Today we have photos by Friend of the Site Greg Mayer, who sent these in when the photo well was about to run dry. Greg’s captions are indented, and you can enlarge the photos by clicking on them. This is part 1 of 2.
Southern trees: what’s on them?
One of the things you notice in heading south are the changes in the plants and animals you see. One of the most striking things you notice is the abundance of epiphytes– plants growing on plants– which are much commoner in the southern US than in the north. Epiphytes of all sorts, and often large ones– bromeliads, vines, strangler figs, etc.– are a typical characteristic of tropical forests, but there are a fair number in subtropical Florida. The following pictures are from Jacksonville, in northern Florida.
Among the first “southern” things you notice, even while driving, is Spanish moss (Tillandsia usneoides, in the bromeliad family) dripping off of trees; while driving south I first noticed it in southern Georgia. Unfortunately, there were none where I walked around to take these photos! But there were other air plants– which is what Spanish moss is. Here’s one, another species of Tillandsia, in a lime tree (Citrus sp.).
Air plants have no roots, consisting instead of twisted leaves clinging to other plants and surfaces; they get water and nutrients from the air and the rain. They are not parasitical in the usual sense– they don’t “feed” upon their host– but they are what are known as “support parasites”: their host holds them up, and gets them exposed to sunlight. Some support parasites can be inimical to the host, weighing it down and intercepting sunlight and rain; a friend here in Florida told me that a lot of Spanish moss will kill a tree.
Though the lime tree had no Spanish moss, it was not doing well, and epiphytes (mostly lichens) were abundant on the moribund parts of the tree; compare the left side, with leaves, vs. the nearly barren right side.
A live oak (Quercus sp., I think) with lots of epiphytes was also not doing well. Notice the few bunches of live leaves higher in the tree; the ground below it was covered with broken-off, epiphyte-encrusted, branches. [Edit by GCM: The clumps of live leaves in the tree below are probably mistletoe, an epiphytic parasite, not leaves of the oak. Also the oak is probably not a live oak. See the comments for further details. My thanks to readers Dennis Howard Schneider, j a higginbotham, bruce morgan, and debi!]
The most common epiphytes here are lichens. I won’t even venture an opinion on what species occur here, but there were differences in growth form indicating to me that several species were present. Here’s a wispy kind I found on branches.
Nearby on the same branches could be found a lichen with a more “structured” form, with “chimneys”.
Lichens also grew on trunks; this is the same live oak as shown above.
A common sight in Florida is a palm whose trunk is covered with ferns. The ferns on this one are modestly dense– I’ve seen much denser. I think the tree is one of the twelve native palms of Florida– perhaps cabbage palm. (IDs from readers on this or other plants would be appreciated!)
On this palm, moss is growing on the trunk, and we can see some epiphytic vines dangling.
Finally, neither trees nor epiphytes, and, in fact, not even plants, a couple of fungi on the lawn.
I visited that area before and the gestalt really comes through here – very handy set to learn the biology behind it all.
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“[…] epiphytes– plants growing on plants– which are much commoner in the southern US than in the north.”
Is that simply due to longer freezing conditions in the north – the epiphytes are too finely structured to take it?
Not all epiphytes are delicate– there are huge epiphytic vines and strangler figs in the tropics. The greater number of epiphytic species as you travel south seems to be part of the general increase in species richness in the tropics– a phenomenon known as the latitudinal gradient in species diversity. That’s a huge field of inquiry. The following review articles (which I think are open access by now) will give you some flavor of the many ideas about and studies of the phenomenon.
Pianka (1966) https://www.jstor.org/stable/2459377
Rohde (1992) https://www.jstor.org/stable/3545569
Willig, Kaufman & Stevens (2003) https://www.jstor.org/stable/30033777
GCM
Latitudinal gradient… Cool, thanks!
I think the clumps on the oaks are mistletoe (Arceuthobium). When I lived in Florida I picked some for our Xmas party. They are a partial parasite I believe. In the 1970s I went with a friend and collected Spanish moss from trees in a swamp in New Jersey, which I wasn’t expecting. I have also hiked in Vermont and on the west side of Dorset Peak at the top the trees are covered with various lichens, mosses and ferns. It looked like the Hoh rainforest on the Olympic Peninsula. And it was only here that it was so moist, as we were in a dry spell. You can see lichens etc all over Vt, but this was exceptional.
Yes, it is possible the clumps of leaves up in the oak are mistletoe. There were occasional green leaves of the oak low down where I could see them, so I assumed the green leaves further up were more oak leaves. Unfortunately, I didn’t train my binoculars or zoom lens on them!
If you have specimens or good photos of Spanish moss from New Jersey, you should share them with an herbarium or botanist; Spanish moss is not known north of Virginia.
GCM
Thinking about this years later I thought it was odd. I wasn’t driving at the time so I am pretty sure it was NJ (coming from Staten Island, an afternoon ride). I brought the Spanish moss home and had it hanging in my room for a while. It looked like the pictures of Spanish moss.(Tillandsia usneoides) I was about 20 years old and doing a lot of Psychedelics. Just remember collecting a pitcher plant Sarracenia purpura at the same time.
Look like mistletoe clumps seen in Southern California. Failed to grow Spanish moss out here, way too dry presumably. Although my bald cypress (taxodium distichum) is doing well.
https://i.imgur.com/zRXl2qI.png
https://www.nj.gov/pinelands/about/events/Howe_PSC_LichenEcology_14Mar2015_3.pdf
Thank you, Greg!
Thank you! Fascinating information and great photos. It’s always wonderful to learn something. Much appreciated!
Lichens and mosses are also good air quality indicators, which may be why some will not grow near urban or suburban areas. There are plenty of lichens in cities, but different and lower species diversity than those seen in the wilderness.
Lots of oak types in Florida but live oaks aren’t deciduous, so that guy is not in good shape. Most are more branching as well. https://8billiontrees.com/trees/types-of-oak-trees-in-florida/
Who knew, we have a state lichen https://www.californialichens.org/state-lichen
That is not a live oak. It appears to be a “laurel” oak Quercus hemisphaerica, or possible Q laurifolia. Mistletoe is relatively uncommon in laurel oaks, but that is what the epiphytes appear to be. In the Jax area mistletoe is especially common on pecan trees.
Thanks!
Thanks for the photos and commentary, Greg. I learn so much from WEIT.
If I were passing that oak tree (shot 3) I’d think that was mistletoe but mistletoe is a parasite, correct?
This site is such fun! I learn something every time. The remarkable variety of epiphytes in the US is very enviable.
If I may be permitted a personal anecdote: there is plenty of mistletoe in the UK, but it’s mostly inaccessible high up in trees (oaks, yes, but others too). Traditionalists who want some at Christmas usually have to buy it at excessive cost.
I live near an area where there are lots of apple orchards. One tree, in one orchard, has been colonised by a healthy growth of mistletoe. The landowner has generously not cut it down and burnt it, but left it for foragers to cut a couple of sprigs in December. I’ve done that for the past 6 or 7 years. Long may both the tree and the mistletoe live!
Terrific post! Thanks Greg, great learnings.
Do the same species of lichen grow on all continents? Lichens, outwardly identical to the ones pictured above, grow in the Southwest of Western Australia. I presume lichens are an extremely ancient plant, presumably evolving before the continents drifted apart?