What the heck pollinates Centella?

Centella asiatica

Apiaceae (Carrot Family)

---

In the great big plant world, 250,000 flowering species, only a handful are known to be pollinated by ants.   Let’s guess:  ten species, probably too high.  That’s 0.00004 percent.  Do we have one of them here in PB County?   Maybe, maybe not.

Centella asiatica, sometimes called Pennywort, and sometimes called Gatu Kola, is an odd little wonder.   [Oops, that should be Gotu, see reader comment below.] It grows all around the tropical world, including around here in wet marshy places, although it tolerates seasonal drying.   It is one of those bioactive plants with a million historical and current medicinal and cosmetic uses, in many cultures.   (Careful,  there are toxins.) I’ve never been much interested in “medicinal plants,” so if that’s your interest, there are 100 websites with info on this species.   

How has a small creeping plant crept all over the hot-climate world?   Part of the answer is fragments.   If you take marsh soil and put it in a container nice and wet, up pop lots of baby Centellas.  A whole lot of them.   I don’t think that is from “seeds,” but rather rhizome pieces.  The reasons I don’t like “seeds” is that the flowers and fruits are rare.  I have the species growing at my home, and the babies are coming from tiny unplanted plant pieces.  That ability alone is mysterious.  How can the mud be full of ANYTHING that spawns baby Centellas every few inches?  Maybe it is magic.

To dig in deeper, the floral biology has been studied a little.  Biologist Asma Javaid and collaborators looked into it:   in pots, in  a garden, in Jammu, India.   (How does that relate to a Florida marsh?)    They found the plant to be largely self-pollinated. That I believe.  They also concluded ants are the insect pollinators to the limited extent there are insect pollinators.   But that sets off alarms:

1. See above. Ants pollination is EXTREMELY rare.

2. The results were based on potted plants in a garden.

3. Did the ants merely get on the flowers uselessly or worse, or did they actually pollinate?   In the Jammu study, flowers covered with bags produced more seeds than those open to pollination.  Maybe the ants visited the flowers in a bad way, stealing pollen or otherwise deleterious, and the bags protected the flowers from the ants?

The flowers are minute, not even ¼ inch in diameter,  held near ground level under foliage, maybe an inch in the air,  when you can find them which is not easy.   Find the flower in the photo below. (They are dead-center.)  

Find the flower

But being low does not necessarily = ants.   There are little flying insects, not to mention that pervasive self-pollination.   Today I sat on the soil in the Pine Glades Natural Area all soggy-assed for 24 minutes watching the Centella flowers to see if anything visited. Naw!  But who knows what 24 hours watching might discover.    Wherever and whenever the species originated (tropical Asia?), I’m sure Florida is distant in time and space  from the original pollination context.

So all in all, nobody knows the Florida Centella story.  Self-pollination is surely substantial.  So is super-sprouting from fragments, no doubt.  

I suspect that marsh animals, such as marsh ricerats,  help spread the fragments as they scurry around the marsh on their criss-crossing trails, which can channel flowing water able to relocate plant bits over long distances.   And that’s where it stands with Gatu Kola.   Does anything visit those tiny hidden lilac flowers here?  I’ll place a wager…not ants.

Animal (ricerat?) trail in Centella habitat marsh

 

The Big Yellow Bladderwort and its Little Purple Brother

---

Leafy Bladderwort (Utricularia foliosa), the big brother. Flowers yellow.

Purple Bladderwort (Utricularia purpurea), the little brother. Flowers purple.

Lentibulariaceae

---

Leafy bladderwort, the clouds are the trap-bearing leaves

Same species, red at the growing tip

What gets the most attention about bladderworts is their carnivorous bladders, but that’s all over the Internet already.  Also fancy are their flowers having moveable parts, but we’ll ignore all that and look at something utterly mundane, and unexplored.  I probably need to “get a life,” but I always find it interesting when a pair of closely related species grow together, such as myrtle oak and sand live oak in a scrub, or two tillandsias on a branch, or, today, leafy bladderwort and purple bladderwort in a water-filled ditch (which I waded for a few hundred yards).   By together, think intertangled, but only in certain places.    Both can grow—elsewhere—in large quantities.  But today we’re talking about togetherness.

Hand in hand

The reason why these joint situations interest me starts with “textbook” biology which teaches simplistically that when species are too similar they can’t coexist for long,  because one theoretically outcompetes the a other.  This town ain’t big enough for the two of us!”  True to a degree, but not the whole truth.  Look at it differently…if two unrelated (or related) species share an extreme habitat they both might have similar adaptations to tolerate that harsh habitat.  You know, different desert species can both be succulent and thorny.  OK, fair enough,  maybe it is a matter of degree in part. 

So here is another part to muddy the waters.   What if the two plants sharing a habitat are  related, let’s say two species of the same genus (two oaks, or two tillandsias, or two bladderworts). Close relatives are likely to have similar needs and abilities, so maybe sharing a habitat  comes from shared DNA.  Now we have a dilemma:  if related species are too similar and living together shouldn’t that  competition problem eliminate somebody?   TOO similar may be the key.   Studies have shown that when two species of the same genus occur jointly they are often not TOO closely related.   They might be both oaks but not particularly close within the circle of oaks.    Ditto for tillandsias and bladderworts.

So with leafy bladderwort and purple bladderwort, what are the facts of the case?

1. They are both in the bladderwort genus Utricularia.   Maybe their genetic relationship helps explain how for a long distance there are none, then, pow…they pop up together.  There’s something mysterious in that shared aquatic sweetspot that “bladderworts” (plural) seem to like: correct depth?  water movement?   acidity?   Maybe one modifies conditions that then favor itself and thus the other? Who knows?  (They do.) Or maybe one arrived by bird or hog or water entangled with the other.

2.  The fact that the two species hail from different corners of the Utricularia genus fits the narrative.   Sufficiently closely related to demand the exact same point along a waterway but sufficiently unrelated to each find its own way.

Both float and have filamentous leaves that collectively  make “poofy” clouds in the water that look like algae.  Leafy bladderwort is big and domineering,  and owns lots of  space, forming a filamentous “cloud”  in the water, overall the size of a human body or bigger.   By contrast, purple bladderwort makes a much smaller cloud with less-definite shape.    When it and leafy bladderwort go head-to-head the leafy brother grows right over the top of its purple relative.   But the “subordinate” purple bladderwort has its own little tricks.    Its flowering stalks poke up like periscopes right through the overlying leafy bladderwort.   No problem, thanks for the shade! (Thanks for the debris from above? Thanks for oxygenating the water? Thanks for removing other competitors? Thanks for attracting little victims I can trap in my bladders?)

Leafy bladderwort often tends to be a brighter green (except for red growing tips) , hinting at preference for brighter light .  By contrast, the purple bladderwort is dull-colored, not even particularly green,  and probably (though untested) tolerates deeper-darker or more turbid conditions.   It also grows “every which way,” so that it escapes the smothering leafy bladderwort, and can escape into shallower waters than its big brother.

Just another day in the marsh…

 

The Porous Pipewort and its Periphyton Partner

Ten-Angle Pipewort by John Bradford

South Florida seasonal depression marshescan be vast (or small) shallow basins seasonally flooded more or less a foot or so deep.  Being underwater part of the year, including now, and sun-baked dry in the spring, these flip-flop habitats are intense ecological filters where oddities survive.   Being a challenge to visit half the year, they are scarcely studied.  The animal kingdom is represented with many otters, an occasional wet feral hog, shy snipe, charming tiny fish (otter food?),  extreme ant nests, and long-distance wasps.  Speaking of otters, did you see the report of a man attacked by a rabid otter near Center St. in Jupiter back in September?  

Ten-Angle PW emersed.

Back to the plants.  Among the curiosities are two, and maybe sometimes a rare third,  species of Pipeworts, Eriocaulons.      Ten-Angle Pipewort is a large kinda-domineering clump-making species that grows with most of its spongy foliage in the air and sun above the grassy waters.   

Where the PWs grow

It’s funky little cousin, Flattened Pipework (E. compressum) is curiouser.   When the marsh is flooded for many months the leafy rosette, not only remains submerged, but its covering is not merely water.   The water supports a cloud of periphyton made of variable combinations of algae, blue-green “algae,” microbes,  filamentous floating bladderwort foliage,  and decaying organic debris all tangled into a stringymass.  Sometimes the cloud is essentially all a single species of algae, other times a crazy mix of things, some under a microscope shakin’ their bootys.   Studying periphyton composition, nutrient dynamics, and interactions with larger aquatic life could fill years of research, which remains overall in a primitive state, focused largely on pollution rather then overall marsh ecology.  The periphyton shades the marsh bottom, and as the water recedes becomes a green “paint” on the plants and exposed soil. Periphyton sequesters nutrients to the point of hiding phosphorus from water testing.   Some of the blue-green algae in the soup undoubtedly “fix” (capture) nitrogen.  A tangled web it weaves.  The point being that Flattened Pipewort has its submerged shaded leaves under all that, while it raises its flower stalk like a periscope.

Periscope

Wouldn’t it be fun now to bore you about Google-derived expertise on gas and nutrient exchange between the Pipewort and the periphyton.  That remains for future researchers with cool skills and fancy gear.    But we can peep curiously through a microscope at those submarine FPW leaves.   (When not submerged the plant can make more normal-looking leaves.)  The submerged foliage gets its main support from the water so, like many aquatic plants, the blades are delicate, thin, and translucent, especially toward in the broad basal portion.  They do have little “crossbars” visible in the photo.  Perhaps those help the leaves stay flat.  

Microscope view of submerged Flattened PW leaf. Dark bands are the “crossbars.” Note the pores.

What’s truly odd are “pores” where the leaf cell walls separate, making the blades resemble sponges.  The holes don’t fully extend to the outside. The covering must be extremely thin. The porosity would allow gas exchange among the cells all the way to their outside edges.   That’s handy in the drink where evaporation can’t pull water and nutrients through the plant, as practiced by land plants.    Water plants with filamentous leaves are sort of locked into an aquatic lifestyle (although some can make non-filamentous leaves in dry conditions).     Seems like Flattened Pipewort, by contrast, with its low  rosette passing through submerged and exposed conditions, in some habitats repeatedly,  has found a compromise.   I’ll bet as the habitat dries partially, or goes through periods of intermittent standing water and drying,  those sponge-pores close up allowing the leaves to either weather intermittent exposure, or to tide the plant over as  moisture diminishes until its “dry conditions” leaves take over. Just guessing on that though.

Flattened PW growing like a normal plant un-submerged. By JB.

 

Bird Week

Think I’ll start the year nice and easy. Last few days in this inter-holiday week every botanical site has been better as a bird site. Watching a hummingbird out the window as I type. So glad the preserved fragments of plant world provides big old trees for the owls, and wet marshes for the snipes. Happy new year. Don’t go on a snipe hunt.

 

Floating Bladderwort: Jellyfish of the Marsh

Utricularia inflata

Lentibulariaceae

photo by M. Shattock

That Bladderworts catch mini-prey using trigger-activated suction traps is a famous fact. More interesting in that connection is also, depending on the species and place,  algae live in the traps ,apparently more or less symbiotically.   But that’s old news.

Today, the Cypress Creek Natural Area marshland was holiday-decorated with little yellow candles drifting in the blustery winds on the shallow water: Floating Bladderwort it was.  The species is a pretty novelty here, but is expanding its range dramatically northward, in places becoming an invasive pest, such as in the Adirondacks.

Depression marshes are IMHO the most fascinating local habitats, so rich in odd lifeforms, all of them adapted to the seasonal submerged and then sunbaked conditions, as well as to the thick mat of algal/cyanobacterial periphyton.     At the present season much of the water is oh, say, 6 inches deep, containing the periphyton blanket.    Fun to see how the different plants cope with such conditions.   Emergents,  such as Tracy’s Beaksedge (Rhynchospora tracyi) and many others,  poke above the water surface. These species usually have puffy porous “aerenchyma” tissue to ventilate the submerged parts. Other plant species can live submerged for long periods, such as Flattened Pipewort (Eriocaulon compressum), in contrast with its larger relative Ten-Angle Pipewort (E. decangulare), which rises above the water.   Branched Hedgehyssop (Gratiola ramosa) can toggle:  floating freely when flooded, or rooting when times are dry.

Eriocaulon compressum with underwater leaves

But this is all just a lead-up back to Floating Bladderwort which thinks it is a jellyfish.  A jellyfish is free-floating with a floating (or not floating) disk having attached prey-catching tentacles.    So is Floating Bladderwort, in a sense.    The free-floating disk is the whorl of leaves, looking like horizontal wheel spokes.  Now look deeper:  its predatory “tentacles” dangle in the water below. 

Fills a niche in the shallow brown marsh similar to a jellyfish drifting happily in the deep blue sea.

 

Green Treefrog Has a Complicated Life

---

Hyla cinerea

---

My google book report. Spending much time these days in marshes, I’ve  become friendly with marshy critters from hogs to frogs.   Although not a plant, the Green Treefrog, being green and living in trees, is sufficiently planty for this botanical blog.   They conduct froggy business nocturnally, and pass the day crouched torpidly on vertical emergent marsh plants.  Their coloration adjusts within limits to the lightness or darkness of the background, raising the question: do the frogs prefer different species as perch sites?   Right place right time you can find a whole bunch of them.   Emergent vegetation over open water is a nice place to snooze:  camouflaged from angry birds and defended from ground attack by a moat.   Black racers enjoy a tasty frog, and preliminary indication suggests the GTF to have some resistance to pygmy rattlesnake venom.    No doubt that open water below the perch  helps with temperature and humidity.  

Being eaten as adults may not be the worst problems green treefrogs experience.  They breed in ponds and pools: you know, eggs deposited in water, then tadpoles.   The tadpole stages is where it gets interesting, especially to biologists who have looked into tadpole predation and found surprises. (Prominent mention to Margaret Gunzberger comparatively recently, and earlier Michael Blouin among many.)   Here’s the surprise, at least to me:  The frogs are abundant around shallow seasonally temporary depression marshes locally, but they breed preferentially in permanent year-round ponds, potentially distant from their usually haunts.  

Plenty of room for research here, but part of the puzzle, if there is a puzzle, seems to be differential predation.   There are a lot of small fish even in temporary pools and ditches where little fish become increasingly crowded as the pools dry, shrink, and even disappear.  That’s not good for tadpoles trapped with the crowded hungry fish.   And fish are not the only predators, dragonfly larvae too are tadpole eaters, and they tend to share the frog’s need for emergent vegetation, adding to the risk of the frogs breeding at shallow hangouts.  That’s all somewhat speculative, if also obvious.  What prior researchers have actually demonstrated is that the main tadpole predators in permanent ponds, bluegill have a distaste for Green Treefrogs, making the tadpols perhaps “safer” in a pond than in a temporary pool.  (Interestingly, there’s a closely related treefrog with the opposite preferences, but that’s a separate story.)

As anybody who goes outdoors knows, South Florida freshwaters suffer from nutrient pollution, chemical contamination, and Bluegreen “Algae” (Cyanobacteria).   You might ask, how does that big fact impact today’s little frog?   I don’t know,except for one odd little slice of that pie:   as recently as 2014 a new species of Bluegreen Alga (Aetokthonos hydrillicola) was discovered associated with invasive hydrilla, and it does not play nice, making trouble mostly a little north of Florida but also in Central Florida.   The alga got famous as a suspect in Eagle deaths.    It kills frogs too.   The GTF appears so far to be immune or resistant, good news for it, if not for the overall balance of nature.   Maybe its immunity comes from a long history living in little ponds with high Bluegreen Algae exposures.    The frog is expanding its range northward, with the obvious supposition being climate change, although there are alternate possibilities such as uneven parasite or toxin distributions, and aquarium releases.

 

Liatris and Smoked Seeds

---

Liatris chapmanii, L. spicata, and several additional species

Asteraceae

---

Working in the marshlands out to the west of Jupiter,  a couple days ago I glanced up from my clipboard upon hearing a grunt behind my back.   Found myself  within the family circle of a mother hog and her little piglets.   Perhaps not a good idea to drift  between a mother with tusks and her smelly little cuties, so I migrated promptly.   To be fair, the benign sow showed no grumpiness, but I’m a craven coward when it comes to critters with very big teeth.

The other thrill of the outing justified the brush with disembowelment because along the drainage canals big showy purple Liatris wands were waving in the wind.  As tall as a person. Hundreds of them. Always great fun to find flowers “a-buzz” with pollinators.    

That always feels like “real biology” if that makes sense.    Anyhow, the Liatris was hosting honeybees, bumblebees, Monarch Butterflies, Skippers, and  the poorly named  “Ailanthus Moth.”  Poorly named because Ailanthus (Tree of Heaven, a northern urban weed tree) is not native to the U.S., but the moth is.   What were absent-to-scarce were native bees other than Bumblebees.  

The Liatris inflorescences were oddly diverse, from candle-shaped and erect to baseball-shaped, or branched like a candelabra.  Some were twisty-curly, even hanging down.   Normal variation?  Distorted from herbicides?  Something funny in the canal water?   Hybridization?   (Some Liatris species, including L. spicata,  do hybridize.)  Got me, but fun to see. All the variants below are in the same clump.

Now here is the weird thing.  It is no doubt advantageous for some species in fire-prone habitats to sprout on the freshly cleared, freshly “fertilized” ground after a fire.  But how does a seed know when that time has come?  Heat—yes, sometimes.  But also, where there’s fire, there’s smoke.    Florida ecologists Heather Lindon and Eric Menges in 2008 exposed 20 Florida species seeds to smoke, and found enhanced germination in three species, including Liatris chapmanii.   The graph below is from their work.    It hurts my head to envision smoke being a germination cue for seeds,  that’s just weird, but other ecologists in other places have found other examples.

Germination rate vs. minutes of smoke exposure. By H. Lindon and E. Menges.

---

BTW, to folks who ordered the tree book, thank you.   It should have reached you by now, and hopefully you enjoy it.  If any other reader might still want one, we still have some copies. E-mail George Rogers (rogersg515@gmail.com).

 

Why Do Many Wetland Plants Have Mixed Flower Colors on Different Individuals?

---

Note about treebook sales:

Books will be mailed to everyone who asked for one, Sunday or Monday. Today and tomorrow are the “last chance” for that mailing. Happily (or sadly) we still have some available, so it is not too late. Anyone still wishing to purchase, e-mail rogersg515@gmail.com.

---

Are wetland plants more likely to have different individuals sporting different flower colors than upland plants?   I think so, but am biased by dint of more time in wet places than dry.   Whatever happens on the dry side, it is fun to find marsh species where some individuals have violet flowers and other white, or less often other combos.  Almost all of today’s photos are by John Bradford. Examples of mixed-color species include:

Alligator Flag (Thalia geniculata)

American Bluehearts (Buchnera americana, not always in wetland)

Asters (Symphiotrichum dumosum)

Bluethreads (Burmannia biflora) rich violet to nearly white

Dwarf Butterwort (Pinguicula pumila)  purplish and white, also yellow

Glades Lobelia (Lobelia paludosa)

Grasspink Orchids (Calopogon pallidus)

Manyflower Beardtongue (Penstemon multiflorus) purplish and near-white

Pickerel Weed (Pontederia cordata)

Slender Foxglove  (Agalinis linifolia)   purplish and white

Pretend for the moment that mixed colors are especially common in wetlands.   Why are mixed violet and white so common there?  No single answer. 

There exist a lot of suggested explanations, not all mutually exclusive:

1. SIGNALLING.  Some flowers start out one color, then change, such as Dwarf Butterwort.  That may be a signal to pollinators, or could  merely be aging.  
2. SUNSCREEN. In some species, flower color may be more related to UV protection than to insects.
3. DIVERSIFY YOUR ASSETS. Some parent plants may benefit by producing offspring of mixed colors, attracting different insects.  Would be fun to know if different colors experience different visitation.
4. COLOR TIED TO DIFFERENT TRAITS.  Say, for example, a gene that turns on protective darkening in the leaves darkens the flowers incidentally.
5. MUTATION.  My favorite.    The purple vs. white toggle switch might be very simple genetically,  probably sometimes one gene.  A single mutation could probably “flip the switch.”  A marsh seems like a good place for mutations (DNA damage), with seeds buried in suffocating mud for years,  tender young plantlets  growing oxygen-deprived through mud,  warm water loaded with natural and unnatural chemicals and with microbes,  and blazing sun.
6. INBREEDING.  Way out in a marsh is a tough place to get bug-pollinated.  Many wetland plants self-pollinate.   That is ultra-inbreeding, and inbreeding has a way of making mutations show up.
7. RHIZOMES.  A lot of marsh plant spread by rhizomes, or by horizontal floating stems, or by breaking apart.   If one such plant has a mutation, and it carpets the marsh by vegetative growth that mutation is magnified over a large distance.

So, next time you’re around wetland plants, or any plants with mixed flower colors, good luck figuring out why!  But it is fun to try.    And it’s is all about pretty:  such as “blue” bladderworts with big white flowers.

Purple Bladderwort (Utricularia purpurascens)  purplish and white, yesterday

 

Under The Sand Pines

Plants help each other, not deliberately..    Most helpful facilitations occur no doubt by happenstance, the presence of one species improving conditions for the other.  Much like the light over my neighbor’s garage illuminating my driveway for carrying in groceries.  As a green example of facilitation,  I’ve spent hours working around Lovevine where insect floral visits almost never occurred.  That changed, however, when Cassine Holly common in the same habitat came into bloom attracting bees. Suddenly the Lovevine became popular, receiving visits from the bees originally drawn to the Holly.

Under a nurse tree

I’ve always “had a thing” for nurse trees, maybe left over from prior life in harsh habitats, such as California.  A nurse tree hovers over smaller plants, which may ultimately grow big. The nurse provides shelter and more:  fallen leaves as “mulch”,  soil-nutrients,   broken-off “nurse logs” with baby plants in the decaying bark, perches for seed-dropping and guano-dropping birds,  shelter for nitrogen-dropping creatures,  rain capture and channeling, support for climbers, and  probable benefits concerned with soil chemistry and microbes.

Dry desert where there are no trees.

Walking in the scrub today among “mature” Sand Pines, magical little gardens of young plants were thriving under the boughs surrounded by comparatively sterile parched desert away from the trees.   In addition to a naturally short lifespan, Sand Pines grow where the relentless salty winds blow, where hurricanes blow bigger, and where fires and the sun both scorch the earth.   Walk through a stand of Sand Pine, and it is easy to find fallen individuals, ones with major limbs broken off, and gaps.    

Above: Smilax under the pine. Below: Baby Smilax preparing for growing up—already starting tuber.

How often do scrub plants start life under a nurse pine, then complete their life cycle after the pine is gone?   Literally crawling under a pine today, the youngsters poking through the pine needle mulch included hogplum, myrtle oak, palafox, and smilax—that is, every woody-ish species within a stone’s throw except maybe Sand Live Oak.

A nitrogen contribution

The benefits of nurse plants to their underlings are obvious, but…do the proteges ever benefit their nurses?   An intriguing answer, not original with me, is yes, probably in the next generation.   What species was missing from the under-the-pine list above?  Sand Pine. 

Palafox, I think

Never say never but there is an apparent tendency in many species for a tree’s offspring to rise up someplace other than as a competitor under the parental branches. (I dare you to find a baby Hogplum under a large mature parent.)   

Oakling

This tendency is not adequately studied, but for the sake of argument let’s pretend it holds.    What species serve as nurses to baby Sand Pines?   Do the species nursed  by pines “return the favor”?  The idea of generationally flip-flopping nurse services has raised its head in botanical literature, although has not been demonstrated in the local scrub ecosystems to my knowledge.

Hogplum

And now a word from our sponsors

 

Sample pages