The woolly bear presidential election outlook, 2016

In the age of cell phones, accurate polling of the electorate has become difficult. In a world where a disproportionate percentage of people answering landlines for pollsters is white and over 50, we desperately need a new method of predicting elections. As the 2016 presidential election looms, a crack team of UC Davis innovators has a promising new source of information, woolly bear caterpillars (Platyprepia virginalis).
A woolly bear contemplates the madness of the 2016 election cycle while resting on its preferred host plant, a coastal lupine. Photo: Eric LoPresti
Rick Karban, a UC Davis professor of entomology, has tracked woolly bear caterpillar abundance since the early 1980’s at Bodega Bay, California. Each March, Karban censuses the same patches of lupine that he has for over 30 years. The study asks a vexing question: Why are there are so many caterpillars in some years and so few in others? Many insects, including pests cycle like this, therefore it is of keen interest to many. Dozens of papers later, Karban, his students, and his collaborators have answered a great many questions, including how caterpillars deal with parasites, whether population cycles are influenced by rain, whether caterpillars enjoy eating plant hairs, and how caterpillars avoid their predators.
The population highs and lows seem random at a first pass, a jagged line moving up and down each year.
The collected data, 1983-2015, full data available here.
What separates high years from low years? These motivated researchers have found a striking pattern in this data. This data set includes eight presidential election years, with four Democrat and four Republican victories. Plotted with colors corresponding to the party association of the winner, the pattern becomes obvious.
Red corresponds to Republican presidential victories and blue to Democrats. To reiterate: this is actual data!
Woolly bears have years of high abundance when Democrats win and low when Republicans win. The average woolly bear abundance was 0.21 (+0.07 se) woolly bears per lupine in Republican years and 1.96 (+0.27 se) in Democratic years.  This data shows that woolly bear abundance in March is a good predictor of presidential victories in the general election.
It is tempting to assume that woolly bears are Democrats (and were particularly thrilled by second-term Bill Clinton), but we cannot exclude the possibility that their abundance is a protest gesture.
Note that 2016 is not included on the preceding two graphs. For about a year, news sources have made predictions about the primary race and have even speculated about the general election. Given their wildly erroneous predictions thus far for both primaries, trusting their predictions for the general election seems ill-advised. The woolly bears, on the other hand, have a 100% accurate prediction record over the past 30 years. In years of low abundance, a Republican is elected, and in years of high abundance, a Democrat.
Therefore, we are pleased to announce the woolly bears’ prediction. In mid-March of this year, Karban censused the woolly bears for their opinion on this volatile election year where no subject seems out of bounds and the populist wings of each party have come out like no election in recent memory. Even the woolly bears seem hesitant this year.
Full data, including this year’s census (conducted in March).
A superficial examination suggests that 2016 will be a Republican year – woolly bear abundance is not particularly high. However, looking a little closer, it may not be. The number of woolly bears per lupine bush in 2016 (0.53) is higher than the average Republican year by 152% and is 36% above the highest Republican year ever recorded (1988). However, it is only 27% of an average Democratic year and still only 36% of the lowest Democratic year (2008). This result is without presidential precedent in the last 30 years.
We suspect that the Republicans have the edge. However, a valid hypothesis would be a third-party winner, such as a right-leaning independent (a logical placeholder in between Democrats and Republicans). Perhaps Donald Trump will take particular interest in our data. Alternately, a contested Republican convention could produce a fractured party and the old Republican woolly bear average would not accurately represent the mean caterpillar abundances seen by this new party.
The mainstream media have been shockingly inaccurate in their predictions so far, even despite complex and supposedly accurate statistical models. We need a new strategy to predict key events such as the 2016 presidential election. Rather than trust the opinion of a few people with a pulpit, the historically robust predictions of this population of caterpillars may serve as a better guide.
A congregation of woolly bears meets on a lupine flower spike, presumably to discuss politics. Photo: Eric LoPresti

(This research has been in progress and was presented at ESA 2014)

This post was written by Eric LoPresti, Mikaela Huntzinger, Patrick Grof-Tisza, Ian Pearse, and, of course, Rick Karban (who we suspect is not fooling these infallible caterpillars with his Bernie Sanders impersonation). 

Rick Karban/Bernie Sanders. Who is who? Photo on left stolen from Berniesanders.com, right: Mikaela Huntzinger.

Data I’ll never publish: Antirrhinum herbivory

Inspired by this post, I’m going to try to put the results of small (but interesting) experiments up here every once and awhile. In the summer of 2014, I spent a lot of time washing plants. I was – and still am – curious of the function(s) of plant exudates. I primarily did this with Trichostema laxum and Atriplex rosea (in 2013), but I also did it with Mimulus layneae and Antirrhinum cornutum (California snapdragon). The snapdragon gave me interesting results.

(this post should also be regarded as potential project for someone else: I started it in May – there is plenty of time to get up to McLaughlin and do it again this year).

One of the experimental A. cornutum, showing leaf damage.

This snapdragon, while not as heavily glandular as Trichostema or that Mimulus, is fairly glandular-sticky, even entrapping a small number of minute insects (see the table/supplementary material). Under the microscope, you can see the fairly dense short glandular trichomes (the longer trichomes are mostly nonglandular) on the stalk and flower bud.

Stem of A cornutum with an entrapped insect.
Flower bud showing short glandular and long nonglandular trichomes.

Wondering whether the glandular exudate is defensive, I did an experiment where I removed it with water. Most glandular exudates in CA summer annuals seem water soluble, so a spray bottle rainfall takes off much of the exudate (observationally verified in situ with a 20x loupe – plus whatever was in this exudate made suds on the plant!). This manipulation was my first treatment group. Of course, adding water to a plant has an effect of its own, so I also had a water control group, where I added the same amount of water below the plant’s leaves, as to not wash off any exudates. Finally, I had a true control group, which received no water whatsoever. I instituted these treatments on the 30th of May and reapplied them on the 17th of June. Each time, I recorded the number of leaves, flowers, fruit, and plant height, as well as any damage. I also checked the plants, but did not reapply treatments on the 2nd and 19th of July (the last check all were senescent).

During the experiment, plants suffered two main forms of herbivory. The first type, which was most common and most destructive, was that the stems were entirely clipped off. I’m nearly positive this was by jackrabbits (indicated by a single flat cut diagonally across the stem) and it usually killed the plant. The photos below shows what remained.

A killed experimental A. cornutum plant. See it?!? Its the little stem to the bottom left of the flag. Also notice a nice healthy Lessingia in the background. They, too, are extremely glandular and sticky.
A survivor of mammalian herbivory. If the meristem was not completely destroyed, they often came back and branched like this. Like the classic overcompensation “herbivore-plant mutualisms”, the resulting plants were often bigger than the others, with more reproductive structures, but unlike this “mutualism”, it was too late in the season and they had low fitness, as they could not mature these structures.

The mammalian herbivory was not random. Of the 25 plants per treatment, 11 in the control group, 13 in the rainfall simulation (exudate removal) and a whopping 20 in the water control group were eaten by mammals (this is nonlethal, lethally was 10, 12, 18). With a simple chi-squared test, we can demonstrate that this was likely nonrandom (X2 = 7.3688, df =2, p = 0.025) (for lethal, X2 = 5.5714, df=2, p = 0.062). Why were the mammals targetting the water control plants so heavily?

Were they bigger and thus easier to find or just more profitable to eat? They were not significantly different in height, fruit or flower numbers from the other two groups during any check. I don’t have data on plant quality (perhaps the less water-limited plants were more nutritious or something?).

The other type of damage was equally-interesting. Heliothis phloxiphaga is a generalist caterpillar on glandular plants. It was the primary herbivore on my columbines, as well as a common herbivore on Trichostema laxum and other sticky plants. Like most heliothiine noctuids, it feeds primarily (but not exclusively) on reproductive structures. I only observed it once on Antirrhinum (eating a fruit), but all the fruit damage I found was consistent with it (and that’s one more time than I saw a jackrabbit eat it!).

The other type of damage: caterpillar fruit predation.

I had hypothesized, that if the exudate were defensive, the washed plants would be most heavily eaten. This hypothesis was supported with the fruit damage. Rainfall plants received far more damage than the other groups. (note: I didn’t actually analyze this with zero-inflated binomial, as it should be. There is a problem, in that only 7/25 of the water control plants had any fruit at all because of the rabbits.)

A crumby excel graph of proportion fruits damaged.

What does this all mean? Obviously, it means that mammalian and insect herbivores are responding to different plant traits. What they are exactly, I’m not sure (especially for mammals). If anyone (nudge, nudge, wink, wink) were to repeat this experiment, with a larger sample size, and maybe some other mechanistic experiments (perhaps cage controls and lots more trait data to see what is different in the water control and rainfall manip groups), I think its a pretty good system that someone could get a paper – if not a few – out of.

Mark and recapture project for students!

I’ve had the pleasure of teaching many groups children from preschool to high school age during the last decade or so in a variety of settings: camps, classrooms, field trips and informal natural history discoveries on the sidewalk (just recently jumping galls in the Central Valley here).

One activity that I have done a few times, and particularly enjoyed, was doing a mark and recapture study on dragonflies with elementary/middle school students. In my opinion, it is a pretty perfect project – you get to teach the scientific method, a little bit of math, and a good bit of natural history. I didn’t come up with this project (I think Taylor Yeager, of Mass Audubon, suggested doing it with grasshoppers, initially – but that was the summer of 2006 or 2007, so my memory is a bit hazy) but I’ve run it a few times with kids from ~9 years old to high school age.

Hetaerina americana, the American rubyspot, my favorite odonate in California. A damselfly, these are just as suitable for the study described here, though a little more fragile.

The goal of the project is simply to estimate the number of dragonflies in a given area such as a large field or a pond. You could easily adapt this to grasshoppers, milkweed beetles or any other larger invertebrate that can be easily handled and marked (bumblebees or butterflies might not be as good). Mark and recapture is a standard technique used in wildlife studies and the basic idea of it is very simple – you mark a known number of animals, then you go back and capture a bunch and see what proportion of that sample was marked. Obviously, in real-world applications, the math is much more complicated, but for our purposes, if we mark ten bugs the first day and capture 10 the second day, two of which are marked, we have a population size of 50.

 

You’ll almost certainly see Pantala flavescens, the world’s most widespread dragonfly. Catching them is a bit harder – they fly high and fast! This is a female.

Dragonflies are supremely suited to this activity however. They are often abundant, easy to handle and mark, children generally have no aversion to them and they are just challenging enough to catch to occupy students for hours (and to get lots of energy out while running around the field with nets!).

Rhionaeschna sp. Chiloe Island, Chile. WHO DOESN’T LOVE DRAGONFLIES?!?

Of course, the first thing you should do is to get all the students to guess the number of dragonflies in that area. They generally have no idea; guesses vary by orders of magnitude (from 10 to 1 million!). Then it is just a matter of giving everyone nets, teaching them to safely handle dragonflies and going out and catching ’em. We’ve used normal sharpies and put a dark band on both forewings of the individuals we captured as a mark. For easier record-keeping, we set up a station in the center with the sharpies. I found with younger students, it was easier (and safer for the insect) if I took it out of the net and marked it (those being the two steps where wings are easily shredded or broken), then let the students identify and measure it. Taking dragonflies out of nets isn’t hard – put your pointer and middle fingers on opposite sides of their body and gently move their wings up so that you have all four together and remove from net. Even 12 year-olds can remove and mark with proper instruction. Most dragons will need a few seconds to pump haemolymph back into their wings after this process; you can place the dragonfly on the catcher’s nose – this is especially entertaining for all others involved!

An Aeshna/Rhionaeschna sp. This is the proper way to hold dragonflies; using two fingers, pinch the four wings together gently. To mark it with sharpie, it helps to put the wings flat on a clipboard and gently put a small mark. This is a female – note the lack of a bulge on the bottom of the first couple abdominal segements (compare to photos below).

 

The other way to hold dragonflies is to firmly grip the upper segments of their legs (I usually try to hold two – though I am holding only one in this photo) between thumb and forefinger. This allows viewing of the wing pattern and veination, but is trickier and requires some practice to not rip off legs and let the dragonfly get away. They can also bite you in this grip, not a problem for little ones, but big Aeshnids can draw blood!

With high school groups, I’ve taught them how to sex the dragonflies and then made comparisons of male and female sizes and sex ratios. This is an interesting activity, as in upland areas, most caught are females and near water bodies, most are males (you can count on this result with all but a few uncommon species). The reason is that males of most species patrol territories near prime egg-laying spots and catch the females and mate with them immediately prior to egg laying. Females, being harassed constantly near water, generally forage in areas farther away. This is especially pronounced in Enallagma damselflies – the bright blue males may be found by the hundreds at any pond, but its really hard to find the duller females nearby – sex rations on a local scale may be 100:1 or more!

Blue dasher, Pachydiplax longipennis, one of the most abundant dragonflies in the US. Note the water mites on its abdomen – these have really interesting natural histories (too long to describe here, but look them up). Also, note the bulge on the lower side of the first couple abdominal segments – this is a male (compare above).

The next day, we go back out and catch them again – to avoid double counting individuals, we use a second color sharpie on these. Then we conclude by doing the calculation of total population size, figuring out who was closest (the most exciting part for the students) and discussing the drawbacks. The students have always come up with good hypotheses for why the estimate might not be accurate (there were too many high-flying dragonflies, one day was cloudy, etc.) and it generally provides good fodder for a short and informative discussion. With older students, summary statistics on sex ratio, the body size measurements and population sizes of each species can be done and discussed.

The only individuals we don’t mark are tenerals – these are just emerged and they have not fully dried their wings and marking would almost certainly hurt them). Note the glistening wings and really pale body. In another day or two, this Sympetrum sp. will be cherry red!

 

No dragonfly post would be complete without this monster. Arguably the world’s largest dragonfly, Phenes raptor lives in bogs in Patagonian Chile and Argentina and has somewhat terrestrial nymphs, an oddity for an odonate. Males also have the coolest set of abdominal claspers (those projections at the tip of the abdomen) of any of the hundreds of species I’ve seen!

 

The eyes of emeralds, family Corduliidae, lend them that common name.

 

What you’ll need (not very much!):

1) Nets – 1 per student is ideal, but partners are fine, too. Wooden-handled aerial nets are not expensive (<$10) and will last a long time and take a good bit of abuse.
2) Sharpies
3) A good field guide. I use Dennis Paulson’s excellent guides for the US, though there are really good regional ones, like Blair Nikula’s Massachusetts guides and others. Identifying dragonflies and damselflies in all but a few genera (Sympetrum, Enallagma) is really simple and can be done by most high school age children with pretty good accuracy.
4) Clipboard, data sheets.
5) Two days of predicted sunny weather!

You could have students make nets. During a trip to Peru, my net was stolen within a week. I bought some mosquito netting, bailing wire and made this net for <$1. It lasted me the whole season without issue – several of the dragonflies on this page were caught with it.

Do give this a try next year if you have students for a couple days! Let me know if you do, I’d love to hear how it goes.

Another interesting thing to note – and could be measured by the students – is the size of the wings (length, width). This dragonfly, Pantala flavescens, has HUGE wings for its size. Unsurprisingly this species is probably the most migratory and best dispersing insect – of any group – on earth. You can find this species near you – pretty much nomatter where you live!

 

A meadowhawk (Sympetrum sp.) like above. This is a male – told by the bulge in the abdominal segments as well as its red color (females of this genus are yellowish).

 

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

Trichostema laxum research update: the first interesting data?

Awhile back, I wrote about the beginnings of some research on Trichostema laxum. I’ve been slogging through the disappointing amount of data I gathered this field season and doing a little bit of writing. While I was, and still am, really excited about the project on T. laxum, it took a backseat to columbine and tarweed work this field season (most of which burned up). I did get some new data and perhaps gained some insight into the system.

A normal array of plants in the site: normal purple Trichostema laxum, an individual with the common white and purple lower lip phenotype and some Zeltnera trichantha intermixed (a really cool plant)
My main question in the system is: how is this polymorphism in flower color maintained? If it were a fitness benefit, we might expect a high proportion of it. If it were deleterious, it should be lost (especially as it is at reasonably low frequency). If it is neutral, it might be drifted out. I actually suspect the answer is quite a bit more complicated.
Once you start looking for variation, you find it! I don’t know what this doubled lower lip is about (it showed up in a plant grown in the greenhouse – on most flowers). The plant was male-sterile, I believe. I’ll be looking for it in the field though!
The first question is, of course, how common is the color polymorph? I censused the focal patch/population (separated by ~300 meters from others) in 2014 and 2015. In 2014, the polymorph was 2.0% (46/2278 individuals) in 2015, 3.7% (102/2757). Neither of these censuses was a complete census of the population – necessarily, I cannot assess the phenotype of any pre- or post-flowering individuals. Both were done roughly in the peak flowering time (over several days), so I do think it is close to accurate. I think its safe to conclude that the proportion stayed the same or even went slightly up in 2015.
A rather large w/p morph individual.
The next logical question is: do the two morphs have similar field fitness? Any “fitness” measure (e.g. reproductive success, height, etc.) of these plants is dictated mostly by microhabitat location. In this rocky, heavily serpentine site, most plants stay under 20 cm tall and never put out more than 50 flowers (mints have 4 ovaries per flower, so maximum seed set is four times flower number). In a wetter, less serpentine and rocky meadow, I once found a plant on a gopher mound (which brings up nutrients) that was nearly a meter wide and better than a half meter tall. It probably had >5000 flowers throughout the season.
A veritable field of Trichostema! Not my field site – this site has huge plants (~500 flowers/plant) and very little flower color variation. It is a nice place to look at the insect communities on T. laxum, as it has really high densities of herbivores and predators (T. laxum gets most of the sticky plant predators)
Because of this microhabitat variation, the best comparison to make is nearest neighbors which differ in flower color. In both 2014 and 2015, I took data on 41 pairs (coincidentally!) of white/purple and purple/purple neighbors. I found no significant differences, either year, between any fitness variables (number of buds, flowers, fruit, height and, in 2014, number of leaves and herbivory [too low in 2015]).
A more normal-sized (for this population) individual.
This, ostensibly, seems like the trait is fitness neutral (and lab growouts seem to bear this out – more data soonish). Given that this site burned in August this year (after most had flowered, but some [probably few] were still maturing seeds), I was curious about whether the morphs differed in phenology. Hindsight is 20/20 (I should have censused biweekly!), but the neighbor pairs data can be used to examine this in a roundabout way; I have data on buds, flowers and fruit, so later phenology plants should have a higher proportion of buds to flowers and fruit than earlier phenology plants.
In both years, the white/purple plants had a lower proportion of buds than the purple plants (it is marginally significant). This suggests that they have a earlier phenology – which could be what is under selection – not the flower color itself. I am super, super, super, excited about this (the only positive result so far from anything in T. laxum) – there was possibly a big selective event (a fire) on 12-August (I think – could have burned on the 13th). From this, I’d predict that the w/p morph may have dehisced a higher proportion of their seed set by the fire. I’ll be paying far more attention to the phenology, and recensusing more often this upcoming season.
I also analyzed the pollinator data from 2014 and got no particularly useful insights (I wondered if there was some degree of isolation between the morphs). The pollinator communities using each morph were pretty similar and the only real differences were:  a bee on a purple flower was more likely to visit a w/p next than a bee starting on a w/p* and, only bees that started on w/p flowers next visited a snapdragon, Antirrhinum cornutum (but only 3% of the time). This last result is interesting as the snapdragon also has whitish purple flowers AND the T. laxum population with the w/p flowers is the only one  (out of ~15) I’ve found interspersed with large numbers of A. cornutum. I’ll have to get MUCH better data for any hypotheses about its effect.
Antirrhinum cornutum, grown in lab, showing the pale purple/white flowers.
I’m working now on the “genetics” (well, inheritance, but that’s as close as I ever get to ATGC) of the polymorphisms (this one and selfing). Could w/p be recessive and heterozygous in more individuals (~25% under HW assumptions)? I don’t think it is (entirely) developmentally induced, as in the first grow out, I only got this polymorphism from this population (I grew individuals out from 4 populations). More soon! Do let me know if you have other ideas about the system!
Heliothis phloxiphaga was a very common herbivore on T. laxum in 2014 (this plant had two – I didn’t stage this), but nearly absent in 2015 – though it was still common on columbines and tarweeds.
*I think this is confounded, as I watched two plants during each observation – nearby plants that were similar in size. Therefore, I suspect that it was more likely that a bee on the p/p plant would encounter a w/p than one from the w/p.