Understanding the current status of rare plant populations is critical for the development of conservation strategies. Critical types of needed information include updated inventories, accurate mapping and knowledge of population dynamics, ecological characterization of habitats, and an understanding of the effects of anthropogenic disturbances. Unfortunately, such information is often lacking for many rare plants species. Several different types of conservation projects have begun adopting the use of geographic approaches (Alexander et al., 2005; Anderson and Martinez-Meyer, 2004; Vanderpoorten et al., 2005). GIS/GPS methods can be effectively used in data collection, record management, and population inventorying. GIS further allows analysis to be conducted across several different layers of environmental variables (Clark et al., 1993). This enables models to be developed that characterize current habitats and predict unknown habitat locations (Rotenberry et al., 2006). Knowledge concerning the exact locations and environmental requirements of threatened and endangered plants is crucial when developing management plans. With this information, managers can make informed decisions regarding establishment of protected areas, collection for ex situ conservation, and exploration for unknown populations.
Georgia plume [Elliottia racemosa (Ericaceae)] is a small tree that is endemic only to the state of Georgia, where it is listed as a threatened species (Georgia Department of Natural Resources, 2006). Georgia plume is known for its large, white, plume-like inflorescences that are born in June and July. First discovered by William Bartram in the 1770s (Ewan, 1968), it is confined mainly to the Coastal Plain region. Georgia plume is one of the rarest native plants in Georgia (Santamour, 1967). Attesting to the rarity of the species, no wild populations were known from ≈1875 to 1901, during which time georgia plume was thought to be extinct in the wild. More recent assessments have described the plant to occur in ≈36 locations (Patrick et al., 1995). However, many reported populations are now thought to be destroyed or much reduced (Chafin, 2007).
The extreme scarcity of the plant is caused in part by low to no fruit production that has been observed for much of the plant’s known history and noted by several authors (Del Tredici, 1987; Elliott, 1821; Faircloth, 1970; Fordham, 1991; Miller, 1978). In recent times, no seedling recruitment has been observed in the wild. Our recent work suggests georgia plume may have reproductive challenges, including low pollen viability, separation in the timing of male and female function within flowers, and sexual self-incompatibility (Radcliffe et al., 2010). Low genetic diversity has been reported from allozyme analysis of several populations (Godt and Hamrick, 1999). In a molecular analysis of georgia plume populations using random amplified polymorphic DNA, the small number of individuals and geographic isolation characteristics of many populations were associated with high within-population genetic similarity suggesting that narrow genetic variation in some populations may be contributing to lack of sexual reproduction in the wild (Porter et al., 2012). The combination of these factors explains serious biological reasons for the rarity of the species in the wild.
In addition to reproductive issues, habitat loss is likely a contributing factor to losses of georgia plume. The clearing of forest lands for agricultural and timber uses is a major contributor to georgia plume habitat loss (Duncan and Duncan, 1978; Patrick et al., 1995). Modern land use techniques including increased agricultural land use have been shown to pose threats to sensitive plants. Anthropogenic influences can be major contributors to loss of diversity, habitat, and populations of rare plants (Brockerhoff et al., 2008; Ceballos et al., 2010; Vargas-Rodriguez and Platt, 2012).
Georgia plume has been reported to appear in a range of habitats including sand ridges, dry oak ridges, evergreen hammocks, sandstone outcrops, and sandy soil conditions ranging from moist to xeric (Patrick et al., 1995). The apparently wide variety of habitats but limited number of locations in which georgia plume occurs has made it difficult to draw any definitive conclusions as to the distribution and preferred habitat of the species. Current distribution maps are often based on plant sightings and contain limited environmental data. In the current study, GPS- and GIS-based surveys were integrated to map the distribution and characterize the ecological habitat of georgia plume. An advantage of this approach is that locations of populations and individual trees can be accurately recorded, which can be extremely useful in long-lived species. This is paramount when locating georgia plume populations because they tend to be small in size. It is also possible to conduct censuses of populations and determine distances between individuals for use in other studies such as genetic analysis. Other advantages of keeping population records in a GIS are the ability to store several types of attributes easily, flexibility in recording information as needed, and ease in updating attribute information. By recording habitat attributes concurrently with spatial information, analyses of populations or individuals can be conducted on these attributes in relation to other environmental variables. This would lead to a better understanding of the diverse environmental conditions in which georgia plume occurs.
In this study, census and distribution data were collected, and the ecological habitat was characterized for all known populations of georgia plume. The objectives of this study were to: 1) develop a GIS-based conservation management tool capable of inventorying populations and recording habitat conditions; and 2) assess potential causes for population losses and decline by relating previously described historic locations containing georgia plume with currently active and inactive sites. Spatial and environmental data were collected during field visits. In cases in which ground visits were not possible, aerial analysis was used. Although information presented here is specifically related to georgia plume, the methodology could readily be used as a model system for other threatened or endangered species.
Alexander, M.T., Worthen, L.M. & Craddock, J.H. 2005 Conservation of Castanea dentata germplasm of the southeastern United States Acta Hort. 693 485 490
Anderson, R.P. & Martinez-Meyer, E. 2004 Modeling species' geographic distributions for preliminary conservation assessments: An implementation with the spiny pocket mice (Heteromys) of Ecuador Biol. Conserv. 116 167 179
Brockerhoff, E.G., Shaw, W.B., Hock, B., Kimberley, M., Thomas, P., Quinn, J. & Pawson, S. 2008 Re-examination of recent loss of indigenous cover in New Zealand and the relative contributions of different land uses N. Z. J. Ecol. 32 115 126
Bruna, E.M. 2002 Effects of forest fragmentation on Heliconia acuminata seedling recruitment in central Amazonia Oecologia 132 235 243
Ceballos, G., Davidson, A., List, R., Pacheco, J., Manzano-Fischer, P., Santos-Barrera, G. & Cruzado, J. 2010 Rapid decline of a grassland system and its ecological and conservation implications PLoS One 5 1 12
Chafin, L.J. 2007 Field guide to the rare plants of Georgia. The State Botanical Garden of Georgia, Athens, GA
Clark, J.D., Dunn, J.E. & Smith, K.G. 1993 A multivariate model of female black bear habitat use for a geographic information system J. Wildl. Mgt. 57 519 526
Coates, D.J., Sampson, J.F. & Yates, C.J. 2007 Plant mating systems and assessing population persistence in fragmented landscapes Aust. J. Bot. 55 239 249
Dudash, M. & Fenster, C.B. 2000 Inbreeding and outbreeding depression in fragmented populations, p. 35–53. In: Young, A.G. and G.M. Clarke (eds.). Genetics, demography and viability of fragmented populations. Cambridge Univ. Press, New York, NY
Elliott, S. 1821 A sketch of the botany of South Carolina and Georgia. Vol. I. J.R. Schenk, Charleston, SC
Georgia Department of Natural Resources 2006 Georgia’s state protected animals and plants. Wildlife Resources Division—Nongame Conservation Section, Social Circle, GA
Godt, M.J.W. & Hamrick, J.L. 1999 Population genetic analysis of Elliottia racemosa (Ericaceae), a rare Georgia shrub Mol. Ecol. 8 75 82
Hensen, I. & Wesche, K. 2006 Relationships between population size, genetic diversity and fitness components in the rare plant Dictamnus albus in central Germany Biodivers. Conserv. 15 2249 2261
Matthies, D., Brauer, I., Maibom, W. & Tscharntke, T. 2004 Population size and the risk of local extinction: Empirical evidence from rare plants Oikos 105 481 488
Miller, H.A. 1978 The story of Elliottia, a primitive, slow-growing member of the heath family that is rare in more ways than one Amer. Forests 84 24 27
Patrick, T.S., Allison, J.R. & Krakow, G.A. 1995 Protected plants of Georgia. Georgia Department of Natural Resources, Social Circle, GA
Porter, J.A., Wetzstein, H.Y., Berle, D., Wadl, P.A. & Trigiano, R.N. 2012 Molecular analysis for conservation of georgia plume, a threatened endemic, using random amplified polymorphic DNA HortScience 47 563 569
Radcliffe, C.A., Affolter, J.M. & Wetzstein, H.Y. 2010 Floral morphology and development in georgia plume, Elliottia racemosa (Ericaceae), a rare coastal plain endemic HortScience 135 487 493
Vanderpoorten, A., Sotiaux, A. & Engels, P. 2005 A GIS-based survey for the conservation of bryophytes at the landscape scale Biol. Conserv. 121 189 194
Vargas-Rodriguez, Y.L. & Platt, W.J. 2012 Remnant sugar maple (Acer saccharum subsp. skutchii) populations at their range edge: Characteristics, environmental constraints and conservation implications in tropical America Biol. Conserv. 150 111 120
Young, A., Boyle, T. & Brown, T. 1996 The population genetic consequences of habitat fragmentation for plants Trends Ecol. Evol. 11 413 418