Author Archives: George Rogers

This morning John and George pondered the ways of lichens in Halpatioke Park in Stuart, Florida.   There’s always much to learn and say about these biological  curiosities.  First we’ll knock off the “Botany 101” basic lichen facts you could find all over the internet, then attempt something more off the beaten path.

A branched “fruticose” lichen, by John Bradford.

LICHENS 101

• A lichen is a symbiotic union between a fungus and one or more algae species, or sometimes cyanobacteria, living together as one.
• Lichens are not all related to each other. They evolved many times.
• Lichens favor extreme habitats such as rocks, concrete, sand, and especially tree bark.
• Lichens, when dry, go into suspended animation, and come to life when moist.
• Lichens exhibit three different body forms:  one form resembles paint, one form resembles a crinkled leaf or fried bacon, and the third form is branched and shrubby.  They sell the last-mentioned as shrubs for model railroads and dollhouses.
• Because lichens are two-species species, their reproduction is a coordination problem.  Most lichen reproduction is thought to be tiny clonal fragments where the fungus and alga elope together, although the fungi sometimes form spore-making organs.
• Lichens come in beautiful colors stolen and applied as lichen fabric dyes.
• Some lichens suppress surrounding competing vegetation.

By JB

Okay then we’ve got the lichen picture.  Now for the weirder parts:

Weird thing 1.  Most lichens grow as irregular shapes, or shields, or roundish patches.   They grow in ways consistent with starting from a point and growing outward like ripples on a pond although far more irregular.  But  today John and I noticed something very different:  a tendency for multiple different types of lichens to appear as horizontal bands, partial belts,  across the oak tree trunks, especially laurel oaks.

Lichens often appear as horizontal band aids.

The way that comes about may be sort of obvious but then again, not.   The obvious part is knowing that the tree trunk expands in girth like my waistline after too many donuts.   It stretches horizontally but not vertically.   If you put a roundish paint spot on a tree and let it grow 10 years the dot will be stretched laterally into a horizontal bandaid.  Strtching ought to make it fragmented and thein.     If two kids take a ball of taffee and pull, it will of course get longer and thinner, or may break.  So here is the surprise…when a thickening tree taffee-stretches a lichen laterally,  it usually does not thin or fragment, even if stretched many times its original diameter.  The stretched part seems to self-heal and re-thicken, even filling in the cracks if fragmentation is apparent.   It compensates for the stretching, you might say adapted to its preordained strain.   If you’re going to dwell on a tree trunk, get ready to be stretched.  You don’t see such banded lichens on concrete, or on palm trunks,  which have minimal expansion in girth.

BY JB

Weird thing 2 is the extreme sensitivity of lichens to air pollution.  There they sit on a tree with no roots and no protection, exposed to every breeze and absorbing every drop of mist and rain,  as well as everything carried in that wind, mist, and rain, including nutrients,  radioactivity, and toxic pollutants.   That tendency favors some lichens, for example, if the air pollution is rich in nitrogen compounds, certain lichens may say, “thank you for the free fertilizer.”   Most often though, it seems to me, air pollution diminishes lichen coverage and diversity.   The most obvious sources of air pollution around here are highways, and the pollution-effect was apparent today along ever-busy four-lane Indiantown Rd. in Jupiter.   Adjacent to the road is a bald cypress swamp extending from the edge of the pavement back maybe half a mile or so.     The lichen diversity and coverage is conspicuously diminished with proximity to the traffic.

The case of the disappearing lichen.  The tree(s) in the foreground far from the busy road are rich in light-colored lichens.    Follow your eye out to the road…the darker trees near the road (such as those in front of the black car, or on the far left) have few or none.  All the trees are bald or pond cypress.

Quercus myrtifolia

Fagaceae

John and I sought ecological enlightenment today among the oaks of Halpatioke Park in Stuart, Florida, the home of several oak species, from massive gnarled Live Oaks to knee-high “Dwarf Live Oaks.”   In-between, Myrtle Oak, is the center of today‘s attempt to interpret little things.  Around here, Myrtle  Oak is a a scrub species, usually shrubby or a small tree, potentially fairly good-sized but rarely so..  Its overall range is most of Florida and the coastal regions of nearby states.   This species harbors mites.

This and the following three photos by John Bradford.  All Myrtle Oak.

Male flowers in catkins.

Mites are so small we can scarcely see them, even with magnifiers, which might be why mite-plant relationships are mite-y under-studied.  Gardeners may think of mites as pests, which is true enough, and some cause weird growth irregularities in their botanical hosts, such as bizarrely deformed fruit on Black Olive trees.   But that is not the whole truth and nothing but the truth.  Suppose you’re a plant species plagued by herbivorous mites, what is the best protection?

Predatory mites of course, fight fire with fire, and it turns out that many plant species provide homes for their guardian predators, which is not to say every aspect of mite-plant symbiosis is understood.  Some good mites eat fungi.  Speculators have speculated that mites may benefit host plants by providing a foliar feeding of their nitrogenous waste.   I dunno about that, but it is interesting that the Myrtle Oak domatia seem to fill up with organic matter.

Myrtle Oak hairy armpit domatia on underside of leaf where veins join.

The same with apparent accumulation of organic matter.  Looking lived-in.

Whether or not the little guys make enough manure to matter, plants do provide fine accommodations for “good” mites.  Such “domatia” (think domicile) come in three forms:  leaf pits (as in white mangroves and in buttonwoods), caves under veins (as in grapes), and furry bushes made of tangled plant hairs  where leaf veins join, as in today’s oak and others.  The domatia in Myrtle Oak are conspicuous beneath the leaf.

If you flip over a Myrtle Oak leaf and spy with a hand lens (very) patiently you can spot tiny mites on the prowl, sometimes flushed from a domatium like a bunny from a bush.

CLICK HERE for a quick glimpse of a Myrtle Oak mite on the move.

Those who study mites have found that even “bad” mites have domatia too.   Maybe they merely stole them, but other observers have a more interesting explanation…that to sustain good predatory mites the plant has to offer edible “bad” mites to pay the guardians in red meat.   The plant may adaptively tolerate and even shelter prey for the hunters.

Hibiscus furcellatus

(Hibiscus is an ancient name.  Furcellatus means forked, as we shall discuss)

Malvaceae

Monsoon deluges and fascinating meetings combined to complicate botany fieldtrips this week, although today’s sunny skies lured me to the Delaware Scrub in Jupiter, Florida, into the midst of an old friend in full bloom, full fruit, full bud, and  full cooties.  Today’s blog is a bug-centric revisit to Linden-Leaf Hibiscus.

First and foremost, this is an ant plant.   The buds, flowers, and pods have big showy nectar glands on the outside.   These draw ants by the gazillions, who jostle rudely for a moment at the trough.  Presumably the ants protect the hibiscus from pests out to steal nectar, seeds, or other precious floral commodities.

Space mouse?  No–Hibiscus bud with two big nectaries, and with the forks showing.

It wasn’t just ants hanging around.  There came flies, ladybugs, camouflaged spider, and the orange creeps featured below.

The weird thing about this Hibiscus species is a ring of stiff forks curving up around the flower and fruit base.  Technically the forks are bractlets, that is, drastically modified leaves at the floral base.  Other Hibiscus have bractlets too, but in H. furcellatus they are oversized, stiff, and forked like a snake’s tongue.  They look like they could dispense nectar, but the visiting insects reject that notion.

Perhaps they are protective.  When the blossom is open the forks don’t seem to block anything, but earlier, they form a tight cage around the precious expanding bud.  The two tines on the fork spread across the top of the bud to thwart attack from above.   No beast can feast on that big tasty encaged bud.  Closed until we say so!

Fork cage around bud, orange.  Younger one to the left.

The cage goes through a yellow or yellow-orange phase.   I don’t know if that is significant, although maybe the colorful “false fruit” draws a bird’s eye long enough for the birds  gobble suspicious burglars loitering on the bud.  Just a guess.

The insect posse today included Cotton Stainer Insects boosting seeds from the ripe seedpods.  Cotton Stainers owe their name to their damage to cotton flower heads, and cotton is a close relative of Hibiscus.  All in the family,  although the little orange pirates abuse non-Hibiscus relatives  too.   The bugs poke their proboscis into seeds almost as big as they are.

Watch the Cotton Stainers conduct a raid CLICK

Likewise orange but not vegetarians, assassin bugs too were there to lunch upon some of the Hibiscus visitors.