Niche Conservatism and the Future Potential Range of Epipactis helleborine (Orchidaceae) Marta Kolanowska* Department of Plant Taxonomy and Nature Conservation, University of Gdan´sk, Gdan´sk, Poland Abstract The aim of the present study was to evaluate the current distribution of suitable niches for the invasive orchid species, Epipactis helleborine, and to estimate the possibility of its further expansion. Moreover, niche modeling tools were used to explain its rapid expansion in North America and to test the niche conservatism of the species. The maximum entropy method was used to create models of the suitable niche distribution. A database of E. helleborine localities was prepared based on the examination of herbarium specimens, information from electronic databases as well as data gathered during field works. The differences between the niches occupied by native and invasive populations were evaluated using the niche overlap and niche identity test indexes. Moreover, the coverage of the most suitable habitats for the species was measured for three future scenarios as well as for the present time model. Populations of E. helleborine occupy North American west coast habitats very similar to those preferred by native, Eurasian populations, while the expansion in the east coast is related to the niche shift. The created models of suitable niche distribution indicate that the species does not realize its potential niche in the native range. The total surface of the habitats potentially available for E. helleborine will decrease in all climate change scenarios created for 2080. Citation: Kolanowska M (2013) Niche Conservatism and the Future Potential Range of Epipactis helleborine (Orchidaceae). PLoS ONE 8(10): e77352. doi:10.1371/ journal.pone.0077352 Editor: Judi Hewitt, University of Waikato (National Institute of Water and Atmospheric Research), New Zealand Received June 21, 2013; Accepted September 2, 2013; Published October 15, 2013 Copyright: ß 2013 Marta Kolanowska. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: No current external funding sources for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The author has declared that no competing interests exist. * E-mail: [email protected] Introduction environmental weed according to the Global Compendium of Weeds (www.hear.org). One of the most challenging aspects of world’s biodiversity It has been assumed that E. helleborine was introduced to North conservation is the problem of biological invasions. Vascular plants America by colonists who thought it to be a cure for gout; are among the most often transferred organisms [1], [2]. however, this hypothesis has not been confirmed and the exact Obviously, most studies concern those alien species which source of the invasive populations remains unknown. Squirrell negatively affect the native ecosystems via competition with native et al. [12] deliberated on the possible means of introduction of organisms or changing climatic conditions in the invaded area, Broad-leaved Helleborine and suggested that colonial herbal while the nature of non-harmful species translocations is still gardens and accidental human transport were the most probable poorly recognized [3]. origin of the alien populations, since the species was established in Orchids are rarely found to be invasive and for a long time even North America 250 miles (400 km) inland from the Atlantic naturalized species were not considered to be detrimental for the Ocean. environment [4]. However, the most recent research [5] has The first naturalized locality of the species was discovered in the indicated the negative influence of one species, Asian Spathoglottis USA in 1879 near Syracuse (NY) and at the beginning of the 20th plicata, to native populations of Bletia patula in Puerto Rico. The century Broad-leaved Helleborine was also reported from Cana- transfers of orchids and other vascular plants were related mainly dian Quebec and Ontario [13]. The expansion of the orchid was to the Great Geographical Discoveries and one of the most especially rapid in calcium-rich areas and soon it was also found in spectacular was the introduction of E. helleborine (Broad-leaved California [14]. An increase in the invasion was observed in the Helleborine) to the USA, where it rapidly spread and it is currently 1930 s when the presence of E. helleborine was reported from naturalized in both the USA and Canada. Wisconsin and Missouri [15]. Epipactis helleborine is native to Eurasia, in the north to While the genetic data are not helpful in discriminating between Scandinavia, in the east to central Siberia and the Himalayas single and multiple introductions of E. helleborine to North America, and within this range it is usually found in the shady, moist edges it is worth considering whether the process was likely to be active and clearings of woodlands [6]; however, it also occupies various or passive [12]. anthropogenic habitats, such as roadsides, cemeteries, railway Surprisingly, so far no studies on the possibility of the further embankments, gravel pits, quarries or poplar plantations [7], [8], expansion of the species have been conducted, probably because [9], [10]. It may also appear spontaneously in gardens and town no direct negative effects of the introduction of E. helleborine in parks [11], [6]. It is classified as an agricultural weed, or North America have been reported so far. The aim of the present PLOS ONE | www.plosone.org 1 October 2013 | Volume 8 | Issue 10 | e77352 Niche Conservatism of Epipactis helleborine Figure 1. Native (circles) and invasive (squares) localities of E. helleborine used in the modelling. doi:10.1371/journal.pone.0077352.g001 study was to evaluate the current distribution of suitable habitats tropicos.org) and the nhwildlife.net website as well as data for Broad-leaved Helleborine and to create models for the future gathered during field work conducted in Poland were included to estimate the possibility of the further expansion of this orchid. in the analysis (Table S1). The distribution of the localities used in Here, niche modeling tools are used to estimate not only the the modeling is presented in Fig. 1. The occurrence data were possibility of further expansion of the species, but also to explain selected to be more than 22 km distant one from another and not the rapid expansion of the species in North America, especially in to overlap on the maps used in the analysis which are in 2.5 arc- the context of the results of recent research [16] that have minute resolution. indicated that shifts of climatic niches are rare among terrestrial plant invaders. Georeferencing So far, ENM tools have been used in studies of the potential For the analysis, only those localities which could be precisely expansion of only one invasive orchid species [17], African placed on the map were used. The georeferencing process Oeceoclades maculata, which was naturalized in the Neotropics. In followed [19]. The geographic coordinates provided on the this case, the niches occupied by the native and alien populations herbarium sheet labels were verified. If there was no information differ significantly; however, this species was probably introduced about the latitude and longitude on the herbarium sheet label, we into the Neotropics in the 1500 s, so the invasive populations could followed the description of the collection site and assigned gradually adapt to the new habitats and expand into new areas. In coordinates as precisely as possible to this location. The contrast, Broad-leaved Helleborine occupied both coasts of North geographic coordinates provided on the herbarium sheet labels America rapidly, but so far the nature of this invasion remains were verified. Google Earth (v. 6.1.0.5001, Google Inc.) was used unknown. to validate all gathered information. With this approach we were able to verify and assign coordinates to 56 localities. The data were Materials and Methods divided into two groups: native and invasive. In total, 20 native and 36 invasive locations were used, which is more than the Localities minimum number of localities (.5) required by Maxent to obtain A database of E. helleborine localities was prepared based on the reliable predictions [20]. examination of herbarium specimens stored in K and MO. Herbaria acronyms are cited according to the Index Herbariorum Maximum Entropy Analysis [18]. To enlarge the dataset, information from the electronic The maximum entropy method as implemented in Maxent database of the Missouri Botanical Garden (available at www. version 3.3.2 software was used to create models of the suitable Table 1. Estimates of relative contributions of the environmental variables to the Maxent model created on different datasets. Combined (AUC = 0.991, SD = 0.003) Invasive (AUC = 0.994, SD = 0.001) Native (AUC = 0.986, SD = 0.002) Var_1 Bio19 (28.6) Bio19 (23.9) Bio11 (16.8) Var_2 Bio11 (13) Bio14 (14.7) Bio19 (15.5) Var_3 Bio17 (10.7) Bio4 (12.8) Bio7 (13.7) Var_4 Bio3 (9) Bio2 (9.4) Bio6 (10.4) Var_5 Bio12 (7.9) Bio15 (7.5) Bio17 (9.6) The percent contribution is given in parenthesis. doi:10.1371/journal.pone.0077352.t001 PLOS ONE | www.plosone.org 2 October 2013 | Volume 8 | Issue 10 | e77352 Niche Conservatism of Epipactis helleborine Figure 2. Present distribution of the suitable habitats of E. helleborine. A - combined model, B - invasive dataset, C - native dataset. doi:10.1371/journal.pone.0077352.g002 niche distribution [21], [22]. The application has been widely used worldclim.org) were used. Because Maxent is relatively robust to predict species distributions, as it is supposed to be the most against collinear variables, all available 19 climatic factors were reliable of the available machine learning programmes (e.g [23], used [28], [29].