Lark Bunting, Solano County

I got out this morning for some quick birding with Jay Riggio and Noah Reid. We were hoping to find Mountain Plovers, but had to settle for a nice Lark Bunting instead. We first spotted it foraging in with a flock of Lark Sparrows (another non-lark lark - but we did see the "real" lark - Horned Lark, too). I thought I was going to have to settle for this photo:

But fortunately it came closer. 

The bird was in a small flock (~15) Lark Sparrows in an osage orange hedgerow right on Robinson Road.

Beginning research: floral polymorphisms in Trichostema laxum

The first steps of any research project are, for me, the most exciting. Therefore, I'll write a quick post on something I've been spending a bit of time on. Last summer, I spent most of the summer trying to wash off chemical defenses on leaves. One plant I chose was Trichostema laxum - a mint endemic to California (it may occur in extreme southern Oregon, too) that occurs pretty commonly on dry serpentine streambeds at my field site in Lake/Napa counties. I've already written a quick post mentioning this plant, but I know a LOT more now!

Trichostema laxum, October 2014, McLaughlin Reserve, Napa County. Notice the position of the stigma in relation to the anthers - the style (the stigma's tube) projects well beyond the anthers. This is the "normal" morph of the plant, referenced in the literature and seen in all herbarium specimens I've looked at so far.

While the herbivory and exudate stuff awaits analysis (a dissertation proposal will force me to do that soon!), I discovered the aforementioned flower color polymorphism and took a bunch of baseline data on it, which may be important in the coming months. The flower color polymorphism interests me most because of one population which had a high (~3%) proportion of the white/purple morph - no others had it. Was it just a random neutral mutation that didn't drift out? If not - how is it maintained?

The four polymorphs of flower color. All from summer 2015, McLaughlin Reserve, Napa/Lake Counties.

The first question was, do the various flower colors differ in fitness from the normal (purple) morph? Trichostema laxum along with most other annual plants in California grasslands and serpentine barrens, is extremely variable in size depending on the microclimatic conditions. Within a population, some individuals can have three orders of magnitude more flowers than others (~10 to ~10,000). I found one small bush-sized individual (probably nearly a meter square) on a gopher mound - clearly the gopher had changed the nutrients or hydrology of that specific location favorably! Therefore, I compared polymorphs to their nearest neighbor of the normal morph, in an attempt to minimize this variability. This was a coarse test (without a huge amount of power), but I found no differences, though large variability among individuals. I will - hopefully - be able to confirm this in the laboratory rather easily. I took a good amount of pollinator data - which also awaits analysis.

A pink morph just barely open (though the stigma is open, so maybe its deformed?).  McLaughlin Reserve, Lake County, CA. 

The next logical step in the investigation was to grow plants in the lab and find out whether the color polymorphisms were heritable - an important consideration in any investigation relating to population-level polymorphisms. Trichostema have a reputation for being a tough genus to grow, in fact, a professor at Davis told me a former grad student planned a project on them, but couldn't get any germination. I've been more fortunate (with help from Danny Barney at the USDA) and got decent germination with a rather simple protocol - laxum may be less picky than its relatives. I grew them all fall - they flowered in November and early December.

One of the first individuals in the lab. Isn't it cute?

When I started looking closely at the plants in the lab, I found two more polymorphisms. The first was the lower lip patterning. In normal plants, the lower lip - and sometimes the next lowest two petals, have some purple splotches on them. This is likely a nectar guide, leading pollinators to the reward (and often only visible/really cool in the UV). I knew in the field that the completely white morph lacked a nectar guide as it lacks anthocyanin, the red/purple pigment in most plants, completely, so a purple nectar guide would be precluded. But I was surprised to see a purple flowered plant lacking it.

Clean purple lower lip. December 2014, in lab. 

While interesting, this was only found in one plant (though I have seeds of it now). Another polymorphism was also obvious in the captive plants and it solved one of my summer mysteries. During the summer, I wanted to do crosses with the various colored flowers. I didn't think it would be that hard - an older paper reported that T. laxum was non-selfing and covered plants produced no seed. So I placed pollinator exclosures over a bunch of plants and did crosses by moving pollen from one plant to another. I then covered the plants again, letting them naturally set seed and figuring that the only seed I'd get would be that of the crosses. I pollinated ~10 flowers per plant and since mints have only 4 ovaries per flower, I figured I could get about 40 seeds a plant (probably 30 since my fine motor skills aren't all that great). When I uncaged the plants and collected the seeds in October, I got quite a surprise - large numbers of seeds. Though not a full complement from any plant (there are MANY reasons for this besides lack of pollen), I got way too many seeds to have been either 1) my pollination, or 2) occasional lapses in the pollinator exclosures. Clearly the plants were self-pollinating somehow.

And here is the solution to the mystery! Where is the stigma? Its pretty much in the middle of the anthers. This one isn't quite mature yet, but instead of opening after growing far past the anthers (see the first picture), it will open either right in the anthers or ever so slightly beyond. McLaughlin Reserve, Lake County, CA.

Looking closely at the individuals in the lab revealed the reason for this mystery. Some plants, like the first picture in this post, had long styles, which projected the stigma far past the anthers. Others, like the one above, had short styles and the stigma was amidst, or ever so slightly past the anthers. This proximity (I think) allows the plant to self pollinating either directly, or with the slightest bit of wind or insect movement (the "self-pollinating" morph. In the lab, more than half the plants developed into the self-pollinating morph, and while I hadn't noted it during the season, I was able to go back to the hundreds of pictures I took and found pictures of it in the field. Strangely, they are not in the same proportion - my pictures are primarily of the "normal" variety - which accords with the one paper on the plant, as well as descriptions. I then examined the specimens in the herbarium, all of which were the "normal" morph (and purple, with patterned lower lips). Whether the lab creates the right environment for this morph to develop (whether there is a genetic propensity for it, or it is somewhat environmentally-driven) is unknown now, but I am working on it. Jenny Van Wyk - another grad student at Davis and extremely knowledgeable plant reproductive biologist - have quantified the differences between these morphs and found some really interesting correlates.

Flowers of the two morphs (self-pollinating, top; normal, below), at the same scale (lower lip broken in lower photo). 

Preliminarily - and our sample size is low as of now - the self-pollinating morph has larger flowers (corolla length, display height, style length), produces more pollen (300x more!) and has more, but more dilute, nectar. There is variability within morph, but so far, each plant has fit into one of the two morphs easily. How much this is an artifact of the laboratory setting is unclear, but photos of the self-pollinating morph and the pollinator-excluded plants producing seed point to something interesting happening in the field. Right now we are focused on the laboratory aspect, but we are considering experiments and observational data to be performed/gathered this upcoming year. We'd love to hear what anyone thinks of the system and interesting questions we can ask with it!

I'll have some photos and interesting observations from my three-week trip to Chile soon, too. Lots of interesting botany, entomology and birdwatching (condors!).

Germination of Abronia, a new trick

Abronia, sand verbena, is a cool genus of an odd plant family - the Nytaginaceae "four o'clock family" - that has a number of members in coastal and desert western North America. Growing it is a pain; I've talked to now about a half dozen people who've said they gave up.

Pretty flowers reminiscent of garden Lantana, but not closely related!

Rick Karban and I are doing a project at Bodega on Abronia latifolia and I thought it'd be nice to have some in the lab for a future experiment. I poked about and found that others had some success using various methods: cold stratification, scarification with sandpaper, a ripe apple as a source of ethylene. Others just expressed frustration. I tried the apple, sandpaper and cold stratification without any success.

The cool, weird mine of Lithariapteryx abroniaeella, a mining caterpillar common on A. latifolia at Bodega.

Fortunately, I found a trick that's given me greater than >75% germination. Unfortunately, it is not possible on a large scale (i.e. a couple dozen plants are fine, a couple hundred would be maddening). Abronia seeds come wrapped in an anthocarp. Remove that - most will be empty, but 25-50% will have a seed. Take the seeds and soak them in DI water for a few hours - I generally do this from the morning to the afternoon, so about 4 hours, but I forgot about one batch and left them in for 24 and they were fine. Now the tricky part. Take a pair of fine tipped forceps and carefully remove the entire seed coat. In soaked seeds it will just come off. Be very careful not to damage the seed. Don't worry though, you'll get the hang of it after a few. Then place on wetted blotting paper under a light - don't allow it to dry out. In three or four days, the leaves will be green and roots will have started forming and you can transplant into well-drained soil.

A sand-verbena living up to its name. 

They grow slowly, but seem hearty (n.b. I've only had them alive for a month or so). I don't have seeds of any species besides A. latifolia, so I can't say it works for them, but I'd bet it does (and if anyone does have any, I'd love to get ahold of some). Do let me know if you try!

Cutting up an old friend: the life and times of a suburban tree.

I'm back in the northeast for a bit. My parents had to have an old white oak (Quercus alba) removed from our yard, as it hung over the driveway and the house and dropped a big branch on my dad's car last year. The two trunks stood less than a meter from the driveway and it was shaded on one side by tall white pines (Pinus strobus), the other side by the house and sheltered an understory of pokeweed and poison ivy. Notably, in the mid-90's, I spent considerable time in a rickety treehouse between the two trunks. More recently, I'd watch migrant warblers in the spring and fall and chickadees, nuthatches and creepers in the fall on it - for awhile a suet feeder hung which we watched from the kitchen windows.

The author in the tree "house", 1993. The author is 5, the tree ~ 90.

I only know the history of the tree since ~1991 (and those early years, I don't actually remember). But the removal of the tree offered the opportunity to see its history. What had it seen? How old is it? Did the building of a house/driveway next to it cause it any harm? It was obvious from the start that this "tree" started as two individual oaks, which then joined (inosculated is apparently the correct term for this - see some striking examples here)

Days before its demise. 2014. 

Chainsaw marks had made reading the rings difficult, so I sanded a line on each side of the stump and tried to make out the rings.

In progress. The far right side of this photo actually is asphalt, though hidden under debris - the tree was only 

What I found, indicated that I needed to do more work. A set of really thin lines occurred in the early 1970's on one trunk and late 1970's on the other. So clearly I couldn't delineate them accurately. What caused those really lean years, I figured initially must have been the construction of the house and the building of the asphalt driveway practically on the tree.

Something is wrong here! Blow this up to see better. 

Therefore, my dad and I planed the whole stump (until the planer broke, ~50% done). This allowed us to also see clearly the junction of the two trees.

So what caused that big set of lean years, now correctly dated as 1976-1982? The house was built in 1982... the driveway a few years later - that certainly didn't cause the lean years as I had initially hypothesized. So what happened?

Now, a couple hours later, they line up!

Let's construct the history of the tree. Because the planer broke before I could get to the very center, I actually don't have good resolution the first couple years. The left trunk (father from the driveway), looks to have put down its first ring in ~1900, the other a few years later, ~1904. What was happening in Wrentham at that time? In 1870, Wrentham had 2202 people, 1900 - 2720 and 1910 - only 1748 people. I suspect that loss of populations corresponded with the degradation of farmland, and increased exports of agriculture from the great plains (at least this is what I remember from a New England environmental history course in college). A large dairy farm up the road - Birchwold Farm, now a great conservation area (best place to find black racers around Wrentham) - folded at about the same time.

Had the tree been paying attention to world events, it might have noticed these (a smattering of things I could think of
no rhyme or reason to them). 

So these trees took root - not a meter apart, in the first decade of the century or slightly before on what was likely fallow farmland reverting to mixed deciduous forest - what most of New England has gone through at one point or another. They then grew steadily through the next few decades until 1944-1946, when growth slowed to an inchworm's pace for both stems. Many factors could slow a tree's growth in this way including drought, this hurricane, an abnormally short growing season, an ice storm (leading to loss of healthy limbs), or insect outbreaks, to name but a few. Which ones contributed to this, I don't know, nor can I find any information on anything abnormal happening in that period (but do let me know if you do!).

The next big hit the trees took was in the late 1970's - 1980's. At first glance, the cause is obvious: the two trees hit. When this happened, they seem to have put much effort into wood building at the junction - perhaps as a form of competition - as the lines are quite wide at the junction, but get infinitesimally small around the other 3/4 of the trunk. This period is why I didn't get equal counts from the two trees. Even with a hand lens, I couldn't make out the lines accurately on the first area I sanded. In the center of the junction a crack is visible - this is where vascular tissue never grew, I suspect the soft material in the center is old, compacted outer layers of bark which had nowhere to go when the fusion happened around them.

A branch with some sort of rot - I presume fungal. 

But I suspect that is not the whole story. 1981 was the worst year for both trees - they put on pretty negligible growth even in the usually fat junction area. I suspect this was due to the worst ever infestation of gypsy moths, an invasive caterpillar which defoliated almost 13 million acres of oak and other deciduous trees in this area that year. Because these caterpillars can almost entirely defoliate a tree, that tree won't have much photosynthetic tissue that season and will suffer reduced growth, and if this repeats, as another invasive, the winter moth, often does, it can kill trees.

Since that time, the trees had been growing steadily... gaining a tree "house" in 1993 and losing a limb here or there in a storm, possibly pre-weakened branches because of fungal infection or physical injury.

Two days of this before the fun (the tree rings and research) began.

Now that my parent's house has a wood-burning stove, a tree will have to be taken out every year or so. Will that upset the ecology of the area? It probably won't have a huge effect, but it may midly benefit it by creating a rare microhabitat in the area. Because our neighborhood is suburban, most snags (dead trees) are removed quickly and probably not left on the ground. The stumps and leftover wood which could not be split and used as firewood will lie around, food for insects (perhaps horntails!) or fungi, which will of course attract other insects or birds and continue on up. And for curiousity's sake, the next tree will give us a better idea of what happened in 1944-1946 and the 1970's and 1980's. If we see that the 70's and 80's cruised by without a single hitch, the reduced growth in these trees is probably competitively-caused. If 1981 was a bad year for the new tree - gypsy moths are the likely culprit. If the whole period is bad for the other tree as well, then the microclimate may have been unfavorable. Perhaps before the house was built construction or other land use change occurred, which was unfavorable to the trees.

While it is a little sad to see an old friend go, it was necessary for safety of the house, cars and inhabitants, useful for heating, and the history was exciting and informative. Next time you see a tree down, check it out - much can be learned from it!

ESA2014 preview: External chemical defenses in plants

I'll be presenting this at 1:30 PM on Wednesday in the Plant-Insect Interactions II session in the Compagno room. Fellow GGE student and collaborator Billy Krimmel will follow soon after with an interesting talk on tarweeds. 

I've been studying chenopods and their salt bladder system - which is important both physiologically and defensively for the plant - for awhile and with some gentle nudging from my committee, I've been trying to place the chenopod system into a broader context. Namely, what ecologically and evolutionarily differs between a plant which sequesters its chemical defenses (alkaloids, tannins, etc.) in its tissues and one which secretes them onto plant surfaces?

Glandular trichomes (secretory and non-secretory) cover the surfaces of Trichostema laxum.

Coming from New England, where plants with copious exudates are less common, the summer in California is a bonanza of sticky, oily, slimy (!) and otherwise exudate-covered plants. Is this pattern driven by rainfall? Many of these species have congeners elsewhere without copious exudates (e.g. Trichostema, Lessingia, etc.), which begs the question: are exudates effective defenses only in arid environments? Are the defenses liable to environmental removal?

I therefore set up a series of experiments examining these questions. In one, I simulated rain on individuals in a population of Atriplex rosea - a chenopod with defensive exudates - while holding other individuals as controls and rainfall controls (which received water at the base, not on the leaves) and assessed herbivory at the end of the season. Perhaps unsurprisingly, I found a significant increase in herbivory in the group which received rainfall, suggesting that instead of helping these arid, water-starved plants, the rainfall and subsequent removal of exudates (which are entirely water-soluble in A. rosea) actually increased its susceptibility to herbivores.

Chenopods with external defenses (Atriplex prostrata and rosea) and without (Chenopodiastrum murale) at my field site.

Come to my talk to hear more!