Classic Natural History II: Netje Blanchan’s Wildflowers

Say what you will about Google Scholar’s dominance of scientific literature searching and potentially indexing too much (see specific critiques here and here), but its inclusiveness means that it turns up a wide array of literature that I wouldn’t normally encounter reading the citations of papers or using a more traditional scientific search tool. I often need to spend some time separating the wheat from the chaff (this somehow got archived as a scholarly work), but its often worth it.

Part of the columbine paper I published recently was a list I had been working on for awhile; all the insect-entrapping plants I had come across myself, friends and colleagues had mentioned and I’d encountered in the literature. I hoped it would be a jumping off point for future investigations into the functions of sticky exudates in these plants. It is a most-incomplete list, especially in lesser-studied parts of the world. I added quite a few new genera to it while travelling in Chile (and Chile is well-studied, plus I did spanish language searches as well!). So I expect the list to grow steadily in the coming years.

Two of my favorite plants (I have a lot of them). Blanchan writes of the Impatiens: “These exquisite, bright flowers, hanging at a horizontal, like jewels from a lady’s ear, may be responsible for the plant’s folk name; but whoever is abroad early on a dewy morning, or after a shower, and finds notched edges of the drooping leaves hung with scintillating gems, dancing, sparkling in the sunshine, sees still another reason for naming this the jewel-weed.”

Today, while looking up plants for another project, I happened on Netje Blanchan’s book Wildflowers Worth Knowing (free pdf here – thanks Project Gutenberg). The copy I read, with that title, is an adaptation/reprint of her 1900 book Nature’s Garden. Blanchan was a popular science writer who authored another natural history book, Bird Neighbors (1897), that I picked up at a used book sale awhile back and really enjoyed. Her observations on both birds and wildflowers are astounding – she knew her subjects well and wrote about them effortlessly. Her observations on the ecology and behavior are astounding and the book reads quite differently from modern field guides on wildflowers.

This is a very pretty plate, but imagine trying to find an unknown word in a key from this…

She notes the key characteristics of each plant, as well as her observations of it, including ecology, mostly focused on pollination (apparently a passion of hers), but also herbivores, interactions with other plants, and interesting anecdotes and even literary references. This is the sort of guide that guides a nature walk (with discussion and appreciation of each organism), not just an identification (i.e. a latin name).

For instance, while discussing Pseudognaphalium, she notes: “Ever conspicuous among the larger visitors [is] the beautiful Hunter’s butterfly (Pyrameis huntera) [the American Painted Lady, Vanessa virginiensis], to be distinguished from its sister the painted lady, always seen about thistles, by the two large eye-like spots on the under side of the hind wings. What are these butterflies doing about their chosen plants? Certainly the minute florets of the everlasting offer no great inducements to a creature that lives only on nectar. But that [shelter], compactly woven with silk and petals, which hangs from the stem, tells the story of the hunter’s butterfly’s presence. A brownish-drab chrysalis, or a slate-colored and black-banded little caterpillar with tufts of hairs on its back, and pretty red and white dots on the dark stripes, shows our butterfly in the earlier stages of its existence, when the everlastings form its staple diet.” Not only do you get your flower identified, but you are encouraged to look for the butterfly and the caterpillar – which are, as she notes, very common around this genus, in my experience in both New England and California.

 I’m not sure whether these are post-processing colored, or produced in color (apparently available commercially at that time, according to Wikipedia). The left plant is now Aureolaria virginica, and like all Aureolaria is a hemiparasite (photosynthesizes and obtains some nutrition from its host). On this genus, she describes nectar-robbing as: “Sometimes small bees, despairing of getting into the tube through the mouth, suck at holes in the flower’s sides, because legitimate feasting was made too difficult for the poor little things”.

To get back to the list of sticky plants that I referenced earlier, Blanchan includes quite a number of observations of sticky plants in the descriptions, including a couple that I didn’t have on the list! She had me at the introduction – noting “Is it enough to know merely the name of the flower you meet in the meadow? The blossom has an inner meaning, hopes and fears that inspire its brief existence, a scheme of salvation for its species in the struggle for survival that it has been slowly perfecting with some insect’s help through the ages. … Do you doubt it? Then study the mechanism of one of our common orchids or milkweeds that are adjusted with such marvelous delicacy to the length of a bee’s tongue or of a butterfly’s leg; learn why so many flowers have sticky calices or protective hairs…. What of the sundew that not only catches insects, but secretes gastric juice to digest them? What of the bladderwort, in whose inflated traps tiny crustaceans are imprisoned, or the pitcher plant, that makes soup of its guests?”

Organized by flower color and shape, it is easy to see how dogwood (Rosaceae) and button-bush  (Rubiaceae: coffee family!) got placed next to each other. Of button-bush she writes ” the vicinity of this bush is an excellent place for a butterfly collector to carry his net. Butterflies are by far the most abundant visitors; honey-bees also abound, bumblebees, carpenter and mining bees, wasps, a horde of flies, and some destructive beetles; but the short tongues can reach little nectar”

Her list of sticky plants include three new ones for my list:

Persicaria amphibia “When the amphibious water persicaria (P. amphibium) lifts its short, dense, rose-colored ovoid or oblong club of bloom above ponds and lakes, it is sufficiently protected from crawling pilferers, of course, by the water in which it grows. But suppose the pond dries up and the plant is left on dry ground, what then? Now, a remarkable thing happens: protective glandular, sticky hairs appear on the epidermis of the leaves and stems, which were perfectly smooth when the flowers grew in water. Such small wingless insects as might pilfer nectar without bringing to their hostess any pollen from other blossoms are held as fast as on bird-lime”

This is extremely interesting and represents a whole new plant family for the list. While I’ve encountered this plant many times, I’ve never looked closely enough at it. I wonder if in this environment the glandularity serves as a direct or indirect defense, or whether it reduces water loss? I’m going to pay a whole lot more attention to this plant now.

Pseudognaphalium macounii: A new genus for the list, though I know that other Pseudognaphalium species I’ve seen do not catch insects. She writes: “Ants, which are trying to steal nectar, usually getting killed on the sticky, cottony stem”.

Aureolaria pedicularia is another new genus and species for the list. I found it in August in Massachusetts and noted its stickiness, but did not observe as Blanchan did: “Pilfering ants find death as speedy on the sticky surfaces here as on any catchfly.”

She notes several other genera, which are on the list, notably Cuphea, Rhododendron, Kalmia (Charley Eisemann has excellent photos of this here), Saxifraga, several Polemoniaceae and, of course, the catchflies – Silene.

 

A. canadensis is not a sticky columbine, but it is hummingbird pollinated and beautiful. “Fragile butterflies, absolutely dependent on nectar, hover near our showy wild columbine with its five tempting horns of plenty, but sail away again, knowing as they do that their weak legs are not calculated to stand the strain of an inverted position from a pendent flower”.

She waxes eloquently several times of Silene‘s stickiness: “Alas, for the tiny creatures that try to climb up the rosy tufts to pilfer nectar, they and their relatives are not so innocent as they appear! While the little crawlers are almost within reach of the cup of sweets, their feet are gummed to the viscid matter that coats it, and here their struggles end as flies’ do on sticky fly-paper, or birds’ on limed twigs. A naturalist counted sixty-two little corpses on the sticky stem of a single pink. All this tragedy to protect a little nectar for the butterflies which, in sipping it, transfer the pollen from one flower to another, and so help them to produce the most beautiful and robust offspring.”

“Although a popular name for the genus is catchfly, it is usually the ant that is glued to the viscid parts, for the fly that moves through the air alights directly on the flower it is too short-lipped to suck. An ant catching its feet on the miniature lime-twig, at first raises one foot after another and draws it through its mouth, hoping to rid it of the sticky stuff, but only with the result of gluing up its head and other parts of the body. In ten minutes all the pathetic struggles are ended. Let no one guilty of torturing flies to death on sticky paper condemn the Silenes!”

“Hapless ants, starting to crawl up the stem, become more and more discouraged by its stickiness, and if they persevere in their attempts to steal from the butterfly’s legitimate preserves, death overtakes their erring feet as speedily as if they ventured on sticky fly paper. How humane is the way to protect flowers from crawling thieves that has been adopted by the high-bush cranberry and the partridge pea (q.v.), among other plants! These provide a free lunch of sweets in the glands of their leaves to satisfy pilferers, which then seek no farther, leaving the flowers to winged insects that are at once despoilers and benefactors.”

While a perfectly valid hypothesis – taken from careful observation, we now know that extra-floral nectaries usually assist the “pilferers” in defending the plant (but maybe not always – I bet that her situation occurs sometimes!). It is worth noting that in some species, having EFNs separated from flowers may keen the defending ants from attacking pollinators, so the separation of the “pilferers” from the flowers, as she notes, may be important for the plant’s success.

Of bee balm, she writes “Gorgeous, glowing scarlet heads of bee balm arrest the dullest eye, bracts and upper leaves often taking on blood-red color, too, as if it had dripped from the lacerated flowers. Where their vivid doubles are reflected in a shadowy mountain stream, not even the cardinal flower is more strikingly beautiful. Thrifty clumps transplanted from Nature’s garden will spread about ours and add a splendor like the flowers of salvia, next of kin, if only the roots get a frequent soaking. ” Even horticultural advice is proffered!

I’m going to use this book now to look up any new plant I come across; her excellent observations and interesting thoughts (an appendix for “Unpleasantly scented” plants), I’m sure will come in handy in guiding my future research, and just as importantly, my enjoyment of nature. Like Thomas Huxley once said “To a person uninstructed in natural history, his country or seaside stroll is a walk through a gallery filled with wonderful works of art, nine-tenths of which have their faces turned to the wall.” Blanchan’s book turns those pieces around; giving valuable natural history information, in an easy to read fashion, for each species covered.

*”Liming” refers to the practice of coating a branch with a sticky substance to entrap songbirds, usually for consumption. While illegal in many places, it is still practiced and was the subject of an article in Nat Geo a couple years ago. A pretty illustrative picture accompanies the article

Sticky plant attraction, a new paper

I could not possibly do as good a job as the summary of this paper written by Elizabeth Preston, here, so I’ll first tell the backstory – and when it comes out, I’ll detail another cool part of it (which is not in the preprint version – instead buried in the appendices).

Heliothis phloxiphaga eating a flower bud of Aquilegia eximia, the serpentine or sticky columbine. Lake County, CA. 

Last summer, I spent most of my time studying Trichostema laxum, which I’ve written about in a previous post. I was trying to test my hypothesis that external chemical defenses are easily washed away by rain (which may be driving the pattern that few are found in wet areas) and spent countless hours doing various pieces of this – observing pollinators (the volatiles washed off might affect pollination positively or negatively), counting insects, leaves, buds, flowers and seeds (which can be done in situ!) and by July, the drought and some jackrabbits made this experiment look rather grim. I still haven’t brought myself to analyze these data, as it ended so depressingly…

As the floral color polymorphism was not in the experimental population, I didn’t notice it until the end of the summer, and gathered some, but not enough, data on it. Lake County, CA. 

I was getting a little frustrated and I wandered around, naturalizing, which is always a remedy for frustration (to me at least). I came upon a columbine – Aquilegia eximia – which I instantly knew held some potential for cool experiments. The first thing I noticed was that it was extremely sticky and covered in dead insects and the second was that it had a bunch of predators on it. I immediately thought to Billy Krimmel and Ian Pearse’s cool paper on tarweeds (doi:10.1111/ele.12032) , in which they demonstrated that the dead insects provided food for predators, which protected the plant from herbivores. I figured initially that I would simply test this in another system.

A Hoplinus nymph (probably the most important predator in the system) approaches an
entrapped fly.

Because I was out in the field without access to a genetics lab to get dead flies, I couldn’t replicate their design – where they added dead fruit flies to plants to supplement carrion – so instead I removed all the carrion from half of my 50 plants, hypothesizing that I would get a decrease in predators and an increase in herbivory (which we did!). I also thought hard about what else to test to add to Billy and Ian’s work. I thought that, perhaps, it would be interesting to test whether the plants attracted the various entrapped insects (mostly small flies, wasps and beetles) somehow. Lots of plants attract insects – pollinators are the most obvious, but volatile signals attract predators, other herbivores and even birds (doi: 10.1111/ele.12177). Having petri dishes, plastic mesh and tanglefoot in my field kit – I made little sticky traps, with a sticky mesh top and a petri dish bottom and I put either columbine stems and leaves (a very small amount) or nothing in them. Collecting them 24 hours later, I found that the dishes with columbine had higher insects than the empty ones (which would demonstrate the ambient rate of insects landing on these traps). The trapped insects were also little flies, wasps and beetles, just like on the plants themselves.

Dead Hymenoptera on columbine (I may be giving up entomologist credentials, but I am not sure whether it is a wasp or an ant alate).

So this became a story – perhaps logically – that the plants were somehow attracting insects to kill and feed to the beneficial predators on their surfaces (retaining their services). I presented this work in a talk at a little student conference at Davis during recruitment weekend and played with several ways to frame the story. The first was to be rather dry – columbines attract insects and control a tritrophic defense (or something along those lines). Instead, I thought long and hard about trying to make a metaphor (socialism – a worker’s paradise for the predatory bugs or a Roman bread and circus type thing, but they didn’t really work) and while I don’t remember how I came up with this – I settled on the sirens, figures of classical mythology who lured sailors to their deaths. I therefore framed it as these poor insects – innocent sailors of the California air – are somehow drawn to their deaths on the columbines. Of course, the columbines put the insects to good use in their defense, leaving open the question – which I am sure classical mythologists lose much sleep over – what did the sirens do with their collection of dead sailors?

Serpentine columbines in flower. Lake County, CA. 

Read more here!

Eric F. LoPresti, Ian Seth Pearse, and Grace K. Charles In press. The siren song of a sticky plant: columbines provision mutualist arthropods by attracting and killing passerby insects. Ecology. http://dx.doi.org/10.1890/15-0342.1