Lichen are a classic example of symbiosis. A fungus teams up with an algae or a cyanobacteria, the fungus use their digestive powers to extract nutrients from just about anything while also creating a nice home for the algae or cyanobacteria to turn sunlight into energy. They give and take, and together they can thrive in places where little else survives. Well, it turns out there is another player. Recent research shows that many lichens also contain a third symbiont, a unicellular yeast! The yeast produces an acid that may protect the whole threesome from attack by other microbes. (See this great article about how natural history observations led to this discovery). As much as we often focus on clashes in nature, the predator and prey, the host and parasite, the fierce competitors, it’s easy to forget that the origins of eukaryotic life (the group of organisms that contains all plants, animals, fungi) was made possible by a symbiosis between two different types of bacteria. And studies using new molecular tools are increasingly finding elaborate webs of microbial symbioses across the tree of life, and not a single bird, flower, or beetle could survive without these complex relationships. I honor of these new discoveries, here are some beautiful products of lichenous partnerships I’ve photographed in Michigan, Ontario, South Carolina, and Arizona:
Recently Chad Zirbel posted a photo of a stunning orange lily that I just had to see for myself. He directed me to a nearby high-quality prairie fen. This habitat is flooded with calcium-rich groundwater which selects for a unique community of plants, many of which are adapted to this specific habitat.
The spongy peat and dense communities of sedges where unlike anything I’d seen before.
I got a bit lost though before I made it to the fen, and when I was wandering around the surrounding forest I found this incredible fungus. It looks a lot like the bleeding-tooth fungus (Hydnellum peckii), but with clear secretions instead of red. I suspect this is a related species but I’m not sure. It was visited by lots of small flies and wasps, I like thinking of what this oozing structure would be like to a 2 mm long insect.
I also found this spiky tachinid fly calming visiting flowers, a much more charming place to hang out than the innards of some other animal where it came from. Most tachinids are internal parasites and judging by the size of this fly I’d guess it came out of a vertebrate of some sort.
I found the Michigan Lily (Lilium michiganense)! This species is actually found throughout much of the midwest and southern US and is commonly cultivated. Still, it was a stunning sight to see this one erupting out of the dense mat of prairie grasses.
Swamp milkweed (Asclepias incarnata) is the water-loving cousin of the common milkweed that is commonly seen along roadsides.
Black-eyed Susan (Rudbeckia hirta) is not really a wetland plant but it seemed to be doing just fine in this soggy habitat. There were many more plants that were surely more rare and unique to this habitat but I couldn’t help but be attracted to the ones with the showy flowers. If I had more natural history knowledge of the species I am sure I would have appreciated the community more.
There was one wetland specialist that I recognized though, purple pitcherplant (Sarracenia purpurea). They only grow in highly alkaline or acid environments, places where most plants have trouble acquiring enough nutrients. They make up for it by feasting on insects that are lured into their water-filled leaves.
All plants are involved in an evolutionary battle with herbivores, where plants evolve various traits that deter herbivores and then herbivores evolve the ability to eat them again. This evolutionary struggle has raged on for over 400 millions years, contributing to the massive diversification of both plants and the wide range of herbivores that eat them. So much so that plants and herbivores make up a majority of the diversity of life on earth, at least among organisms bigger than microbes. In some cases this evolutionary struggle results in plants and herbivores that have all sorts of fascinating traits and behaviors.
Milkweeds (genus Asclepias) evolved an impressive array of defenses against herbivores, including toxic cardenolides that stop insects’ hearts, gooey latex which gums up their mouths, and obnoxious hairs which make munching through leaves a hassle. These defenses work really well because most insects don’t even bother trying to eat milkweeds at all. But, unfortunately for the milkweeds, and fortunately for fans of really awesome insects, there are a bunch of herbivores from all across the insect tree of life that evolved to feed on milkweeds and only milkweeds, and they’ve gotten really good at it. Most of them are brightly colored to warn predators of their toxicity (called aposematic coloration). And they are toxic because, amazingly, they can tolerate the toxic cardenolides in the milkweeds and then incorporate them into their tissues. An exceptionally clever adaptation that turns a plant’s defense into a tool to deter predators.
In a recent walk around Sleepy Hallow State Park outside of Lansing, Michigan, I saw a bunch of these milkweed specialist. First is a one we are all familiar with, the caterpillar of the monarch butterfly:
The fruits of some of the milkweeds were coated with large milkweed bugs (Oncopeltus fasciatus):
Then I found one of my favorites, the swamp milkweed beetle (Labidomera clivicollis):
There are two aphid species that commonly feed on milkweeds, the bright yellow oleander aphid (Aphis nerii), which is actually and introduced species in North America, and the more drab-colored milkweed aphid (Aphis asclepiadis). Both are commonly tended by ants who collect sugary honeydew they excrete and then, in some cases, protect them from predators.
I found one more caterpillar that feeds on milkweed, the delightfully fuzzy milkweed tussock caterpillar (Euchaetes egle):
As the sun set I was excited that I found so many fascinating and photogenic animals during a short walk near the lake.
Thinking about the perennial struggle between plants and herbivores reminds me of the last line in Darwin’s Origin of Species “from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved”, which so succinctly summarizes how fulfilling it is to carefully observe, understand, and appreciate the marvelous diversity of life which surrounds us.
Here are three looks at a stunning jumping spider I found on a tall reed near the Savannah River in South Carolina. First with a white background showing the huge fuzzy forelegs and red-spotted abdomen, then a close-up portrait with the metallic green chelicerae, then a wide angle macro shot with a horse pasture, trees, and rainbow in the background :)
I found some insect eggs on a basswood (Tilia sp.) tree. I brought them home and when they hatched I learned they were shield bugs (Pentatomoidea). The photos below span over 3 days.
I found abundant signs of life and death in a recent walk through the woods
Jumping spider eating a midge
Assassin bugs stalking
Carpenter ants dragging a still living fly back to their colony
Blow fly waiting for something to die
Squeaks from a hollow tree trunk
Raccoon cubs squabbling and breastfeedingAnd skunk cabbage emerging after a long winter
Expansive live oaks dripping with spanish moss–a quintessential scene of the southeastern United States.
Contrary to the common name they are not actually a moss, rather a flowering plants in the Bromeliad family. They can reproduce from seed or by chunks moved by wind or birds, who use them for nest building. Their arboreal tangles provide important habitat for a wide diversity of arthropods including a highly specialized jumping spider which appears to only live in spanish moss.
Spanish moss (Tillandsia usneoides) live a pretty strange life style, for a plant. As “air plants” they spend their whole lives draped over tree branches far from anything resembling soil. So despite inhabiting only wet semi-tropical regions they are at serious risk of desiccation. To combat this they have a specialized water efficient form of photosynthesis called CAM Photosynthesis. This is the same trick that cacti use to conserve water. Up in the trees spanish moss must also find nutrients. Instead of having roots their long slender leaves are covered in scaly hairs that can absorb nutrients and water. Nutrients comes through rainwater and dust and also from the trees they inhabit. They are not stealers like parasitic mistletoe, rather, they soak up what washes out of tree bark and leaves. This source of nutrients is important enough that trees which leach few nutrients do not provide suitable habitat for spanish moss.
Spanish moss is also quite useful to humans. Up until the advent of synthetic fibers spanish moss was harvested from the ground after storms or directly from trees, then heaped into piles to decompose for a few weeks leaving just the dark elastic cords that make up the plants’ center. These were dried and cleaned, then used to stuff mattresses, car seats, or spun into rope, just to name a few uses. Spanish moss is also potentially useful as a simple way to monitor air pollution. Because they absorb particulates from the air which then accumulate in their tissues, measuring levels of toxic substances like Mercury in spanish moss may provide an accurate measure of air pollution in the area.
The South provides many natural history gems, but the ones hanging from the trees are among my favorites.
Photos taken on Sapelo Island, Georgia