Deadly windows

A white-throated sparrow caught during the experiment. You can see the band on it’s leg, used to make sure they did not record the same bird more than once.

The activities are as follows:

Glass makes for a great windowpane because you can see right through it! However, the fact that windows are see-through makes them very dangerous for birds. Have you ever accidentally run into a glass door, or been confused by a tall mirror in a restaurant? Just like people, birds can mistake a see-through window or a mirrored pane for an opening to fly through or a place to get food, and will accidentally fly into them. These window collisions can hurt the bird, or even kill it. Window collisions kill nearly 1 billion birds every year!

Urban areas, with lots of houses and stores, have a lot of windows. Resident birds that live in the area may get to know these buildings well, and may learn to avoid the windows. However, not all the birds in an area live there year-round. There are also migrant birds that fly through urban areas during their fall migrations. They will use gardens and parks in urban areas to rest along their journeys to their winter southern homes. During the fall migration, people have noticed that it seems like more birds fly into windows. This may be because migrant birds are not familiar with the local buildings. While looking for food and places to sleep, migrant birds might have more trouble identifying windows and fly into them more often. However, it could also be that there are simply more window collisions in the fall because there are more birds in the area when migrant and resident birds co-occur in urban areas.

Researchers identify the species of each bird caught in one of the nets used in the study. They then place a metal bracelet on one leg so they will know if they catch the same bird again.

Natasha was visiting a friend who worked at a zoo when he told her about a problem they were having. For a few weeks in the fall, they would find dead birds under the windows, more than they would during the rest of the year. He wanted to figure out a way to prevent birds from hitting the exhibit windows. Natasha became interested in learning whether migrant birds were more likely to fly into windows than resident birds, or if the number of window collisions only increase in the fall because there are lots of birds around. To do this she would have to count the total number of birds in the area, and also the total number of birds that were killed in window collisions. To count the total number of birds in the area, Natasha hung nets that were about the same height as windows. When the birds got caught in the nets, Natasha could count and identify them. This data could then be used to calculate the proportion of migrants and residents flying at window-height. She put ten nets up once a week for four hours, over the course of 3 months, and checked them every 15 minutes for any birds who got caught.

Researcher identifying a yellow-rumped warbler, one of the birds captured in the net as part of the study.

Then, she also checked under the windows in the same area to see what birds were killed from window collisions. She checked the windows every morning and evening for the three months of the study. Different species of bird are migratory or resident in the area where Natasha did her study. Each bird caught in nets was examined to identify it to species using its feathers, which would tell us whether the bird was a migrant or a resident. The same was done for birds found dead below windows.

If window collisions are really more dangerous for migrants, she expected to see a higher proportion of migrants would fly into windows than were caught in the nets. But, if window collisions were in the same proportion as the birds caught in the nets, she would know that windows were just as dangerous for resident birds as for migrants.

Featured scientist: Natasha Hagemeyer from Old Dominion University

Flesch–Kincaid Reading Grade Level = 8.7

There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below:

Marsh makeover

A saltmarsh near Boston, MA being restored after it was degraded by human activity.

The activities are as follows:

Salt marshes are diverse and productive ecosystems, and are found where the land meets the sea. They contain very unique plant species that are able to tolerate flooding during high tide and greater salt levels found in seawater. Healthy salt marshes are filled with many species of native grasses. These grasses provide food and nesting grounds for lots of important animals. They also help remove pollution from the land before it reaches the sea. The grass roots protect the shoreline from erosion during powerful storms. Sadly today, humans have disturbed most of the salt marshes around the world. As salt marshes are disturbed, native plant biodiversity, and the services that marshes provide to us, are lost.

A very important role of salt marshes is that they are able to store carbon, and the amount they store is called their carbon storage capacity. Carbon is stored in marshes in the form of both dead and living plant tissue, called biomass. Marsh grasses photosynthesize, taking carbon dioxide out of the atmosphere and storing it in plant biomass. This biomass then falls into the mud and the carbon is stored there for a very long time. Salt marshes have waterlogged muddy soils that are low in oxygen. Because of the lack of oxygen, decomposition of dead plant tissue is much slower than it is in land habitats where oxygen is plentiful. All of this stored carbon can help lower the levels of carbon dioxide in our atmosphere. This means that healthy and diverse salt marshes are very important to help fight climate change.

However, as humans change the health of salt marshes, we may also change the amount of carbon being stored. As humans disturb marshes, they may lower the biodiversity and fewer plant species can grow in the area. The less plant species growing in the marsh, the less biomass there will be. Without biomass falling into the mud and getting trapped where there is little oxygen, the carbon storage capacity of disturbed marshes may go down.

Jennifer, working alongside students, to collect biomass data for a restored saltmarsh.

It is because of the important role that marshes play in climate change that Jennifer, and her students, spend a lot of time getting muddy in saltmarshes. Jennifer wants to know more about the carbon storage capacity of healthy marshes, and also those that have been disturbed by human activity. She also wants to know whether it is possible to restore degraded salt marshes to help improve their carbon storage capacity. Much of her work focuses on comparing how degraded and newly restored marshes to healthy marshes. By looking at the differences and similarities, she can document the ways that restoration can help increase carbon storage. Since Jennifer and her students work in urban areas with a lot of development along the coast, there are lots of degraded marshes that can be restored. If she can show how important restoring marshes is for increasing plant diversity and helping to combat climate change, then hopefully people in the area will spend more money and effort on marsh restoration.

Jennifer predicted that: 1) healthy marshes will have a higher diversity of native vegetation and greater biomass than degraded salt marshes, 2) restored marshes will have a lower or intermediate level of biomass depending on how long it has been since the marsh was restored, and 3) newly restored marshes will have lower biomass, while marshes that were restored further in the past will have higher biomass.

To test her predictions, Jennifer studied two different salt marshes near Boston, Massachusetts, called Oak Island and Neponset. Within each marsh she sampled several sites that had different restoration histories. She also included some degraded sites that had never been restored for a comparison. Jen measured the total number of different plant species and plant biomass at multiple locations across all study sites. These measurements would give Jen an idea of how much carbon was being stored at each of the sites.

Featured scientist: Jennifer Bowen from Northeastern University

Flesch–Kincaid Reading Grade Level = 11.0

Sticky situations: big and small animals with sticky feet

Travis in the lab measuring the stickiness of a gecko’s toe.

Travis in the lab measuring the stickiness of a gecko’s toe.

The activities are as follows:

Species are able to do so many amazing things, from birds soaring in the air, lizards hanging upside-down from ceilings, and trees growing hundreds of feet tall. The study of biomechanics looks at living things from an engineering point of view to study these amazing abilities and discover why species come in such a huge variety of shapes and sizes. Biomechanics can improve our understanding of how plants and animals have adapted to their environments. We can also take what we learn from biology and apply it to our own inventions in a process called biomimicry. Using this approach, scientists have built robotic jellyfish to survey the oceans, walking robots to help transport goods, and fabrics that repel stains like water rolling off a lotus leaf.

Travis studies biomechanics and is interested in the ability of some species to climb and stick to walls. Sticky, or adhesive, toe pads have evolved in many different kinds of animals, including insects, arachnids, reptiles, amphibians, and mammals. Some animals, like frogs, bats, and bugs use suction cups to hold up their weight. Others, like geckos, beetles, and spiders have toe pads covered in tiny, branched hairs. These hairs actually adhere to the wall! Electrons in the molecules that make up the hairs interact with electrons in the molecules of the surface they’re climbing on, creating a weak and temporary attraction between the hairs and the surface. These weak attractions are called van der Waals forces.

Travis catching lizards in the Dominican Republic.

Travis catching lizards in the Dominican Republic.

The heavier the animal, the more adhesion they will need to stick and support their mass. With a larger toe surface area, more hairs can come in contact with the climbing surface, or the bigger the suction cup can be. For tiny species like mites and flies, tiny toes can do the job. Each fly toe only has to be able to support a small amount of weight. But when looking at larger animals like geckos, their increased weight means they need much larger toe pads to support them.

When comparing large and small objects, the mass of large objects grows much faster then their surface area does. As a result, larger species have to support more mass per amount of toe area and likely need to have non-proportionally larger toes than those needed by lighter species. This results in geckos having some crazy looking feet! This relationship between mass and surface area led Travis to hypothesize that larger species have evolved non-proportionally larger toe pads, which would allow them to support their weight and stick to surfaces.

To investigate this idea, Travis looked at the data published in a paper by David Labonte and fellow scientists. In their paper they measured toe pad surface area and mass of individual animals from 17 orders (225 species) including insects, arachnids, reptiles, amphibians, and mammals. From their data, Travis calculated the average toe pad area and mass for each order.

Travis then plotted each order’s mass and toe pad area on logarithmic axes so it is easier to compare very small and very large values. Unlike a standard axis where the amount represented between tick marks is always the same, on logarithmic axes each tick mark increases by 10 times the previous value. For example, if the first tick represents 1.0, the second tick will be 10, and the next 100. As an example, look at the graphs below.

gecko-graph

The left plot shows hypothetical gecko species of different sizes, but with proportional toes. Their mass per toe pad area ratio (g/mm2) varies, with larger species having larger g/mm2 ratios. In this case, larger species have to support more mass per toe pad area. In the right plot, larger gecko species have disproportionally larger toes. These differences change each species’ mass per toe pad area ratios, so that all species, regardless of their size, have the same mass per toe pad area ratio.

Featured scientists: David Labonte, Christofer J. Clemente, Alex Dittrich, Chi-Yun Kuo, Alfred J. Crosby, Duncan J. Irschick, and Walter Federle. Written by: Travis Hagey

Data Nugget Flesch–Kincaid Reading Grade Level = 10.3

Scaling Up – Math Activity Flesch–Kincaid Reading Grade Level = 9.5

There is a scientific paper associated with the data in this Data Nugget. The data was used with permission from D. Labonte.

Labonte, D., Clemente, C.J., Dittrich, A., Kuo, C.Y., Crosby, A.J., Irschick, D.J. and Federle, W., 2016. Extreme positive allometry of animal adhesive pads and the size limits of adhesion-based climbing. Proceedings of the National Academy of Sciences, p.201519459.


dr-fowleriAbout Travis: Ever since Travis was a kid, he was interested in animals and wanted to be a paleontologist. He even had many dinosaur names memorized to back it up! In college he discovered evolutionary biology, which drove him to apply for graduate school and become a scientist. There, he fell in love with comparative biomechanics, which combines evolutionary biology and mechanical engineering. Today Travis studies geckos and their sticky toes that allow them to scale surfaces like glass windows and tree branches.

Are you my species?

Michael holding a male darter. The bright color patterns differ for each of the over 200 species. Photo by Tamra Mendelson.

Michael holding a male darter. The bright color patterns differ for each of the over 200 species. Photo by Tamra Mendelson.

The activities are as follows:

What is a species? The biological species concept says species are groups of organisms that can mate with each other, but do not reproduce with members of other such groups. But how do animals know who to choose as a mate and who is a member of their own species? One way is through communication. Animals collect information about each other and the rest of the world using multiple senses, including sight, sound, sonar, and smell. These signals may be used to figure out who would make a good mate and who is a member of the same species.

Michael snorkeling, looking for darters.

Michael snorkeling, looking for darters.

Michael is a scientist interested in studying how individuals communicate within and across the boundaries of species. He studies darters, a group of over 200 small fish species that live on the bottom of streams, rivers, and lakes. Michael first chose to study darter fish because the males in these species have bright color patterns during the breeding season. Female darters get to choose which males to mate with, and males fight with each other during the mating season. Females want to make sure they choose a member of their own species to mate with. Males want to make sure they only spend energy fighting off males of their own species, who are competing for the same females. What information do females and males use to guide their behavior, and how do they know which individuals are from their own species?

Across all darter species, there is a huge diversity of color patterns. Because only males are brightly colored, and there is such a diversity of colors and patterns, Michael wondered if male color patterns were used to communicate species identity during mating. Some darter species have color patterns that are very similar to those of other darter species. Perhaps, Michael thought, the boundaries of species are not as clear as described by the biological species concept. Some darter species may hybridize, or mate with members of a different species if their color patterns are very close. If color pattern serves as a signal to communicate darter species identity, then Michael predicted that species with similar male color patterns would hybridize and be more aggressive with each other than species with very different male color patterns.

Michael (right) in the field, collecting darters. Photo by Tamra Mendelson.

Michael (right) in the field, collecting darters. Photo by Tamra Mendelson.

Michael collected 8 pairs of darter species (16 species in all) from Alabama, Mississippi, Tennessee, Kentucky, South Carolina, and North Carolina and brought them all back to the lab. For each species pair, he put five males and five females of each species (20 fish total) in the same fish tank and observed their behavior for 5 hours. He did this 8 times, once for each species pair. During the 5 hour observation period, he recorded (1) how many times females mated with their own species or a different species, and (2) how many times males were aggressive to their own species or a different species.

Featured scientist: Michael Martin from the University of Maryland, Baltimore County

Flesch–Kincaid Reading Grade Level = 10.5

Videos showing darter behavior:

Darter species used in the experiment:

darters

When a species can’t stand the heat

An adult male tuatara. Photo by Scott Jarvie.

An adult male tuatara. Photo by Scott Jarvie.

The activities are as follows:

Tuatara are a unique species of reptile found only in New Zealand. While they look like lizards, they are actually in their own reptile group. Tuatara are the only species remaining on the planet from this lineage, one that dates back to the time of the dinosaurs! Similar to tortoises, they are extremely long-lived and can sometimes live over 100 years. Tuatara start reproducing when they are about 15-20 years old and they breed infrequently.

North Brother Island, one of the small New Zealand islands where tuatara are still found today.

North Brother Island, one of the small New Zealand islands where tuatara are still found today. Photo by Jo Monks.

The sex of tuatara is not determined by sex chromosomes (X or Y), as in humans. Instead, the temperature of the nest during egg development is the only factor that determines the sex of tuatara embryos. If the egg develops with a low temperature in the nest it will be female, but if it develops with higher temperatures it will be male. This process happens in many other species too, including some turtles, crocodiles, lizards, and fish. However, most species are the opposite of tuatara, and produce females at the warmest temperatures.

Today, tuatara face many challenges. Humans introduced new predators to the large North and South Islands of New Zealand. Tuatara used to live on these main islands, but predators led them to local extinction. Today they survive only on smaller offshore islands where they can escape predation. Because many of these islands are small, tuatara can have low population numbers that are very vulnerable to a variety of risk factors. One of the current challenges faced by these populations is climate change. Similar to the rest of the world, climate change is resulting in temperatures that are getting higher and higher in New Zealand, and the warm temperatures may impact tuatara reproduction.

Kristine collecting data on a tuatara in the field.

Kristine collecting data on a tuatara in the field. Photo by Sue Keall.

North Brother Island has a small population of tuatara (350-500 individuals) that has been studied for decades. Each tuatara has been marked with a microchip (like the ones used on pet dogs and cats), which allows scientists to identify and measure the same individuals repeatedly across years. In the 1990s, a group of scientists studying tuatara on this island noticed that there were more males than females (60% males). The scientists started collecting data on the number of males and females so they could use long-term data to track whether the sex ratio, or the ratio of males and females in the population, became more balanced or became even more male-biased over time. Because tuatara are long-lived and breed infrequently, the scientists needed to follow the sex ratio for many years to be sure they were capturing a true shift in the sexes over time.

In 2012, Kristine and her colleagues decided to use this long-term data to see if the sex ratio is changing as the world warms. Since the temperature of the nest determines sex, and temperature is going up due to climate change, they predicted that there would be a greater proportion of males in the population over time. This would be reflected in an unbalanced sex ratio that is moving further and further away from 50% males and 50% females. The sex ratio is important because when there are fewer females in a population, there are fewer individuals that lay eggs and produce future offspring. Generally, a population that is highly male-biased will have lower reproduction rates than a population that is more balanced, or is female-biased.

Graph showing mean annual temperatures for New Zealand, made by the National Institute of Water and Atmospheric Research. The y-axis represents the difference in that year’s mean temperature from the average temperature from 1981-2010. Red bars mean the year was warmer than average, and blue mean it was colder. The black line is the trend from 1909 to 2015 (0.92 ± 0.26°C/100 years).

Graph showing mean annual temperatures for New Zealand, made by the National Institute of Water and Atmospheric Research. The y-axis represents the difference in that year’s mean temperature from the average temperature from 1981-2010. Red bars mean the year was warmer than average, and blue mean it was colder. The black line is the trend from 1909 to 2015 (0.92 ± 0.26°C/100 years).

Featured scientists: Kristine Grayson from University of Richmond, Nicola Mitchell from University of Western Australia, and Nicola Nelson from Victoria University of Wellington

Flesch–Kincaid Reading Grade Level = 11.5

Additional teacher resources related to this Data Nugget:


kgAbout Kristine: Kristine L. Grayson received her Ph.D. in 2010 from the University of Virginia under the mentorship of Dr. Henry Wilbur. Her thesis used mark-recapture methods to examine migration behavior in a pond-breeding amphibian. She received an NSF International Research Fellowship to Victoria University of Wellington in New Zealand to conduct research on sex-ratio bias under climate change in tuatara, an endemic reptile. One of Kristine’s claims to fame is capturing the state record holding snapping turtle for North Carolina – 52 pounds! In addition to her passion for amphibian and reptile conservation, Kristine’s current work also examines the spread potential of gypsy moth, an invasive forest pest in North America. Kristine currently is an Assistant Professor in the Biology Department at University of Richmond.

Finding Mr. Right

Mountain chickadee, photo by Vladimir Pravosudov

Mountain chickadee, photo by Vladimir Pravosudov

The activities are as follows:

Depending on where they live, animals can face a variety of challenges from the environment. For example, animal species that live in cold environments may have adaptive traits that help them survive and reproduce under those conditions, such as thick fur or antifreeze in their blood. Animals may also have adaptive behaviors that help them deal with the environment, such as storing food for periods when it is scarce, or hibernating during times of the year where conditions are most unfavorable. These adaptations are usually consistently seen in all individuals within a species. However, sometimes populations of the same species may be exposed to different conditions depending on where they live. The idea that populations of the same species have evolved as a result of certain aspects of their environment is called local adaptation.

Mountain chickadees are small birds that live in the mountains of western North America. These birds do not migrate to warmer locations like many other bird species; they remain in the same location all year long. To deal with living in a harsh environment during the winter, mountain chickadees store large amounts of food throughout the forest during the summer and fall. They eat this food in the winter when very little food is available. There are some populations of the species that live near the tops of mountains, and some that live at lower elevations. Birds at higher elevations experience harsher winter conditions (lower temperature, more snow) compared to birds living at lower elevations. This means that birds higher in the mountains depend more on their stored food to survive winter.

Carrie conducting field research in winter, photo by Vladimir Pravosudov

Carrie conducting field research in winter, photo by Vladimir Pravosudov

Carrie studies mountain chickadees in California. Based on previous research that was done in the lab she works in, she learned these birds have excellent spatial memory, or the ability to recall locations or navigate back to a particular place. This type of memory makes it easier for the mountain chickadees to find the food they stored. Carrie’s lab colleagues previously found that populations of birds from high elevations have much better spatial memory compared to low elevation birds. Mountain chickadees also display aggressive behaviors, and fight to defend resources including territories, food, or mates. Previous work Carrie and her lab mate conducted found that male birds from low elevations are socially dominant over male birds from high elevations, meaning they are more likely to win in a fight over resources. Taken together, these studies suggest that birds from high elevations would likely do poorly at low elevations due to their lower dominance status, but low elevation birds would likely do poorly at high elevations with harsher winter conditions due to their inferior memory for finding stored food items. These populations of birds are likely locally adapted – individuals from either population would likely be more successful in their own environments compared to the other.

In this species, females choose which males they will mate with. Carrie predicted females would prefer to mate with males that are from the same elevation. She thought this because males from the same elevation as the females may be best adapted to the location where the female lives. This means that when the female lays her eggs, her offspring will likely also inherit traits that are well suited for that environment. If she mates with males that match her environment, she is setting up her offspring to be more successful and have higher survival where they will live. This process of females choosing males that are from the same environment could contribute to the populations becoming more and more distinct. Offspring born in the high mountains will continue to inherit genes for good spatial memory, and those born at high elevations will inherit genes that allow them to be socially dominant.

Mountain chickadee, photo by Vladimir Pravosudov

Mountain chickadee, photo by Vladimir Pravosudov

To test whether female mountain chickadees contribute to local adaptation by choosing and mating with males from their own elevation, Carrie brought high and low elevation males and females into the lab. Carrie made sure that the conditions in the lab were similar to the light conditions in the spring when the birds mate (14 hours of light, 10 hours of dark). Once a female was ready to be tested, she was given time to spend time with both males in a cage that is called a two-choice testing chamber. On one side of the testing chamber was a male from a low elevation population, and on the other side was a male from a high elevation population. Each female could fly between the two sides of the testing chamber, allowing her to “choose” which male she preferred to spend time close to (measured in seconds [s]). There was a cardboard divider in the middle of the cage with a small hole cut into it. This allowed the female to sit on the middle of the cardboard, which was not counted as preference time for either male. Females from both high and low elevation populations were tested in the same way. The female bird’s preference was determined by comparing the amount of time the female spent on either side of the cage. More time spent on the side of the cage by one male over the other indicates a preference for that male.

Watch a video of one of the experimental trials:

Featured scientist: Carrie Branch from University of Nevada Reno

Flesch–Kincaid Reading Grade Level = 11.5

Additional teacher resources related to this Data Nugget include:


carrie-branchAbout Carrie: I have been interested in animal behavior and behavioral ecology since my second year in college at the University of Tennessee. I am primarily interested in how variation in ecology and environment affect communication and signaling in birds. I have also studied various types of memory and am interested in how animals learn and use information depending on how their environment varies over space and time. I am currently working on my PhD in Ecology, Evolution, and Conservation Biology at the University of Nevada Reno and once I finish I hope to become a professor at a university so that I can continue to conduct research and teach students about animal behavior. In my spare time I love hiking with my friends and dogs, and watching comedies!

Why so blue? The determinants of color pattern in killifish, Part II

In Part 1, you examined the effects of genetics and environment on anal fin color in male bluefin killifish. The data from Becky’s experiment showed that both genetics and environment work together to determine whether male offspring had blue, yellow, or red anal fins. You will now examine how the father’s genetics, specifically their fin color pattern, affects anal fin color in their sons. When we factor in the genetics of the father, and not just the population he came from, does this influence our interpretation of the data?

The color polymorphism in bluefin killifish – males display anal fins in blue, red, or yellow.

The activities are as follows:

For her experiment, Becky collected male and female fish from both a swamp (26 Mile Bend) and a spring (Wakulla) population. Most of the males in the swamp have blue anal fins, but some have red or yellow. Most of the males from the spring have red or yellow anal fins, but some have blue. Becky decided to add data about the father’s fin color pattern into her existing analysis from Part 1 to see how it affected her interpretation of the results.

In Part 1, Becky was looking at the genetics from the population level. Looking at the data this way, we saw parents from the 26 Mile Bend swamp population were more likely to have sons with blue anal fins than parents from the Wakulla spring. Parents from the 26 Mile Bend were also much more likely to have sons with higher levels of plasticity, meaning they responded more to the environment they were raised in. This means there was a big difference between the proportion sons with blue anal fins in the clear and brown water treatments.

Bringing in the color pattern of the fathers now allows Becky to look at the genetics from both the population and the individual level. From both the swamp and spring population, Becky collected males of all colors. Becky measured the color pattern of the fathers and recorded the color of their anal fins and the rear part of their dorsal fins. She used males that were red on the rear portion of the dorsal fin with a blue anal fin (rb), males that were red on both fins (rr), males that were yellow on both fins (yy), and males that were yellow on the rear portion of the dorsal fin with blue a blue anal fin (yb).

colormorph

She randomly assigned each father’s sons into one of the water treatments, either clear or brown water. Once the sons developed their fin colors, she recorded the anal fin color. This experimental design allowed her to test whether sons responded differently to the treatment depending on the genetics of their father. She thought that the anal fin color of the sons would be inherited genetically from the father, but would also respond plastically to the environment they were raised in. She predicted fathers with blue anal fins would be more likely to have sons with blue anal fins, especially if they were raised in the brown water treatment. She also predicted that fathers with red and yellow anal fins could have sons with blue anal fins if they were raised in the brown water treatment, but not as many as the blue fathers.

Featured scientist: Becky Fuller from The University of Illinois

Flesch–Kincaid Reading Grade Level = 10.9


About Becky: I consider myself to be an evolutionary biologist who studies fishes. I grew up in a small town riding horses in 4-H and working in a veterinary clinic. As an undergraduate at the University of Nebraska at Lincoln, I was interested in biology and considering either medical or veterinary school. Two things led to me research in ecology and evolution. In the summer of 1991, I was taking courses at Cedar Point Biological Field Station which was run by the University of Nebraska. I met Dr. Anthony Joern (Tony) who was studying grasshopper community ecology. Tony hired me onto his field crew that summer after the courses were finished. I went on to do an undergraduate thesis under Tony’s mentorship where I studied predation on grasshoppers. I caught the “science bug” and never looked back. Following my undergraduate work, I went to Uppsala University in Sweden on a Fulbright Scholarship. Here, I developed my love for fish and aquatics. I worked with Dr. Anders Berglund on pipefish in a fjord on the west coast of Sweden. Since then, I have had many wonderful advisers, instructors, mentors, and collaborators who have helped me develop skills along the numerous fronts required for a successful career in science. I consider myself very fortunate to have a job where I can do science and teach young, enthusiastic undergraduates.

Why so blue? The determinants of color pattern in killifish, Part I

The color polymorphism in bluefin killifish – males display anal fins in blue, red, or yellow.

The activities are as follows:

In nature, animals can be found in a dazzling display of different colors and patterns. Color patterns serve as signals to members of the animal’s own species, or to other species. They can be used to attract mates, camouflage with the environment, or warn predators to stay away. When looking at the diversity of colors found in nature, you may wonder, why do animals have the color patterns they do? One way to study this question is to look at a single species that has individuals of different colors. This variation can be used to uncover the mechanisms that determine color.

The bluefin killifish is a freshwater species that is found mostly in Florida. They are found in two main habitats, springs and swamps. An intriguing aspect of this species is that male bluefin killifish are brightly colored with many different color patterns. The brightest part of the fish is the anal fin, which is found on the bottom of the fish by the tail. Some males have red anal fins, some have yellow anal fins, and others have blue anal fins. This variation in color is called a polymorphism, meaning that in a species there are multiple forms of a single trait. In a single spring or swamp you may see all three colors!

Becky in the field, with her colleague Katy, collecting fish in 26 Mile Bend Swamp.

Becky in the field, with her colleague Katy, collecting fish in 26 Mile Bend Swamp.

Becky is a biologist studying bluefin killifish. One day, while out snorkeling for her research, she noticed an interesting pattern. She observed that there were differences in the polymorphism depending on whether she was in a spring or swamp. Springs have crystal clear water that can appear blue-tinted. Becky noticed that most of the males in springs had either red or yellow anal fins. Swamps have brown water, the color of iced tea, due to the dissolved plant materials in the water. Becky noticed that most of the males in swamps had blue anal fins. After noticing this pattern she wanted to find out why this variation in color existed. Becky came up with two possible explanations. She thought males in swamps might be more likely to be blue (1) because of the genes they inherit from their parents, or (2) because individual color is responding to environmental conditions. This second case, where the expression of a trait is directly influenced by the environment that an individual experiences, is known as phenotypic plasticity.

Becky had to design an experiment that could tease apart whether genes, plasticity, or both were responsible for male anal fin color. She did this by collecting male and female fish from the two habitat types, breeding them, and raising their offspring in clear or brown water. If a father’s genes are responsible for anal fin color in their sons, then fathers from swamps would be more likely to leave behind blue sons. If environmental conditions determine the color of sons, then sons raised in brown water will be blue, regardless of the population origin of their father.

Becky’s family helping her out in the field!

Becky’s family helping her out in the field!

Becky and her colleagues collected fish from two populations in the wild – Wakulla Spring, and 26 Mile Bend Swamp – and brought them into the lab. These two populations represent the genetic stocks for the experiment. Fish from Wakulla are more closely related to each other than they are to fish from 26 Mile Bend. In the lab, they mated female fish with male fish from the same population: females from Wakulla mated with males from Wakulla, and females from 26 MB mated with males from 26 MB. The female fish then laid eggs, and after the offspring hatched from their eggs, half were put into tanks with clear water (which mimics spring conditions) and half in tanks with brown water (which mimics swamp conditions). For the brown water treatment, Becky colored the water using ‘Instant, De-caffeinated, No-Sugar, No-Lemon’ tea. They raised the fish to adulthood (3-6 months) so they could determine their sex and the color of the son’s anal fins. Becky then counted the total number of male offspring, and the number of male offspring that had blue anal fins. She used these numbers to calculate the proportion of sons that had blue anal fins in each treatment.

Featured scientist: Becky Fuller from The University of Illinois

Flesch–Kincaid Reading Grade Level = 9.4


About Becky: I consider myself to be an evolutionary biologist who studies fishes. I grew up in a small town riding horses in 4-H and working in a veterinary clinic. As an undergraduate at the University of Nebraska at Lincoln, I was interested in biology and considering either medical or veterinary school. Two things led to me research in ecology and evolution. In the summer of 1991, I was taking courses at Cedar Point Biological Field Station which was run by the University of Nebraska. I met Dr. Anthony Joern (Tony) who was studying grasshopper community ecology. Tony hired me onto his field crew that summer after the courses were finished. I went on to do an undergraduate thesis under Tony’s mentorship where I studied predation on grasshoppers. I caught the “science bug” and never looked back. Following my undergraduate work, I went to Uppsala University in Sweden on a Fulbright Scholarship. Here, I developed my love for fish and aquatics. I worked with Dr. Anders Berglund on pipefish in a fjord on the west coast of Sweden. Since then, I have had many wonderful advisers, instructors, mentors, and collaborators who have helped me develop skills along the numerous fronts required for a successful career in science. I consider myself very fortunate to have a job where I can do science and teach young, enthusiastic undergraduates.

Bon Appétit! Why do male crickets feed females during courtship?

Mating pair of Hawaiian swordtail cricket with macrospermatophore on the male (left). The male and female (right) are marked with paint pens for individual identification.

Mating pair of Hawaiian swordtail cricket with macrospermatophore on the male (left). The male and female (right) are marked with paint pens for individual identification.

The activities are as follows:

In many species of insects and spiders, males provide females with gifts of food during courtship and mating. This is called nuptial feeding. These offerings are eaten by the female and can take many forms, including prey items the male captured, substances produced by the male, or parts from the male’s body. In extreme cases the female eats the male’s entire body after mating! Clearly these gifts can cost the male a lot, including time and energy, and sometimes even their lives.

So why do males give these gifts? There are two main hypotheses explaining why nuptial feeding has evolved in so many different species. First, giving a gift may attract a female and improve a male’s chance of getting to mate with her, or of fathering her young. This is known as the mating effort hypothesis. Second, giving a gift may provide the female with the energy and nutrients she needs to produce young. The gift helps the female have more, or healthier, offspring. This is known as the paternal investment hypothesis. These two hypotheses are not mutually exclusive – meaning, for any given species, both mechanisms could be operating, or just one, or neither.

Biz is a scientist who studies nuptial gifts, and he chose to work with the Hawaiian swordtail cricket, Laupala cerasina. He chose this species because it uses a particularly interesting example of nuptial feeding. In most other cricket species, the male provides the female with a single package of sperm, called a spermatophore. After sperm transfer, the female removes the spermatophore from her genitalia and eats it. However, in the Hawaiian swordtail cricket, males produce not just one but a whole bunch of spermatophores over the course of a single mating. Most of these are smaller, and contain no sperm – these are called “micros”. Only the last and largest spermatophore to be transferred, called the “macro” actually contains sperm. The number of micros that a male gives changes from mating to mating.

From some of his previous research, and from reading papers written by other scientists, Biz learned that micros increase the chance that a male’s sperm will fertilize some of the female’s eggs. Also, the more micros the male gives, the more of the female’s offspring he will father. This research supports the mating effort hypothesis for the Hawaiian swordtail cricket. Knowing this, Biz wanted to test the paternal investment hypothesis as well. He wanted to know whether the “micro” nuptial gifts help females lay more eggs and/or help more of those eggs hatch into offspring.

Biz used two experiments to test the paternal investment hypothesis. In the first experiment, 20 females and 20 males were kept in a large cage outside in the Hawaiian rainforest. The crickets were allowed to mate as many times as they wanted for six weeks. In the second experiment, 4 females and 4 males were kept in cages inside in a lab. Females were allowed to mate with up to 3 different males, and were then moved to a new cage to prevent them from mating with the same male more than once. In both experiments Biz observed all matings. He recorded the number of microspermatophores transferred during each mating and the number of eggs laid. If females that received a greater number of total micros over the course of all matings produced more eggs, or if their eggs had a higher rate of hatching, then the paternal investment hypothesis would be supported.

Featured scientist: Biz Turnell from Cornell University & Dresden University of Technology

Flesch–Kincaid Reading Grade Level = 8.9

Additional teacher resources related to this Data Nugget include:

Winter is coming! Can you handle the freeze?

Doug, and two members of his team, setting up the reciprocal transplant experiment in Scandinavia.

Doug with the reciprocal transplant experiment in Scandinavia.

The activities are as follows:

Doug is a biologist who studies plants from around the world. He often jokes that he chose to work with plants because he likes to take it easy. While animals rarely stay in the same place and are hard to catch, plants stay put and are always growing exactly where you planted them! Using plants allows Doug to do some pretty cool and challenging experiments. Doug and his research team carry out experiments with the plant species Mouse-ear Cress, or Arabidopsis thaliana. They like this species because it is easy to grow in both the lab and field. Arabidopsis is very small and lives for just one year. It grows across most of the globe across a wide range of latitudes and climates. Arabidopsis is also able to pollinate itself and produce many seeds, making it possible for researchers to grow many individuals to use in their experiments.

Doug, and two members of his team, setting up the reciprocal transplant experiment in Scandinavia.

Doug, and two members of his team, setting up the reciprocal transplant experiment in Scandinavia.

Part I: Doug wanted to study how Arabidopsis is able to survive in such a range of climates. Depending on where they live, each population faces its own challenges. For example, there are some populations of this species growing in very cold habitats, and some populations growing in very warm habitats. He thought that each of these populations would adapt to their local environments. An Arabidopsis population growing in cold temperatures for many generations may evolve traits that increase survival and reproduction in cold temperatures. However, a population that lives in warm temperatures would not normally be exposed to cold temperatures, so the plants from that population would not be able to adapt to cold temperatures. The idea that populations of the same species have evolved as a result of certain aspects of their environment is called local adaptation.

To test whether Arabidopsis is locally adapted to its environment, Doug established a reciprocal transplant experiment. In this type of experiment, scientists collect seeds from plants in two different locations and then plant them back into the same location (home) and the other location (away). For example, seeds from population A would be planted back into location A (home), but also planted into location B (away). Seeds from population B would be planted back into location B (home), but also planted at location A (away). If populations A and B are locally adapted, this means that A will survive better than B in location A, and B will survive better than A in location B. Because each population would be adapted to the conditions from their original location, they would outperform the plants from away when they are at home (“home team advantage”).

In this experiment, Doug collected many seeds from warm Mediterranean locations at low latitudes, and cold Scandinavian locations at high latitudes. He used these seeds to grow thousands of seedlings. Once these young plants were big enough, they were planted into a reciprocal transplant experiment. Seedlings from the Mediterranean location were planted alongside Scandinavian seedlings in a field plot in Scandinavia. Similarly, seedlings from the Scandinavian locations were planted alongside Mediterranean seedlings in a field plot in the Mediterranean. By planting both Mediterranean and Scandinavian seedlings in each field plot, Doug can compare the relative survival of each population in each location. Doug made two local adaptation predictions:

  1. Scandinavian seedlings would survive better than Mediterranean seedlings at the Scandinavian field plot.
  2. Mediterranean seedlings would survive better than Scandinavian seedlings planted at the Mediterranean field plot.
Doug's team in the Mediterranean prepped and ready to set up the experiment.

Doug’s team in the Mediterranean prepped and ready to set up the experiment.

Part II: The data from Doug’s reciprocal transplant experiment show that the Arabidopsis populations are locally adapted to their home locations. Now that Doug confirmed that populations were locally adapted, he wanted to know how it happened. What is different about the two habitats? What traits of Arabidopsis are different between these two populations? Doug now wanted to figure out the mechanism causing the patterns he observed.

Doug originally chose Arabidopsis populations in Scandinavia and the Mediterranean for his research on local adaptation because those two locations have very different climates. The populations may have adapted to have the highest survival and reproduction based on the climate of their home location. To deal with sudden freezes and cold winters in Scandinavia, plants may have adaptations to help them cope. Some plants are able to protect themselves from freezing temperatures by producing chemicals that act like antifreeze. These chemicals accumulate in their tissues to keep the water from turning into ice and forming crystals. Doug thought that the Scandinavian population might have evolved traits that would allow the plants to survive the colder conditions. However, the plants from the Mediterranean aren’t normally exposed to cold temperatures, so they wouldn’t have necessarily evolved freeze tolerance traits.

To see whether freeze tolerance was driving local adaptation, he set up an experiment to identify which plants survived after freezing. Doug again collected seeds from several different populations across Scandinavia and across the Mediterranean. He chose locations that had different latitudes because latitude affects how cold an area gets over the year. High latitudes (closer to the poles) are generally colder and low latitudes (closer to the equator) are generally warmer. Doug grew more seedlings for this experiment, and then, when they were a few days old, he put them in a freezer. Doug counted how many seedlings froze to death, and how many survived, and he used these numbers to calculate the percent survival for each population. To gain confidence in his results, he did this experiment with three replicate genotypes per population.

Doug predicted that if freeze tolerance was a trait driving local adaptation, the seedlings originally from colder latitudes (Scandinavia) would have increased survival after the freeze. Seedlings originally from lower latitudes would have decreased survival after the freeze because the populations would not have evolved tolerance to such cold temperatures.

Featured scientist: Doug Schemske from Michigan State University (MSU). Written by Christopher Oakley from MSU and Purdue University, and Marty Buehler (RET) from Hastings High School.

Flesch–Kincaid Reading Grade Level = 12.0

There is one scientific paper associated with the data in this Data Nugget. The citation and PDF of the paper is below.

Agren, J. and D.W. Schemske (2012). Reciprocal transplants demonstrate strong adaptive differentiation of the model organism Arabidopsis thaliana in its native range. New Phytologist 194:1112–1122.