Friday, December 4, 2015

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). 

Monday, November 2, 2015

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

Thursday, October 29, 2015

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. 

Monday, October 12, 2015

Classic Natural History I: Anna Bateson's botany

I've lately had a little bit more free time, having had my experiments burned (more burned in the Jerusalem fire after I wrote the blog post about the Rocky Fire) and having just submitted a manuscript I'd been working on. So I've decided to spend a few hours a week reading older natural history and ecology papers. I've been working through the 1800's in American Naturalist, Annals of Botany and Science Gossip - a wonderful popular magazine including observations of natural history, short articles and summaries of research. I've done this haphazardly, reading the table of contents to find interesting articles. I surely let many interesting ones through, but there is practically limitless material, so that is unavoidable. 

I'm going to try to highlight some of these papers - the astute observations, clever experimentation, often beautiful writing, and a little history, too. I probably would have left out the last piece, but several things - including Charley Eisemann's beautiful history/biography/natural history piece on Annette Braun, a forgotten but influential naturalist; Graham et al's the Essential Naturalist, and Bernd Heinrich's biography of his father - have inspired me over the past few years to think a bit more about the people and history behind old natural history.

Many also have beautiful illustrations (like this domestic hybrid pitcher plant). From M.C. Cooke's Freaks and Marvels of Plant Life (1882).

A few papers I found that seemed quite cool were those of Anna Bateson (1863-1928). She was sister to William Bateson, a famous botanist of the day. She worked at as an "assistant" in Cambridge's Balfour Biological Laboratory for woman students, closely with Darwin's son Francis and built upon Darwin's plant work herself. She helped found the Cambridge Women's Suffrage society in 1884

One thing I often appreciate about older papers is the lack of the standard paper formula (Intro, Methods, Results, Discussion), instead a more narrative style that presents data and observations where necessary in the story. Bateson's "The effect of cross fertilization on inconspicuous flowers" from Annals of Botany in 1888 is a really nicely laid out concise argument. She starts with Charles Darwin's observation that while many small flowers are selfing and not visited often by pollinators, it would be strange that they would still be open if they were completely selfing. 

Darwin did not do these experiments because of the "difficulty of [crossing] them". Bateson did this tedious job for three species (of three families!) and found clear outcrossing benefits in all. Her experimental prowess is obvious, as is her sense of experimental design ("it would have been a better method to have obtained the self-fertilized seeds by artificial fertilization also"). And her conclusion - that outcrossing is a benefit to even usually-selfing plants is certainly correct. 

Also from Cooke's book, where he explains the actions of plant tendrils, a phenomenon still being researched mechanistically.

Another clever experiment concerned geotropism. She and Francis Darwin hypothesized, based on prior theory, that a stem lying directly on the horizontal is the most stimulated to move. They note that this is actually harder to test than it might seem, as if you simply let a stem curl, it will be subjected to varying stimulus as it curls upward (if the hypothesis is correct). Cleverly, they came up with a method to expose plants to varying stimuli independent of their response, by pinning them down for two hours at a given angle (they use three: stem pointed 60 degrees up, 60 degrees down and horizontal). They then released all three treatments for an hour and measured the angle. They got quite clear data supporting their hypothesis. In both cabbage (n=36) and plantain (n = 148), horizontally-placed stems curved more intensely than either down-sloped or up-sloped stems. I don't know much about geotropism, so I can't actually comment on the lasting scientific value of this experiment, but it was an elegant and simple experiment (science fair? lab demonstration?). 

The last paper is more of a monograph and concerns irregular flowers (i.e. not radially symmetric). Anna and her brother William detail many examples of abnormalities in flowers. They suggest that irregular flowers must have evolved from regular ancestors (we know macroevolutionary patterns and part of the molecular basis for this now) and that the best way to study the possibly evolutionary pathway is to look at variation in flowers now, to see what variation evolution is acting on in the present.

Plate of floral mutants in Bateson and Bateson 1891.

They write very clearly about natural selection and macroevolution in the introduction, making clear difficulties with the lack of intermediate forms, determining descent, and the apparent lack of utility of intermediate forms of an organ (essentially Paley's watchmaker argument addressed by Dawkins). They even mention punctuated equilibrium versus gradualism "Supposing, then, that such a series of ancestors were before us, the matter to be determined would be the degree to which the series is continuous or discontinuous: that is to say whether the differences between any one member and its immediate successor are so small as to be imperceptible, or whether there are distinct and palpable difference between them; or whether they are sometimes small, and sometimes so great as to cause interruptions in the series and divide it into groups". They follow this with a nice metaphor of evolution as chemistry or physics. They fall into Gould's camp, clearly thinking that evolution proceeds with discontinuities ("the objections to supposing that the process of evolution of forms is discontinuous are derived, firstly, from the scarcity of observed instances of sudden and large variation,,, it is in the hope of dispelling [this] objection that the present observations are recorded") [1].

The crux of their careful observations of toadflax, speedwell, gladiolus, and Streptocarpus lie in the fact that they are characterizing mutants that show a phenotype of different regularity from the parent. Especially interesting are their findings of apparently radially symmetric speedwell (#19 in the plate) and varying symmetries in all the species examined. They conclude these detailed observations by pointing out that while gradualism may be common, mutations that fundamentally alter an essential feature of a species (regularity of the flower; or Lenski and lab's digestion of citrate by E. coli) do occur. They state "The facts now given, though few, are a contribution to such evidence and, in our judgement, are a sample of the kind of fact which is required to enable us to deal with the problems of descent". Given that we now know that during plant evolution, both to and from irregular flowers has occurred many times, it is likely that the Batesons' work was prescient, it was certainly detailed, well-written and well-reasoned (they present a section at the end detailing the many limitations of their observations that is nowadays hardly admitted in a question and answer session, let alone in the published paper!). 

I spent an enjoyable couple hours reading this papers and composing this post. I'd love to hear suggestions of other interesting papers, comments on these papers, and really anything else natural history. 

[1] This is of course, a sort of contrived analogy on my part, as they are taking a saltatory view - a mutant occurs in one generation in the Batesons' argument, though in my reading, they are taking a wider view in the introduction, even with the preceding "between one member and its immediate successor".

Thursday, September 3, 2015

Fire, transpiration, local hydrology and some very happy sunflowers

The Rocky fire swept through McLaughlin Reserve at the end of July. Nearly five weeks later, I resurveyed some sites that I went through the week after. The amount of life that had survived in the completely wrecked sites was astonishing, as was the quick resprouting of some plants (Rhamnus, Salix, Quercus, Vicia, Brassica, Asclepias, etc.). But the most surprising thing was the "winners" of the fire. I've walked columbine this seep many times a week during the past two summers. This time, I was struck by how large several serpentine sunflowers (Helianthus exilis) and tumbling orache (Atriplex rosea) had become.

Several stupendously super-sized serpentine sunflowers stoutly standing in foreground. A couple orache visible in the background.
Before the fire and all of last year, these were quite small plants, reaching maybe 1-2' tall with a couple dozen flowers. In many places, they end at 6-10" with just a few flowers. These plants were over 3' tall and each had a hundred or more flowers. What happened?

Last year there was a little bit of odd late-summer weather, with a few overcast cooler days (it is usually above 90 and not a cloud in the sky here). On those days, one very small seep that I had a columbine population in would fill up a couple tiny puddles that hadn't had water for months. After a couple times, I mentioned this to the reserve manager here and she pointed out that the plants around the seep don't transpire as much on cloudy days, so the water being put out by the seep was not being used up before it got to the ground. 

What transpires less than plants in overcast conditions? Dead plants. Right after the Rocky Fire, the seep with the sunflowers was flowing again big time (it is much larger and had much denser vegetation around it than the one that I could see the changes before). The amount of water in this seep now is greater than it's been since April or so. While the sunflowers and Atriplex are past the end of the visible water in the seep by a few dozen yards, it is still flowing belowground and these are pretty much the first plants that would be getting any of that water, as all plants upstream are fried.  

This section had been completely dry for months before the plants stopped sucking up all of the water flow. Also note all the greenery. That is resprouting of Aquilegia eximia, Stachys albens, Salix sp. and a few grasses and sedges (you can fire me as your naturalist if you'd like - I have no idea what species are here).  
This was an cool and unexpected - though completely logical - thing to find in the aftermath of the fire. I'm sure its been described before, but it was really eye-opening to me to see how much water those plants were transpiring and just how much influence this had on the hydrology and the success of other plants far below them (it seems like asymmetric resource competition - the manzanita and willows above were dictating the reproductive potential of the sunflowers below).

Something similar may have been happening to trigger this flowering of Mimulus guttatus, but I'm a bit puzzled, as this was in a strange location for that to occur and nothing else around it was doing particularly well. It was certainly a pleasant surprise to see some spring-like color at the end of the summer!
I'll write a longer post about the Jerusalem fire (more lost experiments... but not all!) and some other interesting observations that I've had during my last couple days of wanderings. But I've got more field work to do now. 

Dragonflies were hanging out in the seep like nothing had changed. I believe this is Aeshna walkeri (common last year here and with the same gestalt), though I didn't have my net with me to confirm and I wouldn't have wanted to disturb her egg-laying anyway (I'm a bleeding heart when it comes to dragonflies... and snakes... and beetles... and others). 

Tuesday, September 1, 2015

New paper: plant external chemical defenses!

When I came to grad school, I was convinced I'd be working on plant-caterpillar-parasitoid relationships, with a focus on plant chemistry or biocontrol. I wrote my NSF-GRFP on the artichoke plume moth and several of its parasitoids. I spent a few months looking for plume moth caterpillars on thistles (a scratchy job) with relatively little success, though not for lack of trying. My focus then shifted to a cute little butterfly, Brephidium exilis, with strange population dynamics and then parasitoid sex ratios. All of these failed (either through logistical problems or me half-assing them because they just weren't that interesting to me).

And then I happened onto Blitum (=Chenopodium) californicum at Bodega and my research took an unexpected turn. As I describe here, I was fascinated by the little fluid-filled pockets on leaf surfaces. I ran a number of small tests and found a defensive function of the bladders (probably one of many, many functions) and wrote it up and it was quickly published in Oecologia, a good journal. This being the very beginning of my second year of grad school (fall 2013), I was pretty jazzed. My committee, however, thought that I should be working on "the bigger picture". And so the ideas for this new paper on external plant defenses came about.

Writing this paper was WAY harder than I thought it was going to be. Instead of a formulaic paper, here's why I did the study (intro), here's how I did it (m&m's), here's what I found (results) and here's why its important (discussion), I was faced with a blank slate. I could write this however I wanted and that was a bit daunting. Primary and secondary school taught me how to write a coherent 3-5 paragraph essay, secondary school and college taught me how to write a term paper and college and grad school have taught me how to write a scientific paper, but no one taught me how to write a synthesis/idea/review paper. I'm glad I did it, though I think it will be a few years before I start on another paper like this.

This caterpillar (an unidentified pterophorid) lives on a plant (Hemizonia congesta) with lots of glandular trichomes, the factories of many external defensive chemicals. It blends in nicely with its "glandular trichomes". 
Taking Rick's lab motto, a Buckminster Fuller quote - "dare to be naive" - to heart, I started by thinking of what ecological differences would occur if a defensive plant chemical was situated on the plant surface instead of inside plant tissues. I came up with five basic differences between chemicals on the surface of plants (external chemical defenses: ECDs) and those inside plant tissues (internal chemical defenses: ICDs):

(1) they are in direct contact with the abiotic environment;
(2) they are not in direct contact with plant tissues apart from the cuticle;
(3) they are first contacted by the vast majority of interacting organisms;
(4) they may contact more than just the feeding and digestive parts of interacting organisms;
(5) they are secreted from specialized structures or cells (or derived from a secretion thereof).

As discussed in a prior post, glandular exudates are often sticky and can have cool tritrophic effects. Here is a mayfly (Ephemeroptera) stuck on serpentine columbine (Aquilegia eximia). 
I then took this list and delved into the literature, reading hundreds of papers on plant chemical defenses over a several month period (I cited 180 in the final paper, but probably skimmed or read abstracts of  twice that number). While external chemical defenses had not been formalized as a class, many wonderful studies had investigated plants with ECDs and I was able to find many examples both in terrestrial systems and in marine alga. I wrote up a massive tome - over 18,000 words - with carefully detailed natural history of many of the studied systems. Of course, this was not publishable, though I was proud of it (I like nothing more than to put cool natural history into an ecology/evolution framework). I worked and worked on cutting it down to its basics. In the process, I found more references and presented it at ESA last year, getting some more feedback. The process dragged on and I got more and more interested in doing experiments and less and less interested in this mammoth synthesis paper. I submitted it a couple times in various stages of cutting and was basically told it was too long. So after this past field season, I sat down for a couple weeks with no other distractions and made it into a far more focused paper, which I submitted to Biological Reviews, as it was still a bit long for most other journals. Fortunately, it was accepted with helpful reviews and after tossing a few minor points back and forth with the editor, it is now out for you to read!

Without getting into the specifics (you can read them in the paper, if you so choose), I found that many chemicals are on plant surfaces, many of these chemicals are defensive, and these may be systematically different from internal chemical defenses in the ways I hypothesized. This paper is important for three reasons: 1) hundreds of papers are published on plant chemistry and plant chemical ecology each year, but it is ecologically important where certain chemicals are located; 2) we have a rich body of theory on plant chemical defenses, but some parts of it are rather untested, and ECDs may allow some tests of certain theories (e.g. optimal defense theory) and; 3) many important crop plants have external defenses, which are easily manipulable in many cases, and it may be useful to think about them in this way to come up with better pest management schemes.

I'm really curious about how this paper and this new classification scheme is received. Am I just cluttering the literature with new terms, or are these ecological differences informative and useful? We will see!

Castilleja minor, a species of paintbrush and a hemiparasite, has really cool oily exudates. The pictured caterpillar, possibly an Autographa (?) species, seems undeterred, though it does mostly eat the insides of the flowers and fruit, which may avoid the exudates. 

Sunday, August 9, 2015

Oops, my field site disappeared: lessons learned from the Rocky Fire

Last week, on the 29th, I was coming back in after a day in the field at the UC-Davis McLaughlin Reserve (in Lake County, CA) where I do all my work. I was setting up some insects in containers in the building when some one from next door came over to point out a smoke plume rising NW of the reserve.

I wonder if this is the first photo of the Rocky Fire... it was taken at either 4:01 PM, Cal Fire says it started at 3:29, a few miles NW of the reserve. 
Within a few minutes, it was obvious that this wasn't going to be like the other, smaller fires that were put out quickly the week before in the same area. I continued doing my work and made dinner. I wasn't particularly concerned, since the wind was pushing towards the fire and the plume was making its way away. By nightfall, it got worse, and the wind began to shift.

7:57 PM and the smoke plume still moving away from us.  
At this time, I went next door to the mining building to hang out with the safety guy there, who was on site in case this caused any problems for them. By 10ish, the power had gone out, the wind had come around and there was smoke and a small amount of ash falling. By 11, CalFire had shown up and told us it had jumped the road and that we were going to be evacuated soon. I packed up a few clothes, my bug nets, computer and a little bit of food and was on the road by midnight and back in Davis a little before 3 AM (nearly hitting a deer in the process). I fully expected to be back in a day or two. I had planned to stay there for a couple weeks - my longest continuous trip of the summer - as both the tarweeds and the columbines are in the middle of their season in late July/early August.

Navarretia mellita, the subject of one of my experiments, which was going along swimmingly before I left. 
After the evacuation and my near deer miss, I was running on a bit of adrenaline... I got to sleep by 4 AM or so and was up again by seven. And I spent the better part of the following week that I was evacuated refreshing the CalFire website as the fire grew in waves until nearly 70,000 acres (that is ~110 square miles). My sites all lay pretty much on the fire perimeter - I had no idea what to expect until I got back, as I knew that fires burned patchily.

Doing small-scale insect-plant interactions, I do my experiments on a plant-scale - manipulating traits of one plant, and I mostly work on annuals and all on a yearly basis (which means I can't do a pre-/post-fire comparison). I do many experiments each season - this year I was running 7 at the time of the fire - all in the northern and western parts of the reserve, where the fire was most intense. So my heart was racing the whole trip back, when I was allowed in on Thursday (the 6th - over a week after evacuation). I dropped some refrigerated stuff off and quickly hurried out to my sites...

This is the wet meadow where my recently published experiment took place and where I had another experiment going this year. 
As I drove in to my columbine experiment, I knew it wasn't going to be a pretty sight. You can still see a streambed on the left side. Surrounding it was a nice population of serpentine columbine (Aquilegia eximia), hedge-nettle (Stachys albens) and common monkeyflower (Mimulus guttatus) with a scattered coffeeberrry (Rhamnus sp.) and willow (Salix sp.), bordered by THICK chaparral (manzanitas, oaks, chamise, etc.). I did find remnants of the experiment...

I should have bought the pin flags rated for raging-wildfire temperatures. Next time. 
My next experiment was through a tiny circuitous trail which I had carefully machete hacked earlier in the season through manzanita and cypress. It involved going over and under a number of logs and around small breaks in the chaparral. Yesterday I could walk (and see) in a straight line through a whole lot of nothing. All I found was a tiny bit of melted flagging tape, attached to a columbine stalk that had somehow escaped total incineration...

Based on its location (and most of my landmark shrubs were gone), I think this was control #50. It formerly was under a manzanita. I found it in the middle of a large, barren field.  

All was not lost, however! My next project was a huge set of experiments examining defensive induction in a tarweed, Hemizonia congesta (this specific epitaph is accurate, at least for me). Fire fighters had made a dozer line through the upper end of this field between two roads. The flames reached the two roads and the firebreak, but fortunately never jumped and my site (containing 250 plants which I had been following for months), ~200 meters beyond, remained intact. I was a bit worried that perhaps the insects would have been affected, but the insect communities seemed normal in abundance and identity.

My site is on the middle hump in the mid-ground. You can see the sparse vegetation on those serpentine barrens compared to the field of Avena in the non-serpentine areas. 
The grasslands were wild to walk around. Grass fires don't burn as hot nor for as long as chaparral fires, so some things survived. Not among those surviving were the rabbit-poop looking burnt star thistle flowers and fruit.
It burned the spines right off the thistle flowers. And it looked like most hadn't seeded... hooray!
The living stuff on the right is a variety of tarweeds (Hemizonia, Holocarpha and Calycedinia spp.) growing on a serpentine barren (low biomass). The burned area on the left was Avena and star thistle and had much higher biomass and apparently burns better. 
Like the wicked witch of the west when confronted with water, milkweeds (this is Asclepias eriocarpa) apparently just melt in the face of fire. 

Not all the milkeeds melted, fortunately for this large monarch caterpillar (and the orange oleander aphids out of focus in the foreground). There were a bunch on a small surviving patch of Asclepias fascicularis which was no more than 2 meters from completely scorched earth. I wonder whether they emigrated here from melted plants or if they were all on the one patch to begin with.
The grassy areas had tons of Mourning Doves. More than I've ever seen at one time in my life. Did they group up after the fire and emigrate right to my field site? I don't have a clue. I usually see them near Croton (Eremocarpus) setigerus, but that's not around this site - I wonder if they were eating burned thistle heads or other seeds exposed by the burning of all the grass.

The patchiness of the fire on a microscale was crazy. Here a small patch of seeding Mimulus nudatus (a rare California endemic found only in serpentine soils in a small part of the northern coast range) stands amidst a scorched landscape. 
Another set of experiments I had were also very close to a burned area, but they too, were spared. I was studying the ecology of two sticky species: Navarretia mellita and Madia elegans. Both are weedy species that love disturbance. There is an old road above the center that is drive-able, but rarely driven and hosts nice populations of both species that like the roadside disturbance. The Navarretia experiment was pretty much fine, being about 5 yards from the road. In the couple weeks that I hadn't checked it, some of the seeds had dehisced, but I had final inflorescence number for all the plants, which is enough of a fitness proxy for my purposes.

Big flags, little tiny plants.
The tarweed (Madia elegans), on the other hand, suffered a little bit. During the fire, trucks must have driven by that site hundreds and hundreds of times... I was there for the afternoon yesterday and had 4 or 5 cars drive by twice each (it is a dead-end) - and that was long after the fire was out in that section. Tarweeds are sticky and I was manipulating the amount of insects they caught (following up on Billy and Ian's Madia study and my columbine study). Most of the plants were within a yard of the road edge (non were on the road - none got hit), but with the hundreds of vehicle passes the amount of dirt kicked up and subsequently caught by the tarweeds was crazy. The treatments - varying amounts of dead fruit flies - were sort-of intact, but redoing the treatments was a major trial, as the fruit flies wouldn't stick. This will get better as they grow and they ought to flower for another month or so, so perhaps this won't be a complete wash... we'll see.

Its hard to see in this picture, but pretty much every glandular trichome on the plant had dust stuck to it, rendering it pretty much completely unsticky. 
The last experiment, a manzanita fruit manipulation, had pretty much been doomed from the get-go. I started the experiment early in the season, when the plants thought they had lots of water, but soon after, they aborted all the fruit I had in the experiment. So I moved to a new site, on the edge of a pond, where the shrubs were a little bit happier, but I started it too late (as I was still nursing the first try along a little bit). The fire left only one of those manzanitas standing at all as it whipped around the pond. Not a huge loss, though it would have been nice to get the last set of data.

A dead deer in the pond that the manzanitas were next to. I don't know for sure that this was fire related, but it seems likely as the chaparral up to this pond on three sides was burned completely for hundreds and hundreds of meters. 
 In the pond, besides the dead deer pictured above, life seemed to go on fine. The tule and cattails were intact, as good, water-filled greenery should be. Pied-billed grebes continued to feed streaky little babies and coot made all their funny noises. I finally saw the first Ruddy Duck baby of the year - in years past there have been quite a few in this pond and this year there were quite a few pairs, but only one duckling seems to have come out. A Gadwall nest that I found a few weeks back should have hatched (or been preyed upon by coyotes, raccoons, etc., by now) and a few rather large babies were around the pond, along with the first Green-winged Teal of the season. Tiger beetles ran on the shores and dragonflies flitted by, as if nothing had happened.

I'm not sure where this jackrabbit fled during the fire, but he's a survivor for sure - there wasn't much unparched in the area that I found him. There were a good number of these around - and strikingly, in a lone patch of Garrya, with literally nothing for hundreds of yards around, a chipmunk scolded me!
Other folks lost experiments as well. This was a bird exclosure, under which was a chamise that had been monitored for years. 
The amount of life around, even in burned areas just a week later was astounding. While exploring, I heard a pair of Rufous-Crowned Sparrows chipping from a couple mostly demolished manzanitas along a completely devegetated streambed. They popped out to check me out - I suspect that most territorial animals are dealing with a lot of stragglers coming by. I had a secondhand report of a mountain lion wandering down a road near fire crews in the middle of the day - not a typical behavior. While watching sandpipers, I heard a barking, like that of a large dog coming from near where my truck was parked. Thinking it might be a lost dog displaced by the fire, I headed towards it. As I neared the truck, on a rock above it was a coyote, looking down at me and barking like hell. As I fumbled in my backpack for my camera, he ducked behind the rock and continued berating me until I left.

Walking through dense manzanita chaparral is miserable. Walking through the same area now is quite easy.

Though it makes you quite dirty. This was after only about 10 minutes. After an afternoon of hiking around, I looked like a coal miner.
For a number of reasons, I spend a bit of time looking at spiders: they are important predators on many plants, I've worked on crab spider behavior, and much of the Bahamian island research revolves around them. One of the first signs of life in the fire area was funnel web spider (Agelenidae) webs, which are a thick mat of webbing with hole the size of a nickel or so (like a funnel, as the name suggests). There were tons of them on top of the blacked dirt and vegetation.

A nice clean, fresh, funnel web on top of blackened soil. 
In contrast, in non-burned areas, the webs were messy with ash that was clearly flying in large quantities with the fire nearby. I wondered why the spiders hadn't spun a new web or cleaned it out. I suspect that the reason has to do with how costly spider silk is to the spider. Being made of protein and laid out carefully, it is both nutritionally costly and time-intensive to make a web. Many spiders eat their webs if they take them down and there is even a group of parasitic spiders which eat the webs that other spiders make (!!!).

A web with lots of entrapped ash. I think it is a theridiid, but I didn't look too closely. All the webs were covered like this.
Pocket gophers also survived, with fresh diggings in the 5 or so days since the fire passed through this area. I just saw my first pocket gopher a few weeks ago, while being acquainted with their diggings for years. They have really, really weird ears.

Its been a really interesting time to look at the natural history of this area. The next few years, while I continue my phd, will also be an interesting time of watching fire-following plants, resprouters and who knows what else.

The fire opened up previously hidden scenes from dense chaparral, like this midden. I guess this was from when there was a nearby shale quarry operating, but I'm not sure. Those beer cans look old...

I wrote most of this the night of 8/8/15. About 4 PM today (8/9/15), another call came on the radio about a smoke plume. I hurried outside and shit... another BIG fire, within a couple miles, this time SW of the station. This one has been termed the Jerusalem fire. I hurried and collected some seeds for a friend and reconned some badly dozered sections in the SE portion of the reserve.

Jerusalem fire, ~4:30 PM, 8/9/15. If the twittosphere is to be believed, those two plumes are from two separate arson fires.
These dozer lines are ridiculous. There are at least 4  (and a road) between this particular one and anywhere the Rocky fire actually burned. They tore the shit out of some really nice oak woodland habitat and compacted soil, etc. 
Fire haze does produce extremely beautiful light.

This charred live oak (?) leaf was one of many which rained down during my hike... the fire was 3-5 miles away at this point.

Like ecologists, firefighters seem to like to put flagging tape on anything interesting. Here on abandoned machinery. Its also on gates, fences, various poles, etc. 

A constant part of the wildlife now, these big birds are really thirsty, sometimes drinking 3,000 gallons every few minutes. I'm getting better at my identification of these. I think this is a Boeing 234 "Chinook", but these two rotor helicopters seem almost as confusing as empid flycatchers... field
We'll see how this one pans out... I'm not particularly worried for my experiments now. If they burn, they burn but there is a lot of burned area between this one and them (it is continuous, but the fire would need to turn a couple different ways before it got to anything).

The pond this CH-47 just refilled from is part of the complex where the field component of this paper took place. 

I did learn some field season lessons, as well.

Things I will do differently next summer:

1) Space my experiments out farther! The farther apart they are, the more likely a fire line will go between them in case something like this happens again.
2) Put them a little farther back from roads (this also would protect against accidental drive-overs).
3) Put them in a matrix of previously burned areas. Its hard to reburn the same areas two years in a row (though the Wragg fire managed that this year in Yolo/Solano counties!). That will allow a little extra safety.

And finally - while I lost some work (a couple months on a couple projects), I'll certainly be able to repeat those next year and I'll get a couple completed experiments from the seaon. Thankfully, I didn't lose my house, my pets, my vehicles or my livelihood - others did.

A lone manzanita looks out over a burned land. The road you can see in the back right is Roundtop road, in Knoxville Recreation area. It would be a good place to check this out from (but do not, under any circumstances, camp in the campground there). I guess the area to the right all has already/will burn in the Jerusalem fire, too.