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2-2006 WOY '06: Spicebush Provides a Salad Bar to Some W. John Hayden University of Richmond, [email protected]

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Recommended Citation Hayden, W. John. "WOY'06 Spicebush Provides a Salad Bar to Some Caterpillars." Bulletin of the Virginia Native Plant Society 25, no. 1 (2006): 1+.

This Article is brought to you for free and open access by the Biology at UR Scholarship Repository. It has been accepted for inclusion in Biology Faculty Publications by an authorized administrator of UR Scholarship Repository. For more information, please contact [email protected]. February 2006 Vol. 25, No.1 ISSN 1085-9632

A publication of the VIRGINIA NATIVE PLANT SOCIETY www.vnps.org Conserving wild flowers and wild places WOY '06: Spicebush provides a salad bar to some caterpillars While many wildflower were found to be important consumers of spicebush enthusiasts appreciate leaves. The three most abundant species found on spice- spicebush ( bush in the study were all larvae. These include: 1) benzoin), the 2006 the saddle back (Acharia stimulea), famous for Virginia Wild- the painful sting that it can inflict from its bristles; woolly promethea flower of the bears (Pyrrharctia isabella), whose balance of brown and (spicebush silk moth) Year, for its black bands merely reflects an age progression subtle beauty, plant and not a forecast of im- ecologists have found this humble shrub to be a fruitful pending winter’s se- subject for scientific inquiry. The notes that follow relay just verity as commonly al- a few of the interesting nuggets that can be gleaned from a leged in folklore; and cursory study of the scientific literature about this plant. the caterpillar of the Herbivory, : In a study of the impact of light promethea moth (also regime and herbivory on spicebush growth conducted in known as the spicebush Acharia stimulea (saddle back caterpillar) southeastern Pennsylvania, various lepidopteran larvae (See Caterpillars, page 6) Conservation means always being ready to work Philip Shabecoff, of the New York of reducing large natural areas to level, As development is completed at Times Magazine, once said that “So bleak bare land so that as many dwellings as many of these sites, its residents are is the picture…that the bulldozer and not possible can be built on the site. I see left with a habitat that has been trau- the atomic bomb may turn out to be the this almost everywhere I travel in the matized, or so fragmented that all na- most destructive invention of the 20th state—not just tive plants—flowers, trees, century.” The difficulty in shrubs, grasses—that maintaining the delicate lived in their natural balance between the need setting are no more to provide for our human than a memory, and comforts and the need to a rapidly fading one conserve and protect our at that. A gloomy pic- natural resources serves ture? Yes. Something as a challenge to some, a the conservation- discouragement to oth- minded individual can ers, and an irritant to stop? I don’t think there still others who choose are many of us who be- to ignore conservation lieve that development in favor of other inter- can be halted, con- ests. Many of us live in sumption curbed, resources re- areas where the bulldozer high-density population areas where newed and habitat, including air and is king and development consists you most expect to see it. (See Conservation, page 2) Bulletin of the Virginia Native Plant Society Caterpillars rely on spicebush (Continued from page 1) than did caterpillars from the silk moth, Callosamia promethea), Midwest. Conversely, Mid- among the largest and most beauti- west caterpillars succeeded (spicebush swallowtail butterfly) ful of North American moths. These better on spicebush and All caterpillar illustrations moth caterpillars are all generalist sassafras than on redbay. by Nicky Staunton feeders, being able to thrive on a wide Also, total duration of variety of host plant species. This the larval stage was study found that herbivorous cater- greater for caterpillars pillar abundance per spicebush plant reared on redbay than on does not differ by sex or by habitat of spicebush/sassafras, and this result the shrub, i.e., caterpillar abundance held for larvae from the Midwest, from hand, spicebush presents problems is essentially similar on staminate Florida, and for hybrid larvae result- for hungry waxwings: the lipid-rich (male) and pistillate (female) individu- ing from crosses between individuals pulp digests slowly and the large in- als whether in the sun or shade. How- from these two regions. The scientists edible seeds contribute much weight ever, herbivore damage, expressed as a suggest that redbay contains a toxic and bulk with no nutritional return. percentage of total leaf area eaten was compound absent in spicebush/sas- In nature, waxwings seldom con- somewhat greater in shady habitats, safras and that the two caterpillar sume spicebush seeds. Thrushes, in- populations tested differ in their abil- cluding the American robin, operate ity to detoxify it. (J. K. Nitao et al., “Lar- differently. These birds digest lipid- val adaptation to Lauraceous hosts: rich fruits relatively efficiently and geographic divergence in the spice- they also tend to regurgitate the in- bush swallowtail butterfly,” Ecology edible seeds, thus improving the nu- 1991, 72: 1428-1435.) tritional quality of the food volume entering their digestive system. Rob- Pyrrharctia isabella Frugivory, cedar waxwings and (woolly bear) ins and other thrushes thus serve as American robins: Seed dispersal by dispersal agents for spicebush, albeit possibly a consequence of the fewer birds is, conceptually, a simple mat- the distances involved usually leaf layers found in the shade compared ter: plant makes fruit with seed(s) amount to the span between the point with the denser leaf canopy of sun-ex- consumed by bird that drops undi- of ingestion and the next convenient posed plants. (R. A. Niesenbaum, “The gested seed in a distant location. In perch where seed regurgitation oc- effects of light environment on her- detail, however, dispersal by fruit- curs. As a general rule, seeds adapted bivory and growth in the dioecious eating birds has myriad variations, for through-passage and defecation shrub (),” both on the plant and bird sides of by birds are protected by thick seed American Midland Naturalist 1992. 128: the equation. Two recent studies ex- coats whereas those adapted for dis- 270-275.) amined the differing strategies em- persal by seed-regurgitating birds ployed by cedar waxwings and have thin seed coats. Spicebush Herbivory, spicebush swallow- thrushes (including robins) in the seeds, with their thin seed coat, fit this tail butterfly (Papilio troilus): In con- dispersal of several species of trees general pattern. Also, experimental trast to the moth larvae mentioned and shrubs of eastern North America. evidence shows that removal of the above, caterpillars of the spicebush Relative to other common fleshy- lipid-rich fruit pulp by fruit-eating swallowtail are much more special- fruited plants tested, spicebush fruits birds is essential for germination of ized in their food requirements. As are notable in containing low levels spicebush seeds and this hint from implied by its name, spicebush is one of sugar but high levels of protein and nature should be followed by garden- important larval food plant and sas- lipid (fats, but also aromatic terpe- ers wishing to propagate spicebush safras (), a related nes). Another important factor is that from seed. (G. A. Meyer & M. C. plant, is another. Interestingly, the spicebush seeds are relatively large. Witmer, “Influence of seed process- butterfly ranges into peninsular Waxwings quickly digest and absorb ing by frugivorous birds on germina- Florida, where neither spicebush nor sugars, but their assimilation of lip- tion success of three North American sassafras occurs. Here, the caterpil- ids is much slower. Also, waxwings shrubs,” American Midland Naturalist lars eat leaves of redbay (Persea swallow and, eventually, defecate all 1998, 140: 129-139 and M. C. Witmer borbonia), also a member of fruit seeds consumed in their diet. & P. J. Van Soest, “Contrasting diges- Lauraceae. In a thorough, compara- Sugar-rich fruits with small seeds tive strategies of fruit-eating birds,” tive study, it was found that Florida (like honeysuckles and wild grapes) Functional Ecology 1998, 12: 728-741.) caterpillars survived better on redbay work well for waxwings. On the other W. John Hayden (University of Richmond) VNPS Botany Chair Page 6 February 2006