Tuesday, May 16, 2017

Plants with no names, and other mysteries

It was like being young again. On the road, driving fast, light fading, finally a sign—the wrong sign. Missed the turnoff 40 miles back. Turn north anyway, drive fast, light fading, hit the brakes, back up, take a narrow deep-rutted two-track winding through creosote scrub with no place to turn around. Keep driving, wondering, light fading, rocky hill visible ahead, suddenly arrive and stop. Flat open area, fire ring, fragrance of creosote bush, tiny car lights snaking through the valley below. Far to the east a golden glow edges the jagged mountain crest and the full moon rises—unexpected, unplanned, perfect.

And look what the morning brought:
Morning at the base of Van Winkle Peak.
The desert was in bloom—not the highly-touted “super bloom” of early spring annuals, but rather shrubs covered in flowers. All the moisture had benefitted them too. Most looked familiar, probably because 40 years ago we novice botanists stood before them chanting in Latin. For a moment I hesitated, caught by the reflex. But how absurd! There’s no requirement to name plants to enjoy them.

Of course I recognized creosote bush—I would have recognized it just by its wonderful fragrance (early travelers struggling to cross the Mojave before dying of thirst probably would have disagreed with “wonderful”).
Vigorous creosote bush almost ten feet tall.
Note resinous aromatic leaves.

A yellow-flowered green-stemmed shrub was the main source of color—desert senna, Senna armata, as I later learned from a plant display at the park Visitor Center. It’s a member of the pea family.
Why doesn’t it have pea-like flowers? Because it’s in the subgroup Caesalpinioideae, with flowers only slightly irregular. But it does have compound leaves like many peas, though it took me a moment to see this, with the widely-spaced tiny leaflets on a twisting axis.
Look close – compound leaves!

Next I found a wild buckwheat (Eriogonum sp.) thick with flowers. This genus is easy to recognize, with clusters of small six-parted flowers, but species are often tough. Wild buckwheats are common and diverse in California deserts. During C. Hart Merriam’s Death Valley Expedition of 1891, botanists Frederick V. Coville and Frederick Funston collected 25 species!
Lucky shot—a preoccupied pollinator stumbled into my field of view.

Next to the wild buckwheat was a dead shrub … or so I thought until violet spots caught my eye. This plant’s a total mystery. I don’t know the genus nor the family. It has sharp-tipped twigs, and the stems, leaves and buds are covered in fine gray hairs. Any ideas?

The low shrub below was another a puzzle. It was covered in yellowish fruit, each with two plump locules (chambers) and a persistent style rising between. It had green stems and tiny leaves. Green stems are not uncommon in the desert; they allow photosynthesis to continue after leaves are dropped in response to drought.

Oh boy, chollas ahead! (Opuntia spp.; mid photo below). I spent a fair amount of time among them—I love photographing cactus spines.
Inside the flowers, the stamens were moving, their yellow anthers swaying erratically. Something was rummaging around down at the base of the red filaments. Is there nectar down there, full of drunken pollinators? Finally I caught a shot of one of the culprits.
What is it?

A few annuals were hanging on, the last of the super bloomers. This little beauty was the most common. It’s a member of the aster (sunflower) family.

I spent two nights and two days in the Mojave National Preserve—not nearly enough, not even close. But then I hadn’t planned to go there at all. Seems I always drive across the Mojave in May, when it’s much too hot to stop, but this year things were different, “unusual.” Thunderstorms, heavy rain, flood warnings and finally snow drove me out of New Mexico. I sped across Arizona hoping for dry tolerably-warm Mojave days. Indeed they were.

Continuing on to the coast, I had lots of time to ponder this change. Why are wonderful surprises rare now? Has my venturing into the unknown declined due to age or due to the hyper-availability of information? I thought about all those hours spent on the web the week before I left. Maybe every long trip should include at least one area with little information and no plan. We’ll see if this plan can be implemented ;-)

Tuesday, May 9, 2017

Tree on a Squeeze Up

It’s tree-following week already!—time for a monthly report on the tree I chose to follow this year. But I’m on the road and getting further away from that fossilized palm frond each day. Not that it matters really—it’s just as dead and extinct as it was back in January. The problem is no internet access. Without Google, I can't write about some interesting palm topic, as I've been doing until now. But we’re not without trees, so instead I’m reporting on a local one … and relying on books. How retro!

Here in northeastern New Mexico, I’ve been keeping an eye out for a tree special enough to substitute for my fossilized palm (I knew Pat won’t mind). Yesterday, I found one. Introducing … (fanfare) … a juniper on a squeeze up!

This tree grows along the nature trail near the Visitor Center at Capulin Volcano National Monument. It’s probably a one-seeded juniper, Juniperus monosperma, said to be the “characteristic juniper” of the area. Rocky Mountain juniper also grows here, but it has more drooping branchlets and peeling bark.

Squeeze ups are blobs of magma. Geologists also call them tumuli but I think they say squeeze up just as often, though maybe not in academic publications. Squeeze ups form when a flow has cooled and solidified on the surface, but molten lava continues to flow underneath. Sometimes the magma squeezes up through a fracture in the crusty surface and forms a blob.

At first glance, the landscape here looks like any pinyon-juniper savanna, with trees scattered through grassland. But a closer look reveals that this really is a lava flow. Much of it has been obscured with erosion, deposition (dirt and debris), and plant invasion, but evidence is still visible: rocks, ridges and squeeze ups. Fractured volcanic rocks are great habitat for trees and shrubs, which send roots down to where water accumulates in cracks.
This lava flowed out of Capulin Volcano (cone in photo above), one of the youngest in the Raton-Clayton volcanic field. It came from a boca (Spanish for mouth) near the base of the volcano during one of the last stages of eruption. That was 56,000 years ago, just yesterday geologically speaking. Capulin is a well-preserved cinder cone, beautifully symmetric in spite of its age. Below, Capulin on right, younger Baby Capulin on left.
Squeeze ups seem to be fairly common on this lava flow. Some hide in the junipers, others stand in full view.

How did I get this post online? I sent it down the creek—a message in a bottle with instructions for relaying it to The Squirrelbasket, who kindly hosts our virtual gathering each month ;-)
You can check out the latest news here.

Sunday, April 30, 2017

To the Land of Volcanic Enchantment (LoVE)

New Mexico’s official nickname is “Land of Enchantment”because of its rich scenery, long record of human history (for the US), and the many diverse cultures. Other nicknames popular enough to appear on license plates reference Cactus, Spanish, Sunshine, Delight Makers, Opportunity, Heart’s Desire, and most recently Chile Capital of the World. But oddly, none mention volcanoes.

This is so wrong! Much of the state is covered in volcanic rock, from basalt flows to massive beds of welded tuff. The most recent activity was just 45,000 years ago, and it isn't over yet. For example, only 20 km below the town of Socorro, an area of intense microearthquakes, a huge magma body lies waiting. The state really is a volcanic wonderland  which is why I'm going there later this week.

New Mexico is a geotripper’s paradise in general. Landforms are diverse. Rocks range from ancient crust (1.5+ billion years old) to the recent volcanics. Due to a dry climate, vegetation is sparse and plants don't obscure the landscape. Thus we often can make sense of what we see. However, my specific destination is an exception. The Jemez Lineament is one of the most prominent volcanic features in the state, and yet it may be the most mysterious. In 1984, volcanologists Smith and Luedke called it “the most spectacular phenomenon of its kind in the US … and not easily understood.” Thirty years later, their words still apply.
Volcanic fields of the Jemez Lineament, with Socorro Magma Body added (source unknown).
The Jemez Lineament is an obvious 800-km line of volcanic fields that spans northern New Mexico—from the Raton-Clayton volcanic field in the northeast corner, to the Zuni-Bandera field near Grants, and on into Arizona. It crosses multiple major tectonic provinces: the Great Plains, southern Rocky Mountains, Basin and Range Province, and Colorado Plateau. Features include cinder cones, lava flows, calderas, maars, shield volcanoes, composite cones, volcanic necks and more. The rocks are relatively young, erupted in the last nine million years. Most are basaltic (the one major exception is the Valles Caldera).
Capulin Volcano lies near the northeast end of the Jemez Lineament (L. Crumpler; source).
Aerial view of Valles Caldera—so large that it’s hard to grasp from the ground (L. Crumpler; source).
The Zuni-Bandera field near Grants includes the youngest eruptions in the state, such as McCarty’s flow (view from 20,000 ft; L. Crumpler; source).

Early on, some geologists assumed the Jemez Lineament was a hotspot chain—a line of volcanic activity resulting from the continent moving over a hotspot in the mantle. It parallels a line of volcanism to the north in Idaho and Yellowstone, considered by many to be a hotspot trace. However, the Jemez Lineament doesn't fit the hotspot model because there’s no time progression. Younger and older features are lined up in no particular order. [Even though the hotspot hypothesis has been rejected, Wikipedia refers to the Jemez Lineament as the “Raton hotspot trail.”]

Currently, the most popular hypothesis invokes events from the deep past, when North America was a smaller continent. From 1.8 to 1.6 billion years ago (Paleoproterozoic), several large crustal fragments and/or volcanic arcs drifted north and collided with the southern margin of proto-North America, enlarging it by 1500 km in just 200 million years.
The American Southwest in the Paleoproterozoic Era (source, modified).
The suture between the young continent (aka Wyoming craton, green in map above) and the Mojave and Yavapai terranes is known as the Cheyenne Belt. I live just south of it, and it's nicely exposed in the Medicine Bow Mountains west of town. Very different rocks occur on either side of a narrow zone of contorted rocks mangled during collision; this is the ancient suture. In contrast, the boundary between the Yavapai (pink) and Mazatzal (blue) terranes is “diffuse and elusive” (Magnani et al. 2005). It's considered a broad transition zone (purple in map) where rocks from both terranes are exposed. Even the boundaries of the transition zone are hard to pinpoint; the sharp lines on maps are misleading.

Adding the Jemez Lineament to the map of Paleoproterozoic terranes reveals a seductive pattern (below). The volcanic fields of the Lineament (black blobs) line up with the Yavapai-Mazatzal transition zone! It's tempting to think that crustal collision 1.6 billion years ago is still shaping the landscape. Perhaps the old suture has provided pathways through the crust for magma to reach the surface.

A pre-existing structure shows up in many explanations of the Jemez Lineament:
“magma leaked through the broken crust” (interpretive sign)
“… a zone of apparent crustal weakness geologists call the Jemez lineament” (Price 2010)
“Although there’s no simple answer to this question, clearly the answer must involve some major structural feature deep within the earth’s crust” (Muehlberger et al. 2003).
“Some geologists consider the Jemez lineament to be a reactivated Precambrian suture or boundary; … some structural or tectonic features of the Jemez lineament must penetrate through the crust into the mantle, because the most significant volumes of [Quaternary] volcanic rocks in New Mexico are erupted along this zone (Goff 2009).
“It may coincide with a boundary between Proterozoic lithospheric age provinces (a suture zone), which in effect exerts control on the present-day disassembly of the lithosphere” (Baldridge 2004).
Baldridge’s suggestion that the crust is coming apart (“disassembly”), perhaps along an ancient suture, is not just some wacko idea. Much of New Mexico has been undergoing extension for the last 30 million years. The most obvious evidence is the Rio Grand Rift, which has widened to almost 100 km in places (map below; source). Maybe thirty million years of stretching has loosened the Yavapai-Mazatzal suture enough to allow magma to ascend to form the Jemez Lineament.
In 2005, Magnani and colleagues reported that near Las Vegas, New Mexico, the ancient Yavapai-Mazatzal suture does indeed lie beneath the Jemez Lineament (reflection seismology profile below). They also noted that a mantle anomaly (hotter) had been documented in the same area. In other words, there’s now suggestive evidence for both a magma source and a conduit beneath the Jemez Lineament. Perhaps we’re starting to piece together the story of this “most spectacular phenomenon.”
The magic of reflection seismology requires humongous amounts of computer processing time (source (free)).

If you go …

Though the state nick-namers have ignored New Mexico volcanism, other agencies give it the attention it deserves. The Bureau of Geology and Mineral Resources, and the University of New Mexico Press have published excellent affordable books for those who want to see and learn about the state’s volcanic features and geology in general (flagged ** in Sources below). In addition, several very cool interactive websites can help you plan your trip: Volcanoes of New Mexico and Virtual Geologic Tour of New Mexico.

Sources (in addition to links in post)

** less technical but full of information, with photos, figures, maps and more

Baldridge, WS. 2004. Pliocene-Quaternary volcanism in New Mexico and a model for genesis of magmas in continental extension, in Mack, GH, and Giles, KA, eds. The geology of New Mexico, a geologic history. New Mexico Geological Society Special Publication 11.

Dunbar, NW. 2005. Quaternary volcanism in New Mexico, in Lucas, SG, MOrgan GS, and Zeigler, KE, eds. New Mexico’s ice ages. NM Institute of Mining and Technology Bulletin 28:95-106.

** Goff, F. 2009. Valles Caldera, a geologic history. University of New Mexico Press.

Magnani, MB, et al. 2005. Seismic Investigation of the Yavapai-Mazatzal Transition Zone and the Jemez Lineament in Northeastern New Mexico, in Karlstrom, KE, and Keller, GR, eds. The Rocky Mountain Region—an evolving lithosphere: tectonics, geochemistry, and geophysics. (2005), AGU, Washington, D. C.Geophys. Monogr. Ser. 154: 227-238. Free.

** Muehlberger, WR, Muehlberger, SJ, and Price, LG. 2005. High Plains of northeastern New Mexico, a guide to geology and culture. NM Bureau of Geology and Mineral Resources.

** Price, LG., ed. 2010. The geology of northern New Mexico’s parks, monuments, and public lands. NM Bureau of Geology and Mineral Resources.

Smith, RI, and Luedke, RG. 1984. Potentially active volcanic lineaments and loci in western conterminous United States, in Explosive volcanism: inception, evolution, and hazards. Washington DC, National Academy Press, Washington: 47-66.

Friday, April 21, 2017

Pseudoflowers—Trick or Treat?

A flower-less rockcress.

Every spring some of our rockcresses forego flowering, and instead grow terminal clusters of fragrant yellow leaves dotted with sugary goo. But why? Generally plants produce color, fragrance and nectar to lure pollinators, which carry male gametes (pollen) off to where female gametes (ovules) await fertilization. But the yellow-leaved rockcresses have no flowers, no pollen, no ovules. And yet these plants are all about sex—fungal sex that is.

Rockcresses (Boechera spp.; formerly Arabis) are members of the mustard family. Most are perennials, with a few biennials. They usually produce white to pale pink or purple flowers, but the yellow-leaved versions are common enough to frequently confuse wild-flower enthusiasts.
“Almost every spring, someone brings me a picture or a plant of a strange little flower they’ve never seen before, and can’t key out or even begin to guess the family for.” Irene Shonle
“Strange little flower” (source).
Normal rockcress, and infected rockcress with pseudoflowers (Cano et al. 2013).

The yellowed rockcresses are infected with Puccinia monoica—mustard flower rust. Rust fungi are obligate plant pathogens, and include some of the most destructive agricultural pests (e.g. wheatstem rust, coffee rust). Some have extremely complex life cycles, involving five spore types and multiple host species in a single life cycle! (details here)

The life of the mustard flower rust is simpler, requiring three spore types and one or two hosts (full story here). If a wind-blown basidospore (which has a single haploid nucleus) is lucky enough to land on a suitable host plant, it germinates. Hyphae grow into the stem, tapping into the plant’s nutrient supply. But living happily ever after on a rockcress is not part of the rust's plan. Sex is its goal. Mustard flower rust is heterothallic, meaning opposite mating types are produced by separate “individuals” (rust infections) on separate rockcress plants. Opposite mating types need to get together somehow.

Puccinia monoica solves this problem by creating pseudoflowers. Like real flowers, they attract pollinators (mostly insects) by way of fragrance and the promise of sweet reward. How impressive that a simple little fungus has evolved to to grow such features! … except that’s not what happens, at least not directly. The real story is even more amazing. The plant grows these novel features … under the direction of the rust!
In addition to siphoning off nutrients, the rust reprograms the host plant, somehow changing which genes are expressed when. As a result, the infected rockcress never makes the transition from vegetative growth to flowering. Instead it elongates, grows extra leaves, and produces yellow pigment, fragrant compounds, sugary liquid, and wax. The resulting structure looks, smells and tastes enough like a flower that foraging insects show up, partake of a bit of sugar, and hopefully carry off the spore-like spermatia to receptive hypha on other rockcresses.
Bumps are spermagonia, which contain spores waiting to be dispersed and super-sweet liquid.
Pseudoflowers may mimic other wildflowers, like this nearby sagebrush buttercup (speculation for now).
With today’s molecular analysis techniques and model organisms (Arabidopsis thaliana, the thale cress, is a close relative of rockcresses), it’s possible to delve deeply into pseudoflower biology. In 2013, Liliana Cano and her colleagues looked at developmental changes in rockcresses infected with mustard flower rust. They found that for at least 31 genes, activity was significantly altered (enhanced or reduced), affecting leaf, stem and flower development; metabolism and transport of sugars and lipids; synthesis of volatiles (fragrant compounds); and wax production.

These changes can be interpreted as beneficial to the mustard flower rust. For example, consider wax production. Cano and colleagues suggest that the waxy leaves induced by rust infection serve to reduce water stress. Water-stressed plants often have shorter stems and fewer leaves—not what the rust needs. Perhaps the waxy leaves of infected plants allow taller leafier growth.
Gravelly soil drains rapidly, making for dry habitat. Looks like waxy leaves weren't enough to compensate.

Whatever the mechanisms, by enabling fungal sex, infection clearly benefits the rust. And the rockcress clearly suffers—no flowers, no sex. But what about pollinators? Are they beneficiaries or unsuspecting dupes? Some botanists consider pseudoflowers to be tricksters, luring insects into service with little reward. However in a 1998 paper, Robert Raguso and Bitty Roy pointed out that the super sweet liquid of rockcress pseudoflowers is popular with many kinds of insects, including bees, ants, butterflies and flies. And given how many sugar-oozing spermagonia there are on each yellow leaf, infected rockcresses may actually produce more yummy calories than uninfected plants. If so, then for pollinators, pseudoflowers are not a trick but a treat.
Foraging ant (in a hurry).

Puccinia monoica on Boechera sp. is the latest addition to my iNaturalist project, Plants of the Southern Laramie Mountains (two observations—one for the rust, one for the plant). To identify the rockcress to species, I have to wait until uninfected individuals are in fruit.
I found infected rockcresses scattered through this sagebrush grassland.
It’s still early spring at Blair (8000 feet elevation)—not much flower action.


Thanks to Elio Schaechter of Small Things Considered who recently blogged about Boechera pseudoflowers, which I’ve long ignored.

Caro, LM, et al. 2013. Major transcriptome reprogramming underlies floral mimicry induced by the rust fungus Puccinia monoica in Boechera stricta. PLoS ONE 8(9): e75293. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0075293 (free).

Raguso, RA, and Roy, BA. 1998. ‘Floral’ scent production by Puccinia rust fungi that mimic flowers. Molecular Ecology (1998) 7, 1127-1136.