Taken by Ants in the Prairie Peninsula

Traipsing around in an open savanna under gnarled, seemingly ancient, Bur Oaks trees is like being in a little slice of heaven.  But why are these gigantic mounds of dirt lying about?  

"Solarium"  constructed by Allegheny Mound Ants, central Ohio

The denizens of these mounds quickly showed themselves; large two-colored ants, with red heads and thorax and  large black, shiny gaster or "metasoma".  Based on their appearance and distinctive mounds, I believe they were Allegheny Mound Ants (Formica exsectoides).  

Allegheny Mound Ants (presumably Formica exsectiodes), Crawford Co, Ohio 

Location of  Bur Oak savanna (bounded by the black box) amidst
active agriculture of central Ohio

The site is truly remarkable in the modern day landscape, and has been considered to be the "largest and best preserved remnant of the unplowed, deep soil prairies and savannahs that were present at the easternmost extension of the Prairie Peninsula prior to European settlement" (Mack & Boerner 2004, Castanea).

Bur Oak Savanna dominated by Quercus macrocarpa, Crawford County, Ohio.  

What ecological role could ants be serving in this habitat remnant?

Previously, at this site I had noticed ants clamoring on Sullivant's Milkweed (Asclepias sullivantii). Not being an ant taxonomist, I struggled with whether or not these were the same species as those from the nearby mounds. With the gracious assistance of Dr. Kaloyan Ivanov of the Virginia Museum of Natural History they are tentatively identified as Formica pallidefulva, not the Allegheny Mound Builders.  These ants seemed to be daintily sipping nectar from the flowers (see image below).  Could they be pollinating this prairie species?  

Ants (presumably Formica pallidefulva) sipping nectar from Sullivant's Milkweed in Bur Oak Savanna, Crawford County, Ohio. 

Perhaps, but after a bit of research I learned that ants rarely pollinate flowers.  More often than not, they simply steal nectar, and are often referred to as "nectar robbers".  For example, Wyatt (1980, Bulletin of Torrey Botanical Club) found that ants on a different milkweed species both reduced the amount of nectar available to butterflies and the overall effectiveness of the pollinators.  He termed ants "harmful to evolved pollination systems", and a "maladaptive force".   I looked at further images I had taken of the Sullivant's Milkweed with ants and noticed what appeared to be "maladaptive" behavior taken to a new level.  It appears that the ants were actively chewing away the flower structures, literally tearing open the stigmatic slit (where a pollinator leg would be expected to enter), impacting or even removing the ovary! (see image below).

Ants impacting Sullivant's Milkweed reproductive capacity(?);
arrow illustrates one example of torn flowers & ovary

Damaging milkweed!  Interrupting butterflies!  This behavior must stop! 

Although Allegheny Mound Ants weren't apparently responsible for the milkweed damage, much of  the readily available information on them involved recommendations like, "drenching a mound with liquid insecticide".  Michigan State Extension justifies doing so because, "the ants kill nearby vegetation including small tress and shrubs to keep shade off the mound. They do this by chewing a small hole in the bark and injecting formic acid into the wound" (http://msue.anr.msu.edu/news/mound_ants).  In contrast, Maine State Extension actually recommends ENCOURAGING their populations because the ant "plays a vital role....in a variety of ecosystems" (https://extension.umaine.edu/blueberries/factsheets/insects/195-allegheny-mound-ant/). 
Nice!

Henry McCook ~ 1877 with his beloved
Allegheny Mound Ants

Reverend Henry McCook (image left), was possibly the first and most careful observer of the Mound Ants. At one point he actually dug up an entire mound, frozen in the dead of winter, and transported it intact to the Academy of Natural Sciences in Philadelphia. His assumption that the colony "had gone down for winter-quarters into the deep galleries below the surface" was proven wrong when the mound thawed along with the "horde of hibernating ants within" which poured out all over the museum (1907, Nature's Craftsmen Popular Studies of Ants and other insects).     





In his earlier work, McCook (1877, Transactions American Entomological Society) described the most common size of mounds as 10-12 feet in circumference and 2.5 - 3 feet in height, but also mounds of tremendous size (over 6' in height and 50' in diameter). Andrews (1926, Pysche) suggested the Allegheny Mound Ants were the most common mound builder in North America,  ranging at least from Maine through Georgia.  However, he also suggested they were most often associated with places "left comparatively free from live stock and human interferences".  When encountered, mounds can be quite abundant. The incomparable Reverend McCook reported densities ranging from 25-59/acre.  My observations (see image below) suggest densities can be even higher in some locations.  High population densities, coupled with their reported tendency to kill nearby small trees and shrubs could certainly play a role in maintaining the open structure of prairies and savannas they inhabit.

Allegheny Mound Ant density, evident after prescribed fire, Daughmer Savanna, Ohio

Allegheny Mound Ant surfacing with soil aggregate
Adams County, Ohio

Overall, ants are probably the most consistent and important soil turning organisms worldwide (Tschinkle, 2015, PLoS ONE);
numerous papers describe their contributions to mixing, aerating, and altering nutrient dynamics of  soils they inhabit, and several document vegetation associations with mound ants (see Nemec, 2014, Journal of Insect Conservation).

Consider just the amount of surface area directly affected by the mounds in the image above. Baxter & Hole (1967, Proc. Soil Science Society Abstract, ) studied mound ants of a related species in a prairie remnant in southeastern Wisconsin. They showed the ants (which occupied 1.7% of the surface area) significantly altered the soil surface by bringing material upward and introducing organic material from their feeding habits. Overall, they believed the ants may be responsible for distinguishing the prairie soil from that of an adjacent and comparable forested area.

  In the end, it seems, the ants may create the prairie!

Prairie Goldenrod & Its Unusual Habitats

Prairie Goldenrod (Oligoneuron album) doesn't look like your typical "goldenrod".  But it was once considered a member of the genus Solidago, lending some scientific basis to calling it a goldenrod. To some it is still referred to as Solidago ptarmicoides. This plant has been kicked around taxonomically an almost shocking number of times. But I digress....





Prairie Goldenrod is a legitimate rarity in North Carolina, and is either absent from or rare in most other southeastern states. Why in the world doesn't it occur in Virginia?

The apparent rarity or absence from much of the southeast may not be surprising since it is presumably PRAIRIE Goldenrod and relatively few such habitats occur in the region.  However, one site, perhaps the only extant site in North Carolina, is both botanically rich and very much "prairie-like".

Prairie-like habitat of Oligoneuron album in Granville Co, North Carolina; note faint white specks of Oligoneuron stems in flower., see inset below

Closer view of Oligoneuron album in Prairie-like habitat,in North Carolina; flanked by the basal rosettes of Prairie Dock. (9/18/2013)

The North Carolina site discussed here also includes abundant Prairie Dock (Silphium terebinthinaceum), Stiff Goldenrod (Solidago rigida) and many other species often associated with prairies elsewhere in the country.  This site may be as close to true prairie as it can get in NC and is certainly one of the only known locations resembling a prairie with reasonably intact vegetation on a soil typical of prairie. Broadly, most of the North American Prairie region is closely tied to the occurrence of Mollisols (see map below).

Soil from the North Carolina Oligoneuron "prairie" site,
classified by soil scientists as a Mollisol.
The dark color is one the characteristics of this soil order.

USDA Soil Map, Mollisols

     




It is hard to overstate how unusual this soil is in Carolina.  As the generalized USDA soil map shows, there are no mapped Mollisols of sufficient extent to appear on the map almost anywhere in the southeastern US outside Florida.  A retired University Soil Scientist once told me it took years for the existence of these soils to be accepted in North Carolina, even having the "dirt in hand", since historical convention suggested such soils couldn't develop in the North Carolina climate.  But again, I digress......

This post was supposed to be about Prairie Goldenrod.

Oligoneuerun album apparently thriving in remnant tallgrass prairies in Paintbrush Prairie, Missouri.(08/17/2015)
Rattlesnake Master (Eryngium yuccifolium) is barely visible as well.

Prairie Goldenrod does actually occur in undeniably classic "tallgrass prairies" in the midwestern US, which some refer to as the Central Tallgrass region.  I have observed it in several tallgrass prairie remnants in Missouri such as that shown above.

Taken together, my admittedly few observations seem to fit into a nice and tidy picture of the habitat for Prairie Goldenrod.









But, then I visited alvars along Lake Huron in Ontario Canada.

I was absolutely shocked to find Prairie Goldenrod on lakeshore pavements (on exposed rock I believe is dolomite), and even in loose sandy soil at the margins of Lake Huron!.  These were NOT PRAIRIES.

Prairie Goldenrod on alvar,lakeshore pavement, Misery Bay

Prairie Goldenrod along Lake Huron, Ontario Canada

I did finally find Prairie Goldenrod in one habitat much more akin to prairie near Lake Huron. Much of the ground surface was littered with small boulders that are likely glacial erratics. The matrix soil was primarily sand that apparently washed in under extreme tides or storm events, covering the underlying dolomite flat rock. Such disturbance events, coupled with the underlying pavement, help keep the habitat from becoming overgrown by shrubs and trees. The most visually dominant herb, other than Prairie Goldenrod was Limestone Calamint (Calamintha arkansana). 

Prairie Goldenrod amidst glacial erratics and loose sand near Lake Huron, 

Interestingly, NatureServe uses Oligoneuron album as a nominal in one of its described alvar natural community types, but rather than it being used to name a "grassland" type it is considered part of a shrubland:

(see http://explorer.natureserve.org/servlet/NatureServe?searchSystemUid=ELEMENT_GLOBAL.2.722949)

No matter what habitat seems to support Prairie Goldenrod they are all well worth the look!

Bluehearts

American Bluehearts (Buchnera americana) @ Taberville Prairie, Missouri (8-19-15)

I came across a few individuals of American Bluehearts (Buchnera americana) during recent explorations of the tallgrass prairie. According to Bruce Sorrie and Alan Weakley I was in the "heart of the range" for the species. Back home in North Carolina American Bluehearts is considered an endangered species and is believed to have been lost from nearly every location from which it has been documented. This made finding a few plants feel even more special even if they aren't so rare out in Missouri.  

Savanna Bluehearts (Buchnera floridana); Boiling Spring Lakes Plant Conservation Preserve, Brunswick Co, North Carolina (6-03-15)

Bluehearts was perhaps first documented in Carolina by Reverend Moses Ashley Curtis. In his "Catalogue of the Indigenous and Naturalized Plants of the State" (published in 1867 at the "N.C. Institution for the Deaf, and Dumb and the Blind"), Curtis provided no clues about the abundance of American Bluehearts but listed it only in the "Mid. and Up. Districts", regions most often referred to as the Piedmont and Mountains today. We now recognize an additional Buchnera species found in the coastal plain region as well, Savanna Bluehearts (Buchnera floridana) (see image above).  In contrast with American Bluehearts, Savanna Bluehearts characteristically has fewer and more compact flowers (although taxonomic treatments by Bruce Sorrie emphasize leaf characters to distinguish the two). There are some indications that Savanna Bluehearts may be pretty rare in North Carolina (although comprehensive data are lacking since it is not currently tracked by our Heritage Program). 

Buchnera sp. perhaps intermediate in some characters between B. americana and B. floridana?
St. Marks NWR, Northern Florida (7-05-14)

Savanna Bluehearts don't seem to occur further north than North Carolina, but rather extend southward across parts of the southeastern coastal plain, and may not extend beyond the coastal plain. American Bluehearts is primarily centered in Kansas, Oklahoma, and Missouri with spotty occurrences elsewhere, including into the northeast and to the edge of Lake Huron.  The ranges of the two species may overlap, but the extent to which this happens, especially the mid-south and parts of the southeast, remain unclear (at least to me) (see image above). Part of the reason the distribution and status of both species is uncertain is due to the fact that the two names are considered synonymous in many areas. For example, NatureServe lumps them together and therefore believes the combined entity is perhaps globally secure.  However, American Bluehearts have apparently been extirpated from several states and are considered quite rare or vulnerable in a significant number of others. If the populations consisting of Savanna Bluehearts were seperated from the tally, both species could turn out to be important elements of conservation concern.  

American Bluehearts amidst dense grass cover in tallgrass prairie remnant @ Taberville Prairie, Missouri

In the so-called heart of the American Bluehearts range, where I observed it, the species was found in "tallgrass prairie". Today, there are mere remnants of this once vast ecosystem that the US Fish & Wildlife Service (http://www.fws.gov/midwest/ecosystemconservation/tallgrass_prairie.html) believes has become "functionally non-existent over the last 150 years".   In my recent forays in Missouri prairies, I encountered American Bluehearts only in 2/20 + remnants visited and found < 5 individuals at each (although my observations were not systematic or comprehensive).  Savanna Bluehearts seems to have occupied longleaf pine savannas which could be considered ecologically analagous to tallgrass prairie, and has suffered a similar fate. Importantly both habitats were once subject to frequently recurring fires that likely benefit both Buchnera species.  A large part of the conservation challenge ahead will be to ensure that sufficient high-quality habitat remnants of both ecosystem are protected from ongoing threats and are adequately fire managed.   

Tallgrass Vignettes

Standing amidst this sward of tallgrass prairie in Southern Kansas one evening (08-22-15) brought this line from Willa Cather to mind: ".......I felt the grass was the country, as the water was the sea."

Sweet Coneflowers (Rudbeckia subtomentosa) @ Osage Prairie, Missouri (8-19-15)

Profusion of Flowering Spurge @ Linden's Prairie, Missouri (8-20-15)

A few stalks of flowering Big Bluestem (Andropogon gerardii) stand above patches of Flowering Spurge (Euphorbia corollata) and a few other species @ Paintbrush Prairie, MO (8-16-15)


Stiff Sunflower (Helianthus pauciflorus) patch @ Tallgrass Preserve, Kansas (8-16-15)

Big Bluestem flowering above Flowering Spurge, Rosinweed stem on the left @ Tallgrass Preserve, Kansas (8-16-15)

Ashy Sunflowers (Helianthus mollis) @ Paintbrush Prairie, Missouri (8-17-15)

Flowering assemblage with Blue Sage (Salvia azurea), Ironweed, and Goldenrods @ Taberville Prairie, Missouri (8-18-15)

Getting on to evening at Golden Prairie, Missouri (8-22-15)