An Adaptive Walk with Monarchs

 “The first step…shall be to lose the way.”  Galway Kinnell

(At left, monarch emerging from chrysalis, photo A. Budyak)

Throughout the summer, young citizen scientists in Madison watch the life stages of monarchs and protect vulnerable young butterflies from early predation.  They learn how to see, how to be gentle, and how to let go.  They also learn that bright coloration often says, “I don’t taste good.”  

Why don’t monarchs taste good, or worse?  Their larvae feed on milkweed leaves, and milkweeds contain toxic cardiac glycosides, such as cardinolides and galitoxin, that are poisonous to most vertebrates (think cows, sheep, birds, humans).  These compounds can cause heart rhythm changes, weakness, confusion, seizures, respiratory paralysis, diarrhea, even death in large amounts.

Indigenous medicine incorporated milkweed into treatments for respiratory and gut issues, as well as rashes and swellings, but their safe recipes aren’t widely known.  Also, what is helpful at one concentration can be harmful at another (as in arrow tips dipped in milkweed juices for hunting).  

Monarch larvae are able to eat and tolerate the toxins in milkweed leaves, and adult butterflies retain enough chemical to be a very unpleasant meal for birds.  Yes, some birds (species of orioles and grosbeaks) do more or less happily eat monarchs that are overwintering in Mexico.  They seem to know where in the butterfly the poisons are least concentrated, and likely have some tolerance?  In addition, the toxins in monarch adults break down over time.  (Photo at right of young scientist hand releasing “Ziggy,” by Amanda Budyak.)

Milkweed cardinolides work by interfering with (binding to) the mammalian sodium pump whose function is to re-set nerve cells after they fire.  Spent nerve cells with inoperative sodium pumps are therefore unable to re-charge, resulting in hearts beating irregularly or not at all.  

How did monarchs gain the capacity to eat toxic milkweed?  (See article by Tim Vernimmen of Knowable Magazine October 2, 2019 “How Monarchs Evolved to Eat a Poisonous Plant.”)  It turns out that cardinolides are unable to bind to monarch sodium pumps.  Why?  Apparently, they have three altered genes that carry instructions for making resistant pumps.  How did that evolve?  Can we know?  

(Butterflyweed with Black Swallowtail pollinator, by A. Budyak)

Well, scientists (Noah Whiteman et.al., 2012 in Nature 17 October 2019 v. 574) were able to produce fruit flies that had the same pumped-up pumps by introducing these three gene mutations, one by one.  The first mutation allowed the flies (and original monarchs it is assumed) to tolerate some toxin.  The second repaired damage that the first gene product caused, and the third allowed the flies (and butterflies) to tolerate an even higher toxic dose.  Such a multistep evolutionary gain is called an “adaptive walk,” and my analogy is that you first build a bridge, some cars (toxins) come across, cars cause some damage, you fix it, then even more cars can cross.  This “walk” allows a species to become more fit through time even though each mutation gives only a relatively small advantage.

“The order in which the substitutions evolved was explained by amelioration of antagonistic pleiotropy through epistasis.”

Vernimmen/Whiteman

As much of a mouthful as a monarch.

(At right, a Red Milkweed Beetle on common milkweed flowers at Black Earth Prairie, by S. Slapnick)

Monarchs and Milkweeds

 

The Restoration Manager at Pleasant Valley Conservancy, Amanda Budyak, is pictured at right.  She took most of the milkweed photos in this blog post.  Here, she is capturing turk’s cap lily in the marsh.

“This world of dew, is a world of dew, and yet, and yet… “  Kobayashi Issa

There is always more to be learned and said about milkweeds and monarchs and migrations.  About pollinators and poisons and the forever dance of plants and insects.  The two-step of the plant to attract just enough, yet also to repel.  The insect waltz to get the goodies, yet avoid, or live with, the lethal juices.  

Purple Milkweed (Asclepius purperascens).  This is the milkweed for which Pleasant Valley is known.  It grows in the savannas and is unpredictable from year to year as to whether it will bloom, form a seed pod, or even show up.  We rejoice when it does.  Poke Milkweed (A. exaltata) also grows in the savannas.

Milkweed pollination is accomplished mainly by bees and wasps.  That’s because the milkweed flowers literally saddle the insects with two giant pollen sacs at a time, and the pollinators need to be strong fliers to be able to take off again after this burden is attached against their will.

Butterfly Milkweed (A. tuberosa). Monarchs lay their eggs on milkweeds, and their larvae require milkweed leaves to develop. Over two dozen milkweed species serve this purpose in Wisconsin.  Ironically, Butterfly Milkweed isn’t their favorite for egg laying, but they do enjoy feeding on the nectar of the flowers.  If you want to plant milkweeds for monarchs, be sure to plant those native to your geographic area and plant several different species.  

Besides those pictured here, choose from whorled, prairie, clasping, sand, spider, short green, broadleaf, showy, and more.  Such as:

Swamp Milkweed (A. incarnata). This was the first milkweed scientific name I learned because I love it so, both the name and the plant.  The blossoms are beauty incarnate.  At this time of year they are islands of brightness as you trudge through the marshes, carefully.  All milkweeds develop pods that contain multiple rows of tightly packed flat, silky-winged seeds.  When the pods ripen, they split open, and the seeds are launched by the wind into the wind.  Pods familiar to most are seen below.

.  

Common Milkweed (A. syriaca). This is a favorite of monarchs, is easy to grow, and small amounts of seeds can be obtained for the asking from us or Madison Audubon (I’m making an assumption here).  All milkweeds and all of their leaves, flowers, roots shoots, seed pods, etc contain a milky sap that is toxic.  Do not eat these plants.  Wash your hands after handling the leaves and seed pods.

Monarchs are pretty famous these days, and this is just a brief reminder of their life cycle.  I wonder how their larvae are able to eat so much lethal milkweed toxin and not die.  The adults retain enough of this cardiac glycoside to repel predation, by birds for example.  Do we have any theories about how such a tolerance could have evolved?  We sometimes see orange and black milkweed bugs swarming over the pods.  They must be able to eat this poison too?  What would happen if we did eat milkweed leaves?  Native Americans used milkweed as medicine.  How did that work?  All questions for my next blog, where I will also feature young scientists giving monarchs a helping hand.

Prairie Willow and Sand Cherry

Prairie Willow (Salix humilis) photo by Susan 

Slapnick

Sand Cherry (Prunus pumila) photo

by Kathie Brock

“Do you think that each differs to the other, and is identical to itself?”  Socrates

“There cannot be several things exactly the same, 

for in that case there would not be several things,

but the same thing itself.”  Nicholas of Cusa

Near the entrance to Black Earth Rettenmund Prairie is a steep rise up to the top of the north section.  At the top, to the left, is a “shruby” area with a surprising diversity of native forbs and woodies.  The low-growing Prairie Willow is relatively abundant, even after some years of gentle taming.  And among all are similar-looking small, spreading shrubs, some with large dark fruits that look just like cherries.  Indeed, that is what Kathie Brock re-discovered there recently and even (or of course) ventured a taste.  Yes, thankfully, Sand Cherries are edible and delicious.  Just avoid the pits.

The similarities between Prairie Willows and Sand Cherries are most obvious:  both are shrubs, sprawling and low to the ground in frequently-burned prairies, both have alternate simple leaves about two plus inches long and one inch wide, and both like soil that is sandy and somewhat dry, perhaps acidic.  To see the differences requires looking closer.  The Prairie Willow leaves are medium green above, and below are lighter with fine hairs.  Sand Cherry leaves are dark green above and smooth below.  The stems of the Willow tend to be green to yellow-green, while the young Sand Cherry stems are reddish to brown.

I won’t describe these two any further.  Minnesotawildflowers.info is a good source, and Tom talked about each in his blog (google:  “PVC and Tom’s Blog” and look under Archives), specifically December 9, 2012 for Prairie Willow and May 9, 2014 for Sand Cherry.

The point of all this?  If you see a willow, look again, more closely (more willowfully?).

Spiderwort

Tradescantia ohiensis, Spiderwort, also Dayflower.  Native to the Americas.

Flowers open in the morning, close by evening, and the petals flower only one day.  This species has a bluish tint on thin leaves, lacks obvious hairs on the flowering stems, and is more spindly than the fatter-leaved virginiata.  It’s named after an English gardener to King Charles I, John Tradescant.  In my introductory biology classes, the students called it Turtox, the name of the biological company writ large on the microscope slides showing the stem cross sections of spiderwort illustrating the classic monocot pattern.  You remember, as opposed to dicots?  Corn kernels vs peanuts?  One vs two seedling-nourishing cotyledons?  If you’re a flowering plant, you are one of the two.  Monocots, like grasses, cereal grains, palm, banana, corn, onion, lilies, tulips, orchids and our spiderwort usually have long narrow leaves with parallel veins, a stem with scattered vascular bundles which do not contain a cambium between the xylem and phloem, one cotyledon, a fibrous root system and three-parted flowers (trimerous 3, 6, 9) vs dicots with tetra- and pentamerous flowers.

I was taught that the time to start collecting the spiderwort seed heads is when there is only one flower remaining in the clump.  We usually collect then and also a few days later.  (I’ve never seen a species whose individuals all ripen in the same day, nor would that be advantageous in the long run.)

I collected the heads shown at left on July 3.

The plants were more successful this year in

the prairies adjacent to the wetland.  The upland

areas are suffering from the June drought.  In

our unburned prairies, the Spiderwort hasn’t

been a stand-out in 2023.

Close-up of a clump

of seed pods after

flowering is done.

I love the rectangular

and intricately sculpted

seeds.  But you will see

that I love all seeds.

 

Wisconsin Cactus

 Opuntia macrorhiza (Plains Prickly Pear Cactus, cousin to O. fragilis, the Brittle Prickly Pear).

This species grows in large mats in sand prairies, like Spring Green Prairie, and on Wisconsin River banks and dunes.  Many years ago a friend gifted me a few pads, which, she said, were descendants of a Wisconsin River pad given to her years prior.  I brought about a dozen from my garden to fill in a Pleasant Valley cabin planter at least ten maybe 15 years ago.  I just tucked the pointy end of each pad into the poor, shallow soil and added a little water.  Easy.  Well…  They thrived!  The entire area is now overflowing, and they bloom wildly every year at the end of June.  The long spines and smaller, sharp, detaching prickles (glochids) have kept ground squirrels and interns from nibbling.  That said, the big red fruits called “tuna” or “cactus figs” are sweet and delicious, if you don’t mind a mouthful of marbly seeds with each bite.  The mature pads are also edible and can be fried, baked, or pickled.  The glochids and spines should be washed or pealed away from fruit and pad first though to avoid damage to your lips, tongue and throat.

Prickly Pear species are only native to the Americas and are tolerant of extreme cold.  During the 16th century they were introduced into Europe and are now also found in Africa, Hawaii etc.  In many places they became an invasive weed, notably in Australia, where farmers were driven from their land, calling this cactus a “green hell.”  Some abandoned houses were crushed under the weight of the prickly pear mats, which grew across as much as a million acres per year, according to Wikipedia.  

One woman’s native species can be another’s headache.