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The Case of the 30-year Persistence of the Single Known Population of Panax quinquefolius L. (Araliaceae) in Louisiana
Albert J. Meier, Albert H. Meier, Alden D. Meier, Lowell E. Urbatsch, and Barry McPhail

Southeastern Naturalist, Volume 17, Issue 3 (2018): N56–N59

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2018 Southeastern Naturalist Notes Vol. 17, No. 3 N56 A.J. Meier, A.H. Meier, A.D. Meier, L.E. Urbatsch, and B. McPhail The Case of the 30-year Persistence of the Single Known Population of Panax quinquefolius L. (Araliaceae) in Louisiana Albert J. Meier1,*, Albert H. Meier2, Alden D. Meier2, Lowell E. Urbatsch3, and Barry McPhail4 Abstract - There were a total of 12 documented Panax quinquefolius (American Ginseng) in the only known population in Louisiana in 1986. Our reassessment of the population in 2016 found 16 plants. We suggest that the long-term persistence of this tiny American Ginseng population indicates that simple matrix-population models may be overestimating quasi-extinction numbers and minimum viable populations, perhaps as a result of failing to sufficiently consider influences of environmental conditions. We further suggest that this, the southernmost documented population of the species in the US, has endured beyond expectation but remains at acute risk of extirpation and that any populationspecific genes are at risk of loss if no intervention is made to protect the population. Panax quinquefolius L. (American Ginseng) is an uncommon, widespread, understory herb of the eastern deciduous forest (McGraw et al. 2013). The 1 known population in Louisiana is located in West Feliciana Parish. A population of 12 plants was originally reported by Urbatsch and Meier (1986). The population was located on a west-facing finger of a ridge about 5–10 m above a sand-bottomed, intermittent stream typical of the Tunica Hills, at an elevation of ~65 m. The vegetation reported for the site by Urbatsch and Meier (1986) included Arundinaria gigantea (Walter) Muhl. (Switchcane). Nearby canopy trees included Liriodendron tulipifera L. (Yellow-poplar), Carya glabra (Mill.) (Sweet Pignut), and Fagus grandiflora Ehrh. (American Beech). This tract of land was lightly grazed through 1971. The flora of the Tunica Hills in Louisiana and adjacent southwestern Mississippi includes many Appalachian Pleistocene relict species (Delcourt and Delcourt 1975). A few of these are: Actaea pachypoda Ell. (White Baneberry), Adiantum pedatum L (Maidenhair Fern), Circaea latifolia Hill (Broad-leaved Enchanter’s-nightshade), Deparia acrosticoides (Sw.) Butler (Silvery False Spleenwort), and Pachysandra procumbens Michx. (Alleghany Spurge). This particular tract of land is the location for discovery of 2 other major disjuncts: Asarum canadense L. (Wild Ginger, Aristolochiaceae) (Cox et al. 1987), and Plethodon websteri Highton (Webster’s Salamander) (Rossman and Meier 1979). All of these disjuncts were found at or near the bottoms of moist slopes near the southern terminus of the region described by Delcourt and Delcourt (1975) as the Blufflands pathway , suggesting that these organisms, including American Ginseng, migrated south along the Mississippi River and remained in the cool, moist valleys and ravines that developed in the loess bluffs. Given the perilously low population reported by Urbatsch and Meier (1986), substantial local Odocoileus virginianus (Zimmermann) (White-tailed Deer) populations, and the passage of 29 years, we revisited the site to reassess the population as to both numbers and viability. During 2 recent summers, we returned to this site and thoroughly searched the surrounding area for American Ginseng. On 24 July 2015, we observed only 6 American Ginseng plants on or surrounding the original site. Of the 6 plants, 2 showed evidence of having produced flowers and possibly 1Western Kentucky University, Department of Biology, 1906 College Heights Boulevard #11080, Bowling Green, KY 42101. 27165 Bear Cave Road, Denham Springs, LA 70706. 3Department of Biology, Louisiana State University, Baton Rouge, LA 70803. 4Bayside Academy, 303 Dryer Avenue, Daphne, AL 36526. *Corresponding author - Manuscript Editor: Brett Serviss Notes of the Southeastern Naturalist, Issue 17/3, 2018 N57 2018 Southeastern Naturalist Notes Vol. 17, No. 3 A.J. Meier, A.H. Meier, A.D. Meier, L.E. Urbatsch, and B. McPhail fruit, but only 1 individual bore a single immature or under-developed, greenish fruit; 4 had 2 leaves and 2 bore 3 leaves. The trees, of course, had grown, but otherwise the vegetation remained similar to that originally reported for the site by Urbatsch and Meier (1986). The next summer, on 21 June 2016, we found 16 plants in the same small area (less than 0.1 ha). Of these, 2 had 1 leaf, 11 had borne 2 leaves, and 3 had 3 leaves. Three of the 2-leaf plants had lost a leaf to herbivory. By way of comparison, stem heights (cm) of the 2-leaf plants in the Tunica Hills were short (n = 11, mean = 4.52 cm, SD =0.85 ) relative to those at 3 Mammoth Cave National Park sites in Kentucky: Site 1 ( n = 72, mean = 8.91 cm, SD = 2.71), Site 2 (n = 71, mean = 8.86 cm, SD = 3.17), and Site 3 (n = 87 cm, mean=8.63 cm, SD = 3.09) (USNPS 2005). The independent-sample t-tests (not assuming equal variance) were significant (P < 0.01) in all 3 cases, confirming relatively shorter stem heights in the Louisiana population relative to these Kentucky sites. In 2016, none of the eleven 2-leaf plants produced an inflorescence, but all 3 of the 3-leaf plants each bore an inflorescence, and 2 of these produced a total of 3 fruits. The lack of 2-leaf plants bearing inflorescences stands in contrast to a 40–90% inflorescence rate reported for 2-leaf plants from 6 populations in Kentucky (McGraw et al. 2013). Our result may represent an Allee effect, a condition where there is a correlation between population size and mean fitness. Hackney and McGraw (2001) reported Allee effects in small populations of American Ginseng, but not reduced numbers of inflorescences. Given the small area of the Louisiana population, we felt quite certain that we would not have missed a plant with leaves; given that we found more 2- and 3-leaf specimens in 2016 than the total observed population in 2015, we were in a quandary. However, James McGraw (Department of Biology, West Virginia University, Morgantown, WV, pers. comm.) informed A.J. Meier that when an American Ginseng plant loses its leaves, it does not re-sprout leaves until the following growing season. In 2016, we observed several plants with torn petioles. Hence, we probably missed plants that had gone dormant after being subjected to herbivory, likely by deer. In summary, in both survey years, the plants comprising this population compared poorly to large Kentucky populations in both robustness and reproduction. In their paper on effects of climate change and harvest on extinction risk of American Ginseng, Souther and McGraw (2014) set the quasi-extinction number for population-viability analysis at 20 because experimental tests demonstrated that in populations with less than 20 individuals, Allee effects decreased λ (the finite rate of population increase) (Hackney and McGraw 2001, McGraw and Furedi 2005). Furthermore, in a study of 7 American Ginseng populations, McGraw and Furedi (2005) estimated a minimum viable population of ~800 plants. Applying these numbers to 36 populations in the Appalachians, they projected that none of them were large enough to be considered a minimum viable population. Indeed, they indicated that they were aware of only 2 populations that met their projected minimum viable-population threshold. In any case, by this standard, the Louisiana population has been below both the minimum viable population and the quasi-extinction threshold since at least when it was documented in 1986 (Urbatsch and Meier 1986) and remained so when we surveyed it in 2015 and 2016; yet it has clearly survived and exhibited a long-term λ that approximates one. We wonder whether we have encountered a “black swan” (Mill 1843) in the woods that warns us that population minimum viable-population standards, quasiextinction thresholds, and matrix-model population-projections are questionable guides for predicting future populations of American Ginseng. Crone et al. (2013) found that such models failed to forecast within 95% confidence for 60% of 82 po pulations of 20 species. Perhaps negative density-dependent phenomena including low rates of harvesting, poaching, and disease have outweighed Allee effects for this population. Also, we suggest that a not insubstantial seed bank (McGraw et al. 2013) and long life may allow American Ginseng 2018 Southeastern Naturalist Notes Vol. 17, No. 3 N58 A.J. Meier, A.H. Meier, A.D. Meier, L.E. Urbatsch, and B. McPhail to take advantage of temporal variability in conditions for reproduction and germination. Though difficult to estimate accurately, harvesting has been previously documented to have a strong and pervasive effect on the population demographics of American Ginseng in other areas of its range, even where protected (Rock et al. 1999). Poachers may harvest and return to re-harvest large and dense populations until they are reduced to the more frequently encountered population sizes that are well below the estimated minimum viable-population size, whereupon they cease to exploit them in favor of locations with higher rewards. When growing at high density, American Ginseng is also vulnerable to a number of pathogens including, but not limited, to Alternaria, Phytophthora, and Fusarium (fungal genera; Nicol et al. 2002). We also suggest that harvesters may initiate and manage many well-protected populations. We should not have expected a population as small as this one, with the disadvantages of high temperatures, herbivory, and tiny plants, to have remained extant for 30 y, but these plants persisted beyond hypothetical expectations established by viability analysis. The population is particularly important in the face of climate change because American Ginseng populations are adapted to the local temperatures (Souther and McGraw 2011, Souther et al. 2012). As the southernmost documented population, these Louisiana American Ginseng may have more heat tolerance than most populations. Given the low gene-flow between populations found by Cruse-Sanders and Hamrick (2004a and 2004b), any population- specific heat tolerance genes are at risk of loss. Despite its seeming challenge to theoretical expectations, we recognize that the status of this population is perilous and at high risk of extirpation. The population may be at further risk given its extremely small size. A single poacher could easily dig the entire Louisiana aboveground population in 15 minutes. The small size of the plants may also be an Allee effect. The demonstrated negative influences of higher temperatures on American Ginseng populations (Souther and McGraw 2011, 2014; Souther et al. 2012) should be of particular concern at the southern extreme of its range. Biotic factors, such as browsing by locally abundant deer, can also impact viability (Farrington et al. 2009, McGraw and Furedi 2005, Souther and McGraw 2014). We have noted evidence of herbivory at the site, and West Feliciana Parish ranks 8th in the state for most deer harvested per forested acre (Louisiana Department of Wildlife and Fisheries 2015). In summary, we suggest that the long-term persistence of this tiny American Ginseng population indicates that current models describe population status, but should not be depended upon to project the future status. Alternatively, we suggest that this single, small Louisiana population, the only known natural population of American Ginseng in Louisiana and, according to Kartesz (2015), possibly the southernmost population in existence, should receive management efforts in order to favor increased population-growth rates and create additional populations. Acknowledgments. We are particularly grateful for the exceptionally thoughtful comments of 2 anonymous reviewers. James B. McGraw provided essential valuable advice. We also thank Danielle Racke and John Pickering for editorial suggestions. Literature Cited Cox, P.B., L.E. Urbatsch, E.M. Harris, and A.J. Meier. 1987. Verification of Asarum canadense L. (Aristolochiaceae) in Louisiana. Sida 12:423. Crone, E.E., M.M. Ellis, W. F. Morris, A. Stanley, T. Bell, P. Bierzychudek, J. Ehrlén, T.N. Kaye, T. M. Knight, P. Lesica, G. Oostermeijer, P.F. Quintana-Ascencio, T. Ticktin, T. Valverde, J.L. Williams, D.F. Doak, R. Ganesan, K. McEachern, A.S. 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