Sunday, February 19, 2017

A walk up the Plant Evolutionary Ladder … all the way to flowers

Willow Canyon ahead, what will we find?

On February 12—midwinter—we headed for “Willow Canyon” on the east side of the Laramie Basin, at 7200 feet, in the interior of the continent far from moderating marine influences. Yet it felt like spring … sunny, warm (40º F!), and no wind.

The prairie was brown except for occasional small green blades along the dirt road. Aside from limber pines and Rocky Mountain junipers, trees and shrubs were bare. But after entering the canyon we found much of interest. Emmie wore herself out in her usual futile pursuit of rabbits (enthusiasm far exceeds ability). I was more successful, finding everything from mosses to flowers in what appears to be just another small dry limestone canyon in the foothills of the Laramie Mountains.

Starting low on the evolutionary ladder …
Mosses—no seeds, no vascular tissue.
Mosses lined rock ledges in a shady alcove in the canyon wall. They were surprisingly lush, rich green and moist with recent snowmelt. I saw only gametophytes, with no sign of this year's sporophytes (the two phases of the moss life cycle). The mix of shade and light made photography difficult, so I just shot and hoped for the best.
Mosses reside low on the evolutionary ladder because they produce spores instead of seeds, and they have no vascular tissue—which explains why they’re short. Conducting water very far is difficult without plumbing.

These moss clumps are aggregations of small individual stalks, gametophytes. There may be sex organs hidden at the tips of the gametophytes. If fertilized, female ones will grow into sporophytes (there's more in the elegant life cycle diagram mentioned earlier).
Clump of moss gametophytes, with a few dead sporophytes from last year.
An abundance of sporophytes; fairy for scale.
Lichens also thrived on the limestone ledges (orange and yellow mats above). I couldn’t place them on the plant evolutionary ladder as they’re not a single organism but three, in a beneficial partnership: an alga, a fungus and a yeast (the last is a recent discovery).

I found a few ferns too, though not in the shady alcove as you might expect but rather on exposed rock faces. Tough little cliffbrakes with thickish dull green fronds seem to grow directly out of the rock. This is western cliffbrake (Pellaea occidentalis), which is calciphilic as well as xerophytic—limestone-loving as well as drought-tolerant. [See Plants on Rock for more about plants of Willow Canyon.]
Plant is about 2 in across.
Ferns are vascular plants so are considered more advanced than mosses, but they too produce spores, not seeds. Below is a seed-producer. However its seeds are naked, indicating we still haven't reached the top of the ladder.
My favorite gymnosperm (“naked seed”) in the canyon is this limber pine (Pinus flexilis). It’s a really small “tree” but its life history is impressive: a seed germinated in a dry shallow crack, grew into a seedling, and managed to keep growing with just a bit of moisture and debris each year! The annual rings must be microscopic. Any guesses as to age?

Nearing the top of the evolutionary ladder, I found an angiosperm (“enclosed seed”)a flowering plant. And it was flowering! This may be the only native species blooming in the wild in the Laramie Basin right now (can’t think of any other possibilities).
Well … barely blooming. White hairs were just starting to emerge beyond the bud scales.
North American pussy willows (Salix discolor) bloom long before leafing out. I followed this one in 2015, after discovering flowers on February 26. Leaves didn’t show up until May. It's a male, and the only willow in the canyon. It thrives in an alcove shaded by junipers, with moss at its feet, next to a small waterfall that runs after heavy rains.
Willow Canyon pussy willow two years ago, on February 26.
The willow thrives thanks to great habitat. Water runs off the rock wall, and large junipers provide shade.
I easily walked to the head of the canyon (almost no snow!) and then returned by way of the rim, stopping for a few more views of the willow of Willow Canyon.
Eponymous willow peeks above the canyon rim (center of photo).

Of course, these plants pale in comparison to those being posted by bloggers from warmer zones, where gardens already are filled with color, or from moister climes where walls and nooks are lush with mosses and ferns. But this is southeast Wyoming. This time of year, even the most modest plants thrill us! At the same time, I hope this crazy weather doesn’t prompt more plants to grow and bloom … and then get zapped by repeated hard frosts.

Coda

Though it felt like a spring day, winter made its presence known—best of all, in the form of ice art. Jack Frost produces terrific abstracts. Fortunately, several were still in place.
Jack can turn even the most mundane object into a thing of beauty … like a mud puddle:


Thanks to Beth of Plant Postings for the inspiration to look for plants on rocks in midwinter: It's Only a Rock Wall ... Or Is It?


Friday, February 10, 2017

A Powell Palmetto Perhaps?

Am I following a palmetto?
Sabal palmetto (source).
I’m intent on learning more about palms, as I decided to follow a palm tree this year (unfamiliar with tree-following? click on the link). My tree has a name, Sabalites, but what kind of palm is it? No one is sure. There are lots of choices—the palm family (Arecaceae) is large and diverse. It includes five subfamilies, 16 tribes, 2500 species, and many products consumed by humans: coconuts, dates, oil, betel chew, rattan and more. Most palms grow in tropical or subtropical regions, and occasionally in deserts.
Selected palms of the world; click on image to view details (source).
Palm fruit are beautiful as well as delicious (Dransfield et al. 2008).
Desert fan palms near Twentynine Palms, California (source).
When I lived in California, I was familiar with palm trees—specifically the ones planted along highways and in cities, and the native fan palms of desert oases, Washingtonia filifera. Then I moved to Wyoming where currently it’s much too cold for palms. However, fifty million years ago they lined the shores of huge lakes in the southwest part of the state. Even though their leaves are beautifully preserved in rocks of the Eocene Green River Formation (more here), no one is sure what kind of palms they were. Since I started following this tree, I’ve learned that plant fossil identification is really tough. Even the most challenging living plants are easy compared to fossilized ones.
Fossil Lake of Early Eocene Wyoming (Chicago Field Museum).

In 1870, geologist Ferdinand Vandeveer Hayden’s exploratory expedition stopped near Green River Station, Wyoming, where they found lots of fossils. Some looked very much like palm leaves. In the expedition report, staff paleontologist Léo Lesquereux assigned them to Flabellaria Eocenica. I don’t know why … modern day Flabellaria is not a palm, nor do the leaves resemble palm leaves.

Later, Hayden sent the fossils to paleontologist John S. Newberry of Columbia College, who decided they looked enough like today’s palmettos, genus Sabal, to call them Sabal powellii (I presume in honor of geologist John Wesley Powell, then Director of the US Geological Survey, but I haven’t been able to confirm this). The Powell palmetto was one of ten new fossil plant species from the Green River area published by Newberry in 1882.
8. SABAL POWELLII, n. sp. Leaves of medium size, 4 or 5 feet in diameter, petiole smooth, unarmed, terminating above in a rounded or angular area, from which the folds diverge; beneath concavely narrowing to form a spike 3 to 4 inches in length; rays about fifty, radiating from the end of the petiole, perhaps sixty in the entire leaf, compressed to acute wedges where they issue from the petiole, strongly angled and attaining a maximum width of about 1 inch; nerves fine, about twelve stronger ones on each side of the keel, with finer intermediate ones too obscure for enumeration. Formation and locality. — Eocene strata. Green River Station, Wyoming.
Why did Newberry conclude that these fossils were palmettos? Because the leaves are clearly costapalmate. (Yes, this is an esoteric term, but the concept is easy and useful.)
Costapalmate leaf of the Puerto Rican hat palm, Sabal causiarum (source).
Palm leaves are huge, with blades divided into many narrow segments arranged in several different patterns. In palmate leaves, segments fan out from the base of the blade—like fingers from the palm of a hand. In costapalmate leaves, the leaf stem (petiole) extends up into the blade to form a costa, where leaf segments are attached. The costa is only visible on the underside of the leaf, and from above, leaves look palmate. [Here’s a helpful webpage devoted to costapalmate palm leaves.]

In a paper about extinct floras of North America (1898), Newberry included a photo of a Wyoming palm leaf fossil with an obvious costa. “In the figures given, that on Pl. LXIII, fig. 6, represents the under side of the leaf at its base, showing [a] pointed spike [costa] formed by the prolongation of the petiole.”
From Newberry 1898; no scale provided (leaves can reach 4-5 feet across).
Unfortunately, costas are not unique to palmettos, and in 1930, paleobotanist Edward W. Berry overrode Newberry’s decision, renaming the fossils Sabalites powellii:
[the leaves] “are superficially much like the leaves of the existing species of Sabal, and their northern range appears to afford some corroboration of such a relationship, but this is by no means established, and it appears to me to be a better practice to refer such remains to the form* genus Sabalites rather than to Sabal.”
[*In form classification, fossilized organisms or their fragments are classified based on appearance, not biological relationships. If different parts of a single species are not obviously from the same source, they may end up as different form species or even genera.]

Robert Read and Leo Hickey agreed with Berry in their 1972 Revised Classification of Fossil Palm and Palm-like Leaves. They were adamant that leaves alone are insufficient evidence:
“Numerous similarities in the form and gross external features of [fossil] palm leaves make it difficult or impossible to assign them to modern genera based only on their external morphology. The uncertainty … becomes even greater with the limited, incomplete collections available to the paleobotanist. A modern specialist might speculate that a given fossil closely resembled a modern genus such as Sabal, Geonoma or Thrinax. Such a suggestion would be debatable since it is almost impossible to distinguish these genera … without seeing flowers, fruit or other diagnostic characters. Forced identifications with modern genera contribute nothing to evolutionary theory but give instead a confused picture of the floristics of the geological record. Since it is very difficult to identify specimens of modern palms accurately from their leaves alone, no attempt should be made to place fossil palm fragments in genera of modern palms unless unquestionably identifiable with them.”

Maybe we shouldn’t give up just yet. After all, thousands of fossils are collected from the Green River Formation every year! Maybe some will reveal the true identity of Sabalites powellii. There’s reason for hope. Paleobotanist Sarah Allen has been working nearby on another fossil palm, in the Bridger Formation, and has enough fossils—leaves, flowers and even pollen—to confidently assign the trees to Phoenix, the genus that includes today’s date palms (Allen 2015). Will we be so lucky with Sabalites? Already its fossils include not just leaves, but also apical buds, flowers, inflorescences (flower clusters), and even inflorescences attached to leaves. Are more discoveries likely? When I visit the remains of Fossil Lake later this year, I'll look for some experts and ask them what they think.
Fossil terminal bud, from the Green River Formation (in palms, leaves originate from a single terminal bud at the top of the trunk); University of Wyoming Geology Museum.

Personally, I hope paleobotanists find that Sabalites powellii is indeed a palmetto, and that they resurrect Newberry’s Sabal powellii. “Powell palmetto” has such a nice ring to it ...
We’re off to Fossil Lake to see the Powell palmettos!


Sources

Thanks to the Biodiversity Heritage Library for providing easy access to older paleontological literature, and to Mike for continued guidance in paleontology.

Berry, EW. 1930. A flora of Green River age in the Wind River basin of Wyoming. USGS Professional Paper 165: 67.

Dransfield, J., et al. 2008. Genera Palmarum, the evolution and classification of palms. University of Chicago Press.

Newberry, JS. 1882. Brief descriptions of fossil plants chiefly Tertiary. Proceedings US National Museum 5: 504.

Newberry, JS (A. Hollick, ed.). 1898. The later extinct floras of North America. Washington: Government Printing Office.

Read, RW. and Hickey, LJ. 1972. Revised classification of fossil palm and palm-like leaves. Taxon 21:129-137.

Monday, January 30, 2017

A tree fell … did you hear?

Is it true that if a tree falls in a forest and no one is around to hear, it makes no sound … even if it’s a really big tree? Above, fallen giant sequoia, Alan Beymer photo (source).

In early January, a huge tree fell in a forest. No one was around to hear it, but multitudes heard about it. On January 9, the New York Times announced: “Giant Sequoia ‘Tunnel Tree’ in California Is Toppled by Storm” and devoted ten inches to its life and demise. National Geographic paid tribute, noting that the tunnel may have been a contributing factor. The Los Angeles Times called the tree iconic, and mourned the loss of “one of Calaveras County's oldest residents.” A week later, the sad news showed up in The New Yorker, in a soul-searching article by Nathan Heller, in the Culture section.
“I want, instead of honoring the tree directly, to conjure up the world in which it was a monument for me” (source).
The opening in the Pioneer Tree, carved in 1881, could accommodate a four-horse stagecoach. Thousands of visitors rode or drove through the tree until it was closed to vehicles. Then thousands more hiked the trail to and through the “tunnel tree.”
“Pioneer’s Cabin, Calaveras Grove, Calif., U. S. A.” 1899 (source).
Pioneer Cabin Tree in 1952; click on image to view park ranger (source).
Pioneer Cabin Tree, January 2017 (source). A severe storm saturated the soil around it, probably weakening the already-decaying trunk and roots.

Why did a fallen tree get so much coverage? Because just about everyone still alive who ever drove through a giant tree clicked on a news link hoping it wasn’t that tree … and thereby triggered more articles. I’m sure of it, as that’s what I did. It’s been 40 years since I left California, land of giant sequoias, but whenever I see photos, memories quickly surface.

There are vivid memories of walking on winding trails through aromatic forests, identifying incense cedars, sugar pines, white firs, big-cone Douglas firs and other majestic conifers framed by narrow shafts of light. Then, suddenly, a monster appears!—a tree huge beyond imagining, dwarfing all others. We stand with heads bent back, searching for the top. We inspect the thick furrowed bark, and scan the ground for cones and seedlings. One of us has brought a camera, so we join at the base and that kind soul pushes the button, immortalizing the moment.
Young field botanists in California’s Sierra Nevada.

Then there are dimmer memories—of talks and walks led by my heroes, park rangers. No photos survive. Or maybe none were taken; my parents were frugal with film. But I clearly remember what the rangers told us about sequoias, about their thick fire-resistant bark and absurdly tiny cones with minuscule seeds—such improbable beginnings for ancient giants. “The seed that grew into this tree sprouted during the Revolutionary War!” “This tree was already 500 years old when the Roman Empire fell!” Etc.
Sequoia bark can be up to three feet thick at the base of the tree (source).
Sequoiadendron giganteum cones and seed (source).

And there’s one memory from long long ago, from a time of few memories:
We drove through a redwood tree* in our car!   It barely fit!   Dad stopped inside the tree!   Billy and I sat on the hood and Mom and Dad took our picture!   It was fun!**
Is this memory real? That was so long ago! Or did the photograph save the moment for me? If so, I’m grateful.

we looked down into the viewfinder to
press the button that would keep us there

(from The Last Perfect Season by Joyce Sutphen)


*We called the trees giant redwoods. They’re actually giant sequoias, Sequoiadendron giganteum. Redwoods are Sequoia sempervirens; they grow in the coast ranges of northern California and southernmost Oregon.

**When I compared news photos to mine, I saw that the recently fallen sequoia was not the one we drove through long ago. That was the Wawona Tree in Yosemite National Park. It too fell, in 1969, probably for the same reasons.

Friday, January 20, 2017

“so many fossils that people cry”

Scallop fossils near Lopez Lake. Photo courtesy Monika Wieland Shields, Orca Watcher

Long ago, on our frequent trips to Lopez Canyon, we would often pull off the road just past the lake to comb for seashells. These were fossil shells—exciting treasures common enough for a child to find. But why were they there, far from the sea, high in the rugged California Coast Range? Three hundred years earlier, the great Nicholas Steno, one of the founding fathers of geology, had also pondered this mystery: “in what way marine bodies had been left in places far from the sea.”

Steno concluded that shell-like “bodies” in rock looked like shells because … they once were shells! This seems like a no-brainer today, but in the 1660s it was a profound realization. Marine bodies did grow in the rock, as many thought. Rather they were creatures that lived, died and were buried in sand and mud on the bottom of an ocean. Then disturbance moved the Earth, seas became dry land, muck turned to rock, and seashells ended up in high in the mountains far from the shore.

But why are there so many fossils near Lopez Lake … and off and on for miles to the north? This contradicts basic knowledge. Fossils are rare. In fact, fossils are so rare that Charles Darwin worried they would undermine his theory of evolution:
“Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and gravest objection which can be urged against my theory. The explanation lies, as I believe, in the extreme imperfection of the geological [fossil] record.” On the Origin of Species, 1859.
Not long after Darwin published On the Origin of Species, access to the fossil record grew dramatically. Pioneering paleontologists excavated thousands of fossils, taking them back to their respective institutions. The pace accelerated through the twentieth century and continues today. Even so, fossils remain rare. Though zillions of creatures have come and gone during the 3.65 billion years since life began, precious few died where they or their parts could be preserved. Most decayed. I’ve read that only 1% of all organisms that ever lived have been fossilized, though I wonder … how can we know?

There are spectacular exceptions, sites where fossils number in the millions. These are lagerstätte, meaning “storage places.” German miners use the term for rich seams of ore—mother lodes in English. There are two kinds of fossil mother lodes. In concentration lagerstätten, fossils are exceptionally abundant, but are mainly disarticulated bones or fragments that aren’t always useful in reconstructing organisms.
Above, bones from a dried-up waterhole, during a severe drought circa 20 million years ago. Below, reconstructed Dinohyus (Agate Fossil Beds National Monument Visitor Center).

Most highly prized are conservation lagerstätten, where fate stepped in to preserve quality as well as quantity. Fossils include articulated (connected) skeletons, soft tissues of various kinds, even entire organisms (e.g., flies in amber). Soft tissue fossils can be quite beautiful, with minute details of hair, feathers, muscle tissue, even ovaries with eggs! And soft tissue preservation immortalizes organisms that have no bones or shells, such as insects, spiders and plants.
Above, Jack hunts for sea scorpions (Eurypterus) that swam the seas 400+ million years ago. These are extinct marine arthropods, and not true scorpions. After finding a claw on his first try, he uncovered two beautiful scorpions on his second (below)! Photos courtesy Jack Share of Written in Stone.

Here in Wyoming, we have a world-renown conservation lagerstätte, in the Green River Formation. It's a grand accumulation of exceptionally-preserved fossilized creatures that were buried in lake-bottom muck about fifty million years ago. Some layers are especially rich. The Fossil Butte Member, just 20 m thick, has yielded millions of exquisite fossils of fish, flies, bats, snails, spiders, parrots, mosquitos, crocodiles, and (best of all) plants.

Exceptional preservation requires exceptional conditions. In the case of Green River fossils, frequent floods may have deposited enough sediment on the lake bottoms to quickly bury the dead. Perhaps lake water periodically turned noxious, killing scavengers and microbes that would otherwise devour soft tissues. Whatever the causes, we’re lucky.
We share the Green River Formation with adjacent states (source).
Articulated skeleton of a clawed bat, in beautiful detail (NPS).
Sabalites powellii, an extinct palm (NPS).
Macginitiea wyomingensis, an extinct sycamore.
Plant fossils are especially valuable, for they provide clues for diciphering paleo-environments. A diverse flora with palms, ferns, horsetails, sycamores, sweetgums, catalpas, lotuses and more suggests Wyoming was subtropical (or at least mild) during early Eocene times.
Southwest Wyoming 50 million years ago (artist’s reconstruction; Chicago Field Museum).

Wyoming citizens are rightly proud of the Green River Formation. It’s considered one of three great conservation lagerstätte in the world (Nudds & Selden 2008), the other two being an oil shale deposit near Darmstadt, Germany, and the Florissant Formation of Colorado. But the order may be rapidly fading.

In Patagonia, Argentina, paleontologists are removing thousands of beautifully-preserved fossils from the Lago del Hunco Formation. Like our Green River Formation, it dates from the early Eocene, roughly 52 million years ago, and is composed of lithified lake sediments—specifically a lake in a caldera, a huge volcanic crater. Reports verge on ecstatic:
“There are white rocks that are jam-packed full of fossils, so many fossils that people cry when they see them. I’ve never seen so many beautiful fossils in one place.” —paleontologist Peter Wilf, to a New York Times reporter (italics added)
(Tearful?) paleontologist at a Lago del Hunco quarry (source).
Elsewhere, Wilf declared Lago del Hunco to be one the most fantastic fossil sites in the world, because of the diversity of plants, insects, fish and amphibians. Gosses and colleagues (2006) called it “the world's most diverse Eocene flora.”

Fossils of the Lago del Hunco Formation record a time when a great diversity of plants—probably a rainforest—grew around a lake. Dead plant material that washed into the lake was frequently buried in sediments containing large amounts of volcanic ash and debris. That lake-bottom muck is now tuff containing beautiful soft-tissue fossils, and the rainforest is long gone. Paleontologists work amid dry desolate hills.

In 2003, Wilf and colleagues reported that the Lago del Hunco flora had a richness (number of species) that “exceeds that of any other Eocene leaf flora, supporting an ancient history of high plant diversity in warm areas of South America.” The known flora as of 2013 (listed here) includes ferns, cycads, ginkgos, several unidentified conifers, palms, eucalyptus trees, grasses, many members of the pea family, and more.
Fossils from the Lago del Hunco Formation (Wilf et al. 2003). Scale bars are 1 cm long.
Will Lago del Hunco fossils bump our Green River Formation from its standing as one of the three great conservation lagerstätte? It’s too early to say; much work remains to be done. But an especially charismatic plant appears to be making fossil numbers and quality irrelevant. In slabs of white tuff, Peter Wilf found two tomatillos. Exceptional preservation combined with the popularity of tomatillos among salsa-aficionados was enough to grab the attention of the press.
“Tomatillo Fossils, 52 Million Years Old, Are Discovered in Patagonia” (The New York Times). 
Tomatillos are tomato relatives, with smaller green fruit. They’re distinctive for their thin papery inflated husks. To find these delicate structures preserved in rock 52 million years after death is mind-boggling! This discovery also upsets current thinking about the evolution of the Solanaceae, the family that includes potatoes, tomatoes and nightshades (discussed here and in Wilf et al. 2017).
Garden tomatillo or Mexican husk tomato. The husk, or lantern fruit, is an inflated calyx (source).
One of our wild tomatillos, Physalis heterophylla (source).
“Eocene lantern fruit from Gondwanan Patagonia” (Wilf et al. 2017).
I have to admit, I'm in awe of paleobotanists. I’ve done floristic surveys myself, compiling species lists for areas large and small. We collect plants in identifiable condition, with flowers or fruit, and compare them to herbarium material to verify identification. Sometimes we analyze relationships to well-documented floras elsewhere to determine affinities, and try to tease out biogeographic history and paleoclimate. This isn’t easy, even with fresh specimens, so to identify and coax stories from 52-million-year-old fossilized plants seems magical! Are paleobotanists part shaman—able to bring the dead back to the land of the living? Maybe they're more like Virgil, who visited the past himself and then returned to tell he found.

You gods who rule the kingdom of the rocks! You soundless Shades! …
Grant me to tell what I have seen! With your assent,
May I reveal what lies deep in the gloom of the Underworld!
(Aeneid Book VI, modified only slightly)


Sources (in addition to links in post)

Thanks especially to Mike the rock guy, for help with paleontological issues!

Cutler, A. 2003. The seashell on the mountaintop; how Nicolaus Steno solved an ancient mystery and created a science of the Earth. A Plume Book.

Grande, L. 2013. The lost world of Fossil Lake. University of Chicago Press.

Montanari, S. 2016. What Darwin didn’t know about the fossil record. Forbes, Feb 12, 2016.

Nudds, J. and Selden, P. 2008. Fossils explained 56; fossil-lagerstätten. Geology Today 24:153-158. PDF

Wilf, P, et al. 2003. High plant diversity in Eocene South America: evidence from Patagonia. Science 300:122-125.

Wilf, P, et al. 2005. Eocene plant diversity at Laguna del Hunco and Rio Pichileufu, Patagonia, Argentina. The American Naturalist 165:634-650. PDF

Wilf, P, et al. 2017. Eocene lantern fruits from Gondwanan Patagonia and the early origins of Solanaceae. Science 355:71-75.