lichens of the lower ozark region of missouri and arkansas

INTRODUCTION
This is a preliminary treatment of the lichen flora of the Lower Ozark region of Missouri and
Arkansas. This region includes nine counties with all or part of their area contained within the surface
watersheds of the Current, Eleven Point, and Jack's Fork Rivers or the recharges of the major springs
associated with these rivers. These counties are Carter, Dent, Howell, Oregon, Reynolds, Ri pley,
Shannon, and Texas counties in Missouri and Randolph County in Arkansas (Figure 1).
The Lower Ozark section of the Ozark Natural Division (Thom & Wilson, 1980) lies at the heart of
the Missouri portion of the Ozark uplift, and includes the oldest continually exposed land in
midcontinental North America. Portions of the Ozarks have been continuously available for terrestrial
life since the late paleozoic, some 225 million years ago.
This ancient l andscape consists of a diverse, ruggedly dissected topography that is largely wooded,
wi th oak, oak-pine, and pine woodlands predominating on excessively drained, cherty upland soils.
Springs, caves, bluffs, sinkholes, glades, fens, narrow ridges, and high-gradient streams are
characteristic features in the region. Dolomitic rocks are the most common bedrock type in the region,
resulting in an extensive karst landscape. An average of one billion gallons of water flows daily from
more than 80 named springs along the region's rivers, and more than 800 caves have been documented
in the region. Other bedrock types common in the region include sandstone, localized lenses of chert,
and igneous rocks.
The Lower Ozark region contains the largest uni ts of contiguous native vegetation and highest levels
of endemic, rare, or disjunct biota of any region in Missouri, and has been designated by The Nature
Conservancy as one of 75 regions on the planet having critical biodiversity values. The combination
of an ancient, topographically and geologically diverse landscape and repeated influxes of biota from
diverse regions in response to climatic change have resulted in a unique juxtaposition of organisms
from spatially and temporally disparate biogeographic regions. Many species not typically found in
midcontinental North America have adapted to suitable microhabitats and survived in the region
through changes of climate and process regime.
The Lower Ozark region is rich in endemic species, as well as in populations of species that are either
significantly disjunct from their main range or at the edge of their range. An astonishing 17% of the
vascular flora of the region is disjunct or attains the limit of its range in the Interior Highlands (The
Nature Conservancy 1994). Additionally, a number of vascular taxa, while locally common, are
endemic to the Ozarks, or, for plants such as Scutellaria bushii and Tradescantia longipes, are
essentially endemic to the Lower Ozark region.
The Ozarks have been poorly explored from a biological perspective. While this is true as a general
statement, it is even more compelling from the standpoint of cryptogams and invertebrates. Little
lichen work was done in the region prior to field work conducted by Richard Harris, William Buck,
Gerould Wilhelm and myself beginning in the 1980's. Hale (1957) compiled the first checklist of
corticolous macrolichens in a portion of the Ozarks, stating in his introduction "no professional
lichenologist has ever collected in the region". A sober assessment of the current state of
lichenological knowledge in the region must explicitly acknowledge that there are many more lichens
yet to be documented from the Interior Highlands; preliminary work suggests that there are many
undescribed species in the region (Harris and Ladd 2002).
This is a first attempt to circumscribe the lichen biota of the Lower Ozarks, and to provide information
about lichen dis tribution, abundance, and ecology in the region. Many of the treatments are
preliminary, and in several cases, as indicated in the text, there is considerable uncertainty regarding
the application of a name. Even with these uncertainties, a treatment such as this can be a useful tool
in gaining an understanding of the local biota and facilitating information flow, as long as a rigorous
consistency of concept is maintained.