This is the third in a series of posts on carbon fixation in Mohave desert plants. In this post we will focus on plants that use CAM carbon fixation which includes cactus, yucca and agave. The most important benefit of CAM to plants is the ability to leave most leaf stomata closed during the day. Plants employing CAM are most common in arid environments, where water comes at a premium. Being able to keep stomata closed during the hottest and driest part of the day reduces the loss of water through evaporation and transpiration, allowing such plants to grow in environments that would otherwise be far too dry. Plants using only C3 carbon fixation, for example, lose 97% of the water they take up through the roots to transpiration – a high cost avoided by plants able to employ CAM. The Mojave Desert is the northernmost “hot desert” in North America and essentially a transition land between the Great Basin and Sonoran. It’s the smallest of the Big Four, covering some 54,000 square miles of southeastern California, southern Nevada, and itty-bitty strips of southwestern Utah and northwestern Arizona. Roughly speaking, the Great Basin Desert yields to the Mojave at the northern range limit of creosote bush, the defining shrub of North America’s hot deserts; its distribution essentially outlines them. You can rightly think of it as the hot-desert equivalent of big sagebrush. But the trademark plant of the Mojave, the one whose geography basically maps out this desert, is the Joshua-Tree. This outsized yucca actually flourishes best on the Mojave margins, reaching peak development on middle slopes of foothills and bajadas. Interestingly, the Joshua-Tree uses C3 carbon fixation while most of the remaining yucca and agave use CAM carbon fixation, along with all of the cactus species.
This post is the second on my series on Mohave desert plants, this time focused on C4 plants, not really as complex as it might sound. The C4 photosynthetic pathway has evolved an estimated 45 times in terrestrial plants (Sage 2004), and is most prominent in grasses, which account for roughly 25% of global terrestrial primary production (Still et al. 2003) and include important crop and weed plants and potential biofuels such as maize, sugarcane, sorghum and switchgrass. The highest rate of photosynthesis is typically observed in C4 plants. The photosynthetic rate in such plants is known to be directly related with the variation of the solar rays in the daytime. Maximum rate of photosynthesis occurs in the red and blue regions of the visible light as seen in the absorption spectra of chlorophyll a and b. These are of economic importance as they have a comparatively higher photosynthetic efficiencies in comparison to other plants. C4 photosynthetic plants outperform C3 plants in hot and arid climates. By concentrating carbon dioxide around Rubisco C4 plants drastically reduce photorespiration. The frequency with which plants evolved C4 photosynthesis independently challenges researchers to unravel the genetic mechanisms underlying this convergent evolutionary switch. The conversion of C3 crops, such as rice, towards C4 photosynthesis is a long‐standing goal. Nevertheless, at the present time, in the age of synthetic biology, this still remains a monumental task, partially because the C4 carbon‐concentrating biochemical cycle spans two cell types and thus requires specialized anatomy.
Desert plants tend to look very different from plants native to other regions. They are often swollen, spiny, and have tiny leaves that are rarely bright green. A desert always has a limitation of water but the temperature may be hot or cold, high altitude and cloudy like parts of Costa Rica or low altitude and windy like the Cape Preserve in South Africa. The strange appearance of these plants is a result of their remarkable adaptations to the challenges of the desert climate. Desert plants have developed three main adaptive strategies with diverse implementations often in different species with convergent evolution to the same form: succulence, drought tolerance and drought avoidance in annual plants. Each of these is a different but effective suite of adaptations for prospering under conditions that would kill plants from other regions. These differences often extend to the cellular level with the development of special structures to store water in leaves and stems, the periodic shedding of leaves, and special adaptations to even the basic photosynthesis process. Chlorophyll (the green pigment in plants) is the only known substance in the universe that can capture volatile light energy and convert it into a stable form usable for biological processes (chemical energy) through the Calvin Cycle and the enzyme RuBisCO. Green plants use blue and red light energy to combine low-energy molecules (carbon dioxide and water) into high-energy molecules (carbohydrates or starch), which they accumulate and store as energy reserves. There are at least three variations of photosynthesis, all of which use the same basic mechanism, C3 carbon fixation used by most plants, C4 carbon fixation used in about 3% of plants and the CAM (crassulacean acid metabolism) carbon fixation pathway that evolved in plants like cactus as an adaptation to arid conditions.
Sometimes, looking for plants and flowers in winter can be interesting, particularly near a source of fresh water in the desert. In November, I visited Rogers and Blue Point Springs on the north shore of Lake Mead in the Lake Mead National Recreation Area. Rogers Spring and other springs in the “North Shore Complex” comprise one of the terminal discharge areas for the regional carbonate-rock aquifer system of eastern Nevada and western Utah. The source of the water to this spring and other regional carbonate-rock aquifer springs is uncertain. The prevailing theory suggests that much of the recharge water that enters the carbonate-rock aquifer occurs in the high mountain ranges around Ely, Nevada, located 250 miles north of Lake Mead. As this ground water flows south through the carbonate rocks, it encounters several faults along the way, including the Rogers Spring Fault, which has caused the older carbonate rocks (primarily limestone and dolomite) to be displaced against younger evaporite deposits of the Muddy Creek and Horse Spring formations. Here, the lower permeability of these evaporite deposits, along with high subsurface water pressure, forces the ground water in the carbonate rocks to flow upward along the fault and emerge at the surface as Rogers Spring.
Dragonflies and their relatives are an ancient group. Meganisoptera is an extinct order of very large to gigantic insects, occasionally called Griffinflies. The largest known Griffinfly and/or insect of all time was a predator resembling a dragonfly but was only distantly related to them. Its name is Meganeuropsis, and it ruled the skies before pterosaurs, birds and bats had even evolved. The oldest fossils are of the Protodonata from the 325 Mya Upper Carboniferous of Europe, a group that included the largest insect that ever lived, Meganeuropsis permiana from the Early Permian (300–250 Mya). Meganeuropsis permiana was described in 1939 from Elmo, Kansas. It was one of the largest known insects that ever lived, with a reconstructed wing length of 330 millimetres (13 in), an estimated wingspan of up to 28 inches (710 mm), and a body length from head to tail of almost 430 millimetres (17 in). Nevada designated the Vivid Dancer Damselfly (Argia vivida) as the official state insect in 2009. Sadly, I have no photos of the state insect but Nevada has many eco-zones and the Henderson Bird Viewing Preserve has quite a number of equally beautiful species.
When I first moved to Las Vegas there were virtually no mosquitoes and no flies. However as the population has increased and the local climate has changed with more landscaping and water we have seen a corresponding increase in bugs. That is not to say that there were no insects in the desert, as with flowers and plants you just have to look more carefully. There are an amazing variety of specialized insects living in the desert surrounding Las Vegas under conditions that would be considered hostile for any other insects. Again just like flowers and plants, the insects can come and go quickly over specific times like spring or after precipitation and are often found in specific areas suited to their needs. The Henderson Bird Viewing Preserve is a great place to see lots of unusual insects due to the presence of water and hospitable plants. Bees, wasps, dragonflies and butterflies are diverse and are part of the special ecology of the preserve, both prey and predator for birds and other inhabitants. Fortunately, there are very few mosquitoes, probably due to the dragonflies and the dry heat. Due to carefully selected and strategic native plants, there are a variety of native flowers all summer long which support a diverse and vibrant ecosystem. In this post I thought I would focus on some really interesting bees and wasps which I saw at the preserve.
Butterflies have been held in reverence and high esteem for millennia, enshrined by the ancient Greeks in the mythical love affair between Cupid/Eros and Psyche the butterfly goddess. According to Greek mythology, Psyche was a beautiful maiden who fell in love with Eros/Cupid. Cupid’s mother, Aphrodite, was jealous of Psyche’s beauty and tried to keep the lovers apart. Eventually, however, Aphrodite realized that Cupid and Psyche were destined to be together and so Zeus made Psyche immortal. Psyche is also the Greek word for “soul” and “butterfly.” Although the original Greek story has been lost to history, the mythology of Cupid and Psyche was preserved in the book Metamorphoses written in the 2nd century CE by Platonicus. The Greek story of Eros and Psyche is known from at least the 4th century BCE and was a popular subject in Greek and Roman art. The word for butterfly in formal Greek is psyche, thought to be the soul of the dead. Ancient Greeks also named the butterfly scolex (“worm”), while the chrysalis – which is the next stage of metamorphosis from a caterpillar – was called nekydallon, meaning “the shell of the dead”. The metamorphosis of the butterfly inspired many to use butterflies as a symbol of the soul’s exit from the body. Thus, the myth of Psyche concomitantly signifies soul and butterfly. It has come to mean the story of the soul coupled with divine Eros, but which must nevertheless endure tribulations before achieving immortality. Psyche, a mortal woman, was released from death by Zeus, the father of the gods, who took pity on her and granted her immortality. Psyche’s mythological imagery in ancient art is represented with butterfly wings, amply depicted in pottery as well. Freed from death, the body of the soul could fly freely, soaring, departing from the shackles of the chrysalis. I thought this lovely Greek story would be the perfect introduction to a review of beautiful butterflies.
Since the Covid virus pandemic, I have been sheltering at home like everyone else. Fortunately the Henderson Bird Viewing Preserve has re-opened and I go almost every day. I had been going since December, recording the spring changes of birds and plants but the Coronovirus put all of that on hold for a while. It has been a repetitive comfort to me to have a beautiful place to walk each morning with an ever changing cast of beautiful birds. One constant and always welcome bird companion has been the tiny Verdin who are resident at the bird preserve. The Verdin is a very small bird. At 4.5 in (11 cm) in length, it rivals the American bushtit as one of the smallest passerines in North America and it is smaller than many hummingbirds. At the Henderson Bird Viewing Preserve, Verdin the most common bird, rarely seen but almost always heard. It is most easily detected by its surprisingly loud calls, which sound like “cheep” followed by a pause the another “cheep”. These tiny birds are difficult to photograph, rather like shooting skeet or pinball. The tiny birds are quick and athletic, jumping from branch to branch sideways, up and down. You need a hair-trigger on the shutter, shoot first and check your focus and framing later, you will not get a second chance. Since I have collected quite a number of photographs of my avian friends the Verdin, I decided to make a post of it.
Like many people interested in nature, I have a fairly large set of bird feeders in my back yard. Last year was quite eventful for the feeders, I had several clutches of Gambel’s Quail (Callipepla gambelii) born in the bushes scattered around the yard. Gambel’s Quail are skittish birds, living mostly on the ground, they run for cover at even the hint of a surprise. While they have nested in my yard off and on for several years, last year was the first time they visited the feeders. There is plenty of water, feed and shelter in my backyard and the quail apparently liked what they saw. We had at least 3 clutches and possibly as many as 5–6 with the result of many groups of adult, adolescent and baby quail pretty much all summer. Naturally I took photos, as if I was the proud grandfather. Many of the photos were taken in less than ideal light but gradually they grew more trusting and I managed a few flash captures. I thought the photos would make for a nice post so I organized the best ones to present here.
I like to celebrate the return of spring each year by writing about the beautiful flowers I find around me in Las Vegas. It might be surprising to some to know that Las Vegas and the surrounding desert are full of life, flowers and beauty, especially in spring. The wet El Niño winter this year has brought above average amounts of rain to California and Southern Nevada mostly in February. This has resulted in super blooms of poppies in California, a rare wildflower super-bloom in Joshua Tree National Forest and an unusual simultaneous blooming of Joshua trees and Mohave Yucca around Las Vegas. Joshua trees do not bloom every year. Like most desert plants, their blooming depends on rainfall at the proper time. They also need a winter freeze before they bloom and it was cold last winter with a little snow. The blooming cycle of the Joshua Tree is totally dependant on climatic conditions. Depending on the timing and intensity of winter rains, blossoming can occur any time from March to May, and can vary from very sparse to a rare abundance of blossoms in relative wet years as we see this year.