The Pollinators of Ohio and Michigan Populations of Eastern Prairie Fringed Orchid (Plantanthera Leucophaea)
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Table of Contents Introduction ............................................................................................................1 Orchid Pollination ...............................................................................................2 Materials and Methods ......................................................................................... 3 Study sites........................................................................................................... 3 Pickerel Creek Wildlife Area ........................................................................ 3 Huron County # 1 Site, Michigan.................................................................. 3 Pollinator Activity .............................................................................................. 4 Fruit Set.............................................................................................................. 5 Results..................................................................................................................... 5 Discussion............................................................................................................... 9 Eastern prairie fringed orchid pollinators ......................................................... 9 Non-pollinators ................................................................................................ 11 Unlikely pollinators.......................................................................................... 11 Pollen thieves ................................................................................................... 11 Hawkmoth behavior ......................................................................................... 11 Conclusions and Recommendations .................................................................. 12 Acknowledgements.............................................................................................. 13 Literature Cited................................................................................................... 14 Appendix Platanthera leucophaea abstract for Michigan ................................................ 16 i Introduction Eastern prairie fringed orchid counties (Holmes, Lucas, Sandusky, and (Platanthera leucophaea [Nuttall] Lindley) Wayne) and one west-central county is a federally threatened species known from (Clark). It has been listed as a state approximately 55 populations in seven threatened species by the Ohio Department Midwestern states, primarily Wisconsin, of Natural Resources, Division of Natural Illinois, and Michigan (Bowles 1993). Areas and Preserves, since 1986 (ODNAP Although this may seem like an adequate 1986). Prior to 1986, it was listed first as number of populations within a reasonable extirpated in 1980 and then as endangered range of the Midwest, the majority of these from 1982-1985 following the discovery of populations are small, unprotected, and the Lucas and Wayne county populations. erratic in their persistence. In addition, few Historic records from Ottawa County (North occurrences are in good quality habitat. At Bass Island–1980), Auglaize County (1901), present, only four legally protected Erie County (1916), and Montgomery populations in the U.S. are considered to County (1800s) have not been relocated, have high viability (Bowles 1993). despite recent surveys. There are also Platanthera leucophaea was formerly literature references to historic occurrences widespread in prairies and wetlands east of in Champaign and Franklin counties (Braun the Mississippi River (Bowles 1993). Its 1967) as well as Fairfield County (Schaffner historic range included 13 states extending 1932). None of the extant populations occur from eastern Missouri and Iowa to northwest in counties where there are historic records Pensylvania, western New York, and or references. southern Ontario, with disjunct populations A necessary step in the recovery of in Oklahoma, New Jersey, Virginia, and Platanthera leucophaea is obtaining specific Maine (Bowles 1993). In the U.S., knowledge about its reproductive biology Platanthera leucophaea has declined more including information regarding its than 70% from original county records due pollinators. Important information such as to habitat destruction from agriculture, the role of pollinators in relation to seed-set wetland drainage, and natural succession and their role in maintaining viable orchid (Bowles 1993). This drastic decline led the populations is lacking. Hawkmoths U.S. Fish and Wildlife Service to list (Lepidoptera: Sphingidae) have been Platanthera leucophaea as a federally identified as primary pollinators of threatened species in 1989 (U.S. Fish and Platanthera leucohaea in Illinois and Wildlife Service 1989). Wisconsin (Robertson 1893, Bowles 1983, In Michigan, Eastern prairie fringed and Cuthrell 1994), however little is known orchid was known from 21 counties of their population or habitat status. To our historically (Case 1987). Currently there are knowledge, no Platanthera leucophaea a total of 14 extant populations from nine pollinator studies have previously been counties (Natural Heritage Biological and conducted in Ohio or Michigan. Conservation Data System, 1999). The Pollinator loss or decline can affect species has been listed as a state endangered plants in several ways including most species by the Michigan Department of obviously the loss of, or reduced, seed-set Natural Resources since the inception of the (Tepedino 1979). The production of less Endangered Species Act in 1974. The vigorous offspring is also possible due to populations are found in two main habitat effects of inbreeding depression resulting types: lakeplain prairies and bogs. from a higher percentage of seed-set through In Ohio, Platanthera leucophaea is self-pollination (Kearns and Inouye 1997). presently known to occur in four northern Pollinators may be threatened by habitat alteration including destruction of larval and Eastern prairie fringed orchid pollinators - 1 adult food sources, introduction of alien distance between the viscidia (sticky pads at pollinators, and/or the use of pesticides. the base of the pollinia that become attached The identification and status of to the pollen vector) become important plant pollinators of Eastern prairie fringed orchid characters by governing pollinator position has been identified as a priority research in relation to various floral parts during task in the Federal Recovery Plan for this floral visitation (Inoue 1985, 1986). Moths species (Bowles 1993). This study was with a long proboscis may be able to reach conducted in order to begin to identify the nectar without affecting pollination and are pollinators of Eastern prairie fringed orchid therefore labeled pollen “thieves”. Pollinia in Michigan and Ohio. attachment at the proboscis and the dorsal thorax appears to be the usual situation for pollen vectors of North American orchids Orchid Pollination (Catling and Catling 1991). For example, in The floral biology of the Orchidaceae P. bifolia (L.), the viscidia are spaced close has fascinated biologists for many years together and adhere to pollen vectors at the because of the pollination mechanism base of the proboscis. This type of pollinia exhibited by members of this group (Cole attachment allows for a greater number and and Firmage 1984). Two orchid genera that more diverse set of pollinators, and have attracted considerable attention are pollinator morphologies are not quite as Platanthera L.C. Richard and Habenaria important (Nilsson 1983). Wildenow, which together comprise more Eastern prairie fringed orchid ranges than 800 species of orchids (Nilsson). Most from 20-100 cm tall, producing a terminal of these orchids possess adaptations that and determinate inflorescence with between indicate lepidopteran pollination (van der 5 and 40 flowers comprised of three creamy- Pijl and Dodson, 1966; Catling and Catling white petals backed by three pale green 1991), although other insect taxa have been sepals. The lower petal is modified into a reported as pollinators for some species broad lip which is deeply 3-lobed. Each of (Thien and Utech, 1970; Cole and Firmage the lobes is deeply incised which produces 1984; Patt et al. 1989). the fringed appearance. The lower lip also Most orchid species within these two bears a slender, curving spur that extends up genera can be categorized as either moth- to 5 cm and contains a supply of nectar. The pollinated or butterfly-pollinated species flower also produces a sweet fragrance most based on specialized plant morphologies and pronounced at dusk when the hawkmoths adaptations linked with their primary are beginning their feeding flights. pollinator groups (van der Pijl and Dodson, These orchid morphologies are adapted 1966). Several species of Lepidoptera are to pollination by Lepidoptera. The white, known to be important pollen vectors for nocturnally fragrant flowers help pollinators Platanthera. Pollinator specificity is to locate the plants. Once in close proximity dictated by the placement and positioning of to the flowers, the white-fringed lip directs pollinia (packets of pollen) on the vector. approaching moths to the spur and the Removal of pollinia by attachment to the nectar. The close spacing of the visicidia eyes is one way that pollination takes place allow moths to pick up pollinia at the base in Platanthera and Habenaria (Smith 1975; of their tongue. Only those moths with Smith and Snow 1976, Catling 1984; Inoue compatible tongues