Evening Primroses, Pumps, and Pollinators

Rick Overson is fascinated with insects—especially the kinds that love desert climates like in Arizona, where he grew up and earned his Ph.D. in biology. After completing a postdoctoral assignment in northern California, he decided it was time to get to know the little buggers even better, so Dr. Overson hopped on a plane for Chicago and stepped out into the subzero temperatures of the polar vortex to do just that.

PHOTO: Dr. Rick Overson with hawkmoth specimens.
Dr. Rick Overson with hawkmoth specimens

The devoted entomologist didn’t expect to see the insects in Chicago, but he was eager to join research at the Chicago Botanic Garden. A multidisciplinary team was assembling there to look for scent variations within Onagraceae, the evening primrose family, and connections from floral scent to insect pollinators and predators. The findings could answer questions about the ecology and evolution of all insects and plants involved. Overson is a postdoctoral researcher for the initiative, along with Tania Jogesh, Ph.D.

“Landscapes of Linalool: Scent-Mediated Diversification of Flowers and Moths across Western North America” is funded by a $1.54 million Dimensions in Biodiversity grant from the National Science Foundation. The project is headed by Garden scientists Krissa Skogen, Ph.D., Norman Wickett, Ph.D., and Jeremie Fant, Ph.D. It was developed from prior research conducted by Dr. Skogen on scent variation among Oenothera harringtonii plants in southern Colorado.

“For me, the most important thing coming out of this project is documenting and showing this incredible diversity that happens inside a species,” said Overson. “It’s vitally important for me to break down this idea of a species as a discrete unit. It’s a dynamic thing that is different in one place than another. That factors into conservation and our understanding of evolution.” In this case, he and his colleagues theorize that the evolution of the insect pollinators and predators is connected to the evolution of the scent of the plants.

PHOTO: Evening primrose in bloom on the plains of New Mexico.
Evening primrose in bloom on the plains of New Mexico. Photo by Dr. Rick Overson

The first two years of field work brought Overson back to his desert home. He traveled across Arizona, Utah, and nearby states with a group of about five scientists during summer months when the flowers were blooming. The team visited several populations each of 16 species of flower for a total of 60 locations. Overson and the team identified and documented the insects visiting the plants and compiled scent chemistry from the flowers. Their tool kit included a pump to pull the scent from a flower onto tiny polymer beads that held the scent inside of a vial. From there, they extracted the scent chemicals at the end of the research day or night. “It’s definitely the case that this pattern of scent variation inside a species is very common in this group,” he said of the team’s preliminary findings.

PHOTO: Hawkmoth on evening primrose.
A beneficial pollinator, the hawkmoth, visits an evening primrose (Oenothera harringtonii).

In the field they also took video recordings of pollinator behavior to see who visited which flowers and when. The pollinators, including hawkmoths and bees, follow scents to find various rewards such as pollen or nectar. The insects are selective, and make unique choices on which plants to visit.

Why do specific pollinators visit specific plants? In this case, the Skogen Lab is finding that it is in response to the scent, or chemical communication, each flower releases. “In the natural world those [scents] are signals, they are messages. Those different compounds that flowers are producing, a lot of them are cocktails of different types of chemicals. They could be saying very different things.”

PHOTO: Closeup of a wasp on a closed evening primrose bloom.
Nature is complicated. Here, a wasp lays eggs through a flower bud into a hidden Mompha moth inside. Its larvae will eventually destroy both the moth and the flower. Photo by Dr. Rick Overson

A destructive micromoth called a microlepidopteran (classified in the genus Mompha), has also likely learned how to read the scent messages of its hosts. The specialist herbivore lays eggs on plants leading to detrimental effects for seed production. The team’s field work has shown that Mompha moths only infect some populations of flowers. When and why did the flowers evolve to deter or attract all of these different pollinators? Or was it the pollinators who drove change?

At the Garden, Overson is currently focused on exploring the genomes, or DNA set, of these plants to create a phylogeny, which looks like a flow chart and reads like a story of evolution. “Right now we don’t know how all of these species are interrelated,” he explained. When the phylogeny is complete, they will have a more comprehensive outline of key relationships and timing than ever before. That information will allow scientists to determine where specific scents and other traits originated and spread. He will explore the evolution of important plant traits using the phylogeny including the color of the flowers and their pollinators, to answer as many questions as possible about relationships and linked evolutionary events.

In addition, the team is looking at population genetics so they can determine the amount of breeding occurring between plant locations by either seed movement or by pollinators. They will also look for obstacles to breeding, such as interference by mountain ranges or cities.

“Relationships among flowering plants and insects represent one of the great engines of terrestrial diversity,” wrote principal investigator Krissa Skogen, PhD, in a blog post announcing the grant.

The way that genes have flowed through different populations, or have been blocked from doing so over time, can also lead to changes in a species that are significant enough to drive speciation, or the development of new species, said Overson. “The big idea is that maybe these patterns that are driving diversity within these flowers could ultimately be leading to speciation.”

By understanding these differences and patterns, the scientists may influence conservation decisions, such as what locations are most in need of protection, and what corridors of gene flow are most important to safeguard.

PHOTO: Dr. Rick Overson in the field.
Dr. Rick Overson in the field

“We absolutely can’t live without plants or insects, it’s impossible,” remarked Overson. “Plants and insects are dominant forces in our terrestrial existence. Very few people would argue that we haven’t heavily modified the landscape where these plants and insects live. I think it is crucially important to understand these interactions for the sake of the natural world, agriculture and beyond.”

When Dr. Overson is taking a break from the laboratory, he visits the Desert Greenhouse in the Regenstein Center, which feels like home to him.


©2016 Chicago Botanic Garden and my.chicagobotanic.org

What’s a Little Frass Flicking Between Friends?

I am sure that most of you know what I am referring to when I say “leap year.” Although this is not a leap year, I am suggesting that we unofficially call 2015 “Lep Year”—“lep” being short for Lepidoptera (from the Latin “scaly wing”), the order of insects that includes butterflies and moths. It has probably been a decade or more since I have seen the diversity and abundance of butterflies and moths that I have seen this past spring and summer.

PHOTO: Euchaetes egle (Milkweed tussock moth).
These voracious Euchaetes egle caterpillars were shredding some of the common milkweed plants near the prairie at the Garden this summer.

Lately, the butterflies have gotten the lion’s share of PR. In particular, the monarch butterfly is on nearly everyone’s radar, due to its precarious situation with dwindling wintering grounds and lack of larval food plants—the milkweeds. However, if you compare the two groups, butterflies and moths, the numbers of moth species outnumber the butterflies by more than ten to one in North America! In fact, there is a moth species that is also dependent on milkweeds—the milkweed tussock moth (Euchaetes egle). The caterpillars of this species are black and orange (a similar color combination to the monarch), and they usually occur in large numbers when you find them. The black-and-orange coloration signals to predators not to eat these fuzzy little fur balls.

The main difference between butterflies and moths is that the moths, in general, tend to be rather drab colored and active at night while the butterflies are mostly colorful and active during the day. These are generalities since you can find very colorful moths, rather drab butterflies, and a number of day-flying moths. There are also structural differences most easily seen in their antennae. While butterflies have narrow antennae with club-shaped structures at the end, the moths can have either thread-like antennae that end in a point in females or fern-like antennae in males. The fern-like antennae of the males are used to detect the chemicals, called pheromones, released by the females when they are ready to mate. Some moths can follow these chemical trails for miles.

Sixty percent or more of the diet of some nestling songbirds comes from caterpillars, and these are most certainly moth caterpillars.

Moths are not only extremely diverse in shape and pattern, they also have a wonderful variety of common names that people have come up with to label them. There are sphinx moths or hawk moths, daggers and darts, army worms and prominents, sallows and quakers, owlets and loopers, and marvels and bird-dropping moths. The names go on and on, some attempting to describe the adults and others the larvae.

PHOTO: Cecropia moth caterpillar (Hyalophora cecropia).
This brightly ornamented Cecropia moth caterpillar (Hyalophora cecropia) will turn into North America’s largest native moth.

It is hard to say which stage of the moth life cycle is more impressive. Although the adult moths are so varied in their shape, size, and patterns, the caterpillars are no less amazing. Take for example the strikingly beautiful brown hooded owlet moth caterpillar.

PHOTO: Brown hooded owlet caterpillar (Cucullia convexipennis).
The brown hooded owlet caterpillar (Cucullia convexipennis) is a stunning specimen to find outside my office.

It would be difficult to find a more attractive critter anywhere, and here it was, right outside my office. Equally impressive are the huge silkworm caterpillars. The Cecropia moth caterpillar (Hyalophora cecropia) is almost shocking, not only because of its massive size, but also because of the large orange-and-yellow spiky beads covered in black spots along its back and the smaller turquoise-spiked beads ornamenting its sides.

And who could talk about moth caterpillars without mentioning the infamous woolly bear? These orange and black-banded caterpillars are often consulted to see what the winter will be like. Unfortunately, the banding on the caterpillar has nothing to do with the weather, but at least it has gotten it a lot of attention. The woolly bear eventually turns into the bright orange Isabella tiger moth (Pyrrharctia isabella).

PHOTO: Woolly bear caterpillar (Pyrrharctia isabella).
Who hasn’t been tempted to touch the woolly bear caterpillar (Pyrrharctia isabella)? Photo by By Micha L. Rieser via Wikimedia Commons
PHOTO: Isabella tiger moth (Pyrrharctia isabella).
The Isabella tiger moth retains its orange-and-black caterpillar coloring. Photo by Andy Reago & Chrissy McClarren via Wikimedia Commons

The high diversity and nocturnal behavior of moths make it not unlikely that you might find a moth or caterpillar you haven’t seen before. The other day, while trimming my rambunctious Virginia creeper vine on the side of my house, I spotted an interesting caterpillar that I had never seen before. As a woodland ecologist I have experience with a lot of caterpillars, so it is always interesting when something new comes along. As it turns out, the caterpillar was the larval stage of an Abbott’s sphinx moth (Sphecodina abbottii). Although this was a new find for me, I still have not seen the adult moth.

Every morning when I come into work, I check the wall outside our building under the light to see if any new moths have shown up during the night. Some of the moths I have spotted this summer are the Crocus geometer, Colona moth, Ironweed borer, large maple spanworm, Ambiguous moth, green owlet, and one of the microlepidoptera, the morning-glory plume moth.

PHOTO: Colona moth (Haploa colona).
Colona moth (Haploa colona)
PHOTO: Crocus geometer (Xanthotype urticaria).
Crocus geometer (Xanthotype urticaria)
PHOTO: Green owlet (Leuconycta diphteroides).
Green owlet (Leuconycta diphteroides)
PHOTO: Morning glory plume (Emmelina monodactyla).
Morning glory plume (Emmelina monodactyla)
PHOTO: Ironweed borer (Papaipema cerussata).
Ironweed borer (Papaipema cerussata)

Most moths do not live for very long as adults. Ironically, some of the largest moth species live the shortest lives. I had the opportunity to see a new species of one of these megamoths for the first time this summer when my wife brought home an Imperial moth (Eacles imperialis) that she found clinging to the window of the school where she works. The very large moths in the family Saturniidae (silkworms and royal moths) emerge either from the soil, in the case of the Imperial moth, or from one of the familiar large cocoons you can find attached to a twig, like those of the Cecropia or Promethea moths. Since these moths do not have functional mouth parts, they are unable to feed, so they live off their stored body fat while searching for mates until they die, usually within seven to ten days.

PHOTO: Imperial moth (Eacles imperialis).
This Imperial moth (Eacles imperialis), had a 5-to-6-inch wingspan, and a body as big as my thumb!

Interested in finding out more? Visit the Moth Photographers Group at mothphotographersgroup.msstate.edu or BugGuide at bugguide.net.

Another new species for me was the painted lichen moth. While removing Japanese beetles from my hazelnut shrubs, I spotted what looked like a large firefly. As it turned out, it was not a firefly at all, but rather a moth that mimics one. Since fireflies are toxic to most predators, the moth gets a benefit from looking like the firefly. Another neat trick they employ is a maneuver known as frass flicking. They are able to expel their excrement nearly a foot away from their body. This is important because some predatory wasps locate their prey by homing in on the scent of their droppings.

There are a number of moths—or more accurately, moth larva—that are pests for gardeners. Almost all vegetable growers have run into cutworms at one time or another. Cutworms were given this name because of their habit of cutting off seedling plants in the garden. There are a number of cutworm species native to this country, but all develop into moths later in their life cycle.

PHOTO: Parasitized sphinx moth caterpillar.
The white structures on this parasitized sphinx moth caterpillar are the cocoons of the braconid wasps.

Another familiar larva is the tobacco or tomato hornworm (Manduca sexta). These are the large green larvae of one of our native sphinx or hawk moths. The Carolina sphinx larva is often found on tomatoes. Although they will rapidly chow down on tomato plant leaves, I generally leave them alone until they have had their fill and work their way down into the soil where they pupate to spend the winter. (I find that they rarely put much of a dent in the productivity of my tomato plants.) If you should happen to dig up one of their pupae when turning over the garden soil, they are a dark, shiny brown, pointed at one end, and have what looks like a teapot handle on the side that houses a long, curved proboscis. If you pick them up, you might be startled by the fact that they often times will swivel around at the middle—probably a predator avoidance behavior. Tobacco hornworm and sphinx moth caterpillars commonly fall prey to braconid wasps, which parasitize them. Leaving these parasitized caterpillars in the tomato garden can be an effective method of pest control.

PHOTO: Female gypsy moth (Lymantria dispar).
Female moth (Lymantria dispar)

A more serious pest species is the introduce Lymantria dispar moth. These moths occur in huge numbers and are capable of completely defoliating adult oak trees over large areas. A few years ago, we avoided an invasion of Lymantria dispar moths at the Garden when hundreds of thousands of these moths, in Turnbull Woods forest preserve across Green Bay Road in Glencoe, succumbed to a cool, rainy spring.

 


Photos ©2015 Jim Steffen unless otherwise noted.

©2015 Chicago Botanic Garden and my.chicagobotanic.org

Darwin’s Orchid and the Wardian Case

There’s something very special about this orchid. Can you tell what it is?

PHOTO: Closeup of Angraecum sesquipedale bloom.
A native of Madagascar, Angraecum sesquipedale is an epiphyte that prefers the drier branches and trunks of trees as a host.

 

The nectar of this orchid resides almost entirely at the tip of the orchid's spur.
The nectar of this orchid resides almost entirely at the tip of the orchid’s spur.

If you guessed that it was the long tubular structure coming from the back of the flower, you are right! That spur contains energy-packed nectar and is the reason this plant has a place in history.

Discovery

Angraecum sesquipedale was first described in 1822 by French botanist Louis-Marie Aubert du Petit-Thouars and would be shrouded in mystery for decades after. It arrived in the United Kingdom 33 years later.

ILLUSTRATION: an illustrated plate of Angraecum sesquipedale from 1822.
An illustration of Angraecum sesquipedale from Histoire particulière des plantes orchidées recueillies sur les trois îles australes D’Afrique de France, de Bourbon et de Madagascar (1822) .

At the time  this orchid was discovered, transporting plants from one continent to another was extremely difficult and often unreasonable. The long sea journey, combined with polluted conditions in industrialized cities, made it difficult to collect and maintain specimen plants. This would all soon change.

It was in 1829 that Nathaniel Bagshaw Ward discovered the mechanism that revolutionized horticulture and botany forever. 

The Wardian Case

Nathaniel Bagshaw Ward was an English doctor who spent most of his life in eighteenth-century London. In his youth, he perused the writings of Linnaeus and spent some time in Jamaica, which fostered his love of entomology and botany. As an adult, Ward was inspired to create a wall of ferns and mosses in his own yard, but failed due to the polluted air of East London. He was distraught.

In the summer of 1829, Ward took a glass jar and placed a hawkmoth chrysalis inside, atop a bed of moist leaf mold. Ward regularly checked on the progress of the moth, finding that before it hatched, grasses and a fern emerged from the leaf mold. Ward observed that the glass jar retained moisture because as it warmed up, water evaporated, condensed on the glass, and returned to the base of the jar, never escaping. With this success he repeated his experiment and, to his delight, found that he could keep plants growing within the chamber for years. His discovery brought about the invention of the Wardian case, the predecessor to the modern terrarium. He wrote extensively about this in his book, On the Growth of Plants in Closely Glazed Cases. Soon the Wardian case became a popular feature of the parlor in Victorian society. These parlor versions, both tabletop and freestanding forms, often held one or more plants and could be rather ornate.

PHOTO: A large Wardian case, made of steel and glass—an individual greenhouse for an orchid.
One of four Wardian cases appearing in our Orchid Show this year. Wardian cases like this one could be found in parlors of wealthy Victorians.

In 1843, the Wardian case was used for the first time to bring plants from China by sea. The director of the Royal Botanic Gardens, Kew, observed that in 15 years, the Wardian case brought six times as many plants as had been imported in the last century. If you do the math, that means it made importing plants almost 40 times as efficient as regular ocean travel! This was of particular use to collectors like James Bateman, a wealthy landowner who sponsored several plant exploration trips through the Royal Horticultural Society. One such trip would bring several rare Angraecum sesquipedale from Madagascar to England, and in 1862, this plant would find its way to one of the prominent figures in history.

Charles Darwin

By 1862, Charles Darwin had already become a prominent figure internationally. Having published On the Origin of Species three years earlier, Darwin was already the subject of scrutiny by religious groups and scientists who disagreed with his theories on evolution and natural selection. In this same year that he received a number of orchids from Bateman, Darwin published his book The Various Contrivances by Which Orchids are Fertilised by Insects, which proposed that Angraecum sesquipedale must be pollinated by a “huge moth with a wonderfully long proboscis” (or straw-like tongue). He proposed that it might be a Sphingidae moth since these are typically large. No such moth was known to exist on Madagascar.

Though largely overlooked by the public, his proposal became a subject of controversy, particularly in the religious community. Critics attributed any existence of such a creature to be by divine will and not natural selection; most mocked the possibility of such a moth existing. Others viewed his prediction with skepticism since only smaller moths had been discovered in Madagascar.

PHOTO: Morgan's sphinx moth, with its 30-centimeter tongue unrolled to show its length.
Morgan’s Sphinx moth, the predicted pollinator. Photo by Esculapio (Own work) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons

In 1903, 21 years following Darwin’s death, a subspecies of moth known as Xanthopan morgani praedicta, Morgan’s Sphinx moth, was found in Madagascar. This moth has a wingspan of 5 to 6 inches and a proboscis of 10 to 12 inches long. The subspecies name, praedicta, was intended as an homage to Darwin’s prediction that such an insect existed.

Angraecum sesquipedale, frequently referred to as Darwin’s Orchid, is currently being displayed in the Greenhouse Gallery of the Orchid Show (purchase tickets here) this year.

©2014 Chicago Botanic Garden and my.chicagobotanic.org

Fall Migration is Here!

Twice a year we are blessed with the migration of birds, butterflies, moths, and dragonflies. Many species that we don’t normally see (or don’t see in large numbers) are now moving through the Chicago area. Each day is a mystery as to what I might come across.

These guys were moving through the woods, stopping to eat berries. ©Carol Freeman
These guys were moving through the woods, stopping to eat berries.
©Carol Freeman

Today I chose to head over to McDonald Woods. Before I could even get to the path, I was greeted by red-eyed vireos. I stayed there and watched them for some time. One thing I have learned is to photograph birds wherever I see them, and to avoid the impulse to assume I’ll find more birds, or better birds, elsewhere. Just because the birds are hopping here doesn’t mean they will be hopping everywhere: best to take advantage of the birds wherever they are, even if it’s just the parking lot.

Only when the activity slowed did I head into the woods to see what else might be there. Right away, I saw some movement up high. Yep, warblers. I could tell by the flash of the tail feathers that these were redstarts. My instinct is to try to focus on any bird that moves. However, another thing I have learned is to resist the urge to photograph birds up high and backlit. The best photos are taken at eye-level. I look for movement and listen for bird calls to help me find a likely place to get some good photos. When I do, I relax and wait. Yes, wait. It might take 15 or 20 minutes for the birds to filter down. It is tempting to try to find the birds, or to follow them, but all that tends to do is send the birds higher up.

I was ready when this little one came back to it's favorite perch. ©Carol Freeman
I was ready when this little one came back to its favorite perch.
©Carol Freeman

After just a few minutes, I see a young warbler hopping in the lower branches. I get a few shots before it takes off. Then, in zooms a hummingbird. The nice thing about hummingbirds is that they will often come back to the same perch over and over again. So I slowly move toward where this little one is sitting. Just as I get close, it takes off. So I position myself with a good view of the perch, and wait. Yes, there is that word again. Trust me, the “wait” will be worth it! Soon the hummingbird is back, and yes, it lands right on the same perch, and I’m able to get some really nice shots. Learning about the habits of birds comes in handy. If I did not know that the hummingbird would be back, I would not have been ready to take the photo when it got there. One way to learn about the habits of birds is to hang out and chat with birders. I like to go on bird walks with them and read bird books when I can.

When I’m waiting for warblers and other migrants, I like to practice my photography skills on the more common and perhaps slower-moving birds. It’s a way to make sure that my camera is set properly, and it helps me get comfortable with my equipment choices for the day. If I can’t take an amazing photo of a common bird, it is unlikely that I will take an amazing shot of a tiny, quick-moving rarity. Practice is key! For bird photography, I like to use my 80-400mm lens, but anything over 200mm will work. I keep my shutter speed at 1/400 of a second or faster. Sometimes that means upping my ISO to get the faster shutter speed. Otherwise these little birds will be big blurs.

What a treat to see so many of these buzzing around the garden today.  ©Carol Freeman
What a treat to see so many hawk moths (also called sphinx moths) buzzing around the garden today.
©Carol Freeman

I have to keep an open mind. Even though I might really want to photograph a yellow-winged warbler, what I might get instead is a blue jay, or not even a bird at all. Sometimes my best “bird” shot of the day is a butterfly. Or like today, I was treated to dozens of hawk moths! I’ve never seen so many in one spot, and what amazed me most was how many people walked right past them! They were so focused on something else, they missed what I thought was the coolest migrant of the day. I can’t tell you how many times I went out with one intention and came back with shots of something I could have never predicted—all because I kept an open mind to all the wonders that are out there to discover. There will be a stream of migrants visiting Chicago through November, and I hope you can get out and enjoy the amazing wonders that the autumn migration will bring right to you.


©2013 Chicago Botanic Garden and my.chicagobotanic.org