Tuesday, August 26, 2014

Dogbane beetle

What: The end of summer is the time of the insects! I've been watching the dogbane sprout up new shoots, flower, and finally go to seed over the past three months. Because they're a particularly noxious plant (toxic to almost all vertebrates and many vertebrates - they're related to milkweed which is infamous for its implications for monarch caterpillars), they have insects specialized to feeding on them. Similarly, koalas, which exclusively eat the poisonous leaves of eucalyptus, is specialized to eat one and only one thing. The koala's evolutionary trick was to find a way around the defenses of something so toxic that doesn't have any other predators and then exploit that weakness. So too with the dogbane beetle (Chrysochus auratus). Dogbane is a notorious weed in the midwest, largely because it doesn't have any natural pests that control its population.

On the photo at the bottom, I had actually moved it to a milkweed leaf right next to the dogbane where I found it. There were a number of milkweed aphids on the underside. Once the beetle had crawled to the underside of the leaf it kept stomping its feet and then would fly a few inches to a new spot. It seemed really perturbed by the significantly smaller beetles. After about 30 seconds of "torment" it flew to another leaf.

Sunday, August 3, 2014


Extensive patch of shining club-moss

What: While out on the Long Trail this week with the Crow's Path Adventurers camp (photos here), I was able to return to a patch of shining club-moss (Huperzia lucidula) I had noticed last weekend while scouting with Sam. The patch is located at the turn off to Silent Cliff, just north of Middlebury Gap. It's been about 5 years since I looked more intimately at the club-mosses (family Lycopodiaceae), and I was struck by the strong patchiness of the plant - some of the patches were a dense carpet of up to about a half acre, and it was a rare site along the trail to see any growing by themselves. I have in my head images of little cones sprouting from the tips of clubmosses, and was delighted that, upon closer inspection, there were no cones at all, but a new mysterious type of leaf.

Flattened gemmae, or vegetative propagules, that act in the same way as leaves on jade plants

Ecological notes: Turns out members of the Lycopodiaceae genus Huperzia lack the cones, or strobili. Plants with this strong of a predilection for patchiness typically have vegetative reproduction (e.g. spread by underground roots like staghorn sumacs), really heavy seeds that don't disperse terribly far, seeds that get dispersed by non-volant insects (like trilliums and ants), or extremely narrow and extreme habitat requirements (like cattails in marshes or Green Mountain maidenhair fern in serpentine outcrops).

Each band of spores = 1 yr of growth
Shining club-mosses lack creeping rhizomes/underground stems, which other clubmosses (e.g. Lycopodium spp.) spread laterally out along or just beneath the surface of the soil, so they need to accomplish this in another way. In this case, the gemmae, those flat, paddle-like leaves (they almost look like elm seeds) are vegetative propagules that fall off the parent plant. They don't have far to fall and so aren't carried more than a few centimeters at most from the parent plant. The new plant is a genetic clone of the parent and in time will create its own gemmae (always at the tips of new growth).

Also, unlike similar relatives in the genus Lycopodium, whose sporangia (spore clusters) are borne on cones that reach up into the air waiting to be whisked away by wind, Huperzia have sporangia borne on leaf axils (the little notch where the leaf sprouts off the stem). In the photo to the right, these are the clusters of yellowish bean-shaped things running short segments up the stem. Each band of spores represents a single year of growth, giving some sense of maturity.

There is scant literature around the lifespan of shining clubmoss. A related species, Huperzia sa, can reportedly take 15-20 years just to reach maturity. So it appeared from my brief look into their world that wind dispersal doesn't play much of a role and their presence in large, thick patches indicates that they've been around for a long enough time for their vegetative parts to create dense mats. Maybe it's even an indicator of at least secondary growth.

Where: Unlike the other Huperzia sp. that we have in our state which grow on rocks, H. lucidulum grows on soils. Its preference for rich - yet acidic - moist soils under a hardwood or coniferous canopy make it a common denizen of higher elevation woodlands.