories in his book: Monarchs and Milkweed, which is written for budding scientists and interested naturalists: www.amazon.com/dp/0691166358.
  • Students can learn more about Anurag, his research, and his lab at his website: www.herbivory.com which includes blog posts about monarch conservation, the community of insects on milkweed plants, videos of talks and presentations, and other things related to his research and teaching at Cornell University.
  • A scientific article based on this research: Agrawal, A. A., Fishbein, M., Jetter, R., Salminen, J. P., Goldstein, J. B., Freitag, A. E., & Sparks, J. P. (2009). Phylogenetic ecology of leaf surface traits in the milkweeds (Asclepias spp.): chemistry, ecophysiology, and insect behavior. New Phytologist, 183(3), 848-867.
  • Learn more about Anurag and his research in this YouTube video!

Data Nuggets + Project Biodiversity = DataVersify

Below is a table of all DataVersify Activities – Data Nuggets for which we have a Scientist Profile. Click on the title to open a page displaying the Data Nugget activity, teacher guide, and links to the Profile on Project Biodiversify. The table can be sorted and searched.

For more information on Project Biodiversify, visit their website! For more information on the collaboration between Data Nuggets and Project Biodiversify, check out our Publications & Research page!

Data Nugget TitleScientist ProfilesSummaryContent Level
Do urchins flip out in hot water? Erin de Leon SanchezCorals are the most important reef animals since they build the reef for all of the other animals to live in. But corals only like to live in certain places. In particular they hate living near algae because the algae and coral compete for the space they both need to grow. Perhaps if there are more vegetarians, like urchins, eating algae on the reef then corals would have less competition and more space to grow.1 & 3
Spiders under the influenceAaron CurryPeople use pharmaceutical drugs, personal care products, and other chemicals on a daily basis. Often, they get washed down our drains and end up in local waterways. Chris knew that many types of spiders live near streams and are exposed to toxins through the prey they eat. Chris wanted to compare effects of the chemicals on spiders in rural and urban environments. By comparing spider webs in these two habitats, they could see how different the webs are and infer how many chemicals are in the waterways. 2
Stop that oxidation! What fruit flies teach us about human healthBiz TurnellEach of our cells is home to mitochondria, tiny factories whose job is to turn the food we eat into the energy we need to live. But during this process oxidative damage can cause harm to everything in the cell. There are two ways that bodies can prevent oxidative damage: antioxidants and more efficient metabolic pathways. Biz looked at fruit flies with varying genetics for these two strategies and wanted to test whether the level of oxidative damage in eggs and sperm would influence how many offspring a female had.4
Blinking out?Julia PerroneMany people have fond memories of watching fireflies blink across open fields and collecting them in jars as children. This is one of the reasons why fireflies are a beloved insect species. However, there is concern that their populations are in decline. Scientists turned to the longest-running study of fireflies known to science to see if this is the case!2
pcare2Raising Nemo: Parental care in the clown anemonefishTina BarbaschOffspring in many animal species rely on parental care; the more time and energy parents invest in their young, the more likely it is that their offspring will survive. However, parental care is costly for the parents. The more time spent on care, the less time they have to find food or care for themselves. In the clown anemonefish, the amount of food available may impact parental care behaviors. When there is food freely available in the environment, are parents able to spend more time caring for their young?3
How milkweed plants defend against monarchsAnurag AgrawalFor millions of years, monarch butterflies have been antagonizing milkweed plants. Although adult monarchs drink nectar from flowers, their caterpillars only eat milkweed leaves, which harms the plants. The only food for monarchs is milkweed leaves, meaning they have evolved to be highly specialized, picky eaters. But their food is not a passive victim. Like most other plants, milkweeds fight back with defenses against herbivory. Which defensive traits are helping in the fight against herbivory?3
Mowing for Monarchs Part 1 & Mowing for Monarchs Part 2Gabe KnowlesDuring the spring and summer months, monarch butterflies lay their eggs on milkweed plants. Milkweed plays an important role in the monarch butterfly’s life cycle. When milkweed is cut at certain times of the year new shoots grow, which are softer and easier for caterpillars to eat. Scientists set out to see if mowing milkweed plants could help boost struggling monarch populations.2
Why are butterfly wings colorful?Adriana Darielle Meija BriscoeBig wings allow butterflies to fly everywhere with ease. But you may wonder, why are the wings of some species so brightly colored? The red postman butterfly lives in rainforests in Mexico, Central America, and South America. The color pattern on its wing is usually a mix of red, yellow, and black. These bright colors may warn birds and other predators that they would not make a tasty meal. Another potential reason for butterflies to have bright colors and dramatic patterns is to attract mates.3
junglefoulFeral chickens fly the coopEben GeringSometimes domesticated animals escape captivity and interbreed with closely related wild relatives. Their hybrid offspring have some traits from the wild parent, and some from the domestic parent. Traits that help hybrids survive and reproduce will be favored by natural selection. On the island of Kauai, domestic chickens escaped and recently interbred with wild Red Junglefowl to produce a hybrid population. Over time, will the hybrids on Kauai evolve to be more like chickens, or more like Red Junglefowl?3
Getting to the roots of serpentine soilAllie IgweWhen an organism grows in different environments, some traits change to fit the conditions. Serpentine soils have high amounts of toxic heavy metals, do not hold water well, and have low nutrient levels. Low levels of water and nutrients found in serpentine soils limit plant growth. Because serpentine soils have fewer plant nutrients and are drier than non-serpentine soils, Alexandria thought that plants growing in serpentine soils may not invest as much into large root systems.2
Streams as sensors: Arctic watersheds as indicators of changeArial ShogrenAs the world warms from climate change, the Alaskan Arctic is heating up. This is causing permafrost, or the frozen underground layer of rock and ice, to melt. When permafrost melts, plant material that has been stored for thousands of years begins to decay, releasing carbon and nitrogen from the system. Ecologists can act like “ecosystem accountants” measuring the balance of material that goes into and out of these systems.3
Photo by Tomomi Suwa, 2013Does a partner in crime make it easier to invade?Tomomi SuwaMutualisms are a special type of relationship in nature where two species work together and both benefit. This cooperation should lead to each partner species doing better when the other is around – without their mutualist partner, the species will have a harder time acquiring resources. But what happens when one partner cheats and takes more than it gives?3
Purring crickets: The evolution of a new cricket songRobin TinghitellaAbout twenty years ago, scientists discovered male Pacific field crickets in several spots in Hawaii had stopped making songs due to selection from a parasitoid fly that uses the songs to locate their hosts. One summer, scientists heard what sounded like a purring cat, but there was no cat in sight. This sound was coming from crickets, and was unlike anything ever observed before. Could it be the beginning of evolution of a novel mating signal?3
Buried seeds, buried treasureMarjorie WeberOver 100 years ago, a scientist named William J. Beal had a question: how long do seeds survive underground? He started an experiment by filling 20 bottles with seeds from 50 plant species, buried them on campus, and creating a map to find them in the future. This map have been passed down from scientist generation to generation. The most recent bottle was dug up in 2021, and scientists tested how many seeds were still able to germinate after 142 years underground.2
Does the heat turn caterpillars into cannibals?Kale RougeauWhen Kale started graduate school, they joined a lab that studies how climate change affects the spread of disease in fall armyworms, a type of caterpillar. Fall armyworms can get infected with a special type of virus and it can be spread through cannibalism. Do warmer temperatures cause caterpillars to be hungrier, leading to more cannibalism and disease spread?3
What big teeth you have! Sexual selection in rhesus macaquesRaisa Hernández-PachecoIn Cayo Santiago there is one of the oldest free-ranging rhesus macaque colonies in the world. Scientists have gathered data on these monkeys and their habitat for over 70 years. The program monitors individual monkeys over their entire lives, and when they die their bodies are recovered and skeletal specimens are stored in a museum. These skeletal specimens can be used by scientists today to ask new and exciting questions, for example, what traits are under sexual selection in this population?3
Reconstructing the behaviour of ancient animalsHolly E. AndersonHolly specializes in using fossils to paint a picture of the lifestyles of ancient animals. She uses the shape, structure, damage patterns, and burial poses of bones, and compares them to modern bones. By using what we know about living species, Holly can reconstruct the life and death of ancient organisms. Holly compared a primate skull fossil to its living relatives to see if she can determine if the ancient primate was nocturnal, diurnal, or cathemeral. 4
Farms in the fight against climate changeS. Carolina CórdovaCaro Córdova is a soil scientist and trained agroecologist at the University of
Nebraska-Lincoln. Her research emphasizes carbon sequestration, nitrogen fixation,
and long-term resilience in diverse cropping systems, contributing to advancing
regenerative agriculture globally.		4
3.18.21

Purring crickets: The evolution of a new cricket song

Robin’s team recording purring and typical cricket songs in the field. They analyzed the recordings and discovered that purring was a new song.

The activities are as follows:

Animals use many types of mating signals to attract mates. Some of these signals are probably familiar to you, like the bright colors of birds’ feathers, complex courtship dances of fish, and loud calls of frogs. In crickets, males rub their wings together to produce chirping mating songs that attract females. However, in one species of cricket, these mating songs have led to an issue – while they attract females towards the male, they also attract parasitoid flies. These flies kill the crickets by eating them from the inside out! Parasitoids are animals that lay their eggs in another organism’s body. The eggs develop and usually kill the host.

About twenty years ago, scientists discovered male Pacific field crickets in several spots in Hawaii had stopped making songs. By looking at their wings and DNA, scientists were able to find the exact genetic mutation causing their silence. This change in DNA made some crickets to grow with flat wings that made no sound. Males with this mutation are able to escape detection by the parasitoid flies. However, being silent also posed a struggle because flat winged males could no longer use songs to attract female mates. Scientists waited and watched – would a new way to attract females evolve over time, one that is audible to females, but not to the flies?

Robin is a scientist who has been studying the mating signals in these crickets for many years. One summer, Robin was working in Hawaii and brought a Tupperware container full of crickets into her room. Suddenly, she heard what sounded like a purring cat, but there was no cat in sight. She soon realized the sound was coming from her container of crickets. This song was unlike anything ever observed before in crickets. 

Robin thought that this purring song might be the beginning of the evolution of a novel signal that could be detected by female crickets. If purring is a mating signal, female crickets should have a positive response to purring songs. One way to test this idea is to observe whether females move towards a purring song.

She set out to test her hypothesis with phonotaxis experiments in the lab. During phonotaxis experiments, scientists observe how an organism moves with respect to different sounds. In their first experiment, Robin and her colleagues placed a female at the center of an arena and played a purring song through 1 of 4 speakers. The other 3 speakers were silent. To document the female’s willingness to mate, Robin recorded if the female moved toward the purring and which speakers they contacted. If the purring song was not a mating signal, it should not be attractive to the females and she expected them to contact the speakers at random. This would mean that the purring speaker should be contacted 25% of the time (since only 1 of the 4 speakers broadcast purring). If the purring song was a mating signal, she expected female crickets to contact purring speakers more than 25% of the time.

In a second experiment, Robin investigated whether female crickets prefer purring songs as much as typical mating songs. Using the same set-up, she played either a typical or purring song through 1 of 4 speakers. If females moved toward the speaker playing a  song before the silent ones, she recorded the search time. Search time was calculated as the time it took the female to contact the broadcasting speaker minus the time at which the crickets started looking for the speaker. To see whether the purring song was evolving as a mating signal, she compared the time it took crickets to find speakers broadcasting the purring song compared to the typcal mating song. She predicted that if females still preferred the typical song more than the new song, that they would have longer search times for purring versus typical songs.

Left, a purring male from Moloka’i. Right, a purring male singing to attract mates. Photo credit: E. Dale Broder.

Featured scientist: Robin Tinghitella from The University of Denver.Written by: Gabrielle Welsh

Flesch–Kincaid Reading Grade Level = 9.3

Additional teacher resources related to this Data Nugget include:

2.24.21

Stop that oxidation! What fruit flies teach us about human health

Laboratory fruit flies in their natural habitat: a plastic vial. Photo credit: Conni Wetzker

The activities are as follows:

Have you ever eaten an apple and noticed that, after a while, the core turns brown? That’s because of oxidation – a chemical reaction between the oxygen in the air and the inside of the apple. The same thing is happening inside our own bodies all the time.

Each of our cells is home to mitochondria, tiny factories whose job is to turn the food we eat into the energy we need to live. But mitochondria also make molecules called reactive oxygen species, or ROS. As the name suggests, these molecules contain oxygen and tend to react with the things around them. Like the oxygen in the air reacting with the apple core and turning it brown, ROS react with different parts of the cell, causing oxidative damage. Everything in the cell, including our DNA, can be damaged by ROS molecules. Too much damage contributes to diseases including cancer, heart disease, diabetes, and Parkinson’s.

Bodies can prevent oxidative damage in two ways. First, they can use antioxidants. Antioxidants work by reacting with ROS to stop them from harming cells. Some antioxidants come from the food we eat, while others are made inside the body. If a body doesn’t have enough antioxidants, it can get sick. One example is a genetic mutation called DJ-1. It stops the body from producing antioxidant molecules. Many people with Parkinson’s disease, a neurological illness, have this DJ-1 mutation.

Some living things have evolved a second way to stop oxidative damage: their mitochondria actually make fewer ROS! These species have a special protein called alternative oxidase, or AOX. It works by shortening the pathway that mitochondria use to turn food into energy. A shorter pathway means fewer ROS are made. Scientists have been able to take the AOX gene and move it into other species.

Biz, a scientist studying oxidative damage, wanted to study the effects of the DJ-1 mutation and the AOX gene. To do their research, Biz uses fruit flies. Fruit flies are useful because they are easy to work with and scientists can control the types of mutations and genes they have in the lab. Some of these mutations are the same as those found in humans, so scientists can use them to study human disease. In one study, scientists were able to take the AOX gene and put it into the fruit fly. Fruit flies can also have the DJ-1 mutation that stops antioxidants from being made. Biz used these genetic tools to work with flies that have less oxidative damage (AOX mutants), more oxidative damage (DJ-1 mutants), or normal levels (controls).

Biz was interested in how AOX and DJ-1 affect reproductive cells – sperm and eggs. Oxidative damage is even more dangerous for reproductive cells than for other cells. Whereas most cells can just self-destruct or stop replicating when they build up too much damage, sperm and eggs have to stay healthy up until the moment of fertilization. This wait can last a long time. In many species, females store the male’s sperm inside their own bodies for days, months, or even years after mating! In addition to making their own ROS and antioxidants, sperm and egg cells stored inside the female can be damaged or protected by ROS and antioxidants made by the female’s reproductive tract. Either way, damage to reproductive cells is very important because it can be passed on to future generations or can cause the offspring to die.

Biz wanted to test whether the level of oxidative damage in eggs and stored sperm would influence how many offspring a female had. If cells with oxidative damage do not produce healthy offspring, then fruit flies with less damage should have more offspring.  Biz also expected that fruit flies with more damage should have fewer offspring. To test these ideas, Biz mated normal male fruit flies to three groups of females: females with the AOX gene, females with the DJ-1 mutation, and normal (“control”) females. Aside from having the AOX or DJ-1 gene, the females in all treatments were genetically the same. The males used in the experiment were also genetically identical. After the males and females mated, Biz counted the number of surviving offspring from each group.

Featured scientist: Biz Turnell from Cornell University and Technische Universität Dresden

Flesch–Kincaid Reading Grade Level = 9.0

2.19.21

Getting to the roots of serpentine soils

Alexandria in the field observing the plants and soil.

When an organism grows in different environments, some traits change to fit the conditions. For example, if a houseplant is grown in the shade, it might grow to stretch out long and thin to reach as much light as possible. If that same plant were grown in the sun, it would grow thicker stems and more leaves that are not spread as far apart. This response to the environment helps plants grow in the different conditions they find themselves in.

Flexibility is especially important when a plant is living in a harsh environment. One such environment is serpentine soils. These soils are created from the weathering of the California state rock, Serpentinite. Serpentine soils have high amounts of toxic heavy metals, do not hold water well, and have low nutrient levels. Low levels of water and nutrients found in serpentine soils limit plant growth. In addition, a high level of heavy metals in serpentine soils can actually poison the plant with magnesium!

Combined, these qualities make it so that most types of plants are not able to grow on serpentine soils. However, some plant species have traits that help them tolerate these harsh conditions. Species that are able to live in serpentine soils, but can also grow in other environments, are called serpentine-indifferent.

Alexandria has been working with serpentine soils since 2011 when she was first introduced to them during an undergraduate research experience with her ecology professor. Alexandria was especially intrigued by this challenging environment and how organisms are able to thrive in it, even with the harsh characteristics.

Dot-seed plantain plants in the growth chamber.

To learn more, she started to read articles about previous research on plants that can only grow in serpentine soils. Alexandria learned that these plant species are generally smaller than closely related species. This was interesting, but she still had questions. She noticed the other experiments had compared plant size in different species, not within one species. She thought the next step would be to look at how plants that are the exact same species would respond to serpentine and non-serpentine soil environments. To explore this question, she would need to use serpentine-indifferent plant species because they can grow in serpentine soils and other soils.

Just as a houseplant grows differently in the sun or shade, plants grown in serpentine and non-serpentine soils might change to survive in their environment. Alexandria thought one of these changes could be happening in the roots. She decided to focus on plant roots because of their importance for plant survival and health. Roots are some of the first organs that many plants produce and anchor them to the ground. Throughout a plant’s life, the roots are essential because they bring nutrients to above-ground organs such as leaves. Because serpentine soils have fewer plant nutrients and are drier than non-serpentine soils, Alexandria thought that plants growing in serpentine soils may not invest as much into large root systems. She predicted plants growing in serpentine soils will have smaller roots than plants growing in non-serpentine soils.

To test her ideas, she studied the effects of soil type on a serpentine-indifferent plant species called Dot-seed plantain. She purchased seeds for her experiment from a local commercial seed company. About 5 seeds were planted in serpentine or non-serpentine soils in a growth chamber where growing conditions were kept the same. After the seedlings emerged, the plants were thinned so that there was one plant per pot. The only difference in the environment was the soil type. This allowed Alexandria to attribute any differences in root length to serpentine soils. At the end of her experiment, she pulled the plants out of the soil and measured the root lengths of plants in both treatments.

Featured scientist: Alexandria Igwe (she/her) from University of Miami

Flesch–Kincaid Reading Grade Level = 8.7

Additional resources related to this Data Nugget:

The topics described in this Data Nugget are similar to the published research in the following article:

  • Igwe, A.N. and Vannette, R.L. 2019. Bacterial communities differ between plant species and soil type, and differentially influence seedling establishment on serpentine soils. Plant Soil: 441: 423-437

There is a short video of Alexandria (Allie) sharing her research on serpentine soils.

There have been several news stories and blog posts about this research:

2.4.21

Spiders under the influence

Field picture of an urban web. Dark paper is used to make the web more visible for data collection

The activities are as follows:

People use pharmaceutical drugs, personal care products, and other chemicals on a daily basis. For example, we take medicine when we are sick to feel better, and use perfumes and cologne to make ourselves smell good. After we use these chemicals, where do they go? Often, they get washed down our drains and end up in local waterways. Even our trash can contain these harmful chemicals. For example, when coffee grounds are thrown into the trash, caffeine gets washed into our waterways.

Animals in waterways, like insects, live with these chemicals every day. Many insects are born and grow in the water, absorbing the drugs over their lifetime. As predators eat the insects, the chemicals are passed on, working their way through the food web. For example, spiders living along riverbanks feed off aquatic insects and absorb the drugs from their prey.

Just as chemicals change human behavior, they change spider behavior as well! Effects of drugs on spiders have been studied since the 1940s. Dr. Peter Witt first discovered that chemicals change spider web construction. Peter gave caffeine, and a few other drugs, to spiders to see if they would build their webs during the day instead of at night, which is when they usually work. After giving his test spiders some of the drugs, the spiders still created their webs at night. However, he noticed something unexpected – the web structure of spiders on drugs was completely different from normal webs. The webs were different sizes and had more spacing between each thread. Normal webs help spiders to easily catch prey. Irregularly shaped webs were not good at catching prey because insects could fly right through the large spaces. After his study, Peter knew that drugs were bad for spiders.

Chris (they/them), a current resident of Baltimore and a spider enthusiast, lives in a watershed that is affected by chemical pollution. They wanted to build on Peter’s research by looking at spider webs in the wild instead of in the lab. Chris knew that many types of spiders live near streams and are exposed to toxins through the prey they eat. Chris wanted to compare the effects of the chemicals on spiders in rural and urban environments. By comparing spider webs in these two habitats, they could see how changed the webs are and infer how many chemicals are in the waterways.

Chris worked with Aaron, a local high school teacher, to do this research. They collected images of spiderwebs in areas around Baltimore. They chose two sites: Baisman Run, a rural site far from the city, and Gwynns Run, an urban site close to the city. Chris traveled to the sites and took pictures of eight spiderwebs at each location. Chris and Aaron expected that urban streams would have higher concentrations of chemicals than rural areas because more people live in cities.

When they got back to the lab, Aaron took the pictures and used a computer program to count the number of cells and calculate the total area of each web. These data offer a glimpse into whether spiders near Baltimore are exposed to harmful pharmaceutical chemicals and personal care products. If spiders are exposed to these chemicals, the webs will have fewer, but larger cells than a normal web. The cells will also have irregular shapes.

Featured scientists: Chris Hawn from University of Maryland Baltimore County and Aaron Curry from Baltimore Ecosystem Study LTER

Flesch–Kincaid Reading Grade Level = 7.8

Additional teacher resources related to this Data Nugget include:

  • You can watch Aaron describe his Research Experience for Teachers project here.


7.24.20

Limit by limit: Nutrients control algal growth in Arctic streams

The Arctic Stream Team. Frances, Breck, Abby, Alex, Jay, and Arial at Toolik Field Station in 2019. 

The activities are as follows:

You rely on the nutrients from the foods you eat to grow and thrive. Other organisms, like microbes, do as well! Aquatic algae, a type of microbe that live in the water, need to take in nutrients from their surroundings for growth. Two important nutrients for algal growth are nitrogen (N) and phosphorous (P).

Sometimes the environment does not have all the nutrients that aquatic algae need to grow. When one nutrient is less available compared to others, algae can become nutrient limited. Research on nutrient limitation started with Justus Liebig, a 19th century scientist who proposed the “law of the minimum.” The law states that the nutrient available in the lowest amount relative to demand will limit overall growth and production. This means that growth is not controlled by all the nutrients, but by the scarcest one (the “limiting factor”). When more than one nutrient limits growth, algae are considered co-limited. This just means that a combination of two nutrients are needed for algae to grow. Knowing what nutrients are limiting growth helps scientists understand how an ecosystem is working.  

From other research we know that many ecosystems, including those in the Alaskan Arctic, are phosphorus-limited. Scientists figured this out because they found if they added phosphorus, then algae growth increased. However, climate change could change this. As the Arctic warms, ecosystems on land might start to release nutrients in higher amounts or new proportions into the water. These extra nutrients will likely cause increases in algae growth in streams and ponds, which in turn could change food webs and nutrient cycling. It is therefore important to understand which nutrients are currently limiting algae growth before climate change changes things even more. This starts with tests to see how Arctic algae grow in response to changes in N, P, and N and P in the water.  

A team of scientists got to work on this question! Arial, Jay, Frances, Alex, Breck, and Abby are all interested in understanding how climate change may alter nutrient limitations in Arctic streams. Each team member has a unique role in the larger research project. For example, undergraduate researcher Abby spent her 2019 summer at Toolik Field Station in Northern Alaska as part of a research opportunity. She explored nutrient limitation in one particular lake, called Lake I8. 

Abby used small cups that placed into the streams that fed into Lake I8. These cups were filled with agar gel, a material used in labs to grow microbes. Each cup contained different nutrient treatments. Abby used four different treatments in her cups: (1) a control (agar only), (2) agar + nitrogen, (3) agar + phosphorus, and (4) agar + nitrogen + phosphorus. On the top of each cup, she placed a glass disk to provide a surface for the algae to grow.

A. Cups before going into the stream. B. Abby putting out her cup treatments into an Arctic stream. C. Cups incubating under water in an Arctic stream. D. Analyzing Chlorophyll a extracted from the cups. 

Abby put 5 replicate cups for each treatment at both the Inlet and Outlet streams on the I8 Lake. She left them underwater for 4 weeks. She brought the cups back to the lab to measure the algae that grew on each glass disk. Abby measured how much algae grew on each disk by measuring the amount of Chlorophyll a, the green pigment that helps plants photosynthesize. The more pigment, the more the algae is growing. Abby compared the data from the control to each of the other treatments. When there is more growth in a treatment compared to the control, that means a particular nutrient was limiting at that location. Abby expected that the streams would be limited by the amount of phosphorus, but not the amount of nitrogen. She predicted algae would grow more when they are given additional phosphorus compared to the control treatment.

Featured scientists: Abigail Rec from Gettysburg College; Frances Iannucci, Alex Medvedeff, and Breck Bowden from University of Vermont; Arial Shogren and Jay Zarnetske from Michigan State University

Flesch–Kincaid Reading Grade Level = 8.6

11.4.19

Streams as sensors: Arctic watersheds as indicators of change

Jay taking field notes next to a rocky Tundra stream.

The activities are as follows:

The Arctic, Earth’s region above 66° 33’N latitude, is home to a unique biome, known as tundra. A defining trait of tundra ecosystems is the frozen land. Permafrost is the underground layer of organic matter, soil, rock, and ice that has been frozen for at least 2 full years. Plant material decays slowly in the Arctic because of the cold temperatures. Building up over thousands of years, the plants become frozen into the permafrost. Permafrost represents a very large “sink” of dead plant material, nutrients, and soil that is locked away in a deep freeze. 

Though the Alaskan Arctic may seem far away from where you live, tundra permafrost is important for the entire globe. During the past few thousand years, Earth’s climate has naturally changed a little over time, but because humans are adding greenhouse gases to the atmosphere, the average global temperature may increase by as much as 2 to 4oC over the next century. As a result of global climate change, permafrost has become less stable. By causing warmer and wetter conditions in the Arctic, thawing permafrost soils release ancient material that was previously frozen and locked away. Two important materials are dissolved nitrogen (N), which is a nutrient critical for plant growth, and carbon (C), which is stored in plant matter during photosynthesis. These released materials can be used again by plants, but some is carried away as melted water flows from the land into rivers and streams. You can imagine N and C in permafrost like a bank account where the landscape is the savings account. The land slowly deposits or withdraws N and C from the savings account, while the water receives any excess N and C that the land does not save.

Arial downloads data from a water quality monitoring station at the Kuparuk River. The station is connected a sensor that stays in the river and takes a reading for both carbon and nitrogen concentrations every 15 minutes.

The water that melts as permafrost thaws flows into a stream, ultimately ending up in an ocean. Watersheds are the network of streams and rivers that flow to a single point as they empty out into the ocean. The water at the end of the watershed therefore reflects all the changes that happened across a large area. Scientists use Arctic watersheds as large “sensors” to understand how and when landscapes may be releasing material from thawing permafrost. 

Because the Alaskan Arctic is a vast, sparsely populated area, scientists often rely on established field stations to conduct experiments, collect observational data, and develop new understanding of Arctic ecosystems. One of these field sites is Toolik Field Station. Scientists working at Toolik have been monitoring terrestrial and aquatic Arctic ecosystems since the late 1970s. 

Arial and Jay are aquatic scientists who work at Toolik. They are interested in how Arctic watersheds respond to climate change. Together, Arial and Jay act like ecosystem accountants: they use the chemistry within the water to monitor changes in ecosystem budgets of C and N. Arial and Jay used both historic data and water quality sensors deployed in 2017 and 2018 to monitor the N and C budget in the Kuparuk River. They use this data to calculate how much N and C the river is spending. They measure this as the total export in units of mass per year. This mass per year is determined by multiplying concentration (mass/volume) by flow (volume/day) and adding these values across the whole season (mass/year). These budgets at the watershed outlet help reveal signals of how this tundra landscape may be changing. In this way, they can assess if the landscape savings account for N and C is being depleted due to climate change. 

Featured scientists: Arial Shogren and Jay Zarnetske from Michigan State University

Flesch–Kincaid Reading Grade Level = 10.8

2.5.18

What big teeth you have! Sexual selection in rhesus macaques

Cayo Santiago rhesus macaques. Photo by Raisa Hernández Pacheco.

The activities are as follows:

It is easy to identify a deer as male when you see his huge antlers, or a peacock as male by his stunning set of colorful tail feathers. But you may wonder, how do these traits come about, and why don’t both males and females have them? These extravagant traits are thought to be the result of sexual selection. This process happens when females mate with males that they think have the sexiest traits. These traits get passed on to future male offspring, leading to a change in the selected traits over time. Because females are only choosing these traits in males, sexual selection often leads to sexual dimorphism between males and females. This means that the sexes do not look the same. Often males will be larger and have more elaborate traits than females.

Craniums of an adult male (left) and an adult female (right) rhesus macaque. Photo by Raisa Hernández Pacheco and Damián A. Concepción Pérez.

One species that shows strong sexual dimorphism is rhesus macaques. In this species of monkey, males are much larger than females. Cayo Santiago is a small island off the shore of Puerto Rico. On this island lives one of the oldest free-ranging rhesus macaque colonies in the world. This population has no predators and food is plentiful. Scientists at Cayo Santiago have gathered data on these monkeys and their habitat for over 70 years. Every year when new monkeys are born they are captured, marked with a unique tattoo ID, and released. This program allows scientists to monitor individual monkeys over their entire lives and record the sex, date of birth, and date of death. Once a monkey dies and its body is recovered in the field, skeletal specimens are stored in a museum for further research.

Damián measuring canine length in a rhesus macaque skeletal specimen. Photo by Raisa Hernández Pacheco.

These skeletal specimens can be used by scientists today to ask new and exciting questions. Raisa and Damián are both interested in studying sexual dimorphism in rhesus macaques. They want to find out what causes the differences between the sexes. They chose to focus on the length of the very large canine teeth in male and female macaques. They expected that canine teeth may be under sexual selection in males for two reasons. First, rhesus macaques are mostly vegetarians, so they don’t need long canines for the same purpose as other meat-eating species that use them to catch prey. Second, male rhesus macaques often bare their teeth at other males when they are competing for mates. Females could see the long canines as a sign of good genes and may prefer to mate with that trait. Excited by these ideas, Raisa and Damián set out to investigate the museum’s skeletal specimens to check whether there is sexual dimorphism in canine length. This is the first step in collecting evidence to see whether male canines are under sexual selection by females.

They measured canine length of four male and four female rhesus skeletal specimens dating back to the 1970s. Measurements were only taken from individuals that died as adults to make sure canines were fully developed and that differences in length could not be attributed to age. Raisa and Damián predicted that males would have significantly longer canines compared to those of females. If so, this would be the first step to determine whether sexual selection was operating in the population.

Featured scientists: Raisa Hernández-Pacheco from University of Richmond and Damián A. Concepción Pérez from Wilder Middle School. Research conducted at the Laboratory of Primate Morphology at the University of Puerto Rico Medical Sciences Campus. Skeletal specimens came from the population of rhesus macaques on Cayo Santiago.

Flesch–Kincaid Reading Grade Level = 9.8

Damián and Raisa created a teaching module, called Unknown Bones. It is an inquiry-based educational activity for high school students in which they apply data analysis and statistics to understand sexual selection and illustrate sexual dimorphism in Cayo Santiago rhesus macaques.

About Raisa: I am interested in understanding the drivers shaping population dynamics, and have dedicated my studies to modeling the effects of biotic and abiotic factors on populations of invertebrates and vertebrates. In 2013, I obtained my PhD from the University of Puerto Rico after assessing the effects of mass bleaching on Caribbean coral populations. Right after, I joined the Caribbean Primate Research Center and the Max-Planck Odense Center to study the long-term dynamics of the Cayo Santiago rhesus macaque population. At the Grayson lab, I am studying the population of red-backed salamanders in Richmond; its density, spatial arrangement, and space use.

About Damián: I am a middle and high school Science and Math teacher. I have always been searching for innovative ways to get my students engaged in the science classroom and to connect their new knowledge with the real-world. In thinking of ways to help my students learn, I engaged my self with the scientific community collaborating in scientific projects and creating hands-on, interactive, and inspiring teaching lessons. It is my main interest to develop ideas that could positively contribute to any student’s STEM education.

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

6.26.17

Why are butterfly wings colorful?

The red postman butterfly, Heliconius erato.

The activities are as follows:

Éste Data Nugget también está disponible en Español:

You’ve probably noticed a bright orange butterfly in your garden. It’s hovering over a plant, and then pausing to lay an egg. It’s landing on a flower, and then sipping the tasty syrup. Big wings allow butterflies to fly everywhere with ease. But you may wonder, why are their wings so brightly colored? One reason why butterflies might have brightly colored wings is that these colors warn birds and other predators that they would not make a tasty meal. Another potential reason for butterflies to have bright colors and dramatic patterns is to attract mates. However, there is little research that shows whether color alone or color pattern together deter predators or attract mates.

Susan holding a different species of butterfly in the field.

The red postman butterfly lives in rainforests in Mexico, Central America, and South America. The color pattern on its wing is usually a mix of red, yellow, and black. These patterns vary a lot depending on their location; for instance one variant has a red bar on the forewings and a yellow bar on its hind wings while another variant has red rays on the hindwings and a yellow bar on the forewings. Scientists Susan, Adriana, and Robert have been studying this species for many years. While hiking in the rainforest, they noticed that not all butterfly species are brightly colored. They started to wonder why the red postman butterfly has bright colors, but other species do not. They thought maybe the red and yellow colors and patterns signaled toxicity to predators, like birds; or these wing features may be used to help find and attract mates. Susan, Adriana and Robert predicted that brightly colored butterflies would be avoided by birds and approached more often by other butterflies of the same species. They also predicted that the local color pattern would get the strongest response from predators and mates, because it would be most recognized in that area.

To test their ideas, the team of butterfly scientists created three kinds of artificial red postman butterfly models using paper and a printer. Each model had a plastic body and paper wings. Model A had the same pattern as the local butterflies at the study site in the La Selva Tropical Biological Station in Sarapiquí, Costa Rica, with brightly colored red and yellow wings. Model B also had the same pattern as the local butterflies, but only had black and white tones. Model C had a different pattern than the locals with bright red and yellow colors.

One of the 400 black and white models in the rainforest during the experiment.

To test for differences in predation attempts based on wing color and patterns, they placed 4 of each model at 100 different sites in the rainforest. This made a total of 1,200 model butterflies with 400 of each type! Models were placed far enough apart that they were not within human visible range from one another (on average separated by 5-10 m), and were positioned approximately 1.5 m above the ground, which is consistent with natural roosting heights. The models were left out in the forest for a total of 96 hours. Each day they were inspected and counted for bird beak marks on their wings and plastic bodies. Only new marks were scored each day, so attacks on individual models were only counted once. To test whether red postman butterflies were more attracted to bright colors, or the local wing pattern, Susan and her student field assistants also caught 51 wild red postman butterflies from the rainforest and brought them to a greenhouse. They then presented the live butterflies with the three models and counted how many times they approached each model type.

Featured scientists: Susan Finkbeiner, Adriana Briscoe, and Robert Reed from University of California, Irvine

Flesch–Kincaid Reading Grade Level = 9.9

Watch two videos of experimental trials from the greenhouse experiment:

The first shows a male butterfly approaching a butterfly paper model with color. The second shows a butterfly as it chooses between a butterfly paper model that is black-and-white and one that has color.

poster
Video Trial 1
00:00
--
/
--
poster
Video Trial 2
00:00
--
/
--

There are two publications related to this Data Nugget:

You can follow all three scientists on Twitter where they tweet about the latest scientific discoveries involving butterflies, animals, vision and behavior! Adriana @AdrianaBriscoe, Susan @Fink_about_it, and Robert @FascinatingPupa.

SaveSave

SaveSave

SaveSaveSaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

SaveSave

« Previous Page
Next Page »