Treasure Coast Natives

Are blogs past their prime?  Yes for sure, in a world of podcasts, X, streaming stuff, and laptop & desktop displacement by fancy fones and other devices.    Even so, natural history never gets old (to John and to me), so despite technology leaving us forlorn, here we go again old-school,  today about ants and plants.

Harvester ants. Big heads. Big jaws for seeds and for foes. The crowded door to the underground colony is toward the top left. By John Bradford.

In the white sandy coastal scrub native harvester ants (Pogonomyrmex badius) have some odd ways and means.   Their nests are abundant and easy to find in open sugar sand, resembling an upside pie pan with a busy central portal leading to a huge subterranean colony.  

Colony today with its black charcoal-y fence.

Around the portal is a barren “yard” scurrying with ants, the yard surrounded by a dark “fence.”   That fence is the feature attraction today.  It  is a ring of debris, much of it waste from the nest, no surprise there. The surprise is that the ring is also so loaded up with burned bits of charcoal that the overall coloration is almost black. Bits of charcoal? Yep.  

The ants seem to gather it from past fires.  WT-heck is that all about?  Nobody knows definitively, but not for lack of trying  by biologists over the years.   Several past suggestions exist, some purely speculative, some checked out.   Here’s a quick list of previously published possibilities:

1. To exclude enemies.  The “defensive perimeter” idea is obvious but flawed, especially,  “what enemies?”  The main natural enemies of Florida harvester ants are parasitic wasps.   They fly, so a fence is no D.   Also unfriendly are fire ants, but they did not evolve with harvester ants, and besides, would charcoal chunks block any kind of ant?  Maybe not physically, but perhaps as a “no trespassing” notice to encroachers even of the same species  from different colonies. The defenders have ferocious chompers, and they can sting too.  We’ll come back to the  “no trespassing” concept.

An enemy that attacks ants on the ground—after prior airborne dispersal—are ant lions, and they can lurk around harvest ant habitats.   The lions scoot across the sand to set ant traps, and a fence may discourage violating the  ant campsite.  But the ant colony is mostly subterranean and essentially immune to ant lions.   It is hard to imagine ant lions as a force to reckon with.

2. A different notion is that the black fence is a landmark ant foragers beyond the pale can see from the distance when lugging home the harvest of seeds. A homing beacon.  (Naw)

3. A third proposal is that the black charcoal, like a black car, absorbs heat to warm the nest on chilly mornings.   Trouble is, the nest can be 10 feet deep.

4. Charcoal absorbs organic compounds, perhaps including chemical signals. The resident ants could infuse the charcoal with pheromones, warning unwelcome ants to bug off.  Efforts by other people to test this have come up dry.   

https://drive.google.com/file/d/1YyNXYzAlrvX10lFF14FlGxVC0lJL9iOS/view?usp=sharing

5. A related older speculation is that the charcoal is a favorable seed bed to help stubborn seeds sprout into ant food. Investigated but never demonstrated. Undermining all explanations involving special characteristics of charcoal, non-Florida harvester ant species make similar fences but use non-absorbent pebbles instead of briquettes.  Florida harvesters in sand don’t have pebbles, so maybe the burnt bits are merely locally available substitutes. (Are harvester  ant colonies related in size, health, or abundance to charcoal availability?)   Charcoal pieces are usually sparse on scrub sand, so the investment required to gather thousands of them to the nest site must be costly!   They must also serve an important purpose.     To see if the charcoal ring “matters” to the ants, the other day  I scooped a small portion of a charcoal ring away.  Remarkably, by the following day they had repaired it fully.

John and I discussed the fence question today, and jointly have an idea to “toss into the ring.”   In all the historical speculations, there is little-to-no attention to the second function of fences: confinement.    Let’s say keeping junkyard dogs in the junkyard.    Those big-headed, heavy-jawed, biting “major” ants roaming inside the fence are scaled down junkyard dogs.   It would be a problem to junkyards and to harvester ant colonies to have the guards (and workers) wandering away willy nilly.  We suspect the fence defines the duty station for its occupants. In the video link above you can see ants wandering to the fence, and then redirecting back into the yard to remain effectively useful.

Evening-Primroses, lovely members of the big genus Oenothera with almost 100 species in North America, are well represented as mostly bright yellow wildflowers in Florida,  some in  open sandy habitats. One cosmopolitan beach species, arguably native to Florida, Beach Evening-Primrose (O. drummondii), found itself called out recently as listening for  pollinators.  Yes, listening.

Photo courtesy of Harry Rose.

Biologist Marine Veits and a group of collaborators in 2019 reported honeybee buzz and similar vibes, but not other tones, to induce increased sugar concentration in the nectar.   In their interpretation, this ability sweetens the pot  upon demand, promoting bee pollination yet conserving sugar when there are no customers.   What’s more, the petals resemble one of those parabolic microphones they use to focus birdsongs, to capture frog calls, and to eavesdrop on conversations.

It may all be just as reported and interpreted, but questions come to mind:

1. Are bees meaningful pollinators for evening-primroses?   The flowers are (actually) textbook examples of moth-pollinated blossoms, having long tubes producing nectar way down deep exclusively reached by a moth’s long proboscis.   But bees are known to visit the flowers, perhaps merely gathering pollen, as bees do.   That could result in pollination without nectar consumption.   Then again, who is to say the long tube can’t fill with sweet nectar, allowing an occasional bee sip.  

Nectar is produced at the bottom of the long skinny tube. Bee can’t reach there.

• Would a small increase in sugar content boost pollination?  Not if the bees are there just for pollen. And even if they are obtaining some nectar, it’s not been shown (pretty hard to accomplish!) that marginally raising sugar concentration leads to more pollen deposited by more bees on more stigmas.  

• In 2017 botanist Sebastian Anton and collaborators studied the floral dynamics of several evening-primrose species in Europe and found the flowers to not just release nectar into the tube, but also to suck it back in dynamically, depending on circumstances.  The nectar level waxes and wanes.  As the flowers reduce the nectar volume, the sugar concentration increases.  That is, sugar concentration increases when the flower is stashing away nectar, not dishing it out.   Does buzzing set off a flower alarm:  “Hey, non-moth invaders detected, hide the goodies!”   After all, some types of bees drill into flowers and steal nectar like mosquitoes stealing blood from my elbow.

• Yet another concern is that the flowers don’t have any identified “nervous tissue,” whatever that could be in a plant.   Absence of detection does not prove absence of some subtle signal, duh, but it doesn’t help either.  Plant cells live within extremely thin delicate membranes with their own innate molecular movements and unimaginably delicate processes.  Whether or not buzz detection is usefully adaptive, vibrating cell membranes could conceivably change cross-membrane transfer dynamics, maybe even make membranes “leaky.”   That is, could vibrational sugar leakage take place with no purpose?

Who knows?   The idea is new and fascinating and plausible, and that is how science works.  Taking another look at the same question with additional bee and flower species is joyous future grist for the mill.   The original research was in the Mediterranean. Now somebody should try in Florida.

to see more:

DOI 10.1007/s00425-017-2748-y

DOI 10.1111/ele.13331

Today the Honeycombheads (Balduina angustifolia) were bright in the scrub, blooming massively attracting a whole lot of floral visitors.  We’ve enjoyed them before: https://treasurecoastnatives.wordpress.com/2021/09/10/honeycomb-heads-have-their-very-own-bee/

Most of Florida was submerged several thousand years ago, although sandy dunes and ridges here and there were above the waves.  Those “islands” and more recently exposed dunes became our modern scrub. That poses the fascinating question of, where did all the scrub flora and fauna come from? Without a deep dive into that immense topic, suffice it to say here, some species arrived from the more-arid and scrublike southwest like Scrub Jays, some wandered southward  from points north, some floated from afar by sea (like probably Ximenia), and some evolved on the scrub from variably distributed and wandering ancestors. And so forth.   You could ponder that for a whole career.

So, ya gotta wonder how we got those flamboyant Honeycombheads, which are mostly restricted to sandy open places like scrub in Florida and nearby. And now we shall speculate wildly.  (Yes, a proper DNA-based evolutionarystudy is called for, but in the absence of that I have a license to make something up.)

What makes it fun to wonder is that there are only three species of Balduina, all of them native to the Southeastern U.S., the other two (B. atropurpurea and  B. uniflora) centered on terra firma to the north of Florida. Those two species extend together from North Carolina to the Gulf,  in Floria both limited to the northern counties.  Today’s  species, B. angustifolia, seems likely a sandy scrubby southern offshoot of the more-northern pair Balduinas.   (Interestingly btw, B. uniflora has twice as many chromosomes as the other two species.)

The two “northern” species then could have existed before South Florida emerged from its ancient submersion.   The northern species both favor wet sandy shores.   Having the same number of chromosomes as B. angustifolia, B. atropurpurea (or conceivably an extinct close relative) looks like an older mainland ancestor for B. angustifolia. That species could have split off evolving into newly forming scrubby habitats as Florida rose above the sea. Even today’s scrub is not so different from the ancestral “sandy shores,” just particularly well drained and sterile.

Polygonum polygamum

Polygonaceae

Photos today by John Bradford except the poorly focused wasp

October Flowers declares October is here.    Been too hot through the summer for a’wandering far, but today called out cooler, and the fall floral friends were pleasing: Smilax fruits looking like grapes,   “Florida Paintbrush,”  Tarflower (hey that’s not supposed to be open now!?),  and the feature attraction: October Flower.    Despite prior attention (https://treasurecoastnatives.wordpress.com/2021/08/27/october-flower-is-fun-to-watch/) ,  I can’t resist posting this white delight again.   A thing I love about October Flower is rooted in the ecology of native pollinators:

They’re hurting, especially in disturbed, polluted, urban/suburban woodsy fragments.   Depressing studies (not locally)  tend variably to reveal urban conditions to be harsh for native pollinators.    Nature lovers with suburban gardens, like me, “help the pollinators,”   which can be only partially true since pollinator richness and diversity depend on diverse factors beyond garden flowers. 

We all love honeybees, but, pity, they are invasive exotics al-bee-it with benefits.  All this being so,  I take special joy in native pollinator watching, even though the bee house in my garden is vacant.    Some native wildflowers attract native visitors like bees to honey.   October Flower is one of them, and being abundant in scrub remnants,  it brings a buzz of  “natural pollination” to a nature area near you.

I’m no wasp expert, but I can Google like a pro, and I think today’s visitor is a male “long wasp” (Myzinum sp.).    You see them as floral visitors, having a waspy kinda love for small white blossoms.   Avidly gathering pollen with their faces in the flower,  they seem uninterested in humans with cameras.   As an instant Google expert, let me tell you a fun fact—although the male can’t sting, it has a scary looking Captain Hook  false stinger, and will fake-it if bugged.   Here’s a picture from the UF Museum:

Thalia geniculata

Marantaceae

Today I took a walk on the soggy side among one of my favorite Florida tropical marvels, Alligator-Flag (Thalia geniculata).   Everyone around here knows it whether they know it or not—big roadside ditch plant with “banana” leaves and paired violet flowers aloft on wands as tall as a truck .  They have a complex snap trap mechanical pollination system that would impress an orchid.    That was all written up in this blog, holy smokes, back in 2012.

https://treasurecoastnatives.wordpress.com/category/alligator-flag/

So, after a 13-year gap, it is time for Thalia Phase II:   co-habitant insects.     They are weird and poorly known.  The identities of the today’s Thalia companion species (in addition to the Canna Skipper) are handy thanks to a helping hand from bugnet.guide.

If you go look closely at Alligator-Flag inflorescences, which requires wet feet or a boardwalk such as Wakodahatchee Wetlands or Green Cay, you’ll probably find the True Bug Ischnodemus sallei scurrying, and mating immodestly,  on the branchlets among the flowers.   Related to the chinch bugs of suburban lawn dread,  Ischnodemus sallei feeds on Thalia sap.    The species has a special affinity for Thalia, at least in South Florida.

Below is the lion’s share of the knowledge of its distribution in Florida. Notice anything?  (The non-Thalia reports of this species I’ve seen have been on plants related to Thalia outside of Florida.)

And here is a tidbit from UF entomologist Dr. Susan Halbert:

Don’t want to bore you by getting too far into the weeds.   I just fancy a special relationship between one of our coolest wildflowers and its own bugs, even if they suck.    The Ischnodemus sallei abundance on Thalia is so bountiful locally,  I wonder if the insects disperse with floating plant parts of this shore-dweller.

Also abundant on Thalia,  and also poorly known, is a bigger, showier species of leaf-footed bug, Namacus annulicornis.    If you bother Ischnodemus sallei it disappears furtively into the spaces between the leaf sheaths and the stem. By contrast, when bugged, Namacus flies off in a huff, and seems to emit a stinkum on the way..  

Namacus

This bug appears to have Alligator-Flag as its sole host according to R. Barananowski and  J. Slater in their 1986 account in the Arthropods of Florida:

Eggs

Those bright red nymphs (below) look so much like Assassin Bug nymphs, I wonder if there is mimicry of some sort.

Funny how, when a flower has an “oh-my” pollination system, its more mundane aspects can  go overlooked.

Ludwigia linifolia

Onagraceae   (Evening Primrose Family)

Changing season lengthening days,  heat, rain….and my favorite places after Dunkin’ Donuts, the depression marshes, are awake:    Bushmints, Gratiolas, Milkworts of every color,  Rosegentians, St. Johnsworts,  Stillingias,  Stripeseeds, Yellow Flax.     Flowers flowers and more flowers!   But you know what’s missing?  Pollinators (although there would more if I got moving early in the day).   Where are all the bees?

Part of the answer, I fear without “hard knowledge,” is that a lot of observers have observed a decline is native bees.  Don’t like that!     Somebody should assess the native bees in the rural, exurban, suburban, and urban WPB area.  Somebody did that in Brazil using Mexican-Clover growing along roads leading into urban habitats.   Problem is, Florida native bees may not be that enthusiastic about non-native Mexican-Clover, or about roadsides.    Also, there’s a correlation between more-specialized flowers and native bees.   Bottom line—this concern needs a local assessment!

A second reason for not seeing many pollinators in an expansive marsh is that in my personal experience the farther out across a large depression marsh you wade, the fewer the bees.   The wasps and dragonflies out there are strong long-distance fliers.  But are bees reluctant to cross hundreds of meters of marshland to visit a flower?  This speculation brings us to an important point:   pick any  flower species occurring far out into wet marshlands and odds are it can reproduce without insect pollinators.   Every plant in the list above is either known or strongly suspected of being able to reproduce without insect visitors.

Southeastern Primrosewillow by John Bradford.

A particularly attractive example in flower now is Southeastern Primrosewillow, a modest beauty you don’t see everyday.   It may be shy about hiding its sunshine yellow blossoms among the St. Johnsworts it resembles, but it sure isn’t shy about pollinating itself.   Go visit in the morning, and the pollen-bearing anthers are spread off to the side, out of the way in case a visitor brings pollen to the stigma standing tall at mid flower.  But in the afternoon just before the petals fall off,    the anthers clasp to the stigma and powder it with “self” pollen.    No way that blossom goes to waste, even if the bees let it down.

Morning with four white anthers spread to the side, stigma in the center. Enlarged portion of photo above.

Afternoon, anthers pressed against and pollinating the stigma. The pollen is white.

Southeastern Primrosewillow is native across the southeastern U.S.   But look it up its range in the authoritative Flora North America, and hey what’s that?   Tabasco, Mexico??

Ala., Fla., Ga., Miss., N.C., S.C., Mexico (Tabasco)

That’s 1500 miles away!   The key to that leap must be self-pollination. One seed carried by a bird or a  hurricane or a muddy shoe can establish far from home, self-pollinate, and spawn a nation.   If that is so, wouldn’t today’s pretty wild flower turn up “unofficially”  in additional hot wet places?   Let’s try India.  Yep, , “in rice growing areas.” Africa?—yep, one herbarium specimen in Gabon, and maybe in the People’s Republic of the Congo. You get the idea!   Self-sufficiency of the meek and humble.

Raphanus raphanistrum
Brassicaceae (Mustard Family)

Wild Radish is an Old World weed you don’t see much in South Florida natural areas. In some places, however, they see far more than they’d like, being a bigtime agricultural weed resistant to herbicides and having seeds as bycatch during harvesting. Some non-farmer folks fancy the plants as “edible.” But no no no! It picks up environmental toxins. Edible? Well, it is the parent species of the radish in my salad, and the two can intercross even now. And no, WR does not have a bulbous red root.

Today in Cypress Creek

I don’t want to poison it or eat it, or cross it with salad fixings. The interesting thing, documented back in the 80s by California biologist Maureen Stanton, requires a tiny bit of background:

Here is that background. A long-standing concept in plants and animals is a spectrum of degree of parental investment in offspring. Some species make a huge investment in each offspring, providing each an advantage in establishment: humans, elephants, coconuts. At the other end of the spectrum, some parents release a huge number of undemanding “cheap” offspring into the cruel world betting on quantity instead of quality: rats, spiders, dandelions. No species has to occupy either extreme, most species are intermediate, but what you do not often see (I can’t think of another example) is one species using both strategies, making a mix of high-investment AND cheap skitter-skatter offspring.

The pods break apart rather than opening.

Wild Radish does. As Dr. Stanton documented, the seedpod starts out making one “big” seed at the base. Then higher in the pod it forms one or more smaller cheaper extra seeds. The number of smaller plan-B seeds varies considerably—apparently in good conditions the pod enjoys the luxury of adding several extras. When times are tighter or the season is short, the pods still makes the main seed while holding back on its less-endowed smaller siblings. Sort of like a royal family having a well groomed heir apparent, followed by minor princes in reserve.