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First, acquire knowledge.

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Before a recovery plan for an endangered or threatened species can be written and carried out, knowledge of the species' life history is needed. If critical information is missing, recovery efforts can be thwarted. One small, unknown aspect of a species' life history might be the reason it is listed in the first place. A rare Midwestern orchid species provides an example.

The Fish and Wildlife Service listed the eastern prairie fringed orchid (Platanthera leucophaea) as a threatened species in 1989. This wildflower has declined to roughly 70 percent of its original range, mainly due to habitat loss (Bowles, 1993). It currently grows in remnant mesic (moist) prairie sites in Wisconsin, Illinois, Michigan, and Ohio. A recovery plan adopted in 1999 identified specific recovery tasks, which included site protection, habitat management, seed introduction and augmentation, and research to support recovery. The research was needed for things that were not known about the orchid, such as its population genetics and which species serve as its natural pollinators.

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What has been learned about the orchid is that it requires pollination by hawkmoths for sexual reproduction (Bowles, 1983; 1985). The flowers of this plant have the longest nectar spur (up to 5 centimeters, or about 2 inches) of any north temperate orchid species, and pollination seems to be restricted to hawkmoths with a proboscis long enough to reach the nectar, which is held at the swollen base of the spur (Bowles, 1983; Sheviak & Bowles, 1986). These insects also extract nectar from flowers of many other plants and travel great distances to find food (Fleming 1970). The moths are likely to visit only those orchid populations that are large enough to provide a nectar resource competitive with that of other plants (Bowles 1983).

The prairie fringed orchid's flowers are fragrant only at night, and pollinia are picked up by the proboscises of hawkmoths as they ingest nectar. Flowers are adapted to outcrossing (pollination with flowers of other individuals), but plants appear to be self-compatible, and self-pollination probably occurs at high levels in small populations (Bowles & Bell 1999). However, fruit set appears to be reduced if the plants are self-pollinated (Bowles 1983). Plants with a large inflorescence (cluster of flowers) that are exposed above the prairie canopy, and away from shrub cover, have the highest potential for pollinator visitation and seed production (Bowles 1985).

To confirm a moth species as a pollinator, it has to be caught with orchid pollinia attached to its proboscis. Previous pollinator identification studies in Michigan, Ohio, and Wisconsin identified the pandorus sphinx (Eumorpha pandorus), achemon sphinx (Eumorpha achemon), and hermit sphinx (Sphinx eremitus) hawkmoths as pollinators (Cuthrell 1994, Cuthrell et al. 1999, Crosson et al. 1999). Because there had not been any research of this kind conducted in Illinois or Iowa, a pollinator identification study was initiated in 2004 and continued in 2005. The first objective of this research was to determine if natural pollinators are still available and to identify them. The next objective was to determine if the host plants upon which the moth caterpillars depend also occur at the orchid sites.

Seven sites were surveyed for a total of 29 survey-nights. Surveying included taking nectar measurements from 10 orchids per site each evening and dawn. Two light sheets were used for moth capture. One or two funnel traps were also used per site. Later in the season, a plant species analysis was performed at each site.

On a typical night, surveyors arrived around 5:00 p.m. They began by taking nectar measurements and setting up the equipment, followed by observing the orchids all night, watching for hawkmoths feeding on the orchids. Visual observation was conducted from about 8:00 p.m. to 4:30 a.m., followed by additional nectar measurements.

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The studies confirmed that the hermit sphinx is a pollinator in Illinois and Iowa. Six specimens were caught with orchid pollinia attached to the proboscis. A Carolina sphinx (Manduca sexta) also was caught on one orchid, but it is only considered a "nectar thief" since it did not carry orchid pollinia. Pandorus sphinx and achemon sphinx, confirmed as orchid pollinators in other states were also captured, but none carried orchid pollinia. Analyses of the plant species at each site are still being conducted. Larva food of the hermit sphinx includes beebalm, bugleweeds, mints, and sage.

We anticipate that these studies will give land managers additional knowledge they need to guide the recovery of this spectacular but threatened wildflower.

References

Bowles, M.L. 1983. The tallgrass prairie orchids Platanthera leucophaea (Nutt.) Lindl. and Cypripedium candidum Muhl. Ex Willd.: some aspects of their status, biology, and ecology, and implications toward management. Natural Areas Journal 3(4) 14-37.

Bowles, M.L. 1985. Distribution and reproductive success of the prairie fringed orchid in southeastern Wisconsin sand prairie. M.S. Thesis. University of Illinois, Urbana.

Bowles, M.L. 1993. Recovery plan for the Eastern prairie fringed orchid (Platanthera leucophaea [Nuttall] Lindley). Unpublished 2nd draft for Region 3 of the U.S. Fish and Wildlife Service, Twin Cities, Minnesota, 25pp.

Bowles, M.L. and T. Bell. 1999. Establishing recovery targets for the eastern prairie fringed orchid (Platanthera leucophaea). Unpublished report to the Illinois Endangered Species Protection Board. The Morton Arboretum.

Crosson, A., J.C. Dunford, D.K. Young. 1999. Pollination and other insect interactions of the Eastern Prairie Fringed Orchid (Platanthera leucophaea (Nuttall) Lindley) in Wisconsin. University of Wisconsin, Madison. A report for the U.S. Fish & Wildlife Service.

Cuthrell, D. L. 1994. Insects associated with the prairie fringed orchids, Platanthera praeclara Sheviak & Bowles and P. leucophaea (Nuttall) Lindley. MS Thesis, North Dakota State University, Fargo, ND, 81 pp.

Cuthrell, D. L., Phyllis J. Higman, Michael R. Penskar, Jennifer L. Windus. 1999. The Pollinators of Ohio and Michigan populations of Eastern prairie fringed orchid (Platanthera leucophaea). Prepared for the U.S. Fish & Wildlife Service, Reynoldsburg, Ohio. 20pp.

Fleming, R.C. 1970. Food plants of some adult sphinx moths (Lepidoptera: Sphingidae). Michigan Entomologist (Now Great Lakes Entomologist) 3:17-23.

Sheviak, C.J. and M.L. Bowles. 1986. The prairie fringe orchids: a pollinator-isolated species pair. Rhodora 88:267-278.

Cathy Pallock is a fish and wildlife biologist in the Service's Barrington, Illinois, Field Office (cathy_pallock@fws. gov; 847/381-2253, ext. 239).
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Title Annotation:wildlife conservation
Author:Pollack, Cathy
Publication:Endangered Species Bulletin
Geographic Code:1USA
Date:Mar 1, 2006
Words:1045
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