Variation in phenotype (mutants!)

Obviously, variation in traits is present in all populations and all species, but its quite easy to forget that – a mallard looks like a mallard, right? Evolution acts upon this variation, be it timing of flowering, anti-predator behavior or body size, constantly. I find variation in “characteristic” traits very interesting (and by “characteristic”, I mean how a naturalist would recognize a species, for instance in plants this might be color, growth form, leaf shape, etc.). I’ve been noting these for quite awhile and keeping a photo log – mostly of flower color, which is especially interesting to me – here’s a selection.

This isn’t meant as a real ecology post, just an appreciation for the natural world, but do bear in mind the little tidbits of science thrown in – they’ll only make it more interesting. As Huxley famously said, “To the person uninstructed in natural history, his country or sea-side stroll is a walk through a gallery filled with wonderful works of art, nine-tenths of which have their faces turned to the wall.”

I’ll mostly put a “normal” picture first and then the mutant. Here’s a normal Mimulus guttatus, the common yellow monkeyflower – a widespread, common and lovely species.

McLaughlin Reserve, Lake County, CA. 
And a weird red mutant:

McLaughlin Reserve, Lake County, CA

A normal Tritelia laxa.

Berryessa-Knoxville Rd., Napa County, CA

And a white one:

Berryessa-Knoxville Rd., Napa County, CA

A normal blue-eyed “grass” (really an iris), Sisyrinchium bellum:

McLaughlin Reserve, Lake County, CA

and a white one:

McLaughlin Reserve, Lake County, CA

Normal Mimulus nudatus, a cool serpentine endemic in the northern coast range.

McLaughlin Reserve, Lake County, CA

And a weird beige morph:

McLaughlin Reserve, Lake County, CA

And both normal and white morphs of Collinsia sparsiflora:

McLaughlin Reserve, Napa County, CA

Normal and white morphs of Mimulus layneae. Interestingly, the two white individuals in this population had flatter flowers as well.

McLaughlin Reserve, Lake County, CA

Why are white flowers so common in plants? Purple or reddish colors are caused by a group of chemicals called anthocyanins. These are synthesized in a pretty complex pathway that involves a bunch of steps, all mediated by proteins. If a mutation (or developmental issue), interrupts the function of any of these steps, you get a loss of function, which in this case becomes a white flower.

In some species, there is simply a polymorphism – its not rare to have differently-colored flowers (or -colored seed, or -shaped fruit, etc.). This Leptosiphon sp. has both pink and white flowers in roughly equal proportions in a population I looked at.

McLaughlin Reserve, Lake County, CA
Like Leptosiphon, many other members of the Polemoniaceae have white/colored polymorphisms within populations. Navarretia mellita (often a sandy plant!), is one:
McLaughlin Reserve, Lake County, CA

McLaughlin Reserve, Lake County, CA

Of course, color polymorphisms aren’t restricted to flowers, or even plants. A cool hypothesis to explain the existance of color polymorphisms in many species of raptors is that it is harder for prey to figure out what is a predator if they all look different. To the best of my knowledge, that hypothesis is still up for debate, but its clever and seems logical. Here is a pair of Variable Hawks, Buteo polyosoma:

Bosque del Pomac, Lambayeque, Peru
And another morph, of the same species!
A juvenile, I think. Bosque del Pomac, Lambayeque, Peru
I don’t know any hypotheses for the maintenance of color polymorphisms in caterpillars, but some have them. Hyles lineata feeding on Abronia villosa:
San Diego Co., CA

San Diego Co., CA

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