Monday, January 5, 2015

Biodiversity Hotspots Hold the Key to New Species Discovery in the Southeast

New species are still being discovered with regularity. Nearly every week there are posts of newly discovered species on Facebook's Novataxa page of some recently found frog from the Congo or new plant from the Peruvian Amazon. The majority of new species are being discovered in remote tropical areas - places like Borneo, Laos, Brazil, and Madagascar -  that are still relatively understudied and have a considerable amount of unexplored territory. Most of these are from regions called global biodiversity hotspots. Worldwide, there are 35 global biodiversity hotspots recognized by Conservation International. Examples include the Atlantic forests of Brazil, the Caucasus Mountains of Eurasia, and the pine-oak woodlands of Mexico. For a region to be a hotspot it must meet strict criteria aside from just having a high number of species. First, It must contain at least 1,500 endemic plant species (endemic species are species restricted to an area that occur nowhere else). Secondly, at least 70% of the region must have suffered from habitat loss or significant degradation such that less than 30% of its original vegetation remains. These threatened hotspots support more than half of all known plant species and more than 40% of mammal, bird, reptile, and amphibian species, despite just making up 2.3% of the Earth's land surface (Conservation International 2015).

Fig. 1. Map of Global Biodiversity Hotspots

Smaller biodiversity hotspots can also occur on a regional scale. For example in the mountains of southwestern China - which is itself a global biodiversity hotspot - there are specific mountains or watersheds that harbor their own sets of narrow endemics that can be thought of as local or regional hotspots. 

A new paper by Reed Noss and colleagues, entitled How global biodiversity hotspots may go unrecognized: lessons from the North American Coastal Plain, published in 2014 proposes that the southeastern US, specifically the Coastal Plain province, which comprises approximately half of the area known to many as "The South," should be considered the 36th global biodiversity hotspot since it meets the criteria set by Conservation International. Within this newly proposed global biodiversity hotspot, there are also regional hotspots that were identified in 2001 by former University of Tennessee researchers, James Estill and Mitch Cruzan. Their study identified several "centers of endemism" within the South - particular regions that are biodiversity hotspots but on a small regional scale. Examples include the Appalachicola region of the Florida Panhandle, the Southern Appalachian Mountains, and the Central Basin of Tennessee. 

Their maps provide coarse resolution of hotspots and are a good start, but recent data suggests that there are small hotspots even within some of the ones Estill and Cruzan found. For example, the Southern Appalachians contains numerous hotspots of endemism, each likely to harbor undescribed species as well. There a few areas not identified as hotspots by Estill and Cruzan that may in fact be unidentified hotspots that need additional study. Such areas include the upper Cumberland River Valley of Tennessee and Kentucky and the Boston Mountains of Arkansas. 

Estill and Cruzan's (2001) map of southeastern U.S. "centers of endemism."
These can be thought of as biodiversity hotspots within the larger southeastern
U.S. global biodiversity hotspot proposed by Noss et al. (2014).

Given the Southeast's status as a global biodiversity hotspot, It should be no surprise that the region is still yielding many new species of plants and animals despite 350 years of intensive exploration and scientific study. Recent remarkable U.S. examples of new animals include the discovery of four new bass species from Alabama, a new turtle species in Mississippi, and a new giant crayfish in south-central Tennessee. Data compiled independently by Alan Weakley (Univ. of North Carolina, Chapel Hill) and myself reveals that there have been more than approximately 250 plant species described from the Southeast since 1970 and the rate of discovery continues to remain steady at an average of five per year. There may be a few hundred species left to describe from the Southeast.

Vascular plant species described in the southeastern U.S. between 1970-2010.

Now, perhaps more than ever, it is imperative that we find, describe, and study new species because what little remains of our natural habitat in the South is now faced with nearly constant threats stemming from increased population growth. The continued degradation of our Southern landscape has been especially obvious to members of the conservation communities who are now in their 80s and 90s. Dr. Robert Kral, retired Vanderbilt University botanist, relayed the erosion of our biodiversity to me in this way: "Dwayne, 18 out of every 20 sites I've visited over my career that were high quality sites are now gone or degraded beyond repair." Numerous factors are responsible for the degradation of our natural habitats including urban sprawl, habitat fragmentation, wetland destruction, conversion of woodlands to pine plantations, increased herbicide usage, fire suppression, and competition from invasive species. Coastal areas are also under threat from sea level rise due to global warming. The sad reality is that if we don't act fast many species will likely become extinct before we can ever describe them. Given these threats and the potentially great number of species left to find and describe, is there any way to expedite the discovery of the South's undescribed species?

The Race to Discover the South's Remaining Undesribed Species

I believe there is a way to speed up and focus our efforts to identify new species. First, we need to understand the likely characteristics of those species that are still out there. You might think of this as a sort of forensic profile. Here's a list of things to consider:

  1. A significant number of new species, perhaps 50-70%, are very rare and known only from a few populations - thus the reason they've escaped detection.
  2. A high percentage, perhaps 20-40%, are actually quite widespread and have escaped detection because they are cryptic or belong to groups that are taxonomically  or architecturally complex.
  3. Probably at least 75-90% of all species to be described from the Southeast have already been "found" by past botanists and collections likely exist in herbaria, but their distinctiveness has yet to be realized.
  4. Probably only a very small number of species to be discovered have never been collected previously by botanists.
  5. probably less than 25% are species that are immediately recognizable as new species - that is they are so distinct as to be easily separable at a glance. 
  6. The remaining 75% will likely require detailed scientific research involving statistical analyses of morphological variation and examination of DNA sequence data.
  7. More than 90% will have geographic ranges that are restricted to or centered on known biodiversity hotspots.

Since we know that biodiversity hotspots are the areas most likely to contain narrowly endemic species these are the same areas where we should focus our efforts to locate undescribed species. For example, an analysis of the new species described in the past 40 years reveals distinct patterns. Certain areas have routinely yielded new species. For example, there have recently been a number of new species described from the Cumberland Plateau of Alabama and Tennessee in the past few decades (e.g. Blephilia subnudaClematis morefieldiiPenstemon kraliiPolymnia johnbeckiiSolidago arenicola, and Stenanthium diffusum). Other regions that have consistently yielded new species include the West Gulf Coastal Plain of eastern Texas and western Louisiana, the southern Ridge and Valley of Alabama and Georgia, the Florida Panhandle, and the Blue Ridge Mountains. What is clear from these data is that some places just aren't as likely to harbor undescribed species, such as areas along the Mississippi River in eastern Arkansas or western Tennessee.

While it is true that many of the remaining species to be discovered are in remote areas, many, if not most of those left to find in the Southeast literally may be in our backyards, along our favorite hiking trails, or along the side of the busy roads we travel everyday. A 2000 publication by Barbara Ertter (Univ. of California, Berkeley) titled Floristic surprises in North America north of Mexico, described countless examples of new species that were discovered right under our noses. Recent examples of newly discovered species in Southern "backyards" include the endangered John Beck's Leafcup (Polymnia johnbeckii) and the Smoky Mountain Sedge (Carex fumosimontana). The leafcup was discovered in 2008 along the side of Interstate 24 just a few miles west of Chattanooga, Tennessee in the southern Cumberland Plateau ecoregion - an area identified on Estill and Cruzan's map as a hotspot. This new species has escaped detection by countless botanists and millions of passersby over several decades in spite of growing abundantly along rocky ledges within 30 feet of and in plain site of the interstate. The Smoky Mountain Sedge was discovered in another hotspot, the Southern Appalachians. It was found on eastern North America's second highest mountain, Clingman's Dome, in Great Smoky Mountains National Park and was the dominant ground cover beneath the  observatory tower, at what may very well be the single most heavily visited landmark in the US National Park system.

Polymnia johnbeckii (John Beck's Leafcup), a new species discovered D. Estes in 2008
known from two localities just west of Chattanooga, TN and nowhere else.

It is imperative that we continue to conduct, support, and fund inventories of our biodiversity. We also should not take it for granted that just because botanists have studied an area or a group of plants in the past that there's nothing left to do or discover. 

Unfortunately funding for describing species is almost non-existent. It is generally beyond the purview of large granting agencies such as the National Science Foundation. Federal and state agencies charged with environmental protection are also generally reluctant or unable to fund the description of undescribed species since they don't yet officially have a name. This is unfortunate given that most undescribed species that remain are likely the rarest of the rare and many would qualify as candidates for federal listing or at least being tracked as rare species at the state or provincial level. A related factor is lack of time. Many of the people who describe new species are affiliated with academic institutions and between balancing their responsibilities for teaching, advising, committee assignments and research, the meticulous work required to research and describe new species must be moved to the back burner. It often takes 2-5 years of research to do the work necessary to describe a species and prove its distinctiveness. When we couple this with how few researchers there are in the Southeast who are actively working on describing species, it is evident that it could take decades to describe all that are presently known. Many species don't have that kind of time and will face serious depletions in populations sizes, numbers of populations, and perhaps even extinction before we can get to them. 

To highlight just how large the problem is with the new species backlog, consider the figure below that shows numerous undescribed species and some recently described species found within the past few years.

Forty undescribed or recently described species from the Southeast. Twenty-five of the species photographed in this plate are putatively undescribed.

Thursday, January 1, 2015

Pennyroyal Plain Prairies

One of the South's Great Grassland Systems

When people think about grasslands of North America, most picture a flat to rolling landscape typical of the Great Plains of Kansas or Iowa, with tall grasses waving in the wind for as far as the eye can see. If you close your eyes you can almost see it as it was 250 years ago: herds of bison thundering across vast prairies, prairie chickens dancing at dawn, butterflies flitting across dense swards of blazing stars. Would you believe that I just described a prairie landscape that once occurred in Tennessee known as the Pennyroyal Plain prairie? This prairie system, more commonly referred to as the “Big Barrens,” was historically one of the largest prairie types in the Southeast. This vast crescent-shaped prairie extended more than 200 miles in length and averaged 20-35 miles wide. Today, only tiny vestiges remain.

Map of the Pennyroyal Plain and Elizabethtown Plain with black areas
indicating former prairie (Baskin et al. 1994).

Prior to 1800, the Pennyroyal Plain supported vast herds of bison and elk. Prairie chickens lived on the Pennyroyal at least through the 1810's. Wolves, black bears, and cougars stalked the prairies. Early observations and descriptions of the vast Pennyroyal Plain Prairie were provided by numerous early settlers, naturalists, and explorers, including French botanists Andr√© Michaux, Francois Andr√© Michaux, and the future king of France, Louis-Philippe. Albert Ross, one of the early settlers of Clarksville, TN, whose family is the namesake for the community of Rossview east of Clarksville moved to the area in 1812 and described the area between northern Montgomery County, TN and Hopkinsville, KY as follows: 

“Far as the eye could reach, they [the grasslands] seemed 
one vast deep-green meadow...only a few clumps of trees 
and now and then a solitary post-oak were to be seen.”

-Albert Ross (undated)

      The Pennyroyal wasn't just a vast prairie. It was in fact a matrix of mesic tall grass prairie, wet prairie, shorter mid-grass prairie, oak-hickory woodland, savanna, riparian forest, limestone barrens, limestone glades, swamps, and depression ponds. Natural sinkhole ponds dotted the landscape in many areas of the Pennyroyal Plain historically but very few high-quality remnants remain. C.W. Short, an early 19th century botanist stationed in Hopkinsville, Kentucky, provided some the best accounts of these prairie sinkhole ponds:

    "Now, would burst upon the view a smooth sheet of water, 
skirted with the blue and purple hues of the Pontederia 
and Decodon, intermixed with the scarlet berries of the Prinos, 
whilst its surface was covered over with the large and floating leaves 
and splendid flowers of the Cyamus; and then, in endless vistas, 
was stretched before the eye a waving sea of gigantic grasses."

-C.W. Short (1836)

This GoogleEarth map shows a typical Pennyroyal Plain landscape in
Christian Co., KY with water-filled sinkholes. The circled sinkhole is one
of only two localities in Kentucky known to support the very rare
Hall's bulrush (Scheonoplectiella hallii) and mudbabies (Echinodorus tenellus). 

The once vast prairie country of the Pennyroyal began changing soon after the dawn of the 19th century. The major factor that kept the prairie alive was annual fire. Many early writers note the fires that burned the prairies annually. Many attributed this practice to the Indians from adjacent regions who used the area as hunting grounds. Burning by Indians decreased in the first couple of decades of the 19th century and ceased when they were forced west to Oklahoma during the Trail of Tears in 1838-1839. White settlers continued to use fire well into the 20th century but on a much reduced scale. Bison were extirpated from the area by 1800; the effects of their grazing and trampling of the prairie ceased. Undoubtedly, bison were a major force in maintaining the prairie. 

Lightning fire would also have played an important role in the original maintenance of the prairie ecosystem. Just imagine a scraggly, lone blackjack oak standing on a low hill, emerging out of a clump of winged sumac; a sentinel keeping watch over a vast open, grassy landscape. It is late July and the Pennyroyal Plain is parched from the paucity of summer rain. The prairie grasses are dry and crunchy; everything appears greenish-brown and few plants are in flower. In the late afternoon, thunderstorms begin to roll in from the west, bringing with them an impressive lightning storm but little rain. A single bolt of lightning illuminates the darkening sky, striking the solitary oak, igniting it and the surrounding grass. Soon, fire is racing out across the open prairie leaving a black, scorched earth in its wake. Lightning fires like this could have burned for days across the Pennyroyal because unlike adjacent ecoregions where streams and rivers are abundant, the Pennyroyal has very little surface water due to the karst topography. This means that fires either must have either burned themselves out or be extinguished by rainstorms.  

Before the middle of the 19th century the landscape of the Pennyroyal was already undergoing major transformation. Numerous writers wrote firsthand accounts of how the prairie they once saw as children had turned to woodlands by the time they reached adulthood. Most attributed the succession of the prairie to woodland to the dramatic decrease in fire in the area. The decrease likely came as a result of passive fire suppression. As whites settled the area, establishing farms throughout the region,   the landscape would have become much more fragmented. The natural prairie would become broken by small farms and roads, creating fire breaks that didn't exist previously. With more settlers and more fragmentation, the ability for fires to sweep across the landscape would eventually diminish altogether. Fire suppression is the main factor that eliminated the Pennyroyal Prairie.

Ft. Campbell Army Base: US Military Saved the Pennyroyal Prairie

Today, most people would find it hard to believe or imagine Ross's early description of the Pennyroyal landscape. That's because most of the Pennyroyal today has been converted to a matrix of cropland (especially wheat, tobacco, corn, soybean, canola) and small isolated woodlots. It would be hard for most folks to imagine that 250 years ago many of today's major highways in the Pennyroyal region were established along the ancient "highways" or buffalo traces of the bison.

There are no known examples of pristine "virgin" prairie left in the Pennyroyal. It is estimated that more than 95% of the original prairie acreage has been destroyed by agriculture or succession to woodlands and forests. Today, the vast majority of known prairie remnants in both Tennessee and Kentucky are restricted to Fort Campbell Army Base. Even the remnants that now exist at Fort Campbell were once under cultivation or pasturage prior to the base's establishment in the 1940s.

Fort Campbell Army Base (red polygon) is home to 99% of remaining
Pennyroyal Plain prairie remnants. The prairie once covered most of the area in green.

On the 102,000 acre Ft. Campbell base there are approximately 20,000 acres of prairie remnants. About half of these exist in a fairly contiguous region of the impact zone in the northwestern corner of the base. The other half occurs as scattered small remnants throughout the rest of the base. These remnants are threatened by their small size, fragmented nature, and invasion by non-native species like shrubby lespedeza (Lespedeza bicolor) and Chinese lespedeza (L. cuneata). Many of the remnants are being monitored by Ft. Campbell biologists and are managed by prescribed fire.

Fort Campbell Army Base along the Tennessee and Kentucky state line 
northwest of Clarksville, TN. The large brown areas in the western and 
northwestern portions of the base are large prairie remnants. More than 99% 
of the Pennyroyal Plain prairie remnants that exist are found at Fort Campbell.

The prairies at Fort Campbell represent the best remnants left of this system. Understanding their structure, composition, and variation will be critical for future establishment and restoration efforts of other prairies in the region. At least three major types of prairie are found at Fort Campbell, including wet prairie, mesic prairie, and dry prairie. 

Wet prairie are the rarest and least understood type. Important grasses of wet prairie include Eastern gamagrass (Tripsacum dactyloides), prairie cordgrass (Spartina pectinata), Virginia iris (Iris virginica), rushes (Juncus spp.), sedges (Carex alata and many other species), bulrushes (Scripus georgianus), redtop panic grass (Coleotaenia rigidula), seedbox (Ludwigia alternifolia), and swamp milkweed (Asclepias incarnata).

Mesic prairie is dominated by thick stands of tall grass, sometimes up to 10 ft tall. Typical grasses of mesic prairie include Indian grass (Sorghastrum nutans), big bluestem (Andropogon gerardii), and plume grasses (Erianthus alopecuroides). Rare species associated with this habitat include sweet coneflower (Rudbeckia subtomentosa), compass plant (Silphium laciniatum), and inland muhly grass (Muhlenbergia glabriflorus).

Mesic prairie, Fort Campbell Army Base.
Photo by: Dr. E.W. Chester

Dry prairie is the shortest of the three types. It is dominated by little bluestem (Schizachyrium scoparium), three-awn grass (Aristida purpurascens), and a rich variety of sunflowers, asters, goldenrods, and thoroughworts. Prairie willow (Salix occidentalis) is a common shrub in dry prairie. Rare plant species found in this community include earleaf false foxglove (Agalinis auriculata), Skinner's false foxglove (Agalinis skinneriana), and barbed rattlesnake root (Nabalus barbatus).

Dry prairie, Fort Campbell Army Base.
Photo by: Dr. E.W. Chester

Some areas at Fort Campbell may have existed as open oak savannas, especially those in more rolling landscapes. Primary oaks would have been post oak (Quercus stellata) and blackjack oak (Q. marilandica). The photos below represent savanna-like areas at Ft. Campbell Army Base.

Examples of savanna-like areas at Ft. Campbell.
Top photograph was taken by Dr. E.W. Chester who said
"this is the best photograph of the 'barrens" I've ever made."
Bottom photo is of Dr. Chester in a giant stand of blazing star (Liatris spicata)
Photos by: E.W. Chester

Prescribed fire is used to manage many of Fort Campbell's prairie remnants. Those in the impact zone are frequently burned by fires that ignite from firing exercises. Without question, if Ft. Campbell didn't exist then neither would the Pennyroyal Plain prairies. Without the base, those on present base lands would today be agricultural fields, subdivisions, woodlots, or cattle pastures. This is a great example of how military lands are extremely important for preserving some of our rarest ecosystems and species.

Smoke from a prescribed fire at Fort Campbell Army Base.
Photo by: Dr. E.W. Chester

The Pennyroyal Prairie Outside of Ft. Campbell

Today, only a handful of very small prairie remnants exist outside of Fort Campbell, but these are constantly under threat. Well into the 20th century, small isolated prairie remnants existed along rural roadsides, in strips beneath powerlines, along the edges of crop fields, in thin strips along the edges of woodlands, or sandwiched between railroads and highways. Many were no larger than half-acre or may have only occupied a few dozen square feet. It was relatively common for botanists working in Kentucky and Tennessee from the 1930s-1970s to observe such prairie remnants in the Pennroyal. One such remnant that was studied up until the late 1900s was the so-called Warfield Barren or Warfield Prairie (described below).  

One such remnant is the Warfield Prairie located in extreme northeastern Montgomery County, Tennessee. It exists as a linear strip sandwiched in a 30-50 foot wide, 1.5 mile long strip between US Hwy 41 and the CSX Railroad just southeast of the town of Guthrie, Kentucky. Recently, CSX Railroad has collaborated with the Tennessee Department of Transportation (TDOT), the Tennessee Division of Natural Areas (TDNA), Austin Peay State University (APSU), and the Botanical Research Institute of Texas (BRIT) to establish the Pennyroyal Plain Railroad Prairie Natural Area. This is the only Pennyroyal Plain prairie remnant in Tennessee that is known to exist outside of Ft. Campbell and it is a rare example of a wet prairie. Identifying, inventorying, and monitoring of these remnants is needed.

Warfield Prairie remnant as it has appeared for many years.
The prairie grasses are routinely mowed and kept short.
Warfield Prairie remnant, Montgomery Co., TN as it
appeared in 1988 before regular mowing of roadside.
Photo by: Dr. E.W. Chester, 1988

Style of planned kiosk at the
Pennyroyal Plain Prairie RR Natural Area

By the late 20th century sightings of prairie remnants became rare indeed. This was because of changes in highway maintenance. During the 1990s, many highways were widened from two to four lanes, obliterating the former remnants. Roadside embankments that once were grassy or brushy, supporting prairie species, became mowed on an annual basis, thus preventing the prairie flora from flowering and setting seed. To compound the problem, invasive species like common fescue (Schedonorus arundinaceus), Chinese buschclover (Lespedeza cuneata), and Johnson grass (Sorghum halepense) out-competed prairie species. In the early 2000s (and increasing thereafter), there also seemed to be a precipitous increase in the amount of herbicide used to treat roadsides, railroad rights-of-way, fencerows, and ditches. The end result is that roadside remnants, which are the last vestiges for many of the South's great prairie systems, have now become nearly completely eliminated. Once they are gone, the hope for restoration using local genotype seeds will be gone, too.

Future Conservation of the Pennyroyal Prairie

There is so much that needs to be done to conserve the vanishing Pennyroyal Plain Prairie.  

The first goal is to identify known remnants. Remnants are few and far between but they do exist and there are likely many small patches that have never been discovered on private lands. 

APSU and BRIT are also planning to partner with Roundstone Native Seed LLC (Munfordville, KY) and Dunbar Cave State Park in Clarksville, TN to establish a 13-acre prairie at the state park and a 2-acre prairie at the Austin Peay State University Environmental Education Center. The goal is to establish diverse local genotype prairies that mimic those nearby at Ft. Campbell. 

More work is needed to educate the general public about the importance of prairie restoration. Plans are in the works with Julian Campbell of the Bluegrass Woodland Institute to establish a public field trip series to visit remnants and discuss their ecology and conservation. Additionally, we plan to establish a visiting public lecture series intended to be delivered to conservation organizations, citizen groups, agencies, and other groups across the Pennyroyal region. 

Eventually, the plan is to be able to once again see landscapes like the one below return throughout the Pennyroyal Plain.

The largest single open field in Tennessee is this degraded prairie remnant at Ft. Campbell, Montgomery Co., TN. Landscapes like this, where no trees could be seen on the horizon were once the norm for the Pennyroyal Prairie 200 years ago. Can we bring this landscape back by creating a network of prairie preserves throughout the Pennyroyal region?

For more information on Southeastern grasslands, I strongly encourage reading Forgotten Grasslands of the South by Dr. Reed Noss (Univ. of Central Florida). It provides an incredible perspective on the diversity, ecology, and history of the Southeastern grasslands not provided anywhere else.