Ecology and Evolutionary Biology

Fish on film: uncovering the environmental drivers of black spot syndrome

Rachel Sauer — Tue, 12 Nov 2024 17:18:32 +0000

Fish on film: uncovering the environmental drivers of black spot syndrome Rachel Sauer Tue, 11/12/2024 - 10:18

Blake Puscher

�� Boulder researchers use a unique, noninvasive method to determine the environmental factors contributing to several symptoms among tropical fish

For many researchers in biology and other natural sciences, dissecting specimens may not be desirable, though it is often necessary. This is because dissection means killing the animal a researcher is trying to study—a big issue, especially if the species is experiencing population decline.

Over time, such concerns have led scientists to develop a number of non-invasive techniques, including video transects. This is a type of video recording used in marine biology, in which divers film along a line of fixed length and depth to record images for computer-assisted analysis, obtain permanent data that can be reassessed later and survey wider areas in shorter amounts of time.

�� Boulder scientist Pieter Johnson and his research colleagues use a unique, noninvasive method to determine the environmental factors contributing to several symptoms among tropical fish.

A recently published study by Pieter Johnson, a University of Colorado Boulder professor of distinction in the Department of Ecology and Evolutionary Biology, and lead author Cheyenna de Wit of the University of Amsterdam, demonstrates the benefits of recording rather than dissecting specimens.

In their paper on black spot syndrome in ocean surgeonfish, the researchers use video transects to measure the severity of the disease among thousands of fish and identify the environmental factors contributing to its distribution.

What is black spot syndrome?

Black spot syndrome is a collection of several symptoms, the most prominent being the dermal lesions or spots for which the condition is named, according to Johnson. In many species, Johnson says, these lesions are black, “but in some species they’ll show up as white.” They form on the skin, scales and fins of fish.

The spots appear when the free-swimming, larval form of trematodes—commonly known as flukes, a type of parasitic flatworm—penetrate the skin of the fish and form cysts inside them. The distinctive coloration occurs when fish surround the cyst with melanin in response to the invasion, similar to the formation of pearls in oysters.

Relatively little is known about the genus of trematode that causes black spot syndrome, Scaphanocephalus. “Prior to us detecting it in 2017,” Johnson says, “it had never been reported from Caribbean fish. So, it was wholly undescribed from that area.” Much remains unknown about this trematode, including the type of snail that Scaphanocephalus infects before moving on to fish.

However, trematode infection is clearly very common in certain regions: In Johnson’s study, 70% of observed fish showed signs of infection, while a companion study of other Caribbean fish demonstrated both how high the parasite loads are in that region, and how many different fish species seem to be affected, according to Johnson.

As to the consequences of infection for fish, there is some evidence, Johnson says, that infected fish may graze less and have more trouble maintaining buoyancy. Researchers also hypothesize that they are more conspicuous to predators.

“One in particular, of course, is osprey, which are visual, fish-specialized predators that are looking for fish through the water,” Johnson says. “When these infected fish tend to flash or turn sideways, and you can see those black spots, it probably makes it a lot easier for the bird to detect them.”

If this hypothesis is true, black spot syndrome could bolster the numbers of the trematodes that cause it, as Johnson says osprey are their definitive host. That means these trematodes must enter the body of an osprey to reproduce. The transmission of the parasites is trophic, so they are passed along when infected fish are eaten.

Noninvasive methods

While black spot syndrome can have negative effects on infected fish, the most important consequences could be for reef ecosystems. According to Johnson, black spot syndrome has been increasingly prevalent in important herbivorous grazing fish in the Caribbean, such as surgeonfish and parrotfish.

Learn more

For more information on the complex lifecycles of digenetic trematodes, see this article about other research from �� involving the parasites.

“In tropical coral reef ecosystems,” Johnson explains, “surgeonfish and parrotfish, and other herbivores play a key role by grazing on algae.” Since infected fish are evidenced to graze less, and since they may be more likely to be eaten by osprey, the population of algae in the affected area can increase.

“Algae and coral are in a dynamic balance,” Johnson says, and if there is enough algal growth, “it can start to overwhelm and kill corals. So, in these areas, we try to keep those populations of surgeonfish and parrotfish as viable as possible, so that they can continue to regulate and graze down the algae.”

In fact, some studies have even said that grazing fish can help save coral reefs, with particular emphasis on parrotfish because the prior primary grazer in the Caribbean, spiny sea urchins, were killed off by disease in the 1980s. Also, trematode infection isn’t the only thing threatening surgeonfish and parrotfish populations, as they are popular catches for fisheries.

Because the fish being studied are ecologically important, it is particularly important to avoid interfering with their populations. Ordinarily, this is difficult, since dissection is the surest way to confirm a trematode infection—the parasites being clearly visible inside the fish’s bodies. In this case, though, the black spots characteristic of black spot syndrome allowed for a different approach: the video transect method.

To record as many surgeonfish as possible, and therefore provide an accurate estimate of how many fish were infected, S��BA divers filmed at 35 sites along the coast of Curaçao, an island in the southern Caribbean. They recorded two and five meters below water for either 10 minutes or until 20 adult surgeonfish had been filmed.

An ocean surgeonfish with black spot syndrome. (Photo: Cheyenna de Wit)

Environmental factors

Besides determining that 70% of surgeonfish showed visible signs of black spot syndrome, Johnson and de Witt correlated different environmental factors with the severity of the syndrome, which they based on the average number of spots per fish.

One of the most significant effects the researchers observed arose from longitude—that is, the position of fish from east to west along the leeward (downwind) shore. Both the prevalence and intensity of black spot syndrome was lower toward the east and higher toward the west.

Johnson hypothesizes that this effect is caused by urban and industrial development, as the east end of Curaçao, where a portion of the research took place, is privately owned and less developed. The researchers observed the same association between development and infection intensity in Bonaire, the neighboring island.

The first component of the effect was wave intensity, which was negatively associated with infection intensity because the larval form of trematode that infects fish can’t swim well enough to overcome opposing tides. Wave energy is usually greatest at the eastern end of Curaçao, so this will have contributed to the lower intensity of infection at the east end.

The other components were positively associated with infection intensity. Nitrogen concentration increases with sewage and domestic runoff, which can contain nutrients and other pollutants. Nutrients can increase the population of trematode hosts, and pollutants can weaken the immune systems of fish that trematodes infect.

While fishing pressure can be either positively or negatively correlated with parasite abundance, Johnson says, this depends on the species involved. In the case of Scaphanocephalus, fishing pressure could increase abundance if it removed predatory fish from the environment, resulting in an increased snail population.

Student learning

�� Boulder students also play an important role in this research. Undergraduates in the field course Coral Reef Ecology and Conservation (EBIO 4090, taught by Johnson) spend their fall semester learning about coral reefs and the factors that threaten them before traveling to Curaçao over winter break. During a week-long S��BA expedition, students learn how to collect video transect data using the same methods Johnson and his research colleagues use and are contributing valuable data to the understanding of black spot syndrome. For the upcoming trip, students will be revisiting some of the same sites as in the study to assess how black spot severity has changed through time, particularly following recent warm water bleaching events that have killed many corals.

Since most of the factors composing the difference between the east and west ends come from human action, it is possible that the severity of black spot syndrome could be significantly reduced if the handling of runoff and/or fishing behavior were changed.

A unique methodology

One noteworthy part of the way Johnson and de Witt’s study was conducted is that, with the videos collected, the researchers had observers record the number of lesions on each fish. This is unique, as prior studies have simply noted whether lesions were present, leaving the severity of infection uncertain.

Moreover, methods like the one used in this study may help to solve the challenges that come with observing ocean life. “There's a lot of ocean out there and not a tremendous number of people to study it,” Johnson explains, “so I think approaches like this could be applied in other areas where we're detecting blackspot syndrome.” Photos are an especially useful way to study the ocean because they are easy for anyone to take thanks to digital technology, he adds. For this reason, community science platforms like iNaturalist can be used to aggregate a large amount of data.

“When people are on vacation, or they’re diving, or they’re swimming,” Johnson says, “they upload all of their observations and fish photos, and we’ve been using that to scan across large sections of the Caribbean and lots of different fish species; and now some of the undergrads in the lab are also extending that to look into parts of the Indo-Pacific and other regions of the world where Scaphanocephalus occurs.

“So, I think those kinds of approaches, video transects and these community science-uploaded images, together start to give a much bigger picture of patterns of infection over large geographic areas.”

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An ocean surgeonfish with black spot syndrome. (Photo: Cheyenna de Wit)

For some mammals, warming temperatures mean higher elevations

Anonymous — Tue, 15 Oct 2024 17:45:59 +0000

For some mammals, warming temperatures mean higher elevations Anonymous (not verified) Tue, 10/15/2024 - 11:45

In her Distinguished Research Lecture, �� Boulder Professor Christy McCain will highlight how certain traits in some mammal and insect populations indicate who is at greatest risk from climate change

Colorado’s small, mountain-dwelling mammals are moving higher—not for better views or real estate, but because climate change is forcing them to.

This finding is based on a 13-year study of 27 rodent and four shrew species in Colorado’s Front Range and San Juan mountains—research that included trapping, tagging and releasing the various mammals to better understand their range.

While the findings are more complex than a simple trend of animals moving up the mountain, they spotlight the sobering possibility that climate change could force some mammals from Colorado entirely.

Christy McCain, a professor in the �� Boulder Department of Ecology and Evolutionary Biology and curator of vertebrates in the �� Museum of Natural History, will discuss mountain biodiversity and climate change in her Distinguished Research Lecture Nov. 14.

“We’ve been talking about climate change in the Rockies for a long time, but I think we can say that this is a sign that things are now responding and responding quite drastically," Christy McCain, the study’s lead author, told Denver 7 in Feb. 2021.

McCain, a professor in the University of Colorado Boulder Department of Ecology and Evolutionary Biology and curator of vertebrates in the �� Museum of Natural History, uses mountains as natural experiments to study biodiversity, ecological theory, global change, montane ecology and range limits.

She will discuss mountain biodiversity and climate change in her Distinguished Research Lecture Nov. 14, highlighting the research her lab has done to understand how animals—mostly vertebrates and insects—are distributed on mountains around the world.

She and her research colleagues have found that different groups of animals, driven by their evolutionary history and climate, show distinctive patterns. For example, mountain biodiversity for rodents, salamanders and moths is quite different from birds, bats and reptiles.

The conservation priorities for each group of mountain organisms are closely tied to elevational diversity patterns, land-use change and complex interactions with a rapidly warming and drying climate. McCain will explore these topics through case studies of mammal populations in the Front Range and San Juan Mountains and carrion beetles—examining how various physiological traits like heat and desiccation tolerance may be critical to responses to climate change.

�� Christy McCain

McCain received dual bachelor’s degrees in wildlife biology and studio art from Humboldt State University, was a natural-resources and protected-areas specialist in the Peace Corps Honduras and earned her PhD in ecology and evolutionary biology from the University of Kansas.

She was a postdoctoral fellow at the National Center for Ecological Analysis and Synthesis at the University of California Santa Barbara before coming to �� Boulder as an assistant professor in 2008.

If you go

What: 124th Distinguished Research Lecture, Mountain Biodiversity and Climate Change

Who: Professor Christy McCain of the Department of Ecology and Evolutionary Biology and �� Museum of Natural History

When: 4-5 p.m. Nov. 14, followed by a Q&A and reception

Where: Chancellor's Hall and Auditorium, Center for Academic Success and Engagement (CASE)

McCain studies how montane organisms are distributed on mountains around the world and how those populations and species are influenced by human land use and climate change. Her research spans topics across ecology and evolution to understand and conserve biodiversity.

Funded by the National Science Foundation through several grants, her research has appeared in more than 60 peer-reviewed journals, including Science, Ecology Letters, Ecology and Global Change Biology, among others.

McCain is the curator of vertebrate collections in the �� Museum of Natural History, where she is a steward for the continued protection and use of museum specimens for understanding and conserving the world’s biodiversity. Over the years, she has taught mammalogy as well as other topics in field biology, creative conservation messaging and mountain ecology and conservation.

�� the Distinguished Research Lectureship

The Distinguished Research Lectureship is among the highest honors given by faculty to a faculty colleague at �� Boulder. Each year, the Research and Innovation Office requests nominations from faculty for this award, and a faculty review panel recommends one or more faculty members as recipients.

The lectureship honors tenured faculty members, research professors (associate or full) or adjoint professors who have been with �� Boulder for at least five years and are widely recognized for a distinguished body of academic or creative achievement and prominence, as well as contributions to the educational and service missions of �� Boulder. Each recipient typically gives a lecture in the fall or spring following selection and receives a $2,000 honorarium.

McCain and Jamie Nagle, a professor of physics, have been recognized with 2024-25 Distinguished Research Lectureships. Nagle will give his lecture Feb. 6, 2025.

Top image: Eli Allan/Unsplash

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Samuel Ramsey receives the prestigious Lowell Thomas Award

Anonymous — Tue, 17 Sep 2024 19:26:37 +0000

Samuel Ramsey receives the prestigious Lowell Thomas Award Anonymous (not verified) Tue, 09/17/2024 - 13:26

Once frightened of insects, Ramsey has become a leader in the field of entomology

Samuel Ramsey, assistant professor of ecology and evolutionary biology at the University of Colorado Boulder, is one of this year’s recipients of the Lowell Thomas Award.

The Lowell Thomas Award, named after broadcast journalist and explorer Lowell Thomas and given by The Explorers Club, recognizes “excellence in domains or fields of exploration,” according to the award announcement. In particular, the award celebrates “individuals who have grit, tenacity, are undaunted by failure, and endure all obstacles, finding a way forward to discovery and results that expand the limits of knowledge.”

Samuel Ramsey (left) working with the chieftain of a hill tribe village in Thailand to sample domesticated bees for parasites. (Photo: Shin Arunrugstichai/Syzgy Media Co.)

Ramsey, also known as “your friendly neighborhood entomologist,” didn’t always like insects. They used to terrify him. But in the second grade he conquered his fears by learning about insects at his local library.

Now, more than 25 years later, Ramsey is one of the most innovative and distinguished thinkers in the field of entomology. His research has won him numerous awards, including first place in the International Three-Minute Thesis Competition, the American Bee Research Conference’s Award for Distinguished Research and the Acarological Society of America’s Highest Award for Advances in Acarology Research.

Ramsey—a member of the Explorers Club 50, class of 2024—also runs a nonprofit, the Ramsey Research Foundation, which seeks to protect pollinator diversity.

Ramsey’s fellow awardees this year are zoologist Carole Baldwin, ocean conservationist Ellen Pikitch and geothermal scientist Andrés Ruzo. Past recipients include Kathy Sullivan, E. O. Wilson, Kris Tompkins, Isaac Asimov, Sir Edmund Hillary and Carl Sagan.

The 2024 Lowell Thomas Awards Dinner takes place in Austin on Nov. 1.

Top image: Samuel Ramsey researching bee biodiversity in Thailand. (Photo: Shin Arunrugstichai/Syzgy Media Co.)

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Once frightened of insects, Ramsey has become a leader in the field of entomology.

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Studying complex networks of plants and pollinators

Anonymous — Wed, 11 Sep 2024 18:42:15 +0000

Studying complex networks of plants and pollinators Anonymous (not verified) Wed, 09/11/2024 - 12:42

Julian Resasco

I’ve visited the same Rocky Mountain subalpine meadow weekly for a decade of summers looking at plant-pollinator interactions—here’s what I learned

Imagine a bee crawling into a bright yellow flower.

This simple interaction is something you may have witnessed many times. It is also a crucial sign of the health of our environment—and one I’ve devoted hundreds of hours of field work observing.

Interactions between plants and pollinators help plants reproduce, support pollinator species like bees, butterflies and flies, and benefit both agricultural and natural ecosystems.

Julian Resasco is an assistant professor in the �� Boulder Department of Ecology and Evolutionary Biology.

These one-on-one interactions occur within complex networks of plants and pollinators.

In my lab at the University of Colorado Boulder, we’re interested in how these networks change over time and how they respond to stressors like climate change. My team emphasizes long-term data collection in hopes of revealing trends that would otherwise be unnoticed.

Working at Elk Meadow

Ten years ago, I began working in Elk Meadow, which is located at 9,500 feet (or 2,900 meters) elevation at the University of Colorado’s Mountain Research Station.

I wanted a local field site that allowed for frequent observations to study the dynamics of plant-pollinator networks. This beautiful subalpine meadow, bursting with wildflowers and just 40 minutes from campus, fit the bill perfectly.

Since 2015, often joined by members of my lab, I have made weekly hikes to Elk Meadow. We visit from the first flower in May to the last in October. We observe pollinators visiting flowers at plots scattered throughout the meadow, walking the periphery to minimize trampling. The morning is the best time to visit because pollinator activity is high and thunderstorms often roll in at midday during the summer in the Rocky Mountains.

Observing the network

Elk Meadow is rich in biodiversity. Over the years, we have observed 7,612 interactions among over 1,038 unique pairs of species. These pairings were made by 310 species of pollinators and 45 species of plants.

Pollinators include not only a wide variety of bees, but also flies, butterflies, beetles and the occasional hummingbird. Expert entomologists help us identify some of the insects.

Plants include species that are widespread, like the common dandelion, and some that are only found in the Rocky Mountains, like the Colorado columbine.

Common but vital

Collecting data in Elk Meadow is fun, but it is also serious science. Our data is useful for understanding the dynamics of plant and pollinator interactions within and across seasons.

For example, we learned which interactions between plants and pollinators are stable and which change over time and space. We consistently observed interactions between generalist species and their many partners over time and in different plots across the meadow.

Generalist species can tolerate a range of environmental conditions, meaning they are more frequently available to interact.

In other words, generalist species are more likely to be alive, active and foraging in the case of pollinators—or flowering in the case of plants—compared with species that can only survive if environmental conditions like temperature, sunlight and rainfall are just right to support them.

Generalist species are vital in networks, but they often don’t receive the same conservation attention as rare species. Even these common species can decline due to environmental changes destabilizing entire ecosystems. Protecting these species is important for maintaining biodiversity.

Julian Resasco at Elk Meadows at �� Boulder's Mountain Research Station. (Photo: Julian Resasco)

In it for the long term

As we gather more years of data, our study is becoming increasingly useful for understanding how networks and pollinator populations are changing—especially with signs of climate change increasingly emerging. Most ecological studies are only designed or funded for one or a few years, making our 10-year dataset one of only a few for plant-pollinator networks.

It is only with long-term ecological data that we can detect trends in responses to climate change, particularly because of high year-to-year variability in weather and populations.

The National Science Foundation supports a network of long-term ecological research stations across the U.S., including the Niwot Ridge Long-term Ecological Research Program near Elk Meadow, which is dedicated to the study of high-mountain species and ecosystems.

Colorado’s climate, like much of the world, is experiencing significant changes, such as rising temperatures, earlier snow melt and more late-winter and spring rain instead of snow. These changes lead to earlier water runoff from mountains, drier soils and more severe droughts. These shifts can have important consequences for plants and pollinators, including changes in where species are found, how many there are, and when they flower or forage.

High-elevation plant and pollinator communities may be especially vulnerable to climate change impacts since these areas are experiencing greater temperature increases compared with lower elevations.

We have seen warmer and drier conditions at Elk Meadow. Overlaid in this trend, we have observed annual variation in temperature and drought conditions that can help us understand and predict how different species will fare in a hotter and drier future.

Climate change is a driver of pollinator declines and is predicted to become increasingly important in the coming decades. Immediate threats also include pesticide use, light pollution and the destruction of wild habitats for farming and development.

The state of Colorado recently commissioned a study to gauge the health of Colorado’s native pollinators and make recommendations on how to protect them.

Appreciating the current pollinator landscape

Working at Elk Meadow has provided opportunities for my students to conduct independent research and receive valuable training and mentoring.

Seeing the beauty of the living things in the meadow and observing their cycles inspires my students and me.

Elk Meadow is a place to clear my mind and come up with new research ideas. It is also a place to observe and record how one tiny patch of our planet is changing in reaction to bigger changes happening around it.

Julian Resasco is an assistant professor in the Department of Ecology and Evolutionary Biology at the University of Colorado Boulder.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

I’ve visited the same Rocky Mountain subalpine meadow weekly for a decade of summers looking at plant-pollinator interactions—here’s what I learned

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Sphinx moth caterpillars wield an eruptive defense

Anonymous — Thu, 29 Aug 2024 18:21:43 +0000

Sphinx moth caterpillars wield an eruptive defense Anonymous (not verified) Thu, 08/29/2024 - 12:21

Jeff Mitton

Sphinx months have an array of identifiers, one being an unusual defense mechanism

Cindy Burkhardt Maynard had been watching a sphinx moth caterpillar in her garden for several days, but then, it disappeared. Soon after, she saw another trundling across a dirt road on Rabbit Mountain. These were Hyles lineata white-lined sphinx moths which are the most common in this area. As caterpillars progress through 5 developmental stages or instars, their colors and patterns change. In addition, their background colors change from dark green in eastern states to light green in the mountains west to yellow in California. Due to this variability, it can be difficult to identify sphinx moth species from the caterpillar stage alone.

Color patterns of white-lined sphinx moth caterpillars vary with age and geography. Photos by Cindy Burkhardt Maynard.

A caterpillar transforms into a colorful moth with a heavy body about 3 inches long and a wingspan of about 4 inches. Against a brown background, the wings and body have stripes and zones of black, white and salmon or pink.

You may have seen hawkmoths but mistaken them for hummingbirds. Hummingbirds and hawkmoths are about the same size, both are active at dusk and both hover while taking nectar from flowers. Sphinx moths can fly up to 30 mph and while hovering they beat their wings 41 cycles per second (up and down), so fast that they make a buzzing sound.

If I am not thinking critically, the plight of a sphinx caterpillar evokes my sympathy. Imagine—a very large, soft caterpillar that does not bite or sting, devoid of poisonous spines and urticating (barbed) hairs, unable to fly or run away. Admittedly, the colors and patterns of some sphinx moths provide camouflage, but if they cross a road or path or patch of sand, the camouflage fails them. The sphinx caterpillars are also called hornworms due to an ominous, threatening horn projecting upwards from their posterior end, but it is all bluff--the horn is harmless.

Caterpillars of many butterfly species consume plants that have toxic defensive chemicals, which they sequester to specific tissues, such as fat tissues. Predators quickly learn that these caterpillars are toxic and thus inedible. However, the sphinx moths do not either transport or sequester plant molecular defenses. They utilize plant molecular defenses but with another technique.

Endoparasite pupae spill from a sphinx moth puparium.

If a predator approaches a sphinx caterpillar, the caterpillar rears its head in an unmistakably threatening way. If the predator persists and approaches closer, the caterpillar engages in projectile vomiting, spewing a fetid slop of semi-digested food laced with the toxic compounds synthesized by the plants it was eating. The predator, now drenched with a stinking and stinging slime and probably suffering impaired vision and sense of smell, would likely lose its concentration and break off its attack.

Even if all predators can be dissuaded, the caterpillar faces more challenges. A large number of wasps and flies are endoparasitic, meaning that the adult female injects an egg beneath the skin of a caterpillar. If you have ever been stung by a wasp, you know that the wasp can sting while swooping by, without landing. Endoparasitic species may insert one or many eggs, dooming the caterpillar. Endoparasites remind me of "Alien" a horror sci-fi movie that appeared in 1979.

A neighbor was removing a lilac bush when he found a sphinx pupa. After completing all of its instars, it had burrowed into the roots of the lilac and transformed into a pupa. My neighbor showed me the pupa, and we agreed that I would give it loving care so that we could identify the species when the moth emerged as an adult. Neither of us was aware of the load of endosymbiont eggs that were embedded in the pupa. In late summer, too much time had passed, and I knew something was wrong. I cracked open the puparium and endosymbiont pupae spilled out. They had completely consumed all the moths, leaving the sphinx puparium fully packed with endosymbiont pupae.

To identify the species of endosymbiont, I took the capsules to the laboratory of Deane Bowers, a �� entomologist whose lab could rear the endosymbionts. But the endosymbionts were dead and thus unidentified, so I am unable to end this story as I had hoped.

I mentioned that I had sympathy for sphinx moths for they had few defenses against a horde of enemies and thus each had a low probability of surviving to reproduce. An adult female sphinx moth can lay up to 1,000 eggs, but if her population is neither shrinking nor expanding, the average number of eggs that survive to reproduce is two, one for herself and one for her mate. Sphinx moths run a gauntlet to complete their life cycle, but this is the way it is for all species.

Top photo: A sphinx moth hovers while choosing its next nectar source.

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Sphinx months have an array of identifiers, one being an unusual defense mechanism.

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Mountain ball cactus has variation in floral color and scent

Anonymous — Wed, 03 Jul 2024 15:15:18 +0000

Mountain ball cactus has variation in floral color and scent Anonymous (not verified) Wed, 07/03/2024 - 09:15

Jeff Mitton

Lingering question: Do variations in scent correspond to variations in color?

Spring weather in Boulder is difficult to predict because it seems that it is not a time of gradual warming but rather alternating days of summer and winter.

Meyers Gulch, with an elevation of 7,350 feet in the Boulder County Open Space and Mountain Parks, is a fine place to see the first flowers of spring in a highly variable environment. Notable among the earliest blooming flowers are pasque flower and mountain ball cactus, Pediocactus simpsonii.

Scanning through my photos of blooming mountain ball cactus (hereafter MBC) I was surprised to find one photo taken in March and most photos taken in late April—in many years MBC present flowers while it is snowing. Another testimony to its hardiness is that it occurs at the highest elevations of any cactus in North America. It is found from 4,600 to 11,500 feet in elevation, and it grows in places known to have winter temperatures that plunge far below zero degrees Fahrenheit.

MBC has a wide geographic distribution, and it grows in a diverse set of plant communities. It is native to Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, South Dakota and Utah, where it is found in prairie grasslands, piñon-juniper woodlands, sagebrush and coniferous forests.

Among all these places and habitats, MBC exhibits such a bewildering amount of variation that biologists have described 13 subspecies, most of which do not withstand critical scrutiny—only three subspecies are commonly recognized.

One of the examples of extreme variation was described by Dr. Elzada Clover, known for describing new species of cacti during the first botanical expedition through the Grand Canyon in 1938. A few years later, she reported that MBC might be two species based on growth form. The cacti growing on Monarch Pass in Colorado use somatic growth to form densely packed mounds of 25 to 30 balls, each with a diameter of 1 to 2 inches. Just down the road, around Gunnison, MBC grow as singletons reaching 6 inches in diameter.

Floral color variation caught my eye. The flowers that I have encountered in the Front Range are rich magenta, but in other localities the flowers can be white, pink, yellow, or yellow-green. Colorado National Monument has white flowers, Malta, Idaho, has bright yellow flowers.

Mountain ball cactus grow as single balls or mounds of balls produced by vegetative reproduction. (Photos: Jeff Mitton)

Katherine Darrow, in Wild �� Wildflowers, reports lovely pink flowers near Crested Butte, and Al Schneider notes white, pink and yellow flowers in his website Southwest Colorado Wildflowers.

I was unable to find any publications describing geographic or environmental patterns for these flower colors. Surely different colors thrive in xeric piñon-juniper woodlands at low elevations with long growing seasons versus moist coniferous forests with short growing seasons high in the mountains.

Some evolutionary biologists would propose that this is neutral genetic variation, meaning that the alternate flower colors have no consequences that influence any component of life history, such as growth, development, reproduction or survival, that would influence variation in reproductive success. That is, natural selection does not influence flower color and it plays no role in adaptation.

I had found an account that described bright yellow MBC in Malta, Idaho, and it mentioned that they have a lemon fragrance. In Wild about Wildflowers, I read Katherine Darrow's description of pink flowers with a rose fragrance. This covariation of floral colors and fragrance suggests that the key to the floral variation is in the discipline of pollination biology, and it reminded me of important and relevant work

Candace Galen has worked systematically to examine the consequences of floral scent variation in sky pilot, Polemonium viscosum at Pennsylvania Mountain Natural Area west of Fairplay. Sky pilots have variation in floral fragrance and size of the blooms, and these characters covary to adapt sky pilots to their heterogeneous environments.

Individual plants can produce either a sweet fragrance from large blooms or a skunky fragrance from relatively small blooms. Sweet fragrances attract predominantly bumble bee queens, which are nicely accommodated by large blooms. Small flies, seeking rotting flesh or feces, are drawn to skunky fragrances from small blooms. Flies are more reliable pollinators in the low temperatures at high elevations, so sky pilots emitting skunky smells increase with elevation.

This fruitful research program shows that floral fragrance and size can favor different pollinators, and these relationships can vary with elevation, gender of the pollinator and drought versus normal conditions. I see some similarities between sky pilots and MBC.

Will MBC be found to have floral scent and color variation adapting cacti to a wide variety of pollinators and plant communities throughout a large geographic range? Perhaps a first step would be to determine the degree to which floral fragrance differs with flower color.

Will pink (rose fragrance) and yellow (lemon scent) flowers always have the same fragrance? Will pollinators vary among the flower colors? Will the other colors—magenta, white and yellow-green—have their own distinct fragrances? I deeply regret never sniffing the magenta flowers in the Front Range.

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Lingering question: Do variations in scent correspond to variations in color?

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Curly dock has all the traits of a super weed

Anonymous — Tue, 28 May 2024 21:51:48 +0000

Curly dock has all the traits of a super weed Anonymous (not verified) Tue, 05/28/2024 - 15:51

Jeff Mitton

With high levels of oxalic acid, like that in Brussels sprouts, and with a proliferation of seed dispersal, the plant easily establishes itself everywhere except Greenland

During a recent trip to photograph landscapes on the Navajo Nation, I was surprised to see the prairie visually dominated by a robust plant, 3 to 4 feet tall, with thick stems, large leaves and showy plumes of red flowers. On the Colorado Plateau, this species is referred to as Navajo tobacco, but in most places in its immense range it is curly dock, Rumex crispus.

When early botanists compiled lists of species from colonial herbarium collections in North America, curly dock was not found before 1788. However, in lists compiled in 1814 and 1848, curly dock was described as common and very common.

Curly dock is native to northern Europe and Asia and was probably introduced accidentally, as a contaminant in shipments of grain to North America in the 1700s. Today, it is found everywhere except Greenland.

Curly dock grows without herbivore pressure, making it a formidable invader.

The genus Rumex has approximately 200 species, referred to as docks and sorrels. Some docks have small geographic ranges due to exceedingly precise ecological requirements, while others are cosmopolitan due to their ability to thrive in a wide range of habitats.

Some docks are endemics, while others are weedy or invasive and curly dock may be the most invasive. What makes curly dock such a successful invasive species? Common characteristics of invasive species are ability to become established in disturbed environments, good defenses against herbivores, ability to adapt to a wide range of environments and relatively high fecundity.

I stopped at a field to walk among the plants to gain some insight and soon noted that the plants were healthy with no evidence of herbivory by insects, cows, deer or antelope and no obvious seed predation by birds. All of these signs made me suspect that this species synthesized an effective chemical defense.

Curly dock has a familiar defense system, for it synthesizes the same chemical compound, oxalic acid, as brussels sprouts, broccoli, cauliflower, Swiss chard and spinach. Young leaves have tolerable levels of oxalic acid or oxalate, but as the leaves and seeds mature, oxalate levels soar, making them bitter and toxic.

Oxalate binds with calcium ions to form an insoluble compound that damages kidneys. Oxalates in leaves and seeds are toxic to poultry and dangerous to cattle, sheep and horses. Most mammals simply avoid curly dock.

Curly dock quickly becomes established in disturbed environments such as dirt roads, overgrazed fields, or areas swept by floods. Once established, it is extremely difficult to remove. It has a branching taproot that reaches over 3 feet deep and the taproot can form more taproots that feed multiple crowns.

Like dandelions, if the stems are broken off at the surface, roots quickly grow fresh stems and leaves. Each seed is attached to the calyx of its flower, which helps it float in water or attach to animal fur for dispersal. A single plant can produce thousands of seeds, each containing a chemical that prevents microbial decay so the seeds can be viable for 50 years in undisturbed soil. The numbers of seeds in a field may be as high as 5 million per acre.

Curly dock, known as Navajo tobacco on the Colorado Plateau, grows everywhere except Greenland.

Curly dock is remarkably adaptive. It can thrive in disturbed environments, roadsides, on mud in tidal estuaries, meadows, forest edges and shorelines. It hybridizes with other Rumex, both here and in Europe, and while the hybrids do not linger for long, these exchanges could conceivably help curly dock gather genes to adapt to specific environments.

It is also distributed across an incredible range of habitats, from southern Texas and Florida to northern Alaska. It seems that this super weed can go anywhere except Greenland.

While curly dock is a formidable threat to native plant communities, it has some positive aspects. If the leaves are picked while they are young, oxalate is still at low concentrations. If young leaves are boiled with several changes of water to extract oxalate, dock leaves are edible and a good source of iron, potassium and vitamins A and C. Finally, Rumex is a larval host for local copper butterflies in the genus Lycaena, including the purplish copper, blue copper, ruddy copper and bronze copper.

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With high levels of oxalic acid, like that in Brussels sprouts, and with a proliferation of seed dispersal, the plant easily establishes itself everywhere except Greenland.

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Not just a fluke: learning more about trematode infection

Anonymous — Mon, 20 May 2024 21:20:41 +0000

Not just a fluke: learning more about trematode infection Anonymous (not verified) Mon, 05/20/2024 - 15:20

Blake Puscher

Using heatmaps, �� Boulder researchers find that certain parasites congregate in certain parts of amphibians’ bodies, often to dire physical consequences

Trematodes, also known as flukes, are a class of parasitic flatworms with intricate lifecycles. This makes them interesting to scientists, but they are also significant to both human health and wildlife conservation.

Trematodes can cause infection in humans when people eat food the flatworms have contaminated, including raw fish, crustaceans and vegetables. Though this is not a major issue in the United States, the World Health Organization estimates foodborne trematode infection causes the loss of more than 2 million years of life to disability and death worldwide every year, with different species causing cancer, liver cirrhosis and cerebral hemorrhage in extreme cases.

Some trematodes also infest amphibians, contributing to the 3.79% yearly average decline in their overall population. Trematodes such as Ribeiroia ondatrae can play a role in this decline, causing serious malformations in 80% to 90% of frogs in some regions of North America, according to Dana Calhoun, a University of Colorado Boulder senior research associate in the Department of Ecology and Environmental Biology.

Dana Calhoun is a �� Boulder senior research associate in the Department of Ecology and Environmental Biology.

Her recent research shows that different species of trematodes have different distributions through certain amphibians’ bodies, and that parasites went to different places in the bodies of the animals studied. These findings may help scientists better understand the mechanisms of infection.

To understand trematodes more completely, Calhoun, along with Pieter Johnson, a �� Boulder professor of distinction in the Department of Ecology and Evolutionary Biology, and researchers Jamie Curtis and Clara Hassan used heatmaps to characterize the distribution of several trematode species in Pacific tree frogs and two species of newts. Their findings were recently published in the Journal of Helminthology.

The complex lifecycle of digenetic trematodes

Some parasites infect only hosts of a single species while others can infect thousands. One of the attributes that makes digenetic trematodes (those belonging to the subclass Digenea) so special, Calhoun says, is their standard life cycle requires three hosts to complete.

“The main host is called the definitive host,” Calhoun explains. “That could be a mammal, a larger frog, a fish or a bird. In an aquatic system, that host would defecate into the water.” The eggs inside the fecal material hatch and the trematodes try to make their way into their first intermediate hosts. “In the freshwater system, it’s usually a snail,” Calhoun says.

Once the trematodes are in the snails, the hosts will survive, but they are castrated—unable to reproduce. According to Calhoun, this is because “the parasite takes over the gonad area and uses all the resources of the snail to reproduce asexually. This allows the parasite to release a couple of thousand free-living cercariae from the snail daily.” Cercariae are the larval form of trematodes, and given that they are sperm sized, Calhoun says, “there need to be a lot of them if they’re going to get where they need to go within 24 hours,” especially given that they are often preyed upon at that stage.

After that, the parasites will try to enter the second intermediary host, which in this case is generally an amphibian but could also be a fish, invertebrate, or anything that is likely to be eaten by the final, or definitive, host, Calhoun says. This stage is particularly interesting to parasitologists because parasites sometimes alter their hosts to make transmission to the definitive host more likely. For example, the species Ribeiroia ondatrae is able to make frogs grow extra legs, as mentioned in Calhoun’s study.

The trematodes are passed from the secondary intermediate host to the definitive host when the definitive host eats the secondary host. Amphibians with limb deformities caused by trematodes of the genus Ribeiroia are hypothesized to be caught and eaten by definitive hosts more often, according to Calhoun. Parasites are in a somewhat awkward position at this point, given that they don’t want to cause the death of their hosts but do want to be eaten to complete their final stage of their life cycle.

Trematodes also can sometimes have a fourth host, called the paratenic host. These hosts allow parasites to survive during times when definitive hosts are not accessible, Calhoun says.

“It’s a holdover, since the frog will eventually leave the water and that will make it hard for birds to eat it,” she adds. The parasite’s development is paused while it is in a paratenic host.

“Simplified lifecycles are much easier,” Calhoun notes, yet the trematode lifecycle requires many stages of the animal’s life to play out in a particular way. “It seems like there are a lot of ways for this kind of lifecycle to be interrupted, but it’s still so common. Trematodes are all over the world, and to me, that’s what makes them very special.”

Different body parts, different parasites

To produce the final heatmaps showing where the parasites gathered in the amphibians’ bodies, the researchers dissected the frogs and newts and recorded the number and type of parasites in each cell of a grid of the animals’ bodies. This revealed that different species of parasite (Alaria marcianae, Cephalogonimus americanus, several species of Echinostoma and Ribeiroia ondatrae) had different distributions, and that parasites went to different places in the bodies of the newts than they did in the frogs.

Distributional heatmaps, in which a heatmap dot represents the average infection prevalence per grid cell for individual trematode species. Individual trematode distribution are: A. marcianae lime green, C. americanus purple and R. ondatrae as teal.

In the frogs, most of the Echinostoma were found in the kidneys, most of the Ribeiroia were found in the front of the body, most of the Alaria were found in the back of the body (particularly around the neck), and Cephalogonimus trematodes were spread roughly evenly between the front and back. Both Ribeiroia and Cephalogonimus were concentrated in specialized regions and can therefore be considered specialist parasites.

“Specialists usually use a certain area or microhabitat within the host, or they could even specialize in the host itself,” Calhoun says. For example, one of the parasites she studies, Scaphanocephalus, uses osprey as its definitive host, whereas other trematodes can live in all taxa of birds that eat fish. Because of that, there is a risk that the intermediate host will be eaten by a bird other than an osprey, disrupting the parasite’s lifecycle.

There also is some risk of the host species going extinct, which would force the parasite to find a different host. However, Calhoun explains, specialists are adapted to their definitive host, making it less likely that the host will successfully remove them or kill them with its immune system. Moreover, specializing in one animal or area within an animal can reduce competition.

The study also showed that Ribeiroia clustered in different places in newts than in frogs. Ribeiroia were the only parasites found in the newts collected for the study, and they were concentrated in the tissues near the front of the body rather than those nearer to the back. Calhoun says this may be because they enter newts’ bodies differently: “One of the characteristics that’s different between the hosts in the study are that newts are carnivores, so it may be that they are trying to eat the parasites when they are in the water system and therefore getting infected that way.”

The benefits of using heatmaps

Coinfection is the simultaneous infection of a host by multiple pathogen species. According to Calhoun, researchers have seen coinfection by multiple trematodes through wild animal dissection. This study shows that coinfecting parasites often occupy the same spaces, or microhabitats, in hosts.

“In one of our figures,” Calhoun says, “we show that both parasites would be in the same tiny grid cell very commonly. You have this whole dermis of the animal, but they all go to the same area. Heatmaps allowed us to see it, but now we need to investigate why.”

Calhoun says that heatmaps could be generally useful for specifying the positions of parasites within hosts.

A Pacific chorus frog (P. regilla) with limb malformation induced by the Ribeiroia ondatrae trematode. (Photo: Pieter Johnson)

“If I dissect something and I find parasite A in the head and parasite B in the limb,” she explains, “it’s so broad to just say ‘in the head’ or ‘in the limb’ because those areas are so large compared to the parasites. What heatmaps show is that they are in the same 1-by-1 cells on the heatmap grid, basically stacked on top of each other. It shows that there are these coinfection areas in the host that are attractive to parasites compared to other locations. It’s important for researchers to study these microhabitats, especially why multiple parasites use the same microhabitat.”

While some parasites congregate in the same spaces, others do not. For example, Calhoun says that Echinostoma is, for the most part, the only species of parasite found in the kidneys of the amphibians from the study. This suggests that they are uniquely adapted to enter this region of the body.

Heatmaps also helped the researchers explain why frogs infected with Ribeiroia from one region that researchers visited were not malformed as often as frogs from another region.

“In the (San Francisco) Bay Area, you would see (frogs with) six or seven legs, with high loads of Ribeiroia, but we weren’t seeing that same phenomenon in the high elevation areas of California, when load of Ribeiroia was sometimes double,” Calhoun says.

“To explore this trend, we examined the heatmaps of Ribeiroia infections in both areas and found that, for some reason, Ribeiroia in high elevation were going to the head and (jaw) region, not to the hindlimbs. It could be related to the timing. It’s much colder in mountains, and it doesn’t get warm until August in this area, which is when the frogs start to metamorphosize. Therefore, the lack of malformations could be related to missed timing of parasite release and frog development.

Another method involves using florescent labelling. In a laboratory setting, Calhoun explains, labelling the parasites with color prior to their entering the frogs would allow researchers to track how they move, what the consequences of that movement are and whether their location changes over time.

“And if you use dyes like this,” she says, “you could explore single infections in an animal with Echinostoma, Cephalogonimus, or Alaria, and then add in another parasite and see if the distribution changes. Others have demonstrated that with multiple parasites, as you add taxa, the parasites move to different areas. But how does that occur? Where do they go? What if we introduced them at the same time? Using this method combined with heatmaps, a researcher could investigate the mechanism of infections.”

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Using heatmaps, �� Boulder researchers find that certain parasites congregate in certain parts of amphibians’ bodies, often to dire physical consequences.

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Ecological body names �� Boulder’s Mike Gil an early career fellow

Anonymous — Wed, 01 May 2024 15:57:39 +0000

Ecological body names �� Boulder’s Mike Gil an early career fellow Anonymous (not verified) Wed, 05/01/2024 - 09:57

Ecological Society of America recognizes scientist for making ‘outstanding contributions’ to the field

Mike Gil, a marine biologist and University of Colorado Boulder assistant professor of ecology and evolutionary biology, is one of 10 scientists elected as an early career fellow by the Ecological Society of America (ESA), the organization announced Tuesday.

Gil, who received his Ph.D. from the University of Florida, is an empirical and theoretical ecologist who works at the intersection of community ecology, behavioral ecology and conservation.

“My career interests and aspirations have been shaped by the ecologists that make up the Ecological Society of America, past and present. For my work to be formally recognized by my esteemed colleagues is a great honor,” Gil said of the honor.

Mike Gil (here taking a selfie with a shark) pursues research on the relationships between the decision-making of individual organisms and the structure and function of ecosystems, particularly in the face of environmental change.

Gil’s research focuses on the relationships between the decision-making of individual organisms and the structure and function of ecosystems, particularly in the face of environmental change. Much of his work uses coral reef fish as model systems to assess ecosystem-scale consequences of animal behavior. In 2022, Gil and researchers from three partnering universities received a $3 million grant from the National Science Foundation to better understand how complex species interactions affect natural ecosystems.

Gil also is highly active in efforts to diversify involvement in STEM. He founded and directs SciAll.org, a nonprofit that uses personal storytelling in videos published across social media to promote diversity, equity and inclusion in STEM.

ESA early career fellows are members within eight years of completing their doctoral training or other terminal degree who have advanced ecological knowledge and applications and show promise in continuing to make outstanding contributions to a wide range of fields served by ESA. They are elected for five years.

In addition to Gil and the nine other scientists recognized as early career fellows this year, the ESA governing board has named nine new fellows. Fellows are members who have made outstanding contributions to a wide range of fields served by ESA, including those that advance or apply ecological knowledge in academics, government, non-profit organizations and the broader society. They are elected for life.

“I am thrilled to recognize the exceptional contributions of our newly selected fellows and early career fellows,” said ESA President Shahid Naeem in a release announcing them. “Their groundbreaking research, unwavering commitment to mentoring and teaching and advocacy for sound science in management and policy decisions have not only advanced ecological science but also inspired positive change within our community and beyond. We celebrate their achievements and eagerly anticipate the profound impacts they will continue to make in their careers.”

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Ecological Society of America recognizes scientist for making ‘outstanding contributions’ to the field.

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Houndstongue is a noxious, poisonous weed with nasty seeds and pretty flowers

Anonymous — Tue, 30 Apr 2024 19:40:20 +0000

Houndstongue is a noxious, poisonous weed with nasty seeds and pretty flowers Anonymous (not verified) Tue, 04/30/2024 - 13:40

Professor Emeritus takes a closer look at beautiful weeds with a lethal potential to kill livestock, and even, humans

After spending several hours stalking and photographing butterflies on Flagstaff Mountain west of Boulder, I returned home and spent about 10 minutes removing burs from my jeans and wool socks. I was annoyed, for if I only knew what plant bore those burs, I could give it a wide berth.

A year later, when processing my photo of a western tailed-blue (Cupido amyntula) on a cluster of flowers, I found the answer in the photograph. In the foreground were the flowers of houndstongue (Cynoglossum officinale). In the background were the maturing burs or seeds that were so annoying.

Houndstongue takes its common name from the similarity between its leaves and the tongue of a panting dog. Each leaf contains veins or groves that spread down to the distal or outer part of each leaf resembling a green tongue.

Houndstongue is native to the United Kingdom, northern Europe and northern Asia. It was thought to have been introduced to Canada in a contaminated shipment of seed before 1859. No one noticed the contaminated shipment, but specimens of houndstongue were collected in 1859 and deposited in a herbarium in Ontario. It was first reported in the United States in Oregon in 1893 and Montana in 1900. Today, houndstongues are in most of the 48 contiguous states and are listed as noxious weeds in seven western states, including Colorado.

A fertilized flower produces a fruit that is composed of four nutlets, which are thick-walled shells covered with barbed prickles and each containing one seed. (For simplicity, seeds, burs and nutlets will be called seeds). The seeds in the accompanying photo have a dense coat of straight green prickles. As the seeds dry, the prickles become barbed hooks, enhancing their ability to cling to animal hair. The seeds are dispersed by many species of mammalian wildlife, as well as cows, sheep, goats, horses and dogs.

The seeds—which hitchhike on sheep, cows, horses, dogs and hikers—are thoroughly annoying. Sheep wool can be so densely packed with nutlets that the fleece loses value. In the United Kingdom, people who take their retrievers for a walk or to retrieve ducks may spend an hour removing seeds from the dog's pelt and from wool hunting jackets. In the western United States, the seeds slow the marketing of cows, for they must be removed before cattle can be sold.

The seeds are annoying, but their plant defenses cause even greater problems. Like most species of plants, houndstongue has defenses that have evolved to discourage herbivores. Although it has no thorns, it has chemical defenses that are ingested by herbivores that eat its flowers, seeds, leaves and stems. It synthesizes four different pyrrolizidine alkaloids (PAs), which the liver converts to pyrrolic metabolites that cause tumors, damage nuclear DNA and halt protein synthesis in liver cells. So, PAs poison the liver and turn off the cell replication that may have replaced damaged liver cells.

A western tailed-blue butterfly on houndstongue flowers with seeds in the background. Image by Jeff Mitton.

PAs have killed humans, cows, horses, farmed deer, pigs, sheep, goats, poultry and quail. Horses are most susceptible, and sheep and goats are remarkably less susceptible with a tolerance to lethal doses 20 times higher than most animals. Most species of wildlife are not killed, but they learn not to graze on houndstongue. Because wildlife learns to avoid houndstongue, it has a competitive edge over the healthy sources of food both wildlife and cattle eat. In some places, this competitive edge allows houndstongue to become the dominant species, which greatly degrades the value of pastures for grazing.

PAs are synthesized by about 5% of all flowering plants and occur in 20 plant families. More than 600 forms of PAs have been described from the approximately 6,000 species that have been examined. None of these compounds are necessary for plant development, growth or reproduction—their functions are limited to plant defense against herbivores. The efficacy of these compounds can be seen in the speed of their invasion of Canada and the 48 contiguous states, despite efforts to eradicate or control them.

While clinging seeds and PAs give houndstongue a bad reputation, I must say that they have pretty flowers. Five petals fuse to form funnel-shaped flowers that appear from leaf axils and the tips of branches. The flowers are not one hue, but each flower has a combination of reds, blues and purples, so the flowers on one plant exhibit a range of colors. I will continue to enjoy the flowers, but I will approach only tentatively, avoiding seeds, and I certainly will not try the leaves in a salad.

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Top of page: Houndstongue up close look fragile, but are more robust than meets the eye. Images by Ben Legler.

Professor Emeritus takes a closer look at beautiful weeds with a lethal potential to kill livestock, and even, humans.

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