Trees and bushes, home sweet home for warblers

Matt, Sarah, and Hankyu – a team of scientists at Andrews Forest, measuring bird populations.

The activities are as follows:

The birds at a beach are very different from those in the forest. This is because each bird species has their own set of needs that allows them to thrive where they live. Habitats must have the right collection of food to eat, places to shelter and raise young, safety from predators, and the right environmental conditions like temperature and moisture. 

The vast coniferous forests of the Pacific Northwest provide rich and diverse habitat types for birds. These forests are also a large source of timber, meaning they are economically valuable for people. Disturbances from logging and natural events result in a forest that has many different habitat types for birds to choose from. In general, areas of forest that have been harvested more recently will have more understory, such as shrubs and short trees. Old-growth forests usually have higher plant diversity and larger trees. They are also more likely to have downed trees or standing dead trees, which are important for some bird species. Other disturbances like wildfire, wind, large snow events, and forest disease also have large impacts on bird habitat.

At the Andrews Forest Long-Term Ecological Research site in the Cascade Mountains of Oregon, scientists have spent decades studying how the plants, animals, land use, and climate are all connected. In the past, Andrews Forest had experiments manipulating timber harvesting and forest re-growth. This land use history has large impacts on the habitats found in an area. Many teams of scientists work in this forest, each with their own area of research. Piece by piece, like assembling a puzzle, they combine their data to try to understand the whole ecosystem. 

Collecting data on a warbler.

Matt, Sarah, and Hankyu have been collecting long-term data on the number, type, and location of birds in Andrews Forest since 2009. Early each morning, starting in May and continuing until late June, teams of trained scientists hike along transects that go through different forest types. Transects are parallel lines along which data are collected. At specific points along the transect, the team would stop and listen for bird songs and calls for 10 minutes. There are 184 survey locations, and they are visited multiple times each year.

At each sampling point, Matt, Sarah, and Hankyu carefully recorded a count for each bird species that they hear within 100 meters. They then averaged these data for each location along the transect to get an average number for the year. The scientists were also interested in the habitats along the transect, which includes the amount of understory plants and tall trees, two forest characteristics that are very important to birds. They measured the percent cover of understory vegetation, which shows how many bushes and small plants were around. They also measured the size of trees in the area, called basal area. 

Using these data, the research team is looking for patterns that will help them identify which habitat conditions are best for different bird species. With a better understanding of where bird species are successful, they can predict how changes in the forest could affect the number and types of birds living in Andrews Forest and nearby.  

Wilson’s Warblers and Hermit Warblers are two of the many songbirds that these scientists have recorded at Andrews Forests. Wilson’s Warblers are small songbirds that make their nests in the understory of the forests. Therefore, the team predicted that they would see more of Wilson’s Warblers in forest areas with more understory than in forest areas with less understory. Hermit Warblers, on the other hand, build nests in dense foliage of tall coniferous trees and search for spiders and insects in those coniferous trees. The team predicted that the Hermit Warblers would be observed more often in forest plots where there are larger trees.  

Featured scientists: Hankyu Kim, Matt Betts, and Sarah Frey from Oregon State University. Written with Eric Beck from Realms Middle School and Kari O’Connell from Oregon State University.

Flesch–Kincaid Reading Grade Level = 10.5

Additional teacher resource related to this Data Nugget:

Fertilizer and fire change microbes in prairie soil

Christine collecting samples from the experimental plots to measure root growth.
Christine collecting samples from the experimental plots to measure root growth.

The activities are as follows:

Stepping out into a prairie feels like looking at a sea of grass, with the horizon evoking a sense of eternity. Grasses and other prairie plants provide important benefits, such as creating habitat for many unique plants, mammals, insects, and microbes. They also help keep our water clean by using nutrients from the soil to grow. When plants take up these nutrients, they prevent them from going into streams. High levels of plant growth also keeps carbon bound up in the bodies of plants instead of in the atmosphere.  

Prairies grow where three environmental conditions come together – a variable climate, frequent fires, and large herbivores roaming the landscape. However, prairies are experiencing many changes. For example, people now work to prevent fires, which allows forest species to establish and eventually take over the prairie. In addition, a lot of land previously covered in prairie is now being used for agriculture. When land is used for agriculture, farmers add nutrients through fertilizer. With all these changes, prairie ecosystems have been declining globally. Scientists are concerned that as they disappear so will the benefits they provide. 

Lydia and Christine are two scientists contributing to the effort to learn more about how to preserve prairies. They both became interested in studying soil because of their appreciation for prairies at a young age. For Lydia, she lived in an area that was covered by trees and farmland, but knew at one time it used to be prairie. This made her want to learn more about prairie environments and how places like where she grew up have changed through history. For Christine, she grew up surrounded by prairies where she developed a passion and curiosity for the natural world. Especially for the organisms living in the soil that you cannot see, called microbes. 

These are two different experimental plots within the large field experiment at Konza Prairie Biological Station. The one with lots of trees is an unburned plot, the one with lots of grass is a burned plot.
These are two different experimental plots within the large field experiment at Konza Prairie Biological Station. The one with lots of trees is an unburned plot, the one with lots of grass is a burned plot.

Lydia and Christine read about how grassland scientists have been doing research to learn more about what happens when fire is stopped and excess nutrients are added. These changes reduce biodiversity and affect which species of plants can grow in the prairie. However, Lydia and Christine noticed that the research had been mostly focused on what happens aboveground.  Lydia and Christine had a hunch that the aboveground communities were not the only things changing. They thought that belowground components would be changed by fire and fertilizer too. They turned their focus to microbes in the soil, because they also use nutrients. In addition, they thought these microorganism would be affected by the changes in aboveground plant biodiversity. 

To see if this was true, they used data that they and other scientists collected at Konza Prairie Biological Station from a large field experiment. The experiment was set up in 1986 and the treatments were applied at the field site every year until 2017! Lydia and Christine focused on the fertilizer (nitrogen) addition and prescribed burning treatments to answer their questions. The nitrogen treatment had eight plots where nitrogen had been added and eight with no nitrogen as a control. Similarly, the prescribed burn treatment was applied to eight plots, while eight plots had no burning as a control. These two treatments were also crossed with each other, meaning that some plots were burned and nitrogen was added.

Lydia and Christine expected the types of microbes in the soil to change in response to the nitrogen and burning treatments because of the different aboveground plant communities and difference in soil nutrients. Soil microbial communities can change in multiple ways. First, the number of unique species can increase or decrease, measured as richness. The other way is how many individuals of each species there are in the community, measured as evenness. Taken together, richness and evenness give a measure of diversity, which can be summarized using the Shannon-Wiener index. The value will get bigger if either richness or evenness increases because it incorporates both. For example, a community with five species that has equal abundance of each will have a larger Shannon-Wiener index than a community with five species where one species has a lot more individuals than the other four.  

Featured Scientists: Lydia Zeglin and Christine Carson from the Konza Prairie Biological Station. Written By: Jaide Allenbrand

Flesch–Kincaid Reading Grade Level = 10.4

Candid camera: Capturing the secret lives of carnivores

Erik demonstrating how to place a camera trap on a tree on Stockton Island.

The activities are as follows:

Carnivores, animals that eat meat, captivate people’s interest for many reasons – they are charismatic, stealthy, and can be dangerous. Not only are they fascinating, they’re also ecologically important. Carnivores help keep prey populations in balance. They often target old, sick, or weak individuals. This results in more resources for healthier prey. Carnivores also impact prey’s behavior and population sizes, which can have further effects down the food web. For example, if there are too many herbivores, such as deer, the plants in an ecosystem may be eaten to a point where they can’t survive. In this way, carnivores help the plant community by either reducing the number of herbivores in an ecosystem, or changing how or where prey forage for food. 

Despite their importance and our interest in carnivores, they are very hard to monitor. Not only do they have naturally low population sizes because they are at the top of the food chain, they also have a natural ability to hide and blend into their environment. Erik is a wildlife biologist who is interested in taking on this challenge. He wants to learn more about carnivores and what factors affect where they live. Learning more about where carnivores are found can help scientists with conservation efforts.

Erik lives on the southern shore of Lake Superior, the largest lake (by area) in the world. This area is home to the Apostle Islands National Lakeshore – including 21 islands and a 12-mile stretch of the mainland in northern Wisconsin. The Apostle Islands vary in many ways – size, distance from the mainland, highest elevation, historical and current human use, plant communities, and even small differences in climate. The islands are so remote that scientists really didn’t know which carnivores lived on the islands. There is evidence from historical reports that red fox and coyotes lived on some of the islands. More recently, black bears have been observed by visitors as they are hiking or camping. Erik wanted to know which species of carnivores are on each island. As he began to explore methods to document wildlife on the islands, Erik and his collaborators were shocked to discover that American martens, Wisconsin’s only state endangered species, live on some of the islands.

Erik thought a promising step in learning more about what drives carnivores to live on different islands in the archipelago would be to apply what has been learned from islands in the ocean. He referred to a fundamental theory in ecology called the theory of island biogeography. This theory predicts that island size and its distance to the mainland affects the biodiversity, or number of species, found on that island. Specifically, larger islands will have higher carnivore biodiversity because there are more resources and space to support more species than smaller areas. In contrast, islands farther away from the mainland will have lower carnivore biodiversity because more isolated islands are harder for wildlife to reach. 

Erik wanted to test whether the theory of island biogeography also applied to the Apostle Islands. Just like the classic research on island biogeography, some islands are closer to the mainland and they range in size. To inventory where each carnivore is found, Erik and his collaborators and students set up 164 wildlife cameras on 19 of the islands. They made their way out to the remote islands by boat and then bushwhacked their way to the sites, which are not along trails. Often this means they have to push through thick brush and climb over fallen trees, but it’s important to put the cameras in all habitat types, not just those that are enjoyable to walk through. When the research team arrived at a site, they mounted a camera on a tree at waist height. Whenever an animal came into the frame of a camera, a photo was taken and stored on a memory card. The cameras were left on the islands year-round from 2014-2019. Every 6 months Erik and his collaborators would traverse through the thick woods to swap out memory cards and batteries. During this time, they noticed that four of the cameras had not worked properly, so they used the pictures from 160 of the cameras. 

Back at the college, the research team spent countless hours identifying which animals triggered the cameras. The cameras had taken over 200,000 photos over three years including 7,000 wildlife visits. Of these visits, 1,970 were from carnivores! They found 10 different kinds of carnivores, including: American marten, black bear, bobcat, coyote, fisher, gray fox, gray wolf, raccoon, red fox and weasels. After the pictures were processed, Erik used this information to map out which islands the animals were found. For this study, he used species richness, or the number of different species observed on each island, to answer his question. 

Map of the Apostle Islands with the richness, or number of different carnivore species, detected on each island.

Featured scientists: Erik Olson from Northland College, Tim Van Deelen, and Julie Van Stappen from the National Park Service. Support for this lesson was provided by the National Park Service with funding from the Great Lakes Restoration Initiative.

Flesch–Kincaid Reading Grade Level = 11.2

Additional teacher resources related to this Data Nugget:

The study and results described in this Data Nugget have been published:

  • Allen, M.L., Farmer, M.J., Clare, J.J., Olson, E.R., Van Stappen, J., Van Deelen, T.R. 2018. Is there anybody out there? Occupancy of the carnivore guild in a temperate archipelago. Community Ecology 19(3): 272-280.

Citizen science site where students can view and identify animals found in pictures from cameras placed around Wisconsin.

There have been several news articles about this research:

Tree-killing beetles

A Colorado forest impacted by a mountain pine beetle outbreak. Notice the dead trees mixed with live trees. Forests like this with dead trees from mountain pine beetle outbreaks cover millions of acres across western North America.

The activities are as follows:

A beetle the size of a grain of rice seems insignificant compared to a vast forest. However, during outbreaks the number of mountain pine beetles can skyrocket, leading to the death of many trees. The beetles bore their way through tree bark and introduce blue stain fungi. The blue stain fungi kills the tree by blocking water movement. Recent outbreaks of mountain pine beetles killed millions of acres of lodgepole pine trees across western North America. Widespread tree death caused by mountain pine beetles can impact human safety, wildfires, nearby streamflow, and habitat for wildlife.

Mountain pine beetles are native to western North America and outbreak cycles are a natural process in these forests. However, the climate and forest conditions have been more favorable for mountain pine beetles during recent outbreaks than in the past. These conditions caused more severe outbreaks than those seen before.

Logs from mountain pine beetle killed lodgepole pine trees. The blue stain fungi is visible around the edge of each log. Mountain pine beetles introduce this fungus to the tree.

When Tony moved to Colorado, he drove through the mountains eager to see beautiful forests. The forest he saw was not the green forest he expected. Many of the trees were dead! Upon closer examination he realized that some forests had fewer dead trees than others. This caused him to wonder why certain areas were greatly impacted by the mountain pine beetles while others had fewer dead trees. Tony later got a job as a field technician for Colorado State University. During this job he measured trees in mountain forests. He carefully observed the forest and looked for patterns of where trees seemed to be dead and where they were alive.

Tony thought that the size of the trees in the forest might be related to whether they were attacked and killed by beetles. A larger tree might be easier for a beetle to find and might be a better source of food.To test this idea, Tony and a team of scientists visited many forests in northern Colorado. At each site they recorded the diameter of each tree’s trunk, which is a measure of the size of the tree. They also recorded the tree species and whether it was alive or dead. They then used these values to calculate the average tree size and the percent of trees killed for each site.

Featured scientist: Tony Vorster from Colorado State University

Flesch–Kincaid Reading Grade Level = 8.3

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

Bringing back the Trumpeter Swan

Joe with a Trumpeter Swan.

The activities are as follows:

The Kellogg Bird Sanctuary was created in 1927 to provide safe nesting areas for waterfowl such as ducks, geese, and swans. During that time many waterfowl species were in trouble due to overhunting and the loss of wetland habitats. One species whose populations had declined a lot was the Trumpeter Swan. Trumpeter swans are the biggest native waterfowl species in North America. At one time they were found across North America, but by 1935 there were only 69 known individuals in the continental U.S.! The swans were no longer found in Michigan.

The reintroduction, or release of a species into an area where they no longer occur, is an important tool in helping them recover. In the 1980s, many biologists came together to create a Trumpeter Swan reintroduction plan. Trumpeter Swans in North America can be broken up into three populations – Pacific Coast, Rocky Mountain, and Interior. The Interior is further broken down into Mississippi/Atlantic and High Plains subpopulations. Joe, the Kellogg Bird Sanctuary manager and chief biologist, wrote and carried out a reintroduction plan for Michigan. Michigan is part of the Mississippi/Atlantic subpopulation. Joe and a team of biologists flew to Alaska in 1989 to collect swan eggs to be reared at the sanctuary. After two years the swans were released throughout Michigan.

The North American Trumpeter Swan survey has been conducted approximately every 5 years since 1968 as a way to estimate the number of swans throughout their breeding range. The survey is conducted in late summer when young swans can’t yet fly but are large enough to count. Although the surveys are conducted across North America, the data provided focuses on just the Interior Population, which includes swans in the High Plains and Mississippi/Atlantic Flyways.

Featured scientist: Wilbur C. “Joe” Johnson from the W.K. Kellogg Bird SanctuaryWritten by: Lisa Vormwald and Susan Magnoli from Michigan State University.

Flesch–Kincaid Reading Grade Level = 11.5

Additional teacher resource related to this Data Nugget:

A video on Trumpeter Swan reintroduction efforts that could be shown before the Data Nugget to engage students with the topic, or after to expand the research beyond the one study:

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City parks: wildlife islands in a sea of cement

Image of a red fox caught on one of the wildlife cameras.

The activities are as follows:

For most of our existence, humans have lived in rural, natural places. However, more and more people continue to move into cities and urban areas. The year 2008 marked the first time ever in human history that the majority of people on the planet lived in cities. The movement of humans from rural areas to cities has two important effects. First, the demand that people place on the environment is becoming very intense in certain spots. Second, for many people, the city is becoming the main place where they experience nature and interact with wildlife on a regular basis.

Remington and Grant are city-dwellers and have been their entire lives. Remington grew up in Tulsa, Oklahoma and Grant is from Cleveland, Ohio. In Tulsa, Remington fell in love with nature while running on the trails of city parks during cross country and track practices. Grant developed a love for nature while fishing and hiking in the Cleveland Metroparks in Ohio. These experiences led them to study wildlife found in urban environments because they believe that cities can be places where both humans and wildlife thrive. However, to make this belief a reality, scientists must understand how wildlife are using habitats within a city. This knowledge will provide land managers the information they need to create park systems that support all types of species. However, almost all research done on wildlife takes place in natural areas, like national parks, so there is currently very little known about wildlife habits in urban areas. To address this gap in knowledge, Remington, Grant, and their colleagues conduct ecological research on the urban wildlife populations in the Cleveland Metroparks.

Remington prepares to attach the camera to a buckeye tree. He secures them with a heavy-duty lock to keep the cameras safe from theft by people using the parks.

The Cleveland Metroparks are a collection of wooded areas that range in size, usage, and maintenance. Some are highly used small parks with mowed grass, while others are large, rural parks with thousands of acres of forest and miles of winding trails. As they began studying the Metroparks, they noticed the parks were like little “islands” of wildlife habitat within a large “sea” of buildings, pavement, houses and people. This reminded Remington and Grant of a fundamental theory in ecology: the theory of island biogeography. This theory has two components: size and isolation of islands. The first predicts that larger islands will have higher biodiversity because there are more resources and space to support more wildlife than smaller areas. The second is that islands farther away from the mainland will have lower biodiversity because more isolated islands are harder for wildlife to reach. Remington and Grant wondered if they could address this first component in the wide variety of areas that are part of the Cleveland Metroparks. If the theory holds for the Metroparks, it could help them to figure out where most species live in the park system and help managers better maximize biodiversity. It would also provide an important link between ecological research conducted in natural areas and urban ecology.

To evaluate whether the theory of island biogeography holds true in urban areas, Remington and Grant set up 104 wildlife cameras throughout the parks. These cameras photograph animals when triggered by motion. They used these photographs to identify the locations of wildlife in the parks and to get a count of how many individuals there are, known as their abundance. With these data, they tested whether the size of the park would influence biodiversity as predicted by the theory of island biogeography.

One challenge with measuring “biodiversity” is that it means different things to different people. Remington and Grant looked at two common measurements of biodiversity. First, species richness, which is the number of different species observed in each park. Second, they calculated the Shannon Wiener Index of biodiversity for each park. This index incorporates both species richness and species evenness. Species evenness tells us whether the abundances of each species are similar, or if one type is most common and the others are rare. Evenness is important because it tells you whether a park has lots of animals from many different species or if most animals are from a single species. If a park has greater evenness of species, the Shannon-Wiener index will be higher.

Featured scientists: Remington Moll and Grant Woodard from Michigan State University

Flesch–Kincaid Reading Grade Level = 11.4

Additional teacher resource related to this Data Nugget:

Remington, and other members of his lab, have written blog posts about this research. These readings would be appropriate for a middle or high school reading level and would give students more context for the researchSaveSave

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About Remington: Remington is a Ph.D. student and NSF Graduate Research Fellow at Michigan State University in Dr. Bob Montgomery’s lab. Prior to Michigan State, Remington received B.S. and M.S. degrees from the University of Missouri, where he worked with Dr. Josh Millspaugh. Following his M.S., he spent time in Amman, Jordan doing work with the Royal Society for the Conservation of Nature and spent three years teaching high school biology, chemistry, and theology at the Beirut Baptist School in Lebanon.

He uses cutting-edge technologies such as GPS collars and camera-traps to study predator-prey interactions between large carnivores and their prey. He is particularly excited about evaluating how ecological theory developed in “natural” areas like national parks applies to urban contexts. Remington grew up in the city and fell in love with nature and ecology in city parks. Although it carries substantial challenges, Remington believes that humans and large predators can peaceably coexist, even in and around cities. It is his goal to use the lessons learned in his research to help make that belief a reality.

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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

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 similar groups. How then do animals know who to choose as a mate and who is a member of their own species? Communication plays an important role. 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 darters because he was fascinated by the bright color patterns the males have on their bellies during the breeding season. Female darters get to select which males to mate with and the males fight with each other for access to the females during the mating season. Species identification is very important during this time. 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 males use the color patterns 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 be able to hybridize, or mate with members of a different species if their color patterns are very close. Thus, before collecting any data, Michael predicted that the more similar the color patterns between two males, the more likely they would be to hybridize and act aggressively towards each other. If this is the case, it would serve as evidence that color pattern may indeed serve as a signal to communicate darter species identity.

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

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

Michael collected eight 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. In some species pairs the color patterns were very similar, and in some they were very different. For each species pair, he put five males of both species and five females of both species in the same fish tank and observed their behavior for five hours. He did this eight times, once for each species pair (for a total of 1,280 fish!). During the five-hour observation period, he recorded (1) how many times females mated with males of their own species or of a different species and (2) how many times males were aggressive towards males of their own species or of a different species. He used these data to calculate an index of bias for each behavior, to show whether individuals had stronger reactions towards members of their own species.

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

Flesch–Kincaid Reading Grade Level = 10.9

Videos showing darter behavior:

Darter species used in the experiment:

darters

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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 a layer of blubber. 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 when living 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 fresh 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 that 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. 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 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. Carrie wondered if female mountain chickadees prefer to mate with males that are from the same elevation and therefor contribute to local adaptation by passing the adaptive behaviors on to the offspring. This process 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 low 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, she was given time to spend 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 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. The more time a female spent on the side of the cage near one male, the stronger her 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!

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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.