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Rockefellera crossophylla (Pannariaceae) rediscovered in Alabama


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The rediscovery of Rockefellera crossophylla in Alabama, U.S.A. is documented based on six sites discovered between 2015 and 2018. This unusual species was first documented from Alabama by Thomas Minott Peters in the mid-1800’s, but not subsequently seen until rediscovered by the first author in Lawrence County, in 2015, on a sandstone boulder in the Sipsey Wilderness of William B. Bankhead National Forest. Despite extensive fieldwork throughout surrounding areas of central and northern Alabama, no populations outside of Bankhead National Forest have been discovered, further highlighting the biological significance of this small tract of intact, primary habitat within Alabama’s borders.
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Opuscula Philolichenum, 20: 16. 2021.
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Rockefellera crossophylla (Pannariaceae) Rediscovered in
ABSTRACT. The rediscovery of Rockefellera crossophylla in Alabama, U.S.A. is documented
based on six sites discovered between 2015 and 2018. This unusual species was first documented from
Alabama by Thomas Minott Peters in the mid-1800’s, but not subsequently seen until rediscovered by the
first author in Lawrence County, in 2015, on a sandstone boulder in the Sipsey Wilderness of William B.
Bankhead National Forest. Despite extensive fieldwork throughout surrounding areas of central and
northern Alabama, no populations outside of Bankhead National Forest have been discovered, further
highlighting the biological significance of this small tract of intact, primary habitat within Alabama’s
KEYWORDS. Appalachian Mountains, biodiversity, conservation, Cumberland Plateau,
cyanolichen, threatened species.
Rockefellera cryssophylla (Tuck.) Lendemer & E. Tripp [≡ Santessoniella crossophylla (Tuck.)
P.M. Jørg.] is a microfoliose cyanolichen characterized by its minutely digitate lobes, biatorine apothecia
with hemiamyloid hymenia, asci with internal apical ring structures, and smooth ascospores (Lendemer et
al. 2017). This taxon is endemic to eastern North America, where it is rare throughout its range (Jørgensen
2000, Lendemer & Anderson 2008). Recent work in the southern Appalachian Mountains has led to the
discovery of the species at several sites, suggesting this is the center of its extant distribution (Lendemer
2008; Lendemer et al. 2013, 2017). An IUCN Red List assessment by Randlane et al. (2019) listed this
species as Endangered. This listing was attributable primarily to historical population declines, where none
of the historical populations were able to be relocated. The species appears to have been extirpated from
large portions of its historical range.
Rockefellera crossophylla was reported by Mohr (1901, as Pannaria crossophylla Tuck.) based on
a collection made by Thomas Minott Peters from a rock in Lawrence County, Alabama. Hansen (2003)
included the species as present in the state, but recent literature on its distribution in North America omitted
Alabama (Lendemer & Anderson 2008, NatureServe 2020, Randlane et al. 2019, USDA 2020). During
recent fieldwork in northern Alabama, the authors discovered R. crossophylla to be extant at several
locations in a small area of William B. Bankhead National Forest (hereafter BNF). An account of these
occurrences is provided here to support conservation efforts for this species and aid in future assessments
of its conservation status.
J. KEVIN ENGLAND University of West Alabama, Livingston, Alabama 35470. e-mail:; *corresponding author
JAMES C. LENDEMER Institute of Systematic Botany, The New York Botanical Garden, Bronx, New
York 10458. e-mail:
ERIN TRIPP Museum of Natural History and Dept. of Ecology & Evolutionary Biology, University of
Colorado, Boulder, Colorado 80309. e-mail:
Figure 1. Documented locations of Rockefellera crossophylla from the current study (left), placed in the
context of all sites searched for the species in northern Alabama, U.S.A. by the authors (right; red dots =
species detected, black dots = species not detected).
Fieldwork for this study was carried out by the authors in natural areas throughout north Alabama,
U.S.A (Fig. 1). Three smaller sites in north Alabama with habitats and geology comparable to those of the
species were also searched by the authors, resulting in no additional populations. Areas searched in BNF
consisted of sandstone canyons within mixed mesophytic forests on mesic slopes above the floodplain of
creeks and ephemeral drainages. Digital images of the species were obtained in the field using a Canon
EOS Digital Rebel XS with a 55-mm lens with the aid a ruler in each photo for scale. Field images were
then analyzed using Fiji open-source image processing package (Schindelin et al. 2012) to calculate the
area of each patch observed. Azimuth for each patch was documented using a Brunton 8040 G compass.
A search for additional specimens from Alabama was conducted using CNALH (2020) and by
consulting the following herbaria: AUA, COLO, NY, UNA, US, UWAL, and hb-England. In order to avoid
any ambiguity as to the identity of the material in question, small vouchers of the species were collected at
each site where it was found as deposited at AUA, COLO, NY or UWAL (see Appendix I). Specimens
were examined using standard dissecting microscopes and compound light microscopes. The Peters
collection at US was examined using high-resolution micrographs made of the specimen and provided by
the collections staff of that institution.
Previously published accounts of Rockefellera crossophylla from Alabama (Hansen 2003, Mohr
1901,) are presumably attributable to the material collected by T.M. Peters in Lawrence County. The single
specimen made by Peters was originally cited by Tuckerman (1882) and is now deposited in the United
States National Herbarium (US barcode 00945678). We examined digital images of the specimen and
confirmed that it does represent R. crossophylla.
Some 133 years after its first documentation in Alabama, six sites of R. crossophylla were found
by the authors between 2015 and 2018 in BNF (Figs. 1, 2) in northwestern Alabama. These occurrences
confirm the current existence of this rare species in Alabama, remarkably in the same area where Peters
first discovered it in the mid-1800’s. Although it is impossible to determine the precise location where
Peters found R. crossophylla, the rediscovery of the species in the same general area suggests that it has
likely persisted there since that time. It is important to highlight that fieldwork at dozens of sites throughout
Figure 2. Typical occurrence of Rockefellera crossophylla on a boulder in the study area (left), and image
of the species illustrating distinctive thallus color and convex, pale apothecia that are readily visible with
the naked eye (right). Both photographs taken in situ by the first author.
north Alabama, including habitats where R. crossophylla could feasibly occur, did not result in the
discovery of additional occurrences (Fig. 1).
Habitats where we found the species included a mixed mesophytic forest (with Tsuga canadensis
(L.) Carrière, Liriodendron tulipifera L., Fagus grandifolia Ehrh., and Quercus spp.), a high humidity
mesic riparian forest (dominated by mature Fagus grandifolia, mature Tsuga canadensis, mature Pinus
taeda L., and an understory of Ilex spp.), and a mature mixed hardwood forest (with Fagus grandifolia,
Acer saccharum Marshall, Betula lenta L., Ilex opaca Aiton, Magnolia macrophylla Michx., Quercus alba
L., and Q. montana Willd. with the conifer Tsuga canadensis). Substrates where the species was found
include the undersides of non-calcareous rock overhangs, on vertical rock faces of large sandstone cliffs,
and on shaded sandstone boulders (Fig. 2).
The newly documented sites in Alabama provide additional evidence that R. crossophylla is still
extant in contiguous tracts of mature forest ecosystems in the southeastern United States as has already
been discussed by Lendemer et al. (2017). This discovery also increases the percentage of sites located in
protected areas, which supports the conservation of this rare species. Randlane et al. (2019) noted that the
rarity of R. crossophylla was likely due to highly specific edaphic factors such as thalli being restricted to
the bases of large overhangs of acidic rock as well as environments with relatively high and constant
humidity. This was the case for the six sites where we located the species.
At two of the newly discovered sites, census data for 54 patches was recorded. Within the study
sites larger boulders harbored larger patches and more individual patches per occurrence (Appendix II).
Approximately 79% (43 patches) of the observed R. crossophylla patches were small (area < 100 cm2)
(Appendix III); whereas only 9% (5 patches) of the documented patches covered an area greater than 200
cm2. Patches were most common on the faces of south to southwest-facing boulders (Appendix IV);
however, they were generally smaller on these aspects. The largest patches were observed on north-facing
aspect of the boulders (Appendix IV).
The BNF contains many unique habitats, substrates, forest and soil types, and microhabitats that
afford constant humidity, including an appreciable amount of yearly rainfall (Gunasekaran et al. 1992,
Hardin & Lewis 1980, PRISM 2020, Zhang et al. 1999). In addition to ecological and environmental
diversity, the tract includes intact mature, old-growth forest stands in a broader context of primarily native
habitat (Hinkle et al. 1993, Zhang 1999). These important abiotic and biotic factors are likely why there is
significant diversity of rare, federally, and state tracked species in the BNF (ANHP 2019, Keener et al.
2020). To this cohort of unique and threatened taxa can be added R. crossophylla.
We are grateful for Steve Ginzbarg (UNA) providing digital copies of specimen data from the
Thomas M. Peters lichen collection, Sue Lutz (US) for high-resolution specimen micrographs of T.M.
Peter’s original specimen, and Andy Scott (Bankhead National Forest, District Ranger) for providing
background resources included in the paper. The manuscript was significantly improved by the comments
of Gary Perlmutter (NCU) and two anonymous reviewers. Erin Tripp and James Lendemer acknowledge
financial support from the U.S. National Science Foundation (Dimensions of Biodiversity Awards
#1542629 & 1542639).
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Endangered Plants & Animals of Alabama. Alabama Natural Heritage Program, Auburn
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Specimens examined. U.S.A. ALABAMA. LAWRENCE CO.: 4.72 air mi. SW of Youngtown,
Bankhead National Forest, Sipsey Wilderness, Lick Branch Canyon, along W side of Gum Pond Rd.
approx. 2.56 mi. S of jct. with CR7/Ridge Rd., 27.iii.2015, J.K. England 5375 (AUA, UWAL); 6.37 air mi.
ENE of Posey Mill, Bankhead National Forest, Sipsey Wilderness, along trail E of Thompson Creek
trailhead on NW Rd. approx. 1.44 mi. E of jct. with Arnold Motorway, 27.ii.2016, J.K. England 5869
(UWAL), 12.ix.2018, J.K. England 9458 & J. Barrett (UWAL); Bankhead National Forest, Sipsey
Wilderness, confluence W-facing slopes above confluence of East Bee Branch and West Bee Branch, 0.5
mi N of confluence of Bee Branch with Sipsey River, 1.i.2017, J.C. Lendemer 49978 & E.A. Tripp (COLO,
NY); Bankhead National Forest, Sipsey Wilderness Area, slopes above N/W shore of Borden Creek, just S
of jct of FS Trails 224, 207 and 200, 0.5 mi W of terminus of CR5, 3.i.2017, E.A. Tripp 6770 & J.C.
Lendemer (COLO, NY). WINSTON CO.: 4.43 air mi. SE of Grayson, Bankhead National Forest, Brushy
Creek, along W side of Hickory Grove Rd. approx. 1.68 mi. SSW of jct. with Mt. Olive Rd., 19.viii.2018,
J.K. England 9396 (UWAL).
Table 1. Tabular summary of substrate size classes and Rockefellera crossophylla patch sizes.
Average Patch
Area (cm2)
Small Boulder
<= 1.0 m3
Large Boulder
> 1.0 m3
Graphical comparison of R. crossophylla patch areas (cm2) from two localities in Sipsey
Wilderness, Bankhead National Forest, Lawrence County, Alabama, USA
Graphical comparison of relationship between substrate aspect (degrees) and the number of R.
crossophylla patches (left) and the size of R. crossophylla patches (right).
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The taxonomic delimitation and generic placement of Santessoniella crossophylla (Old Gray Crosslobes), a cyanolichen endemic to eastern North America, are revisited based on newly generated nrITS and mtSSU sequences. A population from Nova Scotia whose identification as S. crossophylla has been questioned is confirmed as belonging to the species. The monospecific genus Rockefellera is introduced to accommodate lichens ascribable to S. crossophylla in light of molecular results herein presented. The new name honors the Rockefeller family for their century-long support of North American conservation efforts, particularly with respect to national parks.
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The following species are newly reported for North Carolina: Chrysothrix onokoensis, Dirina massiliensis f. sorediata, Heterodermia casarettiana, Homostegia hertelii, Lichenoconium lecanorae, Mycoporum antecellans, Pyrenula cuyabensis, Santessoniella crossophylla, Trapelia coarctata, Trapeliopsis gelatinosa, Vouauxiomyces truncatus. The distribution of Dirina massiliensis f. sorediata in North American is mapped. The hosts and anamorph-telemorph relationship of Vouauxiomyces truncatus are discussed.
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