The dominant landscaping practice of recent centuries has been to create landscapes designed with ornamental plants that have been introduced from other countries. This practice has been so pervasive that nonnative plant species now outnumber native species in most urban, suburban, and rural landscapes (DeCandido et al., 2004; Dolan et al., 2011; McKinney, 2006, 2008; Qian and Rickleffs, 2006; Standley, 2003). For example, an extensive study of landscape plantings in Washington, DC, suburbs measured 55% nonnative plant biomass (Narango et al., 2017). This imbalance is perpetuated by nursery stock dominated by nonnative ornamentals. A study done at Mt. Cuba Center, a botanical garden dedicated to native plant horticulture and research in Hockessin, DE, found that large mid-Atlantic U.S. wholesale nurseries carried only 25% native species (Coombs and Gilchrist, 2017).
There is growing evidence that the preponderance of nonnative plants in built landscapes may impact the conservation of local biodiversity. Although nonnative plants can extend nectar resources late in the season (Salisbury et al., 2015), their exclusive use in pollinator gardens pose a threat to the dozens of native bee specialists that only reproduce on single native plant genera (Fowler, 2016). Moreover, because native plants support the growth and development of the insects that transfer the most energy from plants to vertebrate food webs far better than nonnative plants (Burghardt et al., 2010; Pearse et al., 2013; Tallamy, 2017; Tallamy and Shropshire, 2009), the lack of native species in urban ecosystems depresses populations of the wildlife that helps run those ecosystems (Burghardt et al., 2008; Narango et al., 2017). This is particularly true for the terrestrial birds in North America, 96% of which rear their young on insects [derived from Peterson (1980)].
There is increasing interest in gardening for wildlife, and consequently a growing market for native landscape plants (American Society of Landscape Architects, 2017; Brzuszeki and Harkess, 2009). This, in turn, has led to questions regarding what is “native” and what is not, what are appropriate constraints from plant provenance, and, most often, are cultivars of native plants (often called “nativars”) the ecological equivalents of the parent species from which they were selected? This last question is particularly important because the increased use of native plants is being driven more by their ecological function in the landscape than by their aesthetic roles. Moreover, the majority of native plants in the nursery trade are available as cultivars (Coombs and Gilchrist, 2017).
There are two primary ways cultivars may impact the insects that use plants for growth and reproduction: 1) A genetic change that creates a desired cultivar trait may alter the leaf chemistry of the plant to the point where insect herbivores no longer recognize the plant as a potential host or are repelled by an increase in distasteful feeding deterrents; 2) cultivars that change the color, shape, or phenology of a flower may inadvertently reduce the amount or quality of the pollen and nectar available for pollinators, or, in the case of double, sterile flowers, may eliminate pollen and nectar altogether. In this study, we focus exclusively on the potential impacts of native cultivars on insect herbivores and leave flower modifications for a later study. Specifically, using a common garden experiment and laboratory feeding preference trials, we measured how six common cultivar traits of trees and shrubs that modify leaf color, disease resistance, fruit size, and plant habit impact the feeding preference, abundance, and diversity of insect herbivores.
American Society of Landscape Architects 2017 Demand high for sustainable, tech-friendly residential landscapes. 15 Mar. 2018. <https://www.asla.org/NewsReleaseDetails.aspx?id=50027>
Brook, A.J., Woodcock, B.A., Sinka, M. & Vanbergen, A.J. 2008 Experimental verification of suction sampler capture efficiency in grasslands of differing vegetation height and structure J. Appl. Ecol. 45 1357 1363
Brzuszeki, R.F. & Harkess, R.L. 2009 Green industry survey of native plant marketing in the southeastern United States HortTechnology 19 168 172
Burghardt, K.T., Tallamy, D.W., Philips, C. & Shropshire, K.J. 2010 Non-native plants reduce abundance, richness, and host specialization in lepidopteran communities Ecosphere 1 1 22
Burghardt, K.T., Tallamy, D.W. & Shriver, W.G. 2008 Impact of native plants on bird and butterfly biodiversity in suburban landscapes Conserv. Biol. 23 219 224
Campitelli, B.E., Stehlik, I. & Stinchcombe, J.R. 2008 Leaf variegation is associated with reduced herbivore damage in Hydrophyllum virginianum Botany 86 306 313
Chappell, M.R., Braman, S.K., Williams-Woodward, J. & Knox, G. 2012 Optimizing plant health and pest management of Lagerstroemia spp. in commercial production and landscape situations in the southeastern United States: A review J. Environ. Hort. 30 161 172
Coombs, G. & Gilchrist, D. 2017 Native and invasive plants sold by the mid-Atlantic nursery industry: A baseline for future comparisons. 17 Feb. 2018. <https://mtcubacenter.org/action/nurserysurvey/>
DeCandido, R., Muir, A.A. & Garguillo, M.B. 2004 A first approximation of the historical and extant vascular flora of New York City: Implications for native plant species conservation J. Torrey Bot. Soc. 131 243 251
Dolan, R.W., Moore, M.E. & Stephens, J.D. 2011 Documenting effects of urbanization on flora using herbarium records J. Ecol. 99 1055 1062
Herbert, J.J., Mizell, R.F. III & McAuslane, H.J. 2009 Host preference of the crapemyrtle aphid (Hemiptera: Aphididae) and host suitability of crapemyrtle cultivars Environ. Entomol. 38 1155 1160
Hochuli, D.F. 1996 The ecology of plant/insect interactions: Implications of digestive strategy for feeding by phytophagous insects Oikos 75 133 141
Holopainen, J.K., Semiz, G. & Blande, J.D. 2009 Life-history strategies affect aphid preference for yellowing leaves Biol. Lett. 5 603 605
Lev-Yadun, S. 2014 Potential defense from herbivory by ‘dazzle effects’ and ‘trickery coloration’ of leaf variegation Biol. J. Linnaean Soc. 111 692 697
Lev-Yadun, S., Dafni, A., Flaishman, M.A., Inbar, M., Izhaki, I., Katzir, G. & Ne’eman, G. 2004 Plant coloration undermines herbivorous insect camouflage BioEssays 26 1126 1130
Lev-Yadun, S. & Gould, K.S. 2009 Role of anthocyanins in plant defense, p. 22–28. In: C. Winefield, K. Davies, and K. Gould (eds.). Anthocyanins. Springer, New York, NY
Narango, D.L., Tallamy, D.W. & Marra, P.P. 2017 Native plants improve breeding and foraging habitat for an insectivorous bird Biol. Conserv. 213 42 50
Peterson, R.T. 1980 A field guide to the birds. Houghton Mifflin, Boston, MA
Potter, D.A. & Redmond, C.T. 2013 Relative resistance or susceptibility of landscape-suitable elms (Ulmus spp.) to multiple insect pests Arboricult. Urban For. 39 236 243
R Core Team 2017 R: A language and environment for statistical computing. 30 Mar. 2018. <https://www.R-project.org/>
Raimondo, S., Strazanac, J.S. & Butler, L. 2004 Comparison of sampling techniques used in studying Lepidoptera population dynamics Environ. Entomol. 33 418 425
Rieske, L.K., Rhoades, C.C. & Miller, S.P. 2003 Foliar chemistry and gypsy moth, Lymantria dispar (L.), herbivory on pure American chestnut, Castanea dentata (Fam: Fagaceae), and a disease-resistant hybrid Environ. Entomol. 32 359 365
Salisbury, A., Armitage, J., Bostock, H., Perry, J., Tatchell, M. & Thompson, K. 2015 Enhancing gardens as habitats for flower-visiting aerial insects (pollinators): Should we plant native or exotic species? J. Appl. Ecol. 52 1156 1164
Smalley, E.B. & Guries, R.P. 2000 Asian elms: Sources of disease and insect resistance, p. 215–230. In: C.P. Dunn (ed.). The elms. Springer, Boston, MA
Smith, A.P. 1986 Ecology of leaf color polymorphism in a tropical forest species: Habitat segregation and herbivory Oecologia 69 283 287
Soltau, U., Dӧtterl, S. & Liede-Schumann, S. 2009 Leaf variegation in Caladium steudneriifolium (Araceae): A case of mimicry? Evol. Ecol. 23 503 512
Tallamy, D.W. 2017 Creating living landscapes: Why we need to increase plant/insect linkages in designed landscapes HortTechnology 27 446 452
Wagner, D.L. 2005 Caterpillars of eastern North America. Princeton Univ. Press, Princeton, NJ
War, A.R., Paulraj, M.G., Ahmad, T., Buhroo, A.A., Hussain, B., Ignacimuthu, S. & Sharma, H.C. 2012 Mechanisms of plant defense against insect herbivores Plant Signal. Behav. 7 1306 1320