Invasive species in an urban flora: history and current status in Indianapolis, Indiana.
An invasive species is defined in the United States by Executive Order as "a species that is: 1) non-native (or alien) to the ecosystem under consideration and 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health" (USDA, NISIC 2016). Invasive species (exotic insects, plants, fish, birds, mammals, and many other organisms) are a serious threat, resulting in estimated costs and damages of more than $120 billion annually in the United States (Pimental et al. 2005) and more than 12[euro] billion annually in Europe (van Ham et al. 2013). Human actions are the primary means of introduction.
Urban areas are often points of introduction for invasives (Pysek 1998). In cities, invasive plants have been shown to alter species composition, resulting in loss of biodiversity and declines in primary productivity, to diminish ecosystem services (e.g., erosion control), to cause infrastructure deterioration, to alter nutrient cycling, and to contribute to declines in property value (van Ham et al. 2013). Additional social impacts include the perception of spaces overgrown with invasives as signs of urban decay, and loss of visual connection with natural features such as riparian corridors (van Ham et al. 2013).
This paper reports on invasive plants known to be present in Indianapolis/Marion County, Indiana, USA. The city and the county are the same governmental unit and so occupy the same geographic space, referred to as Indianapolis in this paper. Indianapolis is a model urban area to study invasive plants for several reasons. Much is known about its floristic composition, from the late 1800s through current times. Indianapolis was almost entirely forested in pre-European presettlement times, but forests were reduced to 13% cover by the late 1900s (Barr et al. 2002). Most of the original forest was converted into row-crop agriculture. Agriculture has declined from 80% of land use in 1922 to 72% in 1953, to 18% by 1990 (http:www.savi.org). The time period from 1953-1990 corresponds with rapid urbanization in the city. This pattern of land use change is likely a model for other cities in the American Midwest. Indianapolis is the twelfth largest city in the United States, with an estimated population of over 900,000 people and total area of 650 [km.sup.2] (105,200 ha). The city is in the Central Till Plain Natural Region of Indiana (Homoya et al. 1985), an area characterized by a terrain of gently rolling hills of glacial till.
Species richness of the Indianapolis flora has been documented by Dolan et al. (2011) at about 700 plants. This number was consistent over a 70 year period, but there has been considerable species turn-over, with a loss of rare native plants and an increase in non-native plants from 20.3% to 27.1 % of the flora over the years covered by the study. These percentages are on par with urban areas across the globe (La Sorte et al. 2014). Not all non-natives in the Indianapolis flora, historically or currently, are considered invasive plants in Indiana (Indiana Invasive Species Council 2016). This report focuses upon invasive species in the Indianapolis flora, including how long they have been known to be present, their origins, and uses or causes of introduction. Finally, the invasive species that are likely to be the biggest problems in the near future for the city are discussed.
For this study, plants were identified as invasive if they were present on the Official Indiana Invasive Plant list, established by the Indiana Invasive Species Council (2016). Nomenclature is based on scientific names used in that list. Sources of information on invasives present in the flora of Indianapolis and dates of first record range from historical journal articles to contemporary web-based records. The oldest record is a county list for Marion and adjacent Hamilton County (Wilson 1895). While not comprehensive, this paper does document species presence, often annotated with comments on abundance. Coulter (1899) produced a state-wide flora that sometimes mentions counties and ranges for plants now recognized as invasives in the state.
Deam's 1940 Flora of Indiana is the last comprehensive manual of the state's plants. Deam's flora presents county-level distribution maps based on herbarium specimen vouchers. Overlease & Overlease (2007) reported weed species distributions for Indiana at the county level, based on their own observations and compared these distributions with records from Deam (1940) and Coulter (1899). Dolan et al. (2011) compiled these and other records, including herbarium specimens (Figs. 1 & 2) from the Friesner Herbarium (BUT) of Butler University, into a historical list for the city (pre-1940) and a more recent list based on species reported by botanists working in the city since that time.
Additional records for invasives in Indianapolis came from the Indiana Plant Atlas (Dolan & Moore 2016), sorted by location (Marion County) and invasiveness, and from Early Detection & Distribution Mapping System (EDDMapS 2016). Origin and mode of introduction of invasives are from Weber (2003) and Czarapata (2005).
Invasive plants that represent the largest current and emerging threats in the city were identified by polling local experts. Eight environmental professionals and knowledgeable amateurs from government agencies, non-profit organizations, private consulting firms, and academia were asked to list the invasive plants they perceive as being the greatest current and emerging concerns in Indianapolis.
RESULTS AND DISCUSSION
Sixty-nine of the 120 species listed on the Official Invasive Plant List for Indiana are known to occur in Indianapolis. These invasives comprise approximately 10% of the flora, somewhat less than the 16% average reported for 110 cites by La Sorte et al. (2014). The majority of invasive plants reported for Indianapolis are ranked as highly invasive (Fig. 3). Most plants (62%) originated in Asia or Eurasia (Fig. 4). Escape from cultivation is, by a wide margin, the most common mode of introduction of invasives in Indianapolis (Fig. 5). Accidental or unknown modes of introduction account for 18% of species, with forage accounting for 12%. The first two introduction pathways are most common for urban floras globally as well (La Sorte et. al 2014). Forage plants may be the remnant of former wide-spread agriculture in the area, or may be the result of contemporary seed mixes used to cover bare ground during construction.
Over half of the invasive plants in Indianapolis were known in the flora prior to 1940 (Fig. 6). Nineteen percent were documented by as early as the 1890s. Most invasives are herbaceous (n = 40) (Table 1). Shrubs are the most commonly represented woody class (n = 19), followed by trees (n = 6) and vines (n = 4) (Table 2, Fig. 7).
Herbaceous invasives have long been in the flora. As early as the late 1800s, Wilson (1895) noted Daucus carota and Glechoma hederacea were very common, Meliolotus officinale and Saponaria officinale were common, and Vinca minor was becoming common. Most herbaceous invasives (60%) were known for Indianapolis by Deamin 1940 (Table 1). Another 20% were noted by Deam (1940) for elsewhere in Indiana, so it would not be surprising if they were present in the city (or soon would be) but had not yet been recorded. Arriving since Deam's publication are Alliaria petiolata, Artemesia vulgaris, Centaurea stoebe, Clematis terniflora, Lespedeza cuneata, Microstegium vimineum, and Najas minor.
Analysis of the dates of record for woody plants reveals a different pattern. Only 14% (4 of 29) were known historically for Indianapolis (Table 2), with another eight present elsewhere in the state based on Deam (1940). As noted by Dolan et al. (2011), non-native shrubs escaped from landscaping are the physiognomic group with the largest increase in numbers of species in the Indianapolis flora over the last 70 years. Many of these plants were planted by the city as part of the Kessler Plan, a parkway and boulevard beautification plan during the 1920s (Table 2). Others were actively promoted by the USDA and other government agencies in the past for wildlife food and cover, erosion control, and other purported benefits (Tables 1 & 2).
Five of the seven species that were most frequently cited by restoration experts surveyed for this study as the biggest current invasive plant problems in Indianapolis are woody (Table 3). Euonymous fortunei and Lonicera maackii tied for first as the biggest current problem. Among plants that were perceived as emerging problems, three (one shrub, one grass and one tree) tied for first: Fallopia japonica, Microstegium vimineum, and Pyrus calleryana.
Early detection and rapid response protocols are the most effective means of preventing the spread of invasive species into new territories. It is widely recognized to be easier to eradicate and control invasive species before they become widely established (e.g., Allendorf & Lundquist 2003). Reports of new sightings posted to EDDMapS and other online sites by consultants, naturalists, academics, and the general public provide the opportunity to track new records and to eradicate plants before they can spread. Greater awareness of invasive plants and their modes or pathways of introduction will hopefully lead to more careful vetting and selection of plants for large-scale landscaping projects in the city and elsewhere.
I want to thank Ellen Jacquart with the Indiana Field Office of The Nature Conservancy for encouraging me to present a paper on this topic for the Midwest Invasive Species Network Symposium, part of the North Central Weed Society Annual Conference in Indianapolis in 2015 and for her tireless work on invasive plant management for many years. A version of the data in this paper was also presented at the Annual Meeting of the Indiana Academy of Science in 2016. I also extend thanks to the restoration professionals in the city who provided anonymous responses to my survey on worst current and emerging invasives, and to the city of Indianapolis' Land Stewardship staff who are often the first to notice, collect, and report new invasive plants. Finally, thank you to Marcia Moore and Butler University undergraduate students for helping advance all Friesner Herbarium projects.
Allendorf, F.W. & L.L. Lundquist. 2003. Introduction: population biology, evolution, and control of invasive species. Conservation Biology 17:24-30.
Barr, R.C., B.E. Hall, J.A. Wilson, C. Souch, G. Lindsey, J.A. Bacone, R.K. Campbell & L.P. Tedesco. 2002. Documenting changes in the natural environment of Indianapolis-Marion County from European settlement to the present. Ecological Restoration 20:37-46.
Coulter, S. 1899. A catalog of the flowering plants and of the ferns and their allies indigenous to Indiana. Indiana Department of Geology and Natural Resources, Indianapolis, Indiana. 1073 pp.
Czarapata, E.J. 2005. Invasive Plants of the Upper Midwest: An Illustrated Guide to Their Identification and Control. University of Wisconsin Press, Madison, Wisconsin. 236 pp.
Deam, C.C. 1940. Flora of Indiana. Department of Conservation, Wm. B. Burford Printing Co., Indianapolis, Indiana. 1236 pp.
Dolan, R.W. & M.E. Moore. 2016. Indiana Plant Atlas. [S.M. Landry and K.N. Campbell (original application development), USF Water Institute. University of South Florida]. Butler University Friesner Herbarium, Indianapolis, Indiana. At: http://indiana.plantatlas.org (Accessed 20 November 2015).
Dolan, R.W., M.E. Moore & J.D. Stephens. 2011. Documenting effects of urbanization on flora using herbarium records. Journal of Ecology 99:1055-1063.
EDDMapS. 2016. Early Detection & Distribution Mapping System. At: https://www.eddmaps.org (Accessed 20 November 2015).
Homoya, M.A., D.B. Abrell, J.R. Aldrich & T.W. Post. 1985. Natural Regions of Indiana. Proceedings of the Indiana Academy of Science 94:245-268.
Indiana Invasive Species Council. 2016. Official Invasive Plant List. At: https://www.entm. purdue.edu/iisc (Accessed 15 November 2015).
La Sorte, F., M. Aronson, N. Williams, B. Clackson, L. Celesti-Grapow, S. Cilliers, R.W. Dolan, A. Hipp, S. Klotz, I. Kuhn, P. Pyuek, S. Siebert & M. Winter. 2014. Beta diversity of urban floras within and among European and non-European cities. Global Ecology and Biogeography 23:769-779.
Overlease, W.R. & E. Overlease. 2007. 100 Years of Change in the Distribution of Common Indiana Weeds. Purdue University Press, West Lafayette, Indiana. 248 pp.
Pimentel, D., R. Zuniga & D. Morrison. 2005. Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecological Economics 52:273-288.
Pysek, P. 1998. Alien and native species in Central European urban floras: a quantitative comparison. Journal of Biogeography 25:155-163.
van Ham, C., P. Genovesi & R. Scalera. 2013. Invasive Alien Species: The Urban Dimension, Case Studies on Strengthening Local Action in Europe. International Union for the Conservation of Nature, Brussels, Belgium. 104 pp.
USDA, NISIC. 2016. The National Invasive Species Information Center. At: http://www. invasivespeciesinfo.gov (Accessed 2 July 2016).
Weber, E. 2003. Invasive Plant Species of the World: A Reference Guide to Environmental Weeds. University of Potsdam, Potsdam, Germany. 560 pp.
Wilson, G.W. 1895. Flora of Hamilton and Marion Counties, Indiana. Proceedings of the Indiana Academy of Science 4:156-175.
Manuscript received 22 July 2016, revised 31 August 2016.
Rebecca W. Dolan (1): Friesner Herbarium, Butler University, Indianapolis, IN 46208 USA
(1) Corresponding author: Rebecca W. Dolan, 317-940-9413 (phone), 317-940-9519 (fax), firstname.lastname@example.org.
Caption: Figures 1-2.--Images of herbarium specimens. 1. Specimen of invasive plant Lythrum salicaria collected by Ray Friesner in Indianapolis in 1925, documenting presence of the species in the city as of that date (left). 2. Specimen of Berberis thunbergii collected by Charles Deam, with the comment on the label that this ornamental plant was collected far from any dwelling. Comments like these are helpful in establishing records for species that might become invasive (right).
Table 1.--Herbaceous species of invasive plants in the Indianapolis, Indiana flora and time of first record. D = listed as present elsewhere in Indiana by Deam (1940); P = planting actively promoted by government agencies at some time. Scientific name Common name Pre-1940 Alliaria petiolata garlic mustard Artemesia vulgaris mugwort Carduus nutans (D) musk thistle Centaurea stoebe spotted knapweed Cirsium arvense Canada thistle x Cirsium vulgare bull thistle x Clematis terniflora sweet autumn clematis Conium maculatum (D) poison hemlock Convolvulus arvense field bindweed x Coronilla varia (P) crown vetch x Cynanchum louiseae black swallow-wort x Daucus carota Queen Anne's lace x Dioscorea polystachya (D) Chinese yam Dipsacus fullonum common teasel x Dipsacus laciniatus cut-leaved teasel x Euphorbia esula leafy spurge x Glechoma hederacea creeping Charlie x Hesperis matronalis dame's rocket x Humulus japonicus (D) Japanese hops Hypericum perforatum St. John's wort x Iris pseudoacorus (D) yellow iris Kummerowia stipulacea (D,P) Korean lespedeza Kummerowia striata (P) striate lespedeza x Lespedeza cuneata (P) sericea lespedeza Lythrum salicaria purple loosestrife x Melilotus officinale sweet clover x Microstegium vimineum Japanese stiltgrass Myriophyllum spicatum (D) Eurasian watermilfoil Najas minor braided naiad Pastinaca sativa wild parsnip x Phalaris arundinacea (P) reed canarygrass x Phragmites australis common reed x Potamogeton crispus curly-leaved pondweed x Ranunculus ficaria lesser celandine Saponaria officinalis bouncing bet x Schedonorus arundinaceus (P) tall fescue x Sorghum halepense Johnson grass x Torilis japonica (D) Japanese hedge parsley Typha angustifolia narrow-leaved cattail x Vicia cracca (P) cow vetch x More Invasive Scientific name recent rank Origin Alliaria petiolata x high Europe Artemesia vulgaris x high Eurasia/N. Africa Carduus nutans (D) x high Europe/N. Africa Centaurea stoebe x high Europe Cirsium arvense x high Eurasia Cirsium vulgare x high Europe Clematis terniflora x caution Asia Conium maculatum (D) x high Eurasia/N. Africa Convolvulus arvense x high Asia Coronilla varia (P) x high Eurasia/N. Africa Cynanchum louiseae x high Europe Daucus carota x medium Eurasia Dioscorea polystachya (D) x high Asia Dipsacus fullonum x high Eurasia/N. Africa Dipsacus laciniatus x high Eurasia/N. Africa Euphorbia esula x high Eurasia Glechoma hederacea x medium Europe Hesperis matronalis x high Eurasia Humulus japonicus (D) x high Asia Hypericum perforatum x Low Europe Iris pseudoacorus (D) x high Europe/Africa Kummerowia stipulacea (D,P) x high Asia Kummerowia striata (P) x medium Asia Lespedeza cuneata (P) x high Asia Lythrum salicaria x high Europe Melilotus officinale x medium Eurasia Microstegium vimineum x high Asia Myriophyllum spicatum (D) x high Europe/N. Africa Najas minor x high Eurasia/N. Africa Pastinaca sativa x medium Eurasia Phalaris arundinacea (P) x high Europe Phragmites australis x high Global Potamogeton crispus x high Europe Ranunculus ficaria x caution Europe Saponaria officinalis x medium Europe Schedonorus arundinaceus (P) x medium Europe Sorghum halepense x high Europe Torilis japonica (D) x caution Eurasia Typha angustifolia x high Eurasia Vicia cracca (P) x medium Eurasia Scientific name Use/mode of introduction Alliaria petiolata food, medicinal Artemesia vulgaris medicinal? Carduus nutans (D) none/unknown Centaurea stoebe none/unknown Cirsium arvense contaminated seed crop? Cirsium vulgare none/unknown Clematis terniflora ornamental Conium maculatum (D) none/unknown Convolvulus arvense ornamental Coronilla varia (P) erosion control Cynanchum louiseae ornamental Daucus carota medicinal? Dioscorea polystachya (D) ornamental, food Dipsacus fullonum wool combing Dipsacus laciniatus wool combing Euphorbia esula accidental contaminant, ornamental Glechoma hederacea medicinal, food Hesperis matronalis ornamental Humulus japonicus (D) ornamental Hypericum perforatum medicinal Iris pseudoacorus (D) ornamental Kummerowia stipulacea (D,P) forage Kummerowia striata (P) forage Lespedeza cuneata (P) erosion control, forage Lythrum salicaria ornamental, medicinal, honey Melilotus officinale forage, honey Microstegium vimineum accidental, in packing material Myriophyllum spicatum (D) aquarium trade, boats Najas minor ships' ballast, ornamental Pastinaca sativa ornamental Phalaris arundinacea (P) hay, forage Phragmites australis ships' ballast? Potamogeton crispus none/unknown Ranunculus ficaria ornamental Saponaria officinalis ornamental, soap Schedonorus arundinaceus (P) forage, erosion control Sorghum halepense forage Torilis japonica (D) none/unknown Typha angustifolia ornamental Vicia cracca (P) forage Table 2.--Woody species of invasive plants in the Indianapolis, Indiana flora and time of first record. Caution means there is reason to believe the species may become a problem, but not enough data yet to support its listing. D = reported by Deam (1940) for elsewhere in Indiana; K = planted by the city in the 1920s as part of the Kessler Plan; P = planting actively promoted by government agencies at some time. Scientific name Common name Pre-1940 Trees Acer platanoides Norway maple Ailanthus altissima tree-of-heaven x Alnus glutinosa (D,K,P) black alder Morus alba (K) white mulberry x Pyrus calleryana Callery pear Ulmus pumila Siberian elm Woody vines Ampelopsis brevipedunculata porcelain berry Celastrus orbiculatus oriental bittersweet Hedera helix English ivy Lonicera japonica (D) Japanese honeysuckle Shrubs Berberis thunbergii (K) Japanese barberry x Elaeagnus angustifolia (P) Russian olive Elaeagnus umbellata (P) autumn olive Euonymus alatus burning bush Euonymus fortunei winter-creeper Fallopia japonica Japanese knotweed Frangula alnus (P?) glossy buckthorn Ligustrum obtusifolium (D) blunt leaved privet Ligustrum vulgare (D) common privet Lonicera maackii Amur honeysuckle Lonicera morrowii (K) Morrow's honeysuckle Lonicera tatarica Tatarian honeysuckle Lonicera 3 bella (K) Bell's honeysuckle Rhamnus cathartica (D,K,P?) common buckthorn Rhodotypos scandens jetbead Rosa multiflora (D,K,P) multiflora rose Rubus phoenicolasius (D) wine raspberry Viburnum opulus var. opulus highbush cranberry Vinca minor periwinkle x More Invasive Scientific name recent rank Origin Trees Acer platanoides x high Eurasia Ailanthus altissima x high Asia Alnus glutinosa (D,K,P) x high Eurasia/N. Africa Morus alba (K) x high Asia Pyrus calleryana x high Asia Ulmus pumila x medium Asia Woody vines Ampelopsis brevipedunculata x caution Asia Celastrus orbiculatus x high Asia Hedera helix x medium Asia/N. Africa Lonicera japonica (D) x high Asia Shrubs Berberis thunbergii (K) x high Asia Elaeagnus angustifolia (P) x medium Asia Elaeagnus umbellata (P) x high Asia Euonymus alatus x medium Asia Euonymus fortunei x high Asia Fallopia japonica x high Asia Frangula alnus (P?) x high Eurasia Ligustrum obtusifolium (D) x high Eurasia Ligustrum vulgare (D) x medium Eurasia Lonicera maackii x high Eurasia Lonicera morrowii (K) x high Eurasia Lonicera tatarica x high Eurasia Lonicera 3 bella (K) x high Eurasia Rhamnus cathartica (D,K,P?) x high Eurasia Rhodotypos scandens x caution Asia Rosa multiflora (D,K,P) x high Asia Rubus phoenicolasius (D) x caution Asia Viburnum opulus var. opulus x caution Europe Vinca minor x medium Europe Scientific name Use/mode of introduction Trees Acer platanoides ornamental Ailanthus altissima ornamental Alnus glutinosa (D,K,P) ornamental Morus alba (K) ornamental, food, silk worms Pyrus calleryana ornamental Ulmus pumila ornamental Woody vines Ampelopsis brevipedunculata ornamental Celastrus orbiculatus ornamental Hedera helix ornamental Lonicera japonica (D) ornamental Shrubs Berberis thunbergii (K) ornamental Elaeagnus angustifolia (P) erosion control, ornamental Elaeagnus umbellata (P) ornamental, wildlife food & cover Euonymus alatus ornamental Euonymus fortunei ornamental Fallopia japonica ornamental, erosion control Frangula alnus (P?) ornamental Ligustrum obtusifolium (D) ornamental Ligustrum vulgare (D) ornamental Lonicera maackii ornamental, wildlife food & cover, erosion control Lonicera morrowii (K) ornamental Lonicera tatarica ornamental Lonicera 3 bella (K) ornamental Rhamnus cathartica (D,K,P?) ornamental Rhodotypos scandens ornamental Rosa multiflora (D,K,P) ornamental, living fence, wildlife cover & food Rubus phoenicolasius (D) ornamental Viburnum opulus var. opulus ornamental Vinca minor ornamental Table 3.--The top five ranked invasive plant species, including ties, that pose the biggest current and emerging threats in Indianapolis, Indiana, based on expert opinion. Rankings represent the frequency of citation, with one (1) being the most frequently cited. Current Rank Scientific name Common name 1 Euonymus fortunei purple winter-creeper 1 Lonicera maackii Amur honeysuckle 3 Alliaria petiolata garlic mustard 4 Celastrus obiculatus oriental bittersweet 5 Euonymus alatus burning-bush 5 Lonicera japonica Japanese honeysuckle 5 Pyrus calleryana Callery pear Emerging Rank Scientific name Common name 1 Fallopia japonica Japanese knotweed 1 Microstegium Japanese stiltgrass vimineum 1 Pyrus calleryana Callery pear 4 Berberis thunbergii Japanese barberry 5 Clematis terniflora sweet autumn clematis 5 Euonymus alatus burning bush Figures 3-7.--Characteristics of invasive species in the Indianapolis, Indiana flora. 3. Invasive rank based on the Official Indiana Invasive Plant List (top left). 4. Continent of origin (top right). 5. Mode of introduction (middle). 6. Time of first record in the flora (bottom left). 7. Physiognomy (bottom right). Use or Cause of Introduction Accidental/unknown 18% Erosion, wildlife food/cover 6% Food/Medicinal 7% Forage 12% Ornamental 53% Other 4% Note: Table made from pie chart. Time First Documented 1890s 19% 1940 35% later 46% Note: Table made from pie chart. Physiognomy Herbs 58% Trees 9% Woody vines 6% Shrubs 27% Note: Table made from pie chart.
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|Author:||Dolan, Rebecca W.|
|Publication:||Proceedings of the Indiana Academy of Science|
|Date:||Nov 22, 2016|
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