Natural Selections

Alcove columbines thrive on vertical stone walls

Anonymous — Thu, 15 Jun 2023 22:29:39 +0000

Alcove columbines thrive on vertical stone walls Anonymous (not verified) Thu, 06/15/2023 - 16:29

Jeff Mitton

My hope for this expedition to the San Rafael Swell was to find flowers on scarlet monkeyflower, which grows in hanging gardens on vertical walls. I had made similar trips in previous years but had not seen monkeyflowers in bloom. This time I spotted flowers growing from the wall, but they were not monkeyflowers. The flowers had the classic form of columbines.

Alcove columbine or small flowered columbine, Aquilegia micrantha, is a species that is endemic to hanging gardens on the Colorado Plateau. That is, it is restricted to the red rock, canyon country surrounding the Four Corners (where CO, UT, AZ, NM meet), and in that vast expanse, it is found only in hanging gardens. The flowers are usually white to cream. In terraces just above the floor of the canyon, alcove columbines were growing in soft sand. In addition, large, healthy, flowering columbines were rooted in small cracks 5 to 20 feet up an overhung wall, with no soil in sight.

A colorful alcove columbine flower found in a hanging garden.

Alcoves form in sandstone, on the steep to vertical surfaces of escarpments and canyons. Sandstone is porous and permeable, so water falling on horizontal surfaces penetrates the stone, moving vertically until it settles on an impermeable layer. Thin, impenetrable lenses of limestone are the petrified remains of bottoms of ancient lakes and ponds. Water moves horizontally on the lens until it encounters vertical walls of escarpments and canyons, where it usually escapes through cracks. The floor of the alcove is the impenetrable lens and water moving over the lens erodes the sandstone to form an alcove.

Many widespread species are found in canyons and alcoves, but biologists who frequent canyon country come away with the impression that the plant communities in alcoves are made unique by the presence of endemic species. A study of 84 hanging gardens found 201 species of vascular plants. Of these, 12 are endemic to the Colorado Plateau and 7 are endemic to the hanging gardens on the plateau.

Surveys of hanging gardens report several species of columbines: alcove columbine (A. micrantha); golden columbine (A. chrysantha); western red columbine (A. formosa); desert columbine (A. desertorum). However, only alcove columbines are specialists to and are endemic to hanging gardens. The other are found in alcoves, but they occur in other environments as well. Alcoves above entrenched creeks or rivers are mesic, shady and cool in comparison to the surrounding slickrock desert. Endemics to these patchy, isolated and unique environments have long distance dispersal, tiny wind-blown seeds, and the ability to flourish in very shady, mesic, and relatively cool environments. Populations in hanging garden can be separated by large expanses of arid, sun-blasted rock desert.

Hanging gardens of columbines form where water seeps from alcove walls.

Some descriptions of alcove columbines describe their range of flower colors as white to cream. But in other places, including the population that I found, flower colors include white, cream, yellow, blue and raspberry. To explain this diversity of colors in some but not all populations, Al Schneider at swcoloradowildflowers.com reminds us that even distantly related columbines hybridize. Given that at least three widespread species of Aquilegia are found in hanging gardens, it is possible that hybridization of alcove columbines is the source of floral color diversity in some populations of A. micrantha. A specific example is seen in the hanging gardens of Zion National Park. Golden columbine (all yellow) hybridizes with western columbine (yellow petals, bright red sepals and spurs) to produce hybrids recognizable by subdued red hues in their sepals and spurs.

Environmental conditions vary considerably between hanging gardens. Some produce abundant water year-round while others dry up in summers. Some are in the sun while others are usually in the shade and a few never experience direct sunlight. Many provide water that is potable, while others have white precipitates indicating high concentrations of calcium carbonate or black stains produced by precipitation of minerals such as oxides of iron and manganese. So not all hanging gardens would support the same community of plants.

Surveys of plants in hanging gardens have noted one general association of endemics. Alcove columbine, A. micrantha, is usually found in the same gardens with scarlet monkeyflower, Mimulus eastwoodiae, and cave primrose, Primula specuicola. This association of three endemic species suggests to me that they have evolved to very similar conditions, and in that process, eroded traits needed to thrive in the relatively harsh environments outside their alcoves.

My hope for this expedition to the San Rafael Swell was to find flowers on scarlet monkeyflower, which grows in hanging gardens on vertical walls.

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What the White Buffalo Calf tells us about Indigenous history

Anonymous — Thu, 11 May 2023 22:16:53 +0000

What the White Buffalo Calf tells us about Indigenous history Anonymous (not verified) Thu, 05/11/2023 - 16:16

Jeff Mitton

Native Americans have been associated with bison in North America for more than 15,000 years

Road construction had closed Route 285 through South Park, detouring traffic to the eastern edge of the park. While inconvenient, it afforded people a sight that they would have missed otherwise. A herd of bison, Bison bison, was grazing next to the road, and in the herd were four white bison.

For more than 2,000 years, Lakota (Sioux) elders have been passing the legend of the White Buffalo Calf Woman to younger generations. The legend tells of a time when the Lakota had lost their ability to pray to the Creator. A young woman in shining white buckskin appeared to teach the people to pray during seven sacred rites, and she gave them the White Buffalo Calf Chanupa, or pipe, which played an important role in each of the rites. As she left, she told them that she would return to establish peace, harmony and balance.

Then she rolled on the earth four times, and each time she appeared as a buffalo of a different color (red and brown, then yellow, then black), finishing this display as a white buffalo calf. Today, the Sioux, Cherokee, Commanche and Navajo celebrate the birth of a white buffalo as a sacred omen indicating that their prayers had been heard and portending much better times.

White buffalo are more common today than 2,000 years ago when the legend of White Buffalo Calf Woman began. Photographed by Jeff Mitton.

Historically, white bison were rare, because they were probably albino (white hair, pink eyes), which occur at a frequency of about 1 in 10 million. But why are white bison so much more frequent now?

The herd in South Park had at least four, and white bison can be seen in three Canadian Territories and about a dozen states. The white bison in South Park have white hair but normally brown and black eyes. The gene for white hair was introduced from cows.

In the late 1800s and early 1900s, cattlemen attempted to cross bison with cows, hoping to gather the best traits from both species into one lineage as docile and manageable as domesticated cows. These experiments had unsatisfactory outcomes, but not before introducing genes from cows into bison.

One of the breeds of cattle in these experiments was Charcolais, which are all white. The gene (Charcolais SILV) producing white hair is recessive, meaning that two copies of the gene are needed to produce white hair. The gene influences hair color, but does not alter eye color. The white bison in South Park have dark eyes, so they most likely have two copies of Charcolais SILV.

Professional breeders would have no problem recovering a lineage of bison that breeds true for the Charcolais white hair, and indeed, herds of exclusively white bison with dark eyes can be found in Ohio, Oregon, Texas and Saskatchewan.

Similar phenotypes—albino vs. white hair produced by two copies of Charcolais SILV, present a conundrum to the Native Americans honoring the legend of White Buffalo Calf Woman. White bison calves are no longer rare.

Native Americans have been hunting bison for thousands of years, even before our contemporary bison evolved. The first of a series of species in the genus Bison migrated from Asia into Alaska via the Bering land bridge between 220,000 and 240,000 years ago.

The immigrant was B. priscus, an enormous animal with very long horns. The direct lineage of bison in North America began with B. priscus, followed by B. latifrons, then B. antiquus and finally our modern B. bison. From B. priscus to B. bison, both body size and horn length decreased.

According to the National Bison Association, one out of every 10 million births a white buffalo is born. Photographed by Jeff Mitton.

For example, large bull B. latifrons, B. antiquus and B. bison measured 8, 7 and 6 feet tall at the shoulder. B. latifrons went extinct 21,000 years ago, and B. antiquus disappeared 10,000 years ago, approximately the time that B. bison arose.

In the early 1900s, anthropologists thought that Native Americans had arrived in North America from Asia about 5,000 earlier, but B. antiquus provided a revelation for our history of Native Americans in North America. Shortly after a disastrous flood in New Mexico in 1908, a black cowboy named George McJunkin found large bison bones exposed by a new arroyo in Folsom, New Mexico.

This self-educated cowboy recognized that the bones came from a species much larger than B. bison. He shared his insight with others, and years later, when archeologists explored the site, they found the bones of 32 extinct B. antiquus and 26 spearheads unlike any that had been found previously.

Carbon dating indicated that these bison lived 12,000 years ago. The arroyo was once a marsh where B. antiquus were stalked by hunters wielding spears with spearheads now called Folsom points. This kill site provided unequivocal evidence that Native Americans had arrived in North America at least 7,000 years earlier than previously thought.

Subsequent to the discovery of Folsom points, Clovis points dating to 13,000 years ago have been found in mammoth kill sites at Clovis, New Mexico, and points dating to 15,500 years ago have been found at the Debra L. Friedkin site, a bison kill site near Dallas. Bison have inadvertently yielded considerable insight to Native American history.

Native Americans have been associated with bison in North America for more than 15,000 years.

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Mormon tea has no flowers or leaves but lots of history

Anonymous — Fri, 03 Mar 2023 21:28:30 +0000

Mormon tea has no flowers or leaves but lots of history Anonymous (not verified) Fri, 03/03/2023 - 14:28

Jeff Mitton

Mormons used the plant to make a caffeine-free hot drink, and Native Americans used it to relieve congestion

As spring swells and climbs through the canyons of the Colorado Plateau, green ephedra, also called Mormon tea, Ephedra viridis, produces arrangements at its branch nodes, and they produce tiny yellow structures that some people might presume are flowers. Ephedra is quite common in some habitats, so this show can be stunning.

But those yellow excrescences are cones, not flowers.

Ephedra is an ancient genus, with fossils reaching back 125 million years and it is a gymnosperm, not an angiosperm. That is, it is more closely allied with pines, spruces and firs than angiosperms such as daisies or aspens.

Green ephedra is a dioecious species, meaning that an individual produces either male cones or female cones. The male cones form at the nodes of stems, and they sprout microsporangia, which release wind-dispersed pollen.

At the top of the page: The yellow cones of a male green ephedra appear in spring on the Colorado Plateau. Above: Green ephedra, E. viridis, has many parallel stems that grow straight up, with cones gathered around branch nodes.

The microsporangia are those yellow things that some people (including me) first take as flowers. Females bear macrosporangia, which, after pollination, produce seeds. Female cones, which are larger than male cones, have more muted colors.

Green ephedra grows as a shrub, usually 1 to 5 feet tall. It roots form rhizomes, which allow it to spread asexually, forming small, dense clusters of shrubs. Its base and branches are woody, and their green stems grow straight up, branching as they grow. Cones are formed at the branch nodes. Ephedra species have tiny, vestigial leaves that appear pigmented but quickly degenerate to dark scales. The conspicuous green stems are photosynthetic.

Approximately 70 Ephedra species are extant, and they are distributed around the world. Three species grow on the Colorado Plateau—green ephedra, E. viridis, Cutler's Mormon tea, E. cutleri, and Torrey's Mormon tea, E. torreyana. E. cutleri typically grows only 2 feet tall, but in mats 10 to 15 feet in diameter. E. torreyana can be identified by its blue-grey-green foliage, intertwined (not parallel and upright) stems and by three leaves in a whorl, rather than two.

Male and female E. viridis are not distributed randomly in patchy habitats. Males are more common on dry sites, while females are about four times abundant as males in relatively mesic sites.

E. viridis are adaptable to their environment. Males tend to populate drier habitats, while females thrive in regularly moist environments.

One can see an evolutionary explanation to this partial specialization, which is shared by four other dioecious species living in arid lands in the west. The hilltops and ridges are relatively dry because they catch the wind and are well-drained, so they are optimal for releasing wind-borne pollen. Nearby bottomlands may have ephemeral streams or ponds. Females need more water than males for their prolonged nuturing of developing seeds in the dry summer heat.

Ephedra is browsed by pronghorn antelope, mule deer, elk, buffalo and horses. Male sheep and cows browse it with no problems, but if pregnant cows or sheep eat it, they die or suffer prolonged discomfort.

Mormons steeped dried ephedra stems to make a caffeine-free hot drink, and Native Americans used an ephedra tea to relieve congestion.

Several thousand years ago, strong pharmaceutical activity was found in E. sinica, which is native to China. The active chemical compound was named ephedrine, and it was used in the United States in the 1950s as an effective treatment for asthma.

Unfortunately, ephedrine was engineered by resourceful chemists to produce an amphetamine, known on the streets as crystal meth. The species in North America do not synthesize ephedrine.

Although all the Ephedra species in North America are wind pollinated, two of the species that evolved earlier than other extant species are pollinated by insects. E. foeminea is one of the species relying on insects, but it also needs the light of a full moon to achieve pollination.

A study of pollination biology in Greece and Croatia recorded the production of the pollination droplet, which appears at the tip of the female cone and facilitates movement of the pollen into the cone.

The pollination droplet appears on the night of the full moon in E. foeminea, but pollination droplets are not synchronized with full moons in a sympatric, wind pollinated E. distachya.

Apparently, E. foeminea can accurately anticipate the date of the full moon to optimally pump out the pollination droplet. The investigators of this study mentioned that, in a dry habitat in the Balkans on the night of a full moon, the many pollination droplets "glitter like diamonds in the full-moonlight." E. foeminea does not produce nectar or a fragrance—insects rely on the light of diamonds to deliver their pollen.

Mormons used the plant to make a caffeine-free hot drink, and Native Americans used it to relieve congestion.

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On the trail of big, ugly mushrooms

Anonymous — Tue, 07 Feb 2023 18:04:32 +0000

On the trail of big, ugly mushrooms Anonymous (not verified) Tue, 02/07/2023 - 11:04

Jeff Mitton

Aspen boletes build physical connections for mutualistic exchanges with quaking aspen

Mushrooms abound on the eastern flank of Owl Creek Pass in Western Colorado in early August, particularly after an unusually rainy summer. Fly agaric (Amanita muscaria), the infamous and deadly red capped mushrooms with white spots, grow in dense clusters near the West Fork of the Cimarron River.

But many other mushrooms were unfamiliar to me and one of these stood out as the clear winner of the big and ugly category. The cap was slightly over six inches in diameter and brown to dark brown, with one small blue structure near the edge of the cap. The stem or stipe was thick, cream colored, with many small dark flecks called scabers.

Professor Alisha Quandt, mycologist in the University of Colorado Boulder Department of Ecology and Evolutionary Biology, identified this as an aspen bolete, Leccinum insigne, and explained that it looked like it had begun to decay—fresh specimens have a flatter cap, colored orange or brownish yellow.

Aspen forests in the West Elk Mountains, Ruby Mountains and Ragged Mountains contain many clones and extend for miles, but all are conceivably connected by the rhizosphere.

This species was first recognized in 1966, so it is relatively new to science. The edibility of L. insigne is either variable, or people vary, for some poisonings have been reported, but others appreciate its taste. Another possibility is that two species, one edible and the other poisonous, are recognized as one species.

The genus Leccinum is closely related to the genus Boletus but these genera are distinguished by scabers on Leccinumspecies but none on Boletus species. Leccinum and Boletus mushrooms do not have gills, those numerous and delicate flaps on the bottom of the cap of some groups of mushrooms.

Instead, the underside of the cap appears first as a smooth surface, but closer inspection reveals a surface of tightly packed tubes with small pores. Both gills and tubes release spores, microscopic analogues of seeds.

The common name of L. insigne is the aspen bolete or orange-capped bolete, which is mycorrhizal on quaking or trembling aspen. Mycorrhizal fungi build mutualistic relationships with their host plants by wrapping their mycelia (analogous to roots) around the fine root fibers of its host to build a bridge for exchange.

Aspen bolete (above) is the most common of more than 50 mycorrhizal fungi in aspen forests. Two king boletes appear at the top of the page. Photos by Jeff Mitton.

Fungal mycelia are much thinner than root hairs, providing a greater surface area for absorbing water and nutrients such as phosphorus and nitrogen, which are transferred to the plant. Photosynthesis in the plant leaves produces sugars such as sucrose and glucose, which are transported to the roots and then from roots to mycelia.

The genus Boletus includes the king bolete or porcini, Boletus edulis, one of the mushrooms prized most by people who search forests for edible mushrooms. It can be quite large, with a cap 12 inches in diameter and the cap and stem weighing more than four pounds. It forms mycorrhizal associations with approximately 30 conifer and deciduous species and is native to Europe, Asia and North America.

Studies of mycorrhizal fungi in the northern Rocky Mountains found that more than 50 species were associated with quaking aspen and noted that the aspen bolete was the most characteristic of aspen stands. A laboratory study of aspen seedling growth compared uninoculated seedlings with seedlings inoculated with one of five native mycorrhizal species.

Growth measurements showed that five of six mycorrhizal fungi improved seedling growth by factors of 2 to 4, an enormous boost. Mycorrhizal associations are common—most plants have these beneficial associations with fungi.

A mycorrhizal fungus can establish bridges to several plants, and biologists have found that mycelial connections may also serve to shuttle warning signals between plants. For example, when a plant is being attacked by aphids, it releases volatile organic compounds (VOCs) that attract predators of aphids. Plants connected to the embattled plant by mycelia but not attacked by aphids also release VOCs, a preemptive defensive action triggered by a chemical alarm.

Every once in a while, while walking through an aspen forest, it is insightful to remember that you might not be walking amongst trees, but within an individual, a clone. Many ramets or stems sharing a root system are physically connected, like the fingers on your left hand are joined at the palm.

An aspen forest may also be composed of many clones, which are separate individuals. But the insight that an aspen forest contains more than 50 species mycorrhizal fungi, aspen bolete prominent among them, connecting different clones and shuttling VOC messages, is epiphanous.

Aspen forests in the West Elk Mountains, Ruby Mountains and Ragged Mountains contain many clones and extend for miles, but all are conceivably connected by the rhizosphere.

Aspen boletes build physical connections for mutualistic exchanges with quaking aspen.

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The Darwin Award goes to a male black swallowtail butterfly

Anonymous — Thu, 05 Jan 2023 19:41:35 +0000

The Darwin Award goes to a male black swallowtail butterfly Anonymous (not verified) Thu, 01/05/2023 - 12:41

Jeff Mitton

The beautiful male emerged in October, eager to mate but destined for disappointment because he emerged too late in the season, just an example of natural selection at work

I received an invitation to photograph a black swallowtail butterfly that had just emerged. It would linger only a short while before emerging, so I hurried over. The date was Oct. 13.

The black swallowtail, Papilio polyxenes, had bright colors and was just gorgeous. Males and females have the same colors and patterns ventrally but their dorsal patterns distinguish the genders. All have orange, yellow and black eye spots, but males have two prominent lines of yellow spots and a light dusting of blue spots, while females have much less yellow and much more blue. This was a male.

I hereby award this male black swallowtail the Darwin Award. While the idea of the Darwin Award reaches back into the mid-1980s, the Award matured around 1993, when Wendy Northcutt, then a graduate student at the University of California Berkeley, established the website "darwinawards.com."

The Darwin Award is a facetious award to people—almost all men—who have improved the gene pool of the next generation by outrageous, idiotic behavior that resulted in their death, and thereby prevented them from passing their genes on to the next generation.

A beautiful male emerged in October, eager to mate but destined for disappointment. Photos by Jeff Mitton.

I am taking a liberty by awarding the prize to an animal, but Northcutt established the animal precedent in 2018 by awarding it to male wooly mammoths. The male swallowtail exhibited foolishly impatient behavior, given that the goal of a male black swallowtail is to mate with as many females as possible. I fear that he did not see another black swallowtail and died a lonely bachelor without siring any offspring.

Black swallowtail pupae overwinter in a chrysalis and emerge in spring. Around Boulder, adults will be flying in May, June and July. The average longevity of the adult form is 14 days, so adults disappear by the end of August. This male emerged in mid-October and was probably the only black swallowtail in Boulder.

His lack of offspring is a dead end for his genes, both beneficial and detrimental. The fitness or success of a genotype is measured by its number of offspring. If his tragically early emergence had a genetic component, this is the mechanism by which detrimental genes are selected against—detrimental genes suppress reproductive success.

This is natural selection, and it is called natural selection because it is not planned, directed or orchestrated by anything other than weather, climate, competition, disease and predation.

Risky or detrimental actions that we describe as poor choices are not uncommon. One that captured widespread news coverage a few years ago was the discovery that three young gray whales had been found trapped by pack ice near Point Barrow, Alaska. No one knows what events led to their separation from their pod and the elders who would have led them south to mating grounds in Mexico.

Thanks to legions of eager bird watchers, we have many examples of vagrants, defined as birds that deviated from established routes of migration. Point Reyes in northern California, because of its geographic location, concentrates birds that are wandering aimlessly, as well as birds whose directional compass is not precisely calibrated, or is precisely mis-calibrated (e.g., directing flight 40 degrees west of south, rather than east of south). Each year, hundreds of vagrants from dozens of species are documented.

A vagrant that caught a lot of attention was a Steller's sea eagle, a resident of east Asia. It was out of its normal range when this large and distinctive bird was seen over the Denali Highway two years ago. Later, it was spotted in southern Texas, then Canada, New England and finally Nova Scotia in April of this year.

Many other examples are documented. The majority of the vagrant wanderers are doomed to a lonely death with a fitness of zero. Genes leading to inappropriate migration routes are removed from the gene pool each and every year.

Sexual reproduction involves replication of the genes to be packaged in sperm and eggs. DNA replication is quite accurate, but genomes are so large that errors—called mutations—occur regularly.

For example, each human is estimated to carry 70 to 200 new mutations. Accumulation of deleterious mutations is opposed by natural selection, which is necessarily relentless. Some mutations promote self-destructive actions so silly that they are celebrated with a Darwin Award.

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Mysterious lumps and swollen bands on aspen

Anonymous — Fri, 09 Dec 2022 20:26:49 +0000

Mysterious lumps and swollen bands on aspen Anonymous (not verified) Fri, 12/09/2022 - 13:26

Jeff Mitton

One puzzle leads to another question, as yet unanswered, about the cause

After a day of hiking the Mill Castle Trail in the West Elk Mountains I had returned to the trailhead, tired but exhilarated by my immersion in fall in the West Elk Wilderness.

I had been looking at and photographing aspen all day, but the aspen at the trailhead had conspicuous growths that I had not previously noticed. The aspen trunks had lumps and girdling swellings of all sizes, some of them covering over a vertical foot of the trunk. The cause of the growths was a puzzle.

My training as a geneticist suggested the hypothesis that a rare genetic mutation caused the growths. Some, but not all of the aspen at the trailhead had the odd growths. Perhaps I had encountered a mutant clone in proximity with a normal clone.

Above and at the top of the page: These unusual lumps and girdling bands were small twiggall fly galls that continued to grow with the tree. Photos by Jeff Mitton.

Remember that aspen roots thrust up numerous shoots or stems that look like individual trees but are parts of a single clonal individual. Separate clones can be distinguished with characters such as bark color, leaf shape and color, dark ticking on the bark, branch angle, etc.

But I saw no evidence that lumpy stems and normal stems were on separate clones. I put the genetic hypothesis aside.

When I returned to Boulder, I searched digitally to find what was known about the cause of the lumps and bands on aspen. Several articles described insects that lay their eggs near the ends of twigs. These include the poplar twiggall fly, Hexomyza shineri, and two species of beetles, the poplar gall saperda, Saperda inorata, and the poplar gall borer, Saperda calcarata.

When the fly or beetle eggs hatch, larvae begin to feed on the soft, growing tissues, which respond by imprisoning the larvae in firm galls that inadvertently protect them from predation. However, these insects do not lay eggs in the main trunk of the tree but at the ends of the slender growing twigs. Furthermore, the galls were small, for example the galls of twiggall flies are about 13 by 8 mm—that is not the sort of growth I saw in the field.

This puzzle was solved by Colorado State University Extension Fact Sheet 5.579, by Whitney S. Cranshaw. He mentioned that the twiggall fly is becoming more common in Colorado and warned that this is a concern because the galls continue to grow and swell as the tree grows.

Small galls grow continually to become permanent disfigurements. That is, if a fly lays several eggs on the leader (the vertical top of the trunk or stem) of a sapling the galls become larger lumps and some grow to a swollen band girdling the tree. Flies that lay eggs in the leader of the same trunk in subsequent years will add more lumps and swollen bands.

Twiggall flies are stout, dark and shiny, about one-sixth inch long. They can often be seen during the day resting on aspen leaves. They usually lay eggs on aspen, but occasionally their galls appear on cottonwoods as well.

These growths were usually covered with unbroken aspen bark. But some were leaking dark fluid that stained the bark. The dark fluid is the exudate from a Cytospora canker, a common fungus. Although the cankers and draining exudate are unsightly, their impact on the health of the aspen is small or negligible.

The twiggall fly is a native to Colorado, but its impact seems to be increasing. About 50 years ago, outbreaks were noticed in the Denver area, but since then observations have increased throughout the range of aspen in the Rocky Mountain region, and the increase has been described as dramatic in the Front Range.

Twiggall flies have few natural enemies. Chickadees are able to open the galls to consume larvae and pupae, and bugbees, Eurytoma contractura, are parasitic wasps that lay their eggs in the galls so that their larvae can consume fly larvae. The rate of parasitism varies from site to site, from 3% of galls to 94%.

It seems that the swollen bands now present another puzzle. Although we know how the lumps and bands form and we know about predators and parasites, we do not yet know why twiggall flies are increasing. Something has changed.

One puzzle leads to another question, as yet unanswered, about the cause.

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Beavers have become established in Boulder Canyon

Anonymous — Wed, 23 Nov 2022 16:32:09 +0000

Beavers have become established in Boulder Canyon Anonymous (not verified) Wed, 11/23/2022 - 09:32

Jeff Mitton

Beavers may appear to be one of the most sedentary of species, living in a secure den or lodge in a pond with all of their food within a short waddle, but now, in Boulder Canyon and in Alaska, it is evident that they are on the move

Beavers have become established in Boulder Canyon. Dave Hoerath, wildlife biologist with Boulder Parks and Open Space, told me that they have been aware of beavers in Boulder Canyon for about 10 years, but we agreed that the pond in the photos illustrating this article appeared recently.

At two sites, 1.5 miles apart, aspen, cottonwoods, and willows have been gnawed down to build dams and to cache branches for winter food.

A beaver pond is the territory occupied by one family of beavers. The parents are monogamous, and they mate for life—longevity has an average of 12 years but fortunate and healthy beavers can live 19 years.

Once the pond is formed, the adjacent soils become saturated, killing some species, but making the area ideal for alders, willows, aspens and cottonwoods—all favored foods of beavers. They may excavate a canal to a nearby grove of trees so they can easily transport branches and twigs to their pond.

They mate in January or February, and usually three or four kits are born in May or June. A family consists of the adults, the kits and yearlings born the previous year. Yearlings leave their natal ponds as they approach their second birthday and a new set of kits is imminent. They travel as far as five or six miles to establish their own territories.

Beavers are large rodents, second only to capybaras in South America. They grow to be a meter long, with one-third of that being their black, flat, naked and scaly tails. They are semiaquatic, with specific adaptations for living in the water. Toes on the back feet are webbed and they can close their nostrils and ears when submerged.

They have clear inner eyelids that they close underwater so they can see without getting sand or detritus in their eyes. They are able to control their breathing and heart rate to remain underwater for five minutes but when a predator is skulking about they can stay down for as long as fifteen minutes.

At the top of the page: Beavers have constructed two dams in Boulder Canyon—this one is about five feet tall. Above: Boulder Creek now flows into beaver ponds that appeared about a year ago; this one is the smaller of the two. Photos by Jeff Mitton.

To warn their family of imminent danger, they slap the water with their flat tails, producing a sharp retort that can be heard both above and below water. While they have a lumbering and ponderous gait on land, they are agile in the water.

Their primary predators are bobcats, coyotes and wolves. In Voyageurs National Park in northern Minnesota, a collared wolf ate 36 beavers in one year. Beavers are most vulnerable when searching for new territories or when collecting logs and branches.

Today, only two species of beavers survive, our North American beaver, Castor canadensis, and the very similar Eurasian beaver, C. fiber. Adults weigh 30 to 70 pounds. Giant species of beavers evolved in Europe and North American during the Pleistocene.

A beaver in North America in the genus Castoroides was as big as a black bear and weighed about 220 pounds. The giantbeaver did not gnaw wood or eat bark, but fed on submerged vegetation in swamps. It went extinct about 10,000 years ago, as North America was becoming more arid and swamps became smaller and less common.

Beavers are frequently presented as nature's engineers, for they change their environment substantially. They gnaw down aspen and cottonwoods more than a foot in diameter to build a dam. Their dam to creates a pond where they then build a den or lodge as a refuge from threatening predators and harsh weather. Dens are at the edge of the pond, while lodges are surrounded by water. Both have underwater entrances to exclude predators.

Once the pond is formed, the adjacent soils become saturated, killing some species, but making the area ideal for alders, willows, aspens and cottonwoods—all favored foods of beavers. They may excavate a canal to a nearby grove of trees so they can easily transport branches and twigs to their pond.

Trout seem to flourish in beaver ponds, and muskrats, mink and ducks drop in as well. Over the years, sediment flowing into the pond makes it shallower, eventually forcing the beavers to abandon the pond as it transitions to a meadow.

Aspen, cottonwood and willow branches not incorporated into the dam or den are cached either underwater or in a storage room inside the lodge so they can eat the bark in the winter. When the pond freezes over, they can safely retrieve branches from underwater caches.

Climate change has been implicated in the movement of the geographic ranges of many species of animals. Many species are expanding their ranges to higher elevations and latitudes in the northern hemisphere. Beavers might be added to this list, for they have moved farther north in the Arctic tundra of Alaska, creating more than 12,000 new ponds.

In 2020 the temperature in the Alaska tundra rose higher than ever in recorded history, coincident with the invasion of the tundra by woody shrubs. This provides the building materials for dams and lodges and food to sustain beavers through the winter.

Beavers may appear to be one of the most sedentary of species, living in a secure den or lodge in a pond with all of their food within a short waddle. But now, in Boulder Canyon and in Alaska, it is evident that they are on the move.

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Saltbush evolved to filter dust from wind to form mounds

Anonymous — Wed, 28 Sep 2022 23:13:43 +0000

Saltbush evolved to filter dust from wind to form mounds Anonymous (not verified) Wed, 09/28/2022 - 17:13

Jeff Mitton

The wind that sculpts the stones also conspires with plants to transform a valley floor to a landscape of mounds with embedded plants

Cathedral Valley, in the northern, primitive portion of Capitol Reef National Park, features magnificent sandstone walls and spires. During a recent visit, I found that the wind sculpting the stones also conspires with plants to transform a valley floor to a landscape of mounds with embedded plants.

The mounds are one to three feet tall, and they bristle with vertical branches bearing leaves and tiny flowers.

I checked the lists of plants for Capitol Reef NP and found that these were Gardner's saltbushes, Atriplex gardneri, which grow on salty and alkaline soils from British Columbia and Saskatchewan to Nevada, Utah, Colorado and New Mexico.

The process of entrapment of dust to mounds around plants eventually causes the demise of the plants, for as the mound grow taller, salts become concentrated at the top of the mound, excluding plants. After the plants die, wind erodes the mound, exposing crust again. This is a recurrent, cycling process.

A deep taproot supports a woody base that branches profusely, producing many vertical branches with grayish green, rounded leaves. This plant has remarkable variation, both within populations and across its wide geographic range.

Seven varieties (similar to subspecies) are recognized, and most are separated geographically and adapted to different habitats. Plants can be annual or perennial, exclusively male, exclusively female, or bearing both types of flowers. Gardner's saltbush can have two copies of each chromosome (as is the case for humans), which is denoted 2n, or they can be 4n, 6n, 8n or 10n. These different chromosomal forms are usually adapted to different habitats.

Perplexing variation within populations is attributable to crossing among chromosomal forms and hybridization with other saltbush species. In Capitol Reef National Park, Gardner's saltbush grows with four-wing saltbush, Atriplex canescens, shadscale, A. confertifolia, and mat saltbush, A. corrugata.

It hybridizes extensively with shadscale and mat saltbush, so intermediate forms occur as well. Incidentally, shadscale has multiple chromosomal forms as well: 2n, 4n, 6n, 8n, 10n, and 12n. All these sources of variation make identification of saltbush species a challenge, and even the professional systematists maintain different opinions of the formal name of Gardner's saltbush—some call it Atriplex gardneri, others insist it is Atriplex cuneata.

In northwestern Nevada, ecologists studied a salt-tolerant plant community occupying mounds around playas, which are ephemeral lakes in shallow desert basins from which water evaporates quickly. One species typically on the mounds is Torrey saltbush, A. lentiformis.

This empirical study found that wind-blown or eolian dust is very common, and it has high salt content. They found that plants, including Torrey saltbush, germinate in crevices in barren crust. As the plants grow, they entrap wind-blown or eolian dust that accumulates around the plants.

At the top of the page: Gardner's saltbush transforms landscapes by forming mounds. Above: The landscape as seen from a broader perspective. Photos by Jeff Mitton.

As the plants grow in height and diameter, the mounds grow to the point that they coalesce. The process of entrapment of dust to mounds around plants eventually causes the demise of the plants, for as the mound grow taller, salts become concentrated at the top of the mound, excluding plants. After the plants die, wind erodes the mound, exposing crust again. This is a recurrent, cycling process.

Similar processes form mounds in Cathedral Valley. Some of the areas around the Temple of the Moon are barren soil crusts with numerous, conspicuous cracks reaching about 3/8 inches into the crust. When occasional snowfall or thunderstorm brings moisture, it would seep into these cracks, where it would evaporate more slowly than on crustal sheets exposed to sun and wind.

A seed blowing into the crack could get a good start, sending up a shoot, developing leaves and sending roots down to find moist soil. Gardner's saltbush has a taproot, and its roots can reach a depth of 4.5 feet. As the leaves proliferate, they baffle the wind, causing dust to accumulate beneath the plant. When a twig contacts the accumulating soil, it develops adventitious roots, allowing the plant to grow in diameter.

The mound would grow in diameter as the root system expanded outward and branches became more numerous. The soil, shaded by twigs and leaves, would retain snowmelt and rainwater much longer than the exposed desert crust, helping the plant survive and grow.

I was unable to find studies recording ages of individual plants, but repeat photography in the Grand Canyon identified four-wing saltbushes over 100 years old.

Plants that are more effective in baffling wind to collect dust and pile it as soil would grow larger and probably be able to produce more seed. Natural selection, driven by differences in reproductive success, makes the next generation of plants similar to the plants that had the highest reproductive success in the previous generation.

Gardner's saltbush has evolved to manipulate the wind, improve water retention and to continue to grow larger as it harvests soil from the wind.

The wind that sculpts the stones also conspires with plants to transform a valley floor to a landscape of mounds with embedded plants.

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Achemon sphinx moths' range is shrinking

Anonymous — Wed, 10 Aug 2022 00:11:05 +0000

Achemon sphinx moths' range is shrinking Anonymous (not verified) Tue, 08/09/2022 - 18:11

Jeff Mitton

No doubt about it, sphinx moths are extraordinary; extinction is forever, and it would be tragic to lose such a remarkable group of moths

While watering my rock garden, I inadvertently flushed an Achemon sphinx moth, Eumorpha achemon, which flew less than 20 feet to clutch onto a Stella D'Oro lily, where it stayed for the remainder of the day.

This species is crepuscular and nocturnal, so it is rarely seen during the day but first appears around dusk and is active most of the night.

Achemon sphinx moths are the smallest in the genus Eumorpha, but are large in comparison to moths in general. They have a body length of up to 2 inches and wing spans from 3.4 to 3.8 inches.

At top of page: An Achemon sphinx moth caterpillar. Above: An Achemon sphinx moth rests on a Stella D'Oro lily. Photos by Jeff Mitton.

On the dorsal side, adult moths have soft brown tinged with pink and dark brown, triangular patches on the thorax next to the wings. The bright salmon colors of the hindwings flash when the moth flutters.

Five instars or stages of caterpillars change colors dramatically as they molt. The first stage is light yellow, with a very prominent horn, which earns the sphinx caterpillars the common name "hornworms."

Second stage caterpillars are either green or brown, while third and fourth stages are green or brown with seven white diagonal stripes on each side. Fifth stage caterpillars are red or brown or green and lack the horn but a conspicuous eye spot appears where the horn was attached.

The puparium is about three inches long, dark brown and rounded at one end, pointed at the other. It is rare to find a puparium, for they are usually buried in the soil beneath the plants that the caterpillars fed on.

Caterpillars eat the leaves of many species in the family Vitaceae which contains species of grapes and Virginia creeper. For this reason, vintners do not welcome Achemon sphinx moths to their vineyards.

Sphinx moths have a number of traits usually described with superlatives. They are strong and fast fliers—top speed is 30 mph and males have been documented to fly over two miles to find a mate.

Their wings beat so fast that they emit a fluttering buzz—wingbeat frequencies during acceleration reach 41 cycles (up and down) per second. Sphinx moths can hover, an ability shared only with hummingbirds, hoverflies and some bats. Their color vision is acute, allowing them to distinguish flower colors at light levels that appear pitch black to you and me.

Odor sensors on their antennae are incredibly sensitive, allowing males to find fragrant flowers at night and to detect a plume of female pheromone being released more than a mile away. A species of sphinx moth native to Madagascar has a tongue 14 inches long to reach nectar in the extremely long spurs of star orchids. They can hear the bat sonar and can mimic it to confuse the threatening bat. No doubt about it, sphinx moths are extraordinary.

About 1,450 species of sphinx moths have been described worldwide and more than two dozen are native to Colorado. The most common sphinx moth in Colorado is the white-lined sphinx, Hyles lineata.

Both Achemon and white-lined sphinx moths have enormous ranges, spanning most of the North American continent. High abundance and a large geographic range usually indicate that the species is secure. But a disturbing trend has been documented in the eastern portions of the ranges.

Sphinx moths have been declining for the last 50 years in New England. Biologists have been documenting this ongoing, ominous trend and trying to determine which factors are driving it. Habitat destruction, coastal development, overgrazing by deer and other factors have been discussed, but David L. Wagner, at the University of Connecticut, has built a convincing case that sphinx declines are attributable to Compsilura concinnata, a parasitic, tachinid fly introduced from Europe to New England in 1906 to control two introduced pests, gypsy moths and brownttail tussock moths.

Unfortunately, C. concinnata is a generalist, laying its eggs on caterpillars of over 200 species in North America. When the eggs hatch, larvae burrow into the caterpillar to consume it from the inside—a grisly demise. Wagner has compiled data documenting the decline of sphinx species in New England, and he is unable to find evidence that either Achamon or white-lined sphinxes still live in Connecticut.

A neighbor gave me an Achemon puparium found among the roots of a lilac tree, and we agreed that I would try to photograph the moth as it emerged. However, it never emerged and when I opened it to see what was wrong, I found that it was completely filled by numerous puparia of a tachinid fly (identified by Valerie McKenzie).

We have several native tachinid flies in Colorado, but I was troubled by the possibility that the tachinid fly that probably drove Achemon and white-lined sphinxes to local extinction in Connecticut had arrived in Colorado.

Well-intentioned biologists have introduced C. concinnata in many other places beyond New England, including Minnesota and California. Fortunately, Wagner informed me that it has not yet appeared in the southern Rocky Mountains. Extinction is forever and it would be tragic to lose such a remarkable group of moths.

No doubt about it, sphinx moths are extraordinary; extinction is forever, and it would be tragic to lose such a remarkable group of moths.

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Downy paintedcup adapts to changes in pollinators and root hosts across its range

Anonymous — Fri, 08 Jul 2022 23:35:42 +0000

Downy paintedcup adapts to changes in pollinators and root hosts across its range Anonymous (not verified) Fri, 07/08/2022 - 17:35

Jeff Mitton

Communities of pollinators and potential root hosts respond to climate change and the ever-increasing impact of humans on natural habitats

The High Plains Trail, in the open space and mountain parks on the plains south and east of Boulder, has several wildflowers that are not found in the foothills or forests of the Front Range. One that I had not seen elsewhere was a small plant with cream, green and pink flowers.

Castilleja sessiliflora is an Indian paintbrush, commonly referred to as prairie fire, Great Plains Indian paintbrush, downy Indian paintbrush or downy paintedcup.

Most of the 200 species of Castilleja share a common flower form and are easily recognized as Indian paintbrush, but I did not recognize paintedcup as a paintbrush. Long, slender flowers extend from green bracts (modified leaves) that can be tinged with pink or red. Petals have fused to a vertical, inch-long corolla tube that curves at the top to an opening with a long upper lip and a shorter lower lip with three lobes.

Indian paintbrushes are facultative root parasites, with their roots grafting to the roots of grasses and forbs to take water, minerals and nutrients. A facultative root parasite can live and survive without hosts, but it grows faster, is more robust and lives longer if it can parasitize neighbors.

But the list of host species is not complete for paintedcup. A study in a dry lime prairie or juniper savanna in Wisconsin found that paintedcup was an obligate root parasite on two junipers, eastern redcedar, Juniperus virginiana, and oldfield juniper, J. communis.

In that environment, paintedcup was always clustered around one or more junipers and not extending beyond the drip line, or the outer circumference of the crown. This pattern of distribution indicates that paintedcup is not able to survive without one of these two juniper hosts.

However, in Minnesota, paintedcup is facultatively parasitic on a variety of grasses, such as hairy grama and June grass as well as other wildflowers. The paintedcup that I found on the High Plains Trail were not close to any junipers.

The same study in Wisconsin identified pollinators visiting wildflowers, including downy paintedcup. The only pollinator servicing paintedcup was the yellow bumblebee, Bombus fervidus, known for its exceptionally long tongue. B. fervidus also has a narrow head and it was believed that the combination of narrow head and long tongue were needed to access the nectaries at the bottom of the long corolla tube.

The petals of downy paintedcup form a long, narrow tube that serves nectar to long-tongued pollinators. Photos by Jeff Mitton.

bservers documented that "the head of the bee plunges as far as possible into the flower" in its effort to reach the nectar. From these observations, one might conclude that only B. fervidus could pollinate paintedcup.

A study of pollinator activity in Minnesota listed six bumblebees pollinating paintedcup, three with long tongues and three with medium length tongues (thanks to Carol Kearns for bee descriptions).

Why is it that only a single long-tongued bee could pollinate paintedcup in Wisconsin, but in Minnesota, bumblebees with either long or medium length tongues pollinate the same species?

A group of biologists led by Krissa Skogen at the Chicago Botanic Garden has been studying downycup across its range. They found that sphinx moths, which have very long tongues, are the most common pollinators at the eastern edge of downy cup's geographic range. They also noted that at the eastern edge of paintedcup's geographic range the corolla tubes were white and very long.

But in the western portion of the range, floral tubes were light pink and shorter and wider. Furthermore, these flowers were pollinated by bees and sphinx moths with either medium or long tongues. These observations are consistent with hypothesis that floral traits evolve to attract adequate and reliable service from the available community of pollinators.

It is evident that downy paintedcup has evolved to different pollinator communities and different communities of root hosts. It is less evident but certainly true that this process continues today, as the communities of pollinators and potential root hosts respond to climate change and the ever-increasing impact of humans on natural habitats.

The communities of pollinators and potential root hosts respond to climate change and the ever-increasing impact of humans on natural habitats.

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