Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
Today’s batch of plant photos comes from Rik Gern of Austin, Texas. His narration is indented, and you can click on the pictures to enlarge them.
Here is another collection of pictures of plants growing in my yard. These were prevalent in March and are either wildflowers or weeds, depending on your perspective.
The first plant, False Dayflower (Tinantia anomala) started making sporadic appearances in the back yard about ten years ago. It didn’t show up every year and when it did, it was only in small clusters, but this year it took over the back corner of the yard. I was surprised to learn that it is found only in parts of central and south Texas, and a few places in Mexico. The flowers look this striking and cartoonish only when they first bloom; after that they shrink up a bit and droop so that the purple specks in the field of green only become visible as you get closer. The young flowers are quite the attention grabbers though, as you can see from these pictures taken in mid-March. The first one looks like a frame from a Pixar animation and I half expect it to start gesturing and speaking!
The Tenpetal Thimbleweed (Anemone berlandieri) grows faster than the grass and stands above it with thick rubbery stems (third photo). Bees and butterflies seem to like it, so it’s a keeper. The petals can come in white, pink, purple, and maybe other colors.
Either this one (6) is a mutant, or they can also come with more than ten petals. I count 14 in this picture.
The prettiest flower in this series is the Purple Heart, or Wandering Jew (Tradescantia pallida). I’m not sure if this is a wildflower or was planted by the house’s previous owner, but it’s been growing in an area by the front fence for the 17 years I’ve lived here and has survived droughts, freezes, trampling and just about any other indignity you can imagine. (As I was typing the last sentence a lightbulb went off in my head—So that’s why it’s called a Wandering Jew!) Most of the pictures I’ve seen online show deep purple leaves, but apparently that has to do with the amount of sunlight it receives. This one lives in a shaded area.
Going from beauty to the beast, here is the mighty and fearsome Prickly Sow-thistle (Sonchus asper). I sent you a whole batch of Prickly Sowthistle pictures a few years ago and have remained intrigued by this plant ever since. You wouldn’t want to have too many of them around, but their shape and structure is fascinating and elegant in its own menacing way.
It is an edible plant, but I just use it as food for my imagination, so here are two photoshopped variations. (9&10). The first variation (Grumpy Thistle) shows what might happen if it spread and took over the world. The second photo (Dragon’s Eye) shows it starting to take over the universe!!!
Please send in your good wildlife photos lest the feature become sporadic or—Ceiling Cat forbid—go extinct.
Today we have some nice photos by reader Mark Sturtevant; his captions are indented, and you can enlarge the pictures by clicking on them.
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This looks to be the last batch of WEIT-worthy pictures that I have from 2021.
First up are some of my favorite dragonflies, starting with the impressive royal river cruiser dragonfly (Macromia taeniolata). These are among the largest dragonflies in my area, but I am fortunate in that they are also among the most approachable. Sure, they will fly at break-neck speed as they patrol along a tree-line, as this one was, but then they hang themselves up at about eye-level, and there they sits. You may then take all the pictures you want, even at close range, and they don’t mind. The link to this species gives an idea about their size and approachability.
Next is our black saddlebags dragonfly (Tramea lacerate). Common in fields, but unlike most dragons in the skimmer family who do more perching than flying, these will fly all day, effortlessly cruising around on those overly-broad wings. But occasionally one will give me a gift by sitting on a perch as this one was at a pond near where I work. So I like them because they play hard to get.
At another park there are redbud trees, and late in the season I noticed that just about every leaf was fastened shut as shown here. What was the surprise inside?
Why, a whimsical caterpillar! A squirmy little Dr. Seussian sock. In olden times, finding an ID of something like this would be a great tedium, but now we have the BugGuide web site. A simple search in there for “caterpillar on redbud”, and immediately we learn that this is the redbud leaffolder, Fascista cercerisella.
One might think that a “March fly” would be a spring insect, but actually members of this family have several generations a year, and they emerge synchronously in large numbers. One day in November just about every leaf along a forest trail had at least one of these odd little flies. They are also known as “love bugs”, as they are often seen mating. This particular species is Bibio albipennis.
I try to carry my wide-angle macro lens when I go out, but I seldom find a scene that will work with it. Here I managed to get a picture among a group of unknown mushrooms. Sorry, I don’t know the species.
One day the wife brought home a Venus flytrap (Dionaea muscipula). A friend from down the street was visiting, and she had never seen one having a meal so I brought in a fly, slightly stunned it, and placed it as shown. As is well known, the trap is sprung if the hairs inside are triggered more than once. Our friend was pleasingly horrified at the sight of botanical carnivory.
Please send in your good wildlife photos to replenish the tank. Thanks!
Today we have a photo-and-text special on brambles from reader Athayde Tonhasca Júnior. His narrative is indented, and you can enlarge the photos by clicking on them.
Thorny issues
Once upon a time, so Charles Perrault (1628-1703) told us, a prince was out enjoying nature by merrily killing animals in the woods, when he spotted a hidden castle deep in the forest. The prince’s myrmidons explained that the castle housed a beautiful princess who had been cursed by an evil fairy; the young lady was to lay in a comatose state until awakened by a handsome prince. His Highness, who obviously had a high opinion of his looks, decided he was the person destined to break the spell. But getting to Sleeping Beauty wouldn’t be easy; the castle was surrounded by trees and a formidable obstacle that would have stopped a less determined hobbledehoy: a wall of brambles.
Having princely clothes ruined by brambles. The Sleeping Beauty, art by Arthur Rackham (1867–1939), Wikimedia Commons.’
Brambles or blackberries comprise many species that are difficult to tell apart; over 300 of them have been recognized in the UK. These related species are known as micro-species, and for practical reasons they are treated collectively as a species complex or as an aggregate group (abbreviated as agg.). So we usually refer to brambles as Rubus fruticosus agg.
Natives to much of Europe, brambles are valued fruit crops when grown as blackberry varieties, but they are also invasive in some circumstances. Their dense thickets are barriers to amorous princes and roaming livestock, and their thorns hurt animals and contaminate wool. Thanks to their vigorous growth (watch their shoots thrusting ahead), brambles can outcompete other wild plants and curtail the development of tree saplings; if left unchecked, brambles can quickly alter the species composition and physical structure of some habitats. For those reasons they are considered invasive weeds in Australia, New Zealand and the USA.
But as we have learned from many a definitive self-help book, problems are opportunities with thorns on them: several birds and small mammals nest or take shelter in bramble scrub. And their berries are food for sundry animals such as badgers, field mice, foxes, moths and voles: watch some of them having a nutritious fruit breakfast. Bramble berries are quite handy when other sources begin to dwindle in late summer and autumn.
But brambles have much more to offer; their open, bowl-shaped flowers, typical of the Rosaceae family, are easily accessible and produce large amounts of pollen and nectar, which are available during most of the season – usually from May to September in the UK. So a range of pollinators and other insects take advantage of these abundant and reliable food sources, from the European honey bee (Apis mellifera), which is one of the most enthusiastic visitors, to scarce species such as the brown-banded carder bee (Bombus humilis) (Wignall et al., 2020).
Brambles have a flexible approach to reproduction. They commonly propagate vegetatively (no seeds are involved) by deploying ‘runners’, shoots that take root when they are touching the ground; they can resort to apomixis, which is the production of seeds without fertilisation; or less frequently, they can use the familiar sexual mechanism of pollen deposition. This diversified strategy helps explains brambles’ complex taxonomy. Plants generated by vegetative growth or apomixis are clones, genetically identical to the parent plant. When they do occasionally outcross and produce seeds from fertilized ovules, the resulting offspring will have genetic profiles slightly different from the parent plant. Given time, these variants become species marginally different from each other, which spread out as clones and readily hybridise (Clark & Jasieniuk, 2012). Untangling these species is a job for a small tribe of patient, dogged taxonomists dedicated to batology (from the Ancient Greek báton, ‘blackberry’): the scientific study of plants in the genus Rubus.
Although infrequent, sexual reproduction is important for maintaining brambles’ genetic diversity, and here insects play their part by cross-pollinating plants. Among brambles’ many flower visitors, several bees and flies have been considered candidates for the job. But this list is biased because it leaves out insects we don’t normally see collecting pollen or nectar – the nocturnal visitors, i.e., moths. And they should not be neglected. Like many other plants, brambles produce nectar with variable concentrations of sugars during the day, and their highest output happens to be from late afternoon into the evening. Such sugary bounty wasn’t likely to go unnoticed by the night shift wanderers. Anderson et al. (2023) reported a range of visitors to brambles flowers during the day (flies and bees, mostly); but at night, moths were almost alone in dropping by for a sip of nectar. But there was more; moths visited fewer flowers per hour than diurnal visitors, but they deposited more pollen grains on stigmas. That’s an important finding. Flower visitation is often – and incorrectly – assumed to be pollination. In fact, many visitors avoid pollen altogether, or manage to remove the pesky yellow grains from their bodies. Pollen deposition is a well-tested method to evaluate who is pollinating what.
So here we are. Blackberry lovers notwithstanding, brambles are generally despised components of our flora, even though they play an important part in supporting pollinators and other animals. These brambles’ customers in turn may depend on secretive moths for the sexual reproduction of their hosts. As is often the case in nature, the plot is considerably thicker than it looks.
The Common Loon breeds in remote lakes of northern North America. Unmistakable with its sleek black and white plumage, dagger-like bill, and fiery crimson eyes, the Common Loon is perhaps better known for its mournful, haunting call. These long-lived birds serve as indicators of the health of aquatic environments, with the record for the oldest female being at least 35 years old. In Vancouver, we typically only catch glimpses of them in non-breeding plumage, so spotting one in full breeding plumage was a wonderful find:
Spring marks the beginning of the breeding season for Anna’s Hummingbirds. These tiny but fierce birds can be found perched high in trees, loudly declaring their territories. Despite their delicate appearance, hummingbirds are surprisingly aggressive and will defend their feeding and nesting sites from other birds, even ones much larger than themselves like hawks and falcons. Since the 1930s, their non-breeding range has expanded significantly from California to Arizona and even southern British Columbia. This expansion can be attributed to their adaptability in urban and suburban environments and the increased popularity of hummingbird feeders:
When you catch sight of iridescent blue Tree Swallows darting and swooping over fields and ponds, you know spring has arrived. Their common name derives from their dependence on tree cavities for nesting. Unable to excavate cavities themselves, they rely on abandoned woodpecker nests. Research has shown they readily accept artificial nest boxes, and many organizations are committed to installing them in suitable habitats. Tree Swallows feed on insects they catch on the wing and play a significant role in controlling insect populations. Regrettably, like most aerial insectivores, their numbers are declining due to the global decrease in insect populations:
Sparrows are not particularly popular birds often dismissed as “LBJs” (little brown jobs). However, the New World Sparrow family (Passerellidae) is incredibly diverse and boasts 132 species across the Americas. Despite being a common songbird, Savannah Sparrows remain relatively unnoticed due to their secretive nature and preference for hiding in fields, marshes, and coastal grasslands. You can recognize them by their distinct call, which sounds a little like an insect’s buzz. I was lucky to spot this bird foraging on a seaweed-covered breakwater at low tide:
Walking the trails through Vancouver’s Stanley Park, I chanced upon a pair of Barred Owls. As you observe these birds up close, you’ll notice something peculiar about their feet. Their toes are covered in feathers, but that’s not so remarkable. Look closer and you’ll see they have two toes facing forward and two pointing backward. Their zygodactyl foot morphology allows them to grip their perches firmly while also effectively capturing prey. Most songbirds, on the other hand, have anisodactyl feet: three toes in front and one at the back. Although it’s something most people don’t consider, a bird’s toe structure can tell us a lot about their evolutionary history and ecological niche. Read more about bird toe morphology!
This boldly marked sparrow is another common songbird that breeds throughout most of North America. With their striking rusty red caps and rapid trill, they’re hard to miss and often show up on suburban lawns. While these birds may be plentiful in other areas, they’re locally uncommon here in Vancouver. That’s why I was pleased to spot a pair foraging in a nearby park, taking advantage of a recently disturbed field:
The Barn Swallow is a globally ubiquitous swallow that breeds across the northern hemisphere and is known for building nests on human-made structures. Not only are they extensively studied, but they also hold significant cultural and historical importance in mythology and religion. While their coloration may resemble Cliff and Cave swallows in North America, their unmistakable forked tails set them apart. You’ll often catch them gathering mud from the edges of ponds and lakes to construct their nests with, like this one I photographed at Jericho Beach Park in Vancouver:
Named in honour of the French ornithologist Charles Lucien Bonaparte (Napoleon Bonaparte’s nephew), Bonaparte’s Gull is one of North America’s smallest gulls. These delicate and charismatic gulls are a brief migratory visitor here in Vancouver, and I always go out of my way to try and see them. Unlike almost all other gulls, they nest in trees, breeding in the forests of Alaska and northern Canada. Their remoteness, elusive nests, and sparse densities make them one of the least studied gulls in North America.
The first photo shows an adult in breeding plumage, the second is an immature gull which looks very similar to an adult’s non-breeding plumage.
Thanks to the wildly captivating and informative Joey Santore at Crime Pays But Botany Doesn’t, I’ve expanded my curiosity beyond birds and delved into the world of plants and fungi. Recently, I stumbled upon a cluster of bracken ferns and took this rather abstract photograph of one unfurling. These weedy, adaptable plants quickly colonize disturbed areas and have spread over most of the world due to their tiny, easily dispersed spores. Despite containing ptaquiloside, a known carcinogen, they have a rich culinary history in many countries:
By far the most widespread fern native to western North America, Western Sword Fern is an evergreen perennial that thrives in the understory of moist coniferous woodlands. It outcompetes many plants in the shady and acidic environment in coniferous forests and forms large colonies. This photo shows the unfurling stem and leaves complete with the circular sori which will eventually produce spores. While ferns might be easy to pass by without paying much attention to, there is something fascinating to me in knowing they’ve been around in one way or another since the late Devonian peroid 360 million years ago:
Drosera rotundifolia, commonly known as the Round-leaved or Common Sundew, is a flowering carnivorous plant that can be found in bogs, marshes, and fens worldwide (what’s the difference, you ask?). This plant’s survival strategy involves producing sticky hairs on its leaves that ensnare unsuspecting insects. Once trapped, the sundew releases digestive enzymes that break down the insect and absorb its nutrients. With its extraordinary adaptation to gain nutrients from insects, Round-leaved Sundew can thrive even in nutrient-poor soils where other plants struggle to survive:
Today’s batch of photos (please send yours in!) comes from reader Joe Baldassano. His notes are indented, and you should click on the photos to enlarge them.
Joe’s intro:
Recently I took a trip to the following national parks: Great Sand Dunes National Park, Colorado, Mesa Verde National Park, Colorado, Petrified Forest National Park, AZ, Saguaro National Park, AZ and White Sands National Monument, NM.
Photo of Sand in the valley which extends high up on the hills:
Great Sand Dunes National Park and Preserve protects the tallest dunes in North America… and a whole lot more. The park and preserve contain ecosystems ranging from wetlands to forest to tundra—each supporting specially adapted plant, animal, and insect life. (Source: National Park Service)
The Ancestral Puebloans, also known as the Anasazi, were an ancient Native American culture that spanned the present-day Four Corners region of the United States, comprising southeastern Utah, northeastern Arizona, northwestern New Mexico, and southwestern Colorado. The Ancestral Puebloans lived in a range of structures that included small family pit houses, larger structures to house clans, grand pueblos, and cliff-sited dwellings for defense. (Source: Wikipedia)
Photos: Walking Path through the forest, and then a Fallen Petrified Tree
Get up close to petrified logs by wandering along trails in the park’s southern section. The Petrified Forest was formed from these ancient trees, given the scientific name Araucarioxylon arizonicum, and have morphed from wood to almost solid quartz, taking on colors from iron, carbon and manganese. The Crystal Forest, Giant Logs and Long Logs trails loop past petrified wood deposits, huge logs and even an ancient log jam. Interested more in ancient fauna than flora? The Rainbow Forest Museum has paleontological displays of prehistoric animal skeletons. (Source: state of Arizona visitor’s Guide)
Me standing in front of a large cacti to show size:
Rainbow over a walking trail through the park (a very lucky shot):
A cactus, showing the landscape.
Tucson, Arizona is home to the nation’s largest cacti. The giant saguaro is the universal symbol of the American west. These majestic plants, found only in a small portion of the United States, are protected by Saguaro National Park, to the east and west of the modern city of Tucson (Source: state of Arizona visitor’s Guide)
Visitors sleigh riding on the sand as if it were snow (I’m told this is a regular pastime for locals):
Sun beginning to set over the sand covered landscape.
Rising from the heart of the Tularosa Basin is one of the world’s great natural wonders – the glistening white sands of New Mexico. Great wave-like dunes of gypsum sand have engulfed 275 square miles of desert, creating the world’s largest gypsum dune field. White Sands National Park preserves a major portion of this unique dune field, along with the plants and animals that live here. (Source: National Park Service)
Today we have a long and edifying photo-and-story contribution from Athayde Tonhasca Júnior. His narrative is indented, and you can enlarge his pictures by clicking on them.
Americana
Together,for better or worse
In 1844, Captain John C. Frémont of the US Army Corps of Engineers, later a US Senator and Governor, was crossing the Mojave Desert when he came across a Joshua tree (Yuccabrevifolia), hitherto unknown to white settlers. In his report, the captain offered a harsh appraisal of his findings: “Associated with the idea of barren sands, their stiff and ungraceful form makes them to the traveler the most repulsive tree in the vegetable kingdom”. But Frémont was moderate when compared to Joseph Smeaton Chase, author of California Desert Trails (1919): “It is a weird menacing object more like some conception of Poe’s or Doré’s than any work of wholesome Mother Nature. One can scarcely find a term of ugliness that is not apt for this plant. A misshapen pirate with belt boots hands and teeth stuck full of daggers is as near as I can come to a human analogy. The wood is a harsh, rasping fibre; knife blades long hard and keen fill the place of leaves; the flower is greenish white and ill smelling; and the fruit a cluster of nubbly pods, bitter and useless. A landscape filled with Joshua trees has a nightmare effect even in broad daylight: at the witching hour it can be almost infernal”.
Frémont’s and Smeaton Chase’s unfavourable aesthetic appraisals are not widely shared: many gardeners and landscapers like the peculiar shapes and looks of yuccas or palm lilies (Yucca spp.), so several species are grown around the world as ornamentals. Most of the ~40 known species grow as shrubs or trees with spiky, sword-shaped leaves; they produce large clusters (panicles) of bell-shaped, creamy-white flowers on stalks rising from the centre of the plant. Yuccas are symbolic of their places of origin, the great open spaces of the American and Mexican deserts. They definitely appealed to German-American physician and botanist George Engelmann (1809-1884), who became the world’s authority on the genus.
From his observations, Engelmann suspected that yucca flowers did not self-fertilize because of their morphology. Their anthers are orientated away and at a different level from the stigma, making it difficult for pollen grains to move from the former to the latter. To make the task even more challenging, yucca pollen is viscous, forming dollops not easily broken apart. Because yuccas tend to bloom at night, Engelmann reasoned that moths must be involved in pollen transport. In 1872, he collected some small, nondescript, whitish moths seen gallivanting around yucca flowers and gave them to British-American entomologist Charles Riley (1843-1895). Geographical serendipity helped Engelmann’s generous act of scientific collaboration: both men lived in St. Louis (Missouri).
Flower of a Spanish bayonet (Y. aloifolia). From The Yucca Moth and Yucca Pollination, by C.V. Riley, 1892. Wikimedia Commons.
Riley took up the challenge, and his discoveries about the role of those obscure white moths in yuccas reproduction were nothing short of spectacular; in a letter to Joseph Hooker in 1874, Darwin described Riley’s findings as ‘the most wonderful case of fertilisation ever published’.
Riley identified and named the yucca moth as Tegeticula yuccasella, from the family Prodoxidae (subsequently, several species from the genera Tegeticula and Parategeticula have been recognised as yucca moths; they are difficult to tell apart, but all more or less follow the T. yuccasella pattern). After mating on a flower of soapweed yucca (Y. glauca) or a related species, the female scrapes pollen from the anthers with a pair of specialised, spiky tentacles: these structures, which are found in no other group of insects, replace the long ‘tongue’ (proboscis) characteristic of most moths and butterflies. Without a tongue, the yucca moth can’t feed. But that’s not a problem, since the moth’s life is very short. The female uses her tentacles and sometimes forelegs to compress the glutinous mass into a ball containing up to 10,000 pollen grains, and holds it under her ‘chin’.
Done with pollen gathering, the moth takes flight in search of another flowering yucca – not an easy job, as the pollen load may weigh up to 10% of her body mass. On arrival, she walks to the base of a flower to find its ovary, opens a small hole in it and lays her eggs inside. Things then become truly interesting. By using the tips of her tentacles, the moth removes a small portion of her pollen load, walks to a stigma and places the pollen on it. You can watch these steps unfolding.
Before leaving the flower, the moth marks it with a pheromone to prompt latecomers to look somewhere else for their own egg-laying. The eggs hatch and the larvae feed on some of the developing seeds. At the end of their development, the larvae leave the fruits resulting from the seeds, fall to the ground, bury themselves in the soil, build their cocoons, and start a new cycle in the following spring.
The yucca moth’s actions deserve pause for thought. When we say that an insect has pollinated a flower, we may assume it’s a deliberate act: almost invariably, that’s not the case. A pollinator would eat or take all pollen back to its nest if it could. Pollination happens by accident, when the flower visitor drops off a few pollen grains in the right spot, or has pollen brushed off by touching some part of the flower. Bees may carry away 95 to 99% of all pollen gathered, leaving the remainder – unintentionally – for pollination. But it is tit for tat in these liaisons: plants have developed adaptations to minimise pollen harvesting, such as inconspicuous anthers, narrow floral tubes, difficult flower structures, or progressive pollen release to force pollinators to make repeated visits. Some plants like orchids also cheat by attracting pollinators with scent but not giving any nectar or pollen in return. Rather than collaborating, then, insects and flowers are taking advantage of each other. Granted, this mutualistic exploitation has been fine-tuned by natural selection to avoid disastrous imbalances: overly rapacious insects and pollen-stingy plants would collapse their dealings. But unusually for these give-and-take relationships, the yucca moth deliberately pollinates yucca flowers. This process guarantees the yucca a faithful and efficient pollinator for the price of a few seeds, while the moth is compensated for its troubles with a safe and nutritious site for its offspring.
Riley, an early evolutionist, understood immediately the implications of this exchanged back-scratching. “These peculiarities are (…) mutually and reciprocally beneficial, so that the plant and the animal are each influenced and modified by the other, and the same laws which produced the beneficial specialization of parts would maintain them by the elimination of all forms tending to depart from them” (Riley, 1873. Transactions of the Academy of Science of Saint Louis 3: 55-64). Darwinian references didn’t go well with evolution-hesitant Engelmann, who mumbled that “such theories would lead us astray” – see Sheppard & Oliver (2004) for a detailed account of Riley and Engelmann’s professional relationship.
It’s not surprising, then, that Riley’s findings thrilled Darwin, who briefly mentioned reciprocally beneficial flower and pollinator traits in the Origin (1859), and developed the idea – which he called co-adaptation – in his book on orchid pollination (1862). Darwin famously predicted that a Madagascan orchid with a very long spur (a tubular projection where nectar is stored), known today as the Darwin orchid (Angraecum sesquipedale), had co-adapted with a then unknown hawkmoth with an exceptionally long tongue. And his prediction turned out to be right.
The concept of co-adaptation was renamed ‘coevolution’ by Ehrlich & Raven (1964) in their celebrated paper on butterflies and their host plants, and it is today understood as a reciprocal evolutionary change resulting from the interactions between species. The extent of coevolution as a force behind pollination has been a matter of debate, since there isn’t much one-to-one specialization involved: insects usually pollinate many flowers, and plants in general are pollinated by more than one flower visitor. Moreover, pollination is mostly a passive byproduct of a visitation for the purposes of gathering pollen, nectar, oils, or other flower resources; see for example Johnson & Anderson (2010) for a discussion. But in the case of yuccas and their moths, it would be difficult to refute coevolution; plants and insects couldn’t survive without the intricate idiosyncrasies that favour each other.
Darwin had a reason to be pleased to learn about the contrivances of some strange plants and their cryptic pollinators from the vast North American deserts. And if Captain Frémont and Smeaton Chase knew about the delicate balance between the Joshua tree and yucca moths, they may have been bestowed a more sympathetic judgement.
Yucca moths on a yucca flower. Photo by Alan Cressler, U.S. Department of Agriculture:
A manly job
When early European colonialists arrived to the Americas, they were puzzled by a farming practice widespread among native peoples: the planting of squash (Cucurbita pepo), beans (Phaseolus vulgaris) and maize (Zea mays) simultaneously in the same field. Such a seemingly cluttered planting system happens to provide a well-balanced, nutritious combination of essential amino acids, complex carbohydrates, fatty acids, proteins and vitamin A to farmers and their families. This intercropping method, known as the Three Sisters, made a fundamental contribution to the flourishing of the Aztec, the Maya, and other American cultures. To this day, the Three Sisters are a common sight in the Central and South American countryside.
One of the Sisters in this fortuitous arrangement, Cucurbita pepo, comprises summer squash, acorn squash, pumpkin, marrow, and courgette – the classification of these plants is complex and far from settled. Squash flowers are either male or female, and open in the morning only, never to reopen. Not only that, their pollen quickly loses its viability, especially in hot or very cold weather. So to reproduce, squash plants need quick and efficient pollen transfer from male to female flowers. Their pollen grains are heavy and sticky, so the wind will not do. This is a job for a group of solitary bees aptly named squash bees from the genera Peponapis (13 species) and Xenoglossa (seven species), which occur throughout the Americas.
The success of the Three Sisters intercropping system was possible thanks to squash bees. Among them, the Eastern cucurbit bee or hoary squash bee (Peponapis pruinosa) is the most abundant and widespread species. This bee takes pollen exclusively from cucurbits (family Cucurbitaceae), and is the only known case of a pollinator following the range expansion of crops: as cucurbits spread throughout North America, the Eastern cucurbit bee was right on their heels.
Honey bees, bumble bees and other insects do pollinate cucurbits: in fact, they are the main pollinators of the various Cucurbita species cultivated worldwide. But these alternative pollinators are not as reliable and efficient as the Eastern cucurbit bee. Squash produce more pollen and nectar per flower than any other bee-pollinated crop, but honey bees and bumble bees will divert their attention to other plants nearby because they don’t digest squash pollen well.
Eastern cucurbit bees crack on with flower visiting at daybreak, when it’s still too cold for honey bees and other potential pollinators. Male visits are shorter than the females’ because they don’t spend any time gathering pollen: they are looking for mates. If none is available, they skedaddle to another flower, having a break now and then for a sip of nectar to keep up their energy levels. As the morning comes to an end, the flowers close and the females divert their attention to nest building on the ground. In fields planted repeatedly with squash or pumpkin, the number of nests will increase steadily to hundreds strong. For males, the afternoon is siesta time. With no females around, they huddle together in a closed flower for a long nap, coming out covered in pollen at dawn and again ready for romance.
Males don’t have scopa (pollen-collecting hairs) on their hind legs as females do, so they are poor pollen carriers. But they practically live on and around flowers, so the few pollen grains attached to them have a good chance of ending up on a female flower. Males are also more abundant than females, which further compensates their morphological shortcomings. It takes six to ten visits to fully pollinate a female flower: a male Eastern cucurbit bee can do that within the first hour of a flower opening. So, in all likelihood, males do most of squash pollination (Cane et al., 2011).
The case of the Eastern cucurbit bee highlights an often overlooked aspect of pollination ecology. Traditionally, males are seen as lazy freeloaders with little to contribute to society (we are still talking about bees here). But drones, or male honey bees, produce body heat that helps maintain the temperature of the hive. And male bumble bees appear to help care for the immature forms, including by incubating pupae. Males of many bee species are poor pollinators, but that’s not the case for the Eastern cucurbit bee, and certainly for many other species yet to be investigated. Three cheers then for the unsung male bees.
On the U.S. of A. theme. Many years ago, I was drifting through the streets of New Orleans at the crack of dawn, as one does, when I was attracted to the sound of blues coming from the riverside. There was no other soul around besides a musician, me, and an uncurious cat: the melody cut through the crisp morning and seemed to diffuse across the city and over the river. After listening for a while, it was to find a McDonald’s. I left the man to his homage to the mighty Mississippi.
Deep South Blues:
On a return visit to the city, someone broke into my barge (a Ford Torino) and pilfered my camera & lenses. It was the end of my paparazzo career.
We have a few new contributors, whom I think for sending in photos. Today’s photos come from Rik Gern of Austin, Texas. Rik’s comments are indented, and you can enlarge the photos by clicking on them:
I’m starting to catch up on some plant identification, so here are some more pictures to submit for your reader’s wildlife feature. Thank you for recommending iNaturalist’s “seek” application; it has already saved me hours of cross-referencing pictures with online images based on hunches and guesses. It doesn’t always work when I ask it to identify plants based on pictures I’ve already taken, and I have a number of those left in my computer, but it’s been helpful with live pictures.
There are two species here; both are native plants growing on my lawn in central Texas. The first pictures are of False garlic, also known as Crow poison (Nothoscordum bivalve). You’ll never see this little beauty if you keep your lawn mowed short and close to the ground, but if you’re a lazy bum like me you just might get lucky and see a blanket of these on the lawn
The presence of pollinators (first photo) allows us lazy folks to feel good about letting the grass grow! I read that most False garlic plants have three to six flowers atop the stalks, but this one has eight (second photo).
It was hard to get a picture of the stalk, but I hope this gives an impression of what it looks like when the plants cover the lawn.
Finally, here’s another closeup of the flowers:
The second species is a follow-through on pictures I sent you in January. These are the same Velcro plants (Galium aparine), just a little older. I usually pull them as soon as they start to spread, but I’d never seen them flower, so I let one patch grow until tiny white flowers started to blossom:
There’s a caterpillar that seems to find the plant tasty, though it appears that it never heard the vernacular expression about not treating the kitchen like a bathroom, which would explain the droppings in the upper left part of the picture!
The lower leaves in this picture show evidence of more caterpillar activity:
Don’t be fooled by the spiked leaves; they are not painful to the touch. I believe they help the plant attach to animals for transport, though they probably also discourage some animals from eating them:
Today’s photos come from UC Davis ecologist Susan Harrison. Her captions and IDs are indented, and you can enlarge the photos by clicking on them. By the way, I have less than a week’s worth of photos left, so I may have to stop this feature or make it more sporadic.
UPDATE to below: The Washington Post has a new piece, with photos, of the amazing blooms in California that resulted from this winter’s excessive snowfall and rainfall.
Carrizo Plain
Dramatic wildflower displays in spring 2023 brought national attention to the Carrizo Plain National Monument, a vast (1,215 mi²) semidesert preserve 90 miles east of San Luis Obispo in the southern Inner Coast Range of California. Carrizo Plain hosts the state’s largest remnant native grassland, which was spared from development by remoteness and lack of water, and is also too arid to be completely overrun by non-native grasses. It’s a major refuge for threatened and endangered wildlife and has been protected since 1988.
In wet years like this one, the hillsides come alive with scenes like this flower-painted hillside:
Hillside Daisy (Monolopia lanceolata) provides the yellow:
Scorpionweed (Phacelia tanacetifolia and other Phacelias) provides the blues:
The plain was formed by the San Andreas Fault, visible as the long narrow escarpment in front of the hills:
Mormon-tea (Ephedra californica), a common shrub, is a “nurse plant” for some wildflowers that grow best in its shade. The pink rings around these shrubs are Parry’s Mallow (Eremalche parryi) and the blue rings are Nightshade (Solanum umbelliferum); in between shrubs is Goldfields (Lasthenia californica):
Wildflowers nearly burying this shrub include magenta Owl’s Clover (Castilleja exserta), violet Thistle Sage (Salvia carduaceae), cream-colored Woolly Desert-Dandelion (Malacothrix floccifera), and yellow Desert Daisy:
Desert Candle (Caulanthus inflatus), the most Dr. Seussian of wildflowers:
Wildlife-wise our most exciting sighting was the San Joaquin Antelope Squirrel (Ammospermophilus nelsoni), a threatened species found only in this region. It jerks convulsively while giving its alarm calls, as it’s doing in this picture, and also responds to the alarm calls of birds:
Framing birds against wildflower backdrops was my pastime on this trip; here are a few.
Send in your photos, folks. We’re doing this feature after my Parisian hiatus, but I always need photos, and in fact we’re running low. Please follow the instructions on the sidebar (or link), “How to send me wildlife photos.” Thanks in advance.
Today’s batch comes from reader Rodney Graetz in Canberra. His narrative and captions are indented, and you can click on his photos to enlarge them.
A Backyard in Autumn
It is Autumn here in Canberra Australia with warm 25°- 30° C (81°F) temperatures in addition to many months of good (La Nina) rainfall, our backyard is humming. Here are a few examples of the activity.
Life at work. We do not feed birds; we do cultivate flowers to attract birds and insects. This flower is a Paper Daisy (Xerochrysum species) native to the arid outback. We chose it for the beauty of its colour and shape and (successfully) predicted that it might also attract insects, even though daisies are not big producers of nectar. If you search this photo, you will find six very different insect species, all foraging in separate parts of the one flower. Life: busy at work.
Look at me, look at me! A light-hearted comment on the strategy of sexual dimorphism – the separate colouring and body shape of male and female organisms and the competition for mating opportunities. Here is the male Orchard Swallowtail butterfly (Papilio aegeus) – I think.
This is the female of the species – I think. She has the wider wingspan with very different wing shape and colouring. Both sexes were happily and simultaneously feeding on the nectar-rich flowers of ‘Butterfly Bush’ (Buddleia sp.), but no display or mating behaviour was noticed.
The body shape of a praying mantis appears too frail for an ambush predator, but obviously, they are successful. Here a slightly battle-worn, thin (starving?) individual; note the tattered antennae. It was still very aware, reacting to my presence metres away shooting with zoom lens. I suspect that the costuming of several of the more bizarre characters in the Star Wars movies, such as Admiral Ackbar, was based on the head shape of a praying mantis.
The ambush predator in action – note the long antennae folded carefully away from the struggle. This mantis – not the same individual as above – hung itself on the underside of a leaf and captured an unsuspecting, daylight-flying Grape Vine Moth. This moth species is a chubby, relatively heavy prey item and it was its vigorous fluttering struggle that I noticed. I was impressed that the mantis was able to continue to hold it while hanging from the leaf. How to stop the fluttering of the heavy moth?
Simple – first, disconnect the control centre.
A familiar fungus (Amanita muscaria), about 3 days old, in the front lawn. Originally a Northern Hemisphere species, now spread world-wide, travelling as a component of the root system mycorrhiza of introduced trees, such as Quercus rubra (Red Oak), a street tree whose scattered, woody leaves are obvious in the photo. I like its symmetrical shape and colour, along with the mystery of its rapid appearance, followed by slow decay, and disappearance. I know it is toxic, but not lethally so, while a close relative, Amanita phalloides (‘Death Cap’), growing just a few streets away, is super-lethal, as two visiting Chinese Chefs recently demonstrated.
A young female (Doe) Eastern Grey Kangaroo [Macropus giganteus], likely less than 3 years old, and her independent young (Joey), both on alert to my presence. This not my backyard – though I have found kangaroos there – but in a nearby (300 metre) nature reserve. Note the focussed orientation of ears, which can rotate about 90°. By her height, this is likely her first joey, which by its size, she can no longer carry in her pouch (marsupium). If you look at her lower abdomen, you can see her pouch is gaping open, indicating that the joey is still suckling. This is one example of why Canberra is called the ‘Bush Capital’.
I’m resuming this feature, but I don’t have a big backlog of photos, so please send your good ones in.
Today we have some desert plants and animals from ecologist Susan Harrison. Her captions are indented, and click on the pictures to enlarge them (twice if you want them really big):
Pink Flowers, Yellow Birds, and Other Desert Wonders
California’s epic wet winter of 2023 brought wildflower displays to some of its southern deserts, including the marvelous Anza-Borrego State Park and its surroundings. On a late March visit, the park seemed especially rich in pink flowers and yellow-to-orange birds, as reflected in the photos below. The birds shown here are mostly spring arrivals, but the winter residents seen during my January 2021 visit were present as well – Verdins, Phainopeplas, California Thrashers and others.
Desert Calico (Loeseliastrum matthewsi) was palely exquisite:
Hooded Orioles (Icterus cucullatus) were abundant, feeding on the nectar of Ocotillo (Fouquieria splendens) and other shrubs:
Bullock’s Orioles (Icterus bullocki) mingled with their hooded cousins:
Scott’s Oriole (Icterus parisorum), an uncommon desert dweller, was my quest-bird on this trip; here is my first ever (a.k.a. “lifer”), building his nest in the skirts of a Fan Palm (Washingtonia filifera):
Lawrence’s Goldfinch (Spinus lawrencei) is a southern coastal and desert bird, and this pair gathering nest material were only the second and third ones I’ve seen:
Orange-Crowned Warblers (Leiothlypis celata) were feeding even more plentifully than Hooded Orioles on flowers of Chuparosa (Justicia californica) and other shrubs:
Common Yellowthroats (Geothlypis trichas) were singing by a desert spring, and this one seemed to be choosing a shrub to match his outfit (Brittlebush, Encelia farinosa):
Rufous Hummingbirds (Selasphorus rufus) were passing through en route from Mexico to Oregon and beyond:
Moving on from orange and yellow birds to less colorful ones, and – perhaps not coincidentally* – from migratory to resident species, here’s a Cactus Wren (Campylorhynchus brunneicapillus) singing his unmelodious song:
Black-Tailed Gnatcatchers (Polioptila melanura) sang only slightly more tunefully than Cactus Wrens:
Long-Eared Owls (Asio otus) residing in Tamarisk Campground are a major attraction for Anza-Borrego birdwatchers, and while I didn’t see them this time, one was observed in Davis a few weeks earlier:
* Is bright male coloration more common in migratory songbirds than non-migratory ones? On a quick bit of post-trip internet searching, I learned that this is a well-known pattern, likely related to the shorter breeding seasons and more intense sexual selection experienced by migrants.
