Monarda Fistulosa: Making Good Scents in Colorado Ken Keefover-Ring Ph.D
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Vol. 30 No. 2 Aquilegia Page 3 Monarda fistulosa: Making Good Scents in Colorado Ken Keefover-Ring Ph.D. Candidate, Ecology and Evolutionary Biology, University of Colorado, Boulder Sometimes you just have to stop and smell types in the species (Marshall and Scora chemotype are excluded from an area due the wild bergamot, and that is exactly what 1972). I have discovered that two of the to temperature has been shown for com- I have been doing for the last four years as known M. fistulosa chemotypes, carvacrol mon thyme (Thymus vulgaris) in the south part of my Ph.D. dissertation research, and thymol, occur in Colorado in pure and of France. In the case of thyme, certain conducted with Prof. Yan Linhart at CU- mixed populations. Additionally, in one chemotypes were absent from the floor of Boulder. Like many species in the mint population in southern Colorado, I have an enclosed basin that regularly experi- family, Monarda fistulosa L. (Lamiaceae), found a previously unknown chemotype enced much colder temperatures than the commonly known as wild bergamot, bee for this species with essential oil composed surrounding uplands (Amiot et al. 2005). balm or horse mint, produces small almost entirely of the monoterpene linalol. To unravel this question in M. fistulosa, I volatile chemicals called monoterpenes in With the support of a Colorado Native plan to monitor temperature, humidity and tiny sacs (trichomes) located on leaves, Plant Society research grant from the John other abiotic parameters at sites with dif- calyces and even flower petals. When one Marr Fund, I have been characterizing the ferent chemotype compositions. rubs bee balm leaves, these trichomes are chemotype variation of M. fistulosa over broken and almost immediately one the landscape and trying to understand Another factor that may shape the chemo- detects the scent of escaping monoter- how these patterns arose and how they are type composition of populations is her- penes. Also known as essential oils, maintained. bivory. At a few sites, I have found plants monoterpenes have been used by humans being fed upon by a small tortoise beetle for thousands of years as fragrances and The first step to understanding chemical (Physonota unipunctata Coleoptera: flavors; however, plants use them for a polymorphism in M. fistulosa was to map Chrysomelidae) that specializes only on variety of functions, including: suppres- chemotype patterns of populations. The M. fistulosa. The larvae of this beetle have sion of plant competitors, repelling herbi- methodology I used was simple. Using a curious defense mechanism; they accu- vores or attracting pollinators and seed dis- historic herbarium records, information mulate their feces on two projections on persers (Harborne 1993). Monoterpenes from locals and by just driving around, I the rear end of their bodies, which they are widely distributed among a variety of located about 50 populations of wild berg- curl upward, holding the "fecal shield" plant families and their variation in natural amot throughout the state. At each site I over their bodies. Since their diet consists plant populations has been extensively randomly collected a single leaf from an exclusively of M. fistulosa, the fecal shield studied. Many labiate species contain average of 20 plants, soaked them in pure is rich in plant monoterpenes, adding a individuals with distinct chemical pheno- ethanol for one week to extract the chemical dimension to their defense strate- types, called chemotypes, which are con- monoterpenes and then analyzed the solu- gy. While the beetle larvae will readily trolled by simple Mendelian genetics tion by gas chromatography, a technique feed on both chemotypes, my preliminary (Vernet et al. 1986, Vokou et al. 1993). that allows separation, identification and data show that when fed only carvacrol Plants of a particular chemotype usually quantification of monoterpenes. foliage they have lower survival and produce one monoterpene that dominates longer development times. Thus, in popu- Chemical analyses of over 900 Colorado their total essential oil composition. This lations where these herbivores feed, thy- plants revealed variation ranging from means that individuals of the same species mol plants may experience more damage populations comprising only carvacrol can have very different smells, tastes and and reproduce less than carvacrol plants. plants to populations comprising only thy- interactions with other organisms, such as mol plants, as well as populations com- Another interesting find along my chemi- herbivores and pollinators. Prior to my prising various mixtures of the two. So, cal odyssey was the discovery of what work, three chemotypes had been identi- what factors are responsible for these pat- appears to be a new chemotype of M. fistu- fied in Monarda fistulosa, containing terns? One explanation may be tempera- losa. On a lonely stretch of highway west either geraniol, carvacrol or thymol as ture. In Boulder County, where almost of Trinidad, Colorado, I spotted an isolated their main monoterpene (Marshall and half of the populations analyzed occur roadside population. Initially, the plant Scora 1972, Weaver et al. 1995, Johnson et (Figure 1), it appears that populations high leaves I collected all seemed to have the al. 1998). The smell of geraniol is sweet or in thymol plants are found at higher eleva- familiar smell of carvacrol or thymol lemony - it is a major component of lemon tions or in colder areas, such as deep chemotypes found at many other sites. oil, whereas carvacrol and thymol remind canyons. These micro site differences may Suddenly, the scent of one plant was com- one of thyme or oregano, both of which be important in M. fistulosa, since in pletely different from any other I had pre- have these chemotypes. While the exis- Colorado it has a large geographical range viously encountered. Upon returning to tence of these three chemotypes in M. fis- over most of the state with diverse habitats my laboratory, I immediately started my tulosa has been known since the early from prairies to high mountain meadows. gas chromatograph and eagerly watched 1970s, only one study presented detailed Also, the idea that plants of a particular the monitor as the sample ran. The results information on the distribution of chemo- Page 4 Aquilegia Vol. 30 No. 2 showed one main peak, which was the monoterpene linalol. “Field Trips” continued from page 2 While linalol has been identified in a closely related species, M. Shale Barrens of the Laramie River Valley didyma, no one has ever reported this compound in M. fistulosa. Date: Saturday, July 29 As grandiose as it may sound, I felt I was witnessing an evolu- Leaders: Rich Scully, Georgia Doyle and Mary Jane Howell tionary event, where a new mutant phenotype had appeared, and if it had some heritable advantage over the resident chemotypes, The upper Laramie River Valley is located in extreme northwest the linalol chemotype may increase. Then again the plant may get Larimer County. Along slope breaks among the sagebrush-cov- mowed by the road maintenance crew before setting seed, a fate ered uplands, there are calcareous shale barrens that host several for which its new mutation would be useless. Anyway, the next rare plant species, including Penstemon laricifolius ssp. exili- time you are hiking and encounter wild bergamot in the wild, folius, Eriogonum exilifolium and Phacelia formosula. The shale don't forget to stop and give it a sniff. You may not find a new barren plant community contains elements of both Colorado and chemotype, but you will sample just a little of the olfactory genet- Wyoming floras, including the only Colorado state record of ic diversity that makes up M. fistulosa in Colorado. Oönopsis wardii. We will make an easy four-mile day hike start- ing in mid-morning and finishing mid-afternoon. For details and References to register for this field trip co-sponsored by the Fort Collins Chapter, contact Rich at 303-823-0766 or [email protected]. Amiot, J., Y. Salmon, C. Collin, and J. D. Thompson. 2005. Differential resistance to freezing and spatial distribution in a Cameron Pass chemically polymorphic plant Thymus vulgaris. Ecology Letters Date: Friday - Sunday, August 4-6 8:370-377. Leaders: Johnny Proctor and Denise Culver Enjoy a weekend on the trail of the elusive moonworts. Get ready Harborne, J. B. 1993. Introduction to ecological biochemistry, 4th to look hard for Botrychium lunaria, B. lanceolatum, B. echo edition. Academic Press, London; San Diego. (G3S3), B. minganense (G4S1), B. simplex (G5S1) and hopefully B. lineare (G1S1). Meet at 6 pm, August 4 at the Aspen Johnson, H. A., L. L. Rogers, M. L. Alkire, T. G. McCloud, and J. Campground for festivities, or meet at 9 am on August 5. Free L. NcLaughlin. 1998. Bioactive monoterpenes from Monarda fis- camping will be available Aug. 4 - Aug. 6. To register for this 11 tulosa (Lamiaceae). Natural Product Letters :241-250. field trip co-sponsored by the Fort Collins Chapter and the Medicine Bow-Routt National Forest and Thunder Basin National Marshall, H. H., and R. W. Scora. 1972. New chemical race of Grassland, please contact Denise Culver at 970.491.2998. Monarda fistulosa (Labiatae). Canadian Journal of Botany 50 :1845-7. South Platte Park Vernet, P., P. H. Gouyon, and G. Valdeyron. 1986. Genetic control Date: Saturday, August 5, 9 am - 12 pm of the oil content in Thymus vulgaris L.: a case of polymorphism Leader: Ray Sperger in a biosynthetic chain. Genetica 69:227-231. Surrounded by Denver metropolitan suburbs, the South Platte Park unit of the South Suburban Parks provides an important site Vokou, D., S. Kokkini, and J. M. Bessiere. 1993. Geographic vari- for wildlife habitat connectivity, as well as functional riparian, ation of Greek oregano (Origanum vulgare ssp. hirtum) essential wetland and upland ecosystems.