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Author Archives: George Rogers

About George Rogers

Professor of horticulture and botany at Palm Beach State College

Grassleaf Spurge

 

Euphorbia graminea

(Euphorbus was a physician in antiquity.  The Gramineae are the grasses.)

Euphorbiaceae

This morning John and I photographed Maggy’s Hammock near Hobe Sound, Florida, one of the few great hammock remnants hereabouts.   John’s working gradually on a photo guide to the natural areas in Martin and St. Lucie counties.

Maggy’s  hammock abounds in biodiversity, and over several years the blog has embraced most of the botanical star players, the species you might expect.  So today here is one you don’t expect.

Euphorbia graminea LW

Grassleaf Spurge

Pronouncements in references on the native-ness of widespread tropical weeds always bug me.   Weeds get around.   That’s what weeds do.   Where “native” ends and “invasive” begins is not always clear.   Today’s little weed is indigenous from northern South America into Mexico.  And yet here it is in Florida.  Did it arrive unnaturally, oh say as seeds stuck in somebody’s shoe, or did it arrive without human assistance, oh say, seeds in a bird?   Did Global Warming warm the welcome?

Euphorbia graminea flower head

The “flower” (more precisely, the cyathium), microscope view.

In any case, in recent years the species has popped up  in  Africa, India,  the Pacific Islands, and more.   It is a tagalong in nursery plants, jumping from pot to pot  using explosive fruits to fling seeds like shrapnel.   Many  members of the Spurge Family  pop their fruits,  famously Sandbox Tree, Hura crepitans, and Brazilian Rubbertree, Hevea braziliensis.    But  neither of those grow at Maggy’s Hammock.

The flowering structure, as with all Euphorbias is complex,  to detail another day.  Suffice it to say that the tiny “flowers” about one mm across almost all produce fruits,  hinting that the species can pollinate itself, as many annual weeds do.   That way, a single individual can found a new population.  Handy in the weed world. Also, I witnessed today the world’s tiniest mini-fly visiting the flowering units.

Euphorbia graminea pods1

Big green poppin’ pods and little white “flowers.”

All who attempt to trace the origins of garden flowers wind up mangled by confusion and contradictions.   The popular garden selection Euphorbia ‘Diamond Frost’ is, according to various sources, including especially the authoritative Flora North America, Euphorbia graminea all dressed up.   But by contrast, the usually accurate Missouri Botanical Garden’s Kemper Center classifies it as Euphorbia hypericifolia.  That too, is a common weed, in my back yard.  The resemblance between it at the garden flower is not that convincing to my eye.   And contradicting both, the company that patented the garden selection calls it a hybrid.   So much for Googling.   But a nice insight into how idiot arguments come about.

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The white selection is Diamond Frost.  Photo by Cultivar413, permitted use via Creative Commons.

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Posted by on October 13, 2017 in Grassleaf Spurge, Uncategorized

 

Buttonsage, Snowbird Warblers, and Nuptial Gifts

Lantana involucrata

(Lantana is an ancient name for Viburnum, a similar genus.  An involucre, IN-vuh-luke-er, is a nest of leaves around a flower cluster.)

Verbenaceae

We’re working on a photoguide featuring John’s photos to the local natural areas,  Peck’s Lake near Hobe Sound, Florida, today.  In the scrubby seaside hammock restoration there John and I encountered many crabs and also the Verbena family presenting flowers and fruits in familial synchrony:  Beautyberry, Fiddlewood, Rough Verbena, and Buttonsage all hanging around and showing off together.

Lantana involucrat 4

Lantana involucrata, by John Bradford.

The last-mentioned is always a treat, with fragrant-foliage, pastel flowers having yellow eyes, and glossy purple fruits.

Those purple fruits are birdfood, and the prime customer is the Kirtland’s Warbler.  Any nature enthusiast growing up in Michigan is familiar with this storied traveler nesting in the northern pine woods and then flying far.  The endangered and recovering  bird winters, likewise in pine woods, in and near the Bahamas, where reportedly one of its staples is Buttonsage fruits, although insects are on the menu as well.  Interestingly, a fruit it likes in Michigan is the blueberry, similar to those of Buttonsage.

Lantana involucrata fruits (1)

Buttonsage fruits today.

Today’s shrub provides a textbook example of butterfly-pollinated flowers, which often look like tightly clustered inverted little witch hats in pastel colors, each having a bright-colored eye.  Bingo…exactly Buttonsage, which feeds more species of butterflies than a witch can shake a broom at.

Lantana involucrata flowers

Today

Beyond butterflies, Buttonsage serves pollen to ground-dwelling bees.  And there’s a hint it may do the same for some butterflies, in particular Heliconius butterflies, such as the gorgeous Zebra Longwing known to visit the flowers.  So now let’s climb out on a creaking limb.   Although butterflies are not generally regarded as pollen-eaters, they carry it from flower to flower as they seek nectar.  However, if you are going to lug around pollen,  why not swipe nutrition from it?    Recent research, featuring Lantana, has shown Heliconius buterflies, after collecting pollen on their sticky proboscis, to extract nitrogen nutrients from the grains for “egg production, increased longevity, and nuptial gifts,” in the words of biologists C. Penz and H. Krenn, citing previous researchers.

 
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Posted by on October 6, 2017 in Uncategorized

 

Hempvines and Sugarcane Plumegrass in the Osprey Circle of Influence

Mikania scandens and Saccharum giganteum (and Pandion haliaetus)

Asteraceae

Osprey 8

Guano makers, by John Bradford

Today John and I walked under an old osprey nesting pole in Halpatioke Park, Stuart, Florida, prompting old curiosity about the effect of big raptor nests on the flora below in the guano zone.   The nest in Halpatioke was too long-abandoned for a great look, so inspired I visited a recently occupied Osprey nest near my home.  That lovenest, vacant now, raised a family just a few months ago, and certainly before.   Today it was empty and storm-whipped, so I felt ok about approaching and photographing, although an unafraid hawk lighted to eye me with its hawkeye for a moment.

Hawk

A family of big birds generates a lot of fertilizer, and also brings vegetative pieces, some green and able to root, not to mention any seeds clinging to talons, feathers, and prey.

The nest pole constructed near my home is in a wet “prairie.”  Away from the nest the dominant vegetation consists heavily of species of Wiregrass, Aristida.

prairie

Wiregrass “prairie”  looking away from the nest pole.

Around the base of the nest pole, by contrast, there’s no Wiregrass.  Instead, there are a couple shrubs (Carolina Willow, Wax Myrtle), and a mix of herbaceous species dominated overwhelmingly by two species of particular note.  Seen from above, the guano zone species look like feeder bands around the eye of a hurricane, the base of the nest pole being the eye.  Outside of the guano zone it is all Wiregrass.

osprey platform still

The vegetation around the pole base is different from the surrounding Wiregrass prairie.  See also video mini-tour below.

Noteworthy Osprey-nest-loving species 1 = Climbing Hempvine, Mikania scandens

Hempvine forms an uneven circular groundcover patch maybe 15 feet in diameter around the base of the nest pole so abundant and dense it is a challenge to walk across.   There is an easy interpretive explanation for its localized exuberance:

Bird guano is a great source of phosphorus, even a commercial source of the nutrient.   In 1999 ecologists P. Vaithiyanathan and C. J. Richardson pinpointed Mikania scandens as an indicator of increasing phosphorus levels in the Everglades, where it  and another phosphorus-lover, Cattails, can  happily coexist in phosphoric bliss.

Mikania

Hempvine by the pole

As an irresistible aside, bird-derived phosphorus fueling harmful algal blooms, and harmful algal blooms as suspected dinosaur killers.   Now back to 2017:

Noteworthy Osprey-nest-loving species 2 = Sugarcane Plumegrass, Saccharum giganteum 

This big beautiful grass related to cultivated Sugarcane is almost absent from the rest of the prairie, yet is co-dominant in the Osprey nest guano circle rising above the Hempvine carpet, mostly in a broad ring around the outer edge of the Hempvine patch.    The association of the big grass with the guano circle is a challenge to explain, so please tolerate my speculations.   Hempvine craves phosphorus, but if the Plumegrass does, I can’t find any sign of it.   This species tolerates different soil conditions, although it does want wet feet and usually open conditions.

Mikania pole base

Sugarcane Plumegrass, the pole base to the right.

My hunch is that the Plumegrass would happily occupy much of the wet prairie if something did not suppress it there.    I think its confinement to the nest island is not because it needs guano, but because that unique circular zone is a safe refuge.     As mentioned earlier, the rest of the prairie is a carpet of Wiregrasses,  with multiple species documented to suppress competitors primarily by poisoning soil microbes involved in nitrogen metabolism.  That reduces the soil nitrogen levels below the tolerances of competing species…such as perhaps Sugarcane Plumegrass.   Remove the Wire Grass and maybe the Plumegrass is liberated…which suggests some experiments.  Whatever the explanation, a big long-standing Osprey nest dramatically alters the flora beneath.

CLICK here to see it as the Osprey does.

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Extra stuff

Relevant earlier blogs:

Hempvines: CLICK

Bird Manure Part I:  CLICK

To dig deeper:  Macrophyte species changes in the everglades: Examination along a eutrophication gradient.  P. Vaithiyanathan, C. J. Richardson  Journal of Environmental Quality 28: 1347. 1999.  [Evaluates the effects of nutrient enrichment on changes in the macrophyte community in the Everglades ecosystem. Mikania scandens and Sarcostemma clausum serve as indicators of increasing phosphorus levels.]

 

 
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Posted by on September 29, 2017 in Osprey Guano, Uncategorized

 

Elephant’s Foot and the Green Treasurechest

Elephantopus elatus

(Translated: Tall Elephant Foot)

Asteraceae, the Aster Family

Among the local wildflowers, Elephant’s Foot is a standout… pretty, weird, and abloom all over Halpatioke Park this morning where John and I pursued a photo project.

Elephantopus elatus 1

Elephant’s Foot with its rosette, photos by John Bradford.

Preferring open dry habitats, its leafy rosettes rest flat upon the earth.   A vertical stalk rises a foot or two, often branching as a perfect Y,  and tipped with three equal bracts embracing a dense bushy-bristly flower head.  The spongy base of the head protects young flowers and fruits, and probably holds moisture funneled inward by those bracts.  Having just a few flowers exposed at any given time allows the reproductive cycle to span weeks accommodating pollinators of every buggy sort.

Elephantopus elatus 3

Most of the foliage sprawls radially on the ground atop a perennial taproot.  Rosettes are common in the Aster Family, and in plants of harsh open environments.   There are multiple advantages to rosettes in such places, including minimal wind exposure, using the ground to support the leaves,  safety beneath most grazers and fires, easy regrowth straight from the root,  and extra water collection.

Members of the Aster Family tend to have a biting pungence, some might find unpleasant while others may approve, Marigolds for example.  Asters are the primary although not sole sources of defensive compounds called lactone sesquiterpenes, which are bioactive as you might expect chemical defenses to be.

Normally I’m skeptically unenthusiastic about the countless historical uses of most plants.  Google a widespread species and see how many ailments it has treated.   Thousands of plants have been screened for antimicrobial activity, and no surprise, many do kill cooties.    Most plants have chemical defenses. (Please do not eat the weeds.)

Elephantopus elatus 2

But there is chasm between historical remedies and modern clinical efficacy.  Today we may witness a potential bridge across that divide.

Lactone sesquiterpenes have attracted attention for anti-cancer activity, and the positive indicators extend promisingly past vague traditional treatments all the way to specific understanding of the biochemical mechanisms by which these chemicals cause programmed cell death (apoptosis), including roles in gene control.   Elephantopus species are players in this realm.

Elephantopus species produce lactone sesquiterpenes, some named for today’s plants: elephantin,  elephantopin,  and others.   These have hit the cancer literature as understood in mechanism, effective in the lab, and worthy of a deeper testing.

This is all promising hand-in-hand with the march of biotechnology, and lactone sesquiterpenes or derivatives from some relatives of Elephantopus have made it to clinical trials, including products from Mulleins, Feverfews, Wormwoods.  All in the Aster Family.

Exciting stuff, and maybe the beginning of the future predicted emphatically by the leading botanist of my generation, Dr. Peter Raven, who was 1999 Time Magazine Hero of the Planet with the message of saving the rainforest as a green treasurechest waiting pharmacological discovery.     Emerging biotechnology of today and tomorrow is the likely  key to that treasure, and maybe some of the gems are behind the soccer field in Halpatioke Park, Stuart, Florida.

elephantopus elatus head

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A start for those who want to dig deeper:  DIG HERE

 

 
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Posted by on September 22, 2017 in Uncategorized

 

Hurricane-Induced Cladoptosis Spreads Across Florida Woodlands

At the suggestion of Virginia nature friend Pat Bowman, how about wild plants and hurricanes. Do the wild plants care?

Some relocate.  It seems that during Hurricane Wilma in 2005, a tropical weedy grass. Steinchisma laxum, previously unknown in North America invaded South Florida Florida arrival was overdue, an easy breezy hurricane hop from the Caribbean, assuming the hurricane did it.   Blog co-conspirator John Bradford standing in Halpatioke Park was the first soul in North America to say, “hey this does not fit the measurements of any grasses expected around here.”    Now you can hardly escape it.

OLYMPUS DIGITAL CAMERA

Steinchisma laxum is everywhere, perhaps thanks to Wilma.

My lawn today still has on it millions of small leafy twigs shed from Live Oaks.  It is obvious to reckon, “well the gusts blew those free.”  True,  and  branches whipping wildly knocked them off too.  But there’s more to it than immediate physical damage.    That something more is cladoptosis, defined as “planned” twigdrop.   It happens in certain trees, notably in Oaks.

Earlier research indicates the tree somehow “decides” which twigs shall live and which shall shed.    Determination occurs early in the life of the twig.  Those fated to shed follow an odd development:  the “veins” connecting them to their parent branch narrow and choke off supply.   It looks like a ring of decay girdles the twig at the snap-off point, and the bark appears to pinch in.   When the twig separates, the severed base is not fractured and splintered, but rather more of a rounded knob, like your femur joining your pelvis, essentially “designed” to drop free smoothly.

cladoptosis 2

Irma-severed end of Live Oak twig.  Unplugged cleanly, not torn, splintered, or fractured.

Why?  The limited literature indicates a hormonal seasonal reaction abetted by stress.  In short, those scattered twiglets were poised to come loose before Irma roared in.   The storm merely shortened the timeframe to hours instead of weeks or months.   The tree conceivably needs all its leaves during the moist growing season, but can’t support the full canopy as the warm wet season winds down and dry times approach.   The hormone ethylene is implicated.   The same hormone serves commercially to defoliate crops for easy harvest.  The twigdrop helps storm-proof the tree by reducing wind drag.  How many wind storms does a 500-year-old Live Oak experience?

Although Slash Pines may fracture or topple, another common probability is shedding, not little twigs, but rather large dead branches low on the trunk.  Ever notice how those trees have nice green canopies up high but not many dead branches down low?    There’s a perception that the branch-shedding is protection from ground fires, and that maybe those old branches even have some basal weakness to set them free.   “Cladoptosis” of large branches?   Maybe…more research needed.  The break-off is not clean, uniform, and mechanical as the Oak twigs.   Walking in The Haney Creek Natural Area today John and I saw the broken pine branches to be all sizes, alive, and dead, and torn and splintered.   Less  convincingly “preplanned” than Oak twiggies.

IMG_0894

Pine branch shedding uneven, messy, and fractured.

Many woodland trees lie prostrate from past thunderstorms and hurricanes.   My favorites are in swamps:  Red Maples and Sweetbay Magnolias where the fallen tree resurrects multiplied as branches rise vertically to become new trunks.  Ex uno plures!  From one comes many, a whole new mini-population.

Busted-off branch bases and torn bark on standing tree trunks invite trouble and may or may not heal.    Healing comes mostly from above, which is why branch-stumps tend to fare poorly…”above” is gone.    Sugars, hormones, and growth processes cover a wound mostly downward, like pulling down a window shade.

After pruning, grazing, or hurricanes new stems grow from the lateral buds situated where the leaf joins a skinny young twig.   Repeat, skinny young twig.   But on any tree damaged in a storm  a few years ago new branches sprout from the thick old trunk.   How can that be, that gnarly old trunk lost its lateral buds decades ago.   Well, not entirely, that old bark has an amazing emergency repair mechanism known as latent buds.  Latent buds creep outward hidden within the bark as the tree expands, waiting for hurricane day.  The equivalent of me sprouting a new leg should one be yanked off.

IMG_0885

Latent buds in bark competing to replace severed stem on Strangler Fig.

The magical regenerative powers of plants go doubly in an environment where storms and fires are endemic, such as here.  Check a wild area after a major storm, and there is likely less damage than expected, in some places no damage is even detectable.  That was almost true in Haney Creek today, Liatris all abloom, Hog Plums with plums still attached, and most foliage intact and green.  The native flora evolved to stand up to trouble.   And where destruction does occur, the ability of life to rise from subterranean structures or from broken plants is quick.    Moreover, the soil seed bank is ready to rise.   Disturbed dirt never stays bare for long.

If you want to find damage, seek it near the sea.  The salty winds “burn” foliage, and sow salt into the soggy earth.   The plants mostly recover ok from the saline attack.   Guess what species is especially resistant.  Live Oak.

Does a big hurricane change the composition of the flora?  Sure, within the constant ebb and flow of species in our dynamic world, but, given the fact that our flora has evolved through thousands of hurricanes, one event won’t cause radical mischief, except maybe where human activity has created an unnatural imbalance.

Upon emerging from our bunkers the morning the tempest subsided, one of the most positive sights after, “hey, we still have a fence,” were blue jays and butterflies.  Where did those jays ride out the fury, and a butterfly in a hurricane, well, that’s just poetic.

 
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Posted by on September 15, 2017 in Uncategorized

 

A Grass, a Fungus, and a Virus Walk Into a Bar…

What a dumb time to write a South Florida blog, as we all wait for Hurricane Irma to blow in some new weed species.   After the house is as ready as possible,  there’s not much to do other than hang around and fret.   So, here’s something to read before the power blinks out.   Today’s core topic came from my second favorite thing after vanilla cream donuts, “This Week in Virology” by Professor Vincent Racaniello who makes all things viral fascinating.

Can a virus be good?  Yes, occasionally, and probably far more often than we know.  Today we shall see a native grass species (if you stretch the taxonomy) and its associated fungus meet a helpful virus.

Dichanthelium,  the Witch Grasses, comprise roughly 80 species,  numbering about a dozen in our usual neck of the woods.   Pretty, often petite, sometimes forming rosettes.

D. chamaelonche 2

Dichanthelium chamaelonche.  All photos by John Bradford.

Today is all about a super-powered grass formerly classified as belonging to our local D. acuminatum.

D. acuminatum - specimen 4

D. acuminatum

Dichantheliums are notoriously tough to classify.  In any case the variants of interest are not known in Florida, but rather at scattered hot springs over a large area of western North America.    A recent and credible classification  interprets the hot-springs-inhabiting populations as a species in its own right, D. thermale.    A grass at home in hot water?    Really hot.

Recently studied in Yellowstone Park the witch powers of Witch Grass are proven where it bubbles bubbles toils and troubles in natural cauldrons as steamy as 65 degrees C (149 degrees Fahrenheit).  For comparison,  hot tap water is typically around 50 degrees C (122 degrees F).

The super-grass hosts a symbiotic fungus called Curvularia protuberata, at first glance a suspect responsible for the empowerment.  But infecting the grass with the fungus doesn’t help.   UNLESS a third player is tossed into the brew, not eye of newt, but a newly discovered virus.    The virus plus the fungus jointly confer heat resistance on the grass.

A big problem with symbiosis is that the codependent species must have coordinated reproduction and dispersal.    Our hotfoot grass turns up in small isolated populations at hot springs sprinkled over hundreds of miles.   Do the Three Musketeers all travel together?    How?  One component is known…the virus moves generation to generation in the fungus within the fungal clonal spores.   Then do those virus-bearing spores ride along somehow in the grass’s seeds?  Unknown, but don’t they have to?  How did the three species hop from Yellowstone to northern California and far beyond?

There may be more similar  fungal-viral-grassy unions to discover, because our fungal genus Curvularia is large, often plant-pathogenic, and frequently consorting with grasses.   The same fungal species in the Witch Grass, Curvularia protuberata, is also a pathogen on rice, so who knows, maybe it helps the rice sometimes?   And if in rice, it must infect additional grasses.  Could the empowering fungus-virus duo help concoct super-powered rice?

DichantheliumerectifoliumJWTOct.[1]

The mechanisms of all this are poorly known so far, but researchers understand a few things.  When the virus infects the fungus, the fungus accumulates mannitol, a sugar-alcohol common in plant defense mechanisms, and also a human medicine, such as a laxative.   Does the viral infection put the fungus into a defensive mannitol-making posture, and then the grass exploits the fungal protective arsenal?  Probably much more complicated than that simplistic first notion.

The grass, fungus, and virus have drawn the active attention of researchers interested in heat tolerant crops.  That’s a big deal in a world where hot conditions limit crop options, and where climate change will boost the mercury.  Experiments have already created heat-tolerant tomatoes by infecting them with the Dichanthelium fungus-virus sidekicks.

D. strigosum

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For those who wish to dig deeper:  CLICK

 
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Posted by on September 7, 2017 in Uncategorized

 

A Tale of Three Species

Where Did Our Locally Endemic Wetland Species Come From?

South Florida has extreme geologic history.    High dry habitats have been exposed above water for eons.    The opposite is today’s topic, wetlands.  Freshwater lowlands are South Florida trademarks.  Our present-day swamps, marshes, depression ponds, wet prairies, soggy pinewoods, and the Everglades hid beneath salty seas as recently as 15,000 years ago speaking very roughly, a teensie winky blink in evolutionary time.    If  their habitats were blue lagoons  until just yesterday, where did our wetland-loving plant species come from?

For species widespread beyond our region, duh, they migrated here from afar when conditions permitted.  But what about species limited to (endemic to) South Florida?  Yes, they could have shown up here from somewhere else and then disappeared there, but unlikely and arbitrarily rejected.  Ground rule—we will trust locally confined species to have originated locally.   Yes, it is all speculation.   We’re just having fun here.

pine glade sundown

Even though most of our present-day lowland areas were beneath saltwater, the exposed elevated uplands were not 100% dry.   Those raised islands must have had rain-fed depressions, ponds, and marshes where freshwater life could take refuge, freshwater Noah’s Arks ready to repopulate the vast lowlands when the salty seas subsided.

Even acknowledging spotty refuges, a massive new start defined soggy South Florida just a few millennia ago.   Huge upheaval, huge abrupt changes.    And that makes it fun to wonder how our locally endemic wetfoot species might have popped up.  Each of those species has to have an oddball story.   Odd circumstances generate odd histories.

Here are three as I see it:

 

Coleataenia abscissa (Panicum abscissum), Cutthroat Grass, and the Running Rhizomes

Cutthroat Grass may be an example of a localized “species” originating as a regional spin-off from a widespread northern species.  Cutthroat grass is so incompletely separated from its ancestral species,  its classification as a species is dubious.  Some taxonomists demote it from species status to a subspecies as Coleataenia longifolia subsp. abscissa, you might say a mere local variant of Coleataenia longifoia.

Coleataenia longifolia ranges across much of North America with additional spinoffs in other places.  Confusing?  Yes.  Species is a human concept…the plants do not read textbooks.  These grasses represent a big messy dynamic splintery complex where “species” are not defined crisply.

Even as a mere splinter group, Cutthroat Grass must have had some way of expanding its new brand while not merging back into its parental species.  Cutthroat Grass is aggressively rhizomatous.  South Florida is filled with rhizome-making plants able to colonize large areas clonally, thus spreading into what some botanists call “microspecies.”

This rhizome-ish microspecie-ish situation with Cutthroat Grass is reminiscent of another local wetland grass limited to Florida, Aristida rhizomophora, named for its prominent rhizomes.    It seems to be a wet foot Florida derivative of the generally more upland Aristida stricta which has no rhizome or just a little, especially in South Florida.   It looks like A. rhizomophora took that little ancestral rhizome and ran with it bigtime, spreading like Cutthroat Grass to become a microspecies or whatever you choose to call it.  The designation matters less than an understanding of what happened. (And I could be wrong.)

 

Polygala smallii,  Small’s Milkwort.   A Pollination Introvert?

A third local twig branched off from a widespread northern species is Small’s Milkwort.   DNA shows it to be a chip off of Candyroot, Polygala nana.  The two are a challenge to distinguish.  Because Small’s Milkwort is often encountered in upland habitats, it may be a stretch in today’s wetland context, but even in uplands it likes relatively moist depressions, and is a facultative (part-time) wetland species.    Also, its  parent species Candyroot prefers moisture.   The taste for uplands while retaining a love for moisture makes Small’s Milkwort a candidate for those refugia mentioned above.

Polygala nana 1

Candyroot, Polygala nana, by John Bradford

A subtle and overlapping difference in flower color helps distinguish the two, with Candyroot brighter yellow than Small’s Milkwort’s slightly-greenish yellow.

This yellow flower business echoes a second Milkwort pair.  The Florida endemic Polygala rugelii has bright yellow flowers.  The similar Polygala lutea favors orange. Thus we have two Polygala pairs, each with one member restricted to Florida and the other widespread and more northern, separated in part by the yellowness of the flowers.  Pollinator color preferences matter.

But then again maybe not always.   What forced Small’s Milkwort to cleave unto its mother Milkwort?   Geographic separation long ago is possible, remember those refugia, but there is a possible second isolation factor.   Small’s Milkwort reportedly appears to be self-pollinating.    That would prevent it from mixing genes with its parent species, thereby allowing a separate new “species”  to diverge.  If you want to keep bloodhounds and boxers separate, don’t let them interbreed.  Same with Polygalas.

Did the Small’s Milkwort flowers evolve from bright yellow to yellow-green because they don’t need to attract pollinators, and does their green tinge add photosynthetic ability?  Objection Your Honor!—that question has no evidentiary basis.  Question withdrawn.

 

Litrisa carnosa (Carphephorus carnosus), Pineland Chaffhead.  Not a Splinter, But a Merger

This case is weirder than the previous two.   If our Cutthroat Grass and Milkwort split off of raggedy bigger northern parent species and stopped interbreeding with them, Pineland Chaffhead is the other side of the coin, a merger.   It originated as a hybrid, reproductively a loner which somehow managed to spread.

Carphephorus carnosus 9

Pineland Chaffhead,  Litrisa carnosa, by John Bradford

Tennessee botanist Edward Schilling seems to have finally nailed this misfit.    The genus Carphephorus where Pineland Chaffhead resided turned out to be a bad genus in the sense that it did not represent a single branch on the tree of life, and had to be dismembered.    Pineland Chaffhead became reassigned to a genus of its own, Litrisa, presciently first proposed by John Kunkel Small two generations before Dr. Schilling’s DNA confirmation in 2011.  That’s the same Small as in Small’s Milkwort.  DNA revealed Pineland Chaffhead to be a probable hybrid bridging two different genera, Carphephorus as newly redefined, and Trilisa.

How might the hybrid Chaffhead have propagated and spread?  Many members of the Aster Family have asexual clonal seeds, with no data for the species in question.  One thing is clear, it makes babies in spades around its feet, removing any questions about its basic ability to go forth and multiply, somehow.

Carphephorus carnosus 8

Despite being an apparent hybrid, Pineland Chaffhead  makes plenty of babies, by John Bradford.

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For readers who want to dig in:  CLICK 

 
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Posted by on September 1, 2017 in Uncategorized, Wetland Species

 
 
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