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The Nature Conservancy

Midwest Regional Office

13l3 Fifth Street S.E., Minneapolis, Minnesota 55414

(612) 379-2207

Element Stewardship Abstract (ESA)

For

Prepared for

Eastern Region, Forest Service, USDA

1990

Headquarters Office, 1815 North Lynn Street, Arlington, Virginia 22209

PMIRIO96HO

>= 0012 STEW-ABS-RESP

MRO

THE NATURE CONSERVANCY

MIDWEST REGIONAL OFFICE

1313 5TH STREET SE, BOX 78

MINNEAPOLIS, MN 55414 612/379-2207

>= 0016 PREPARER

WAYNE OSTLIE (1990)

>= 0020 NAME

IRIS LACUSTRIS

>== 0050 COMMON-NAME

DWARF LAKE IRIS

BABY IRIS

>= 0100 DESCRIPTION

Crispin (1981) described the dwarf lake iris as a low-growing perennial with slender, creeping rhizomes, bearing a fan of flattened leaves less than 6 inches in height at enlarged nodes. Showy blue flowers are born singly on short stems and consist of 3 recurved sepals, each with a lightly-colored bearded crest above. This crest is coveted by a superimposed petal-like style branch. The petals are shorter than the sepals and alternate with them. They appear like typical iris flowers, only in miniature. For a detailed botanical description of the species, see Foster (1937).

Vegetatively, I. lacustris is easily recognized by its light green leaves, which appear translucent when viewed against a summer sky (Crispin and Penskar 1990). Apparently the leaves may be confused with those of Tofieldia glutinosa, but the latter are always less than 8 mm in diameter.

Iris lacustris closely resembles the more southerly distributed Iris cristata. In the past, I. lacustris was considered a variety of I. cristata (Foster 1937). It is now widely recognized as a distinct species based on differences in morphology, habitat, range (Atwood 1933), and chromosome number and configuration (Crispin and Penskar 1990). The dimensions and form of the perianth tube (shorter in length, 1-2 cm) (Waller 1931), its more cuneate sepals, more scarious and shorter spathe-bracts, different chromosome number (2n = 42, instead of 2n = 32) and soil preference distinguish I. lacustris from I. cristata (Braun 1967). Iris lacustris is listed as a federally threatened species by the U.S. Fish and Wildlife Service (USFWS 1988b)

>== 100 HABITAT

The dwarf lake iris is limited in range to the northern extremes of Lakes Michigan and Huron Along a narrow shoreline band (Planisek 1983, Trick and Fewless 1984). Only three known sites (all in Michigan) are significantly inland from the shoreline (14, 10 and 2 miles from shore) (Guire and Voss 1963, Trick and Fewless 1984). Currently, roughly 80 sites are known for the dwarf lake iris along the northern shores of Lakes Huron and Michigan in Wisconsin (15 sites), Michigan (60 sites) and Ontario (Crispin and Penskar 1990, USFWS 1988). Roughly 95% of all known populations occur in Michigan (USFWS 1988).

Present distribution, in many instances, may be linked to historical rather than current habitat regimes (Crispin and Penskar 1990). Many stations in Michigan lie along abandoned shores of the receding post-glacial Great Lakes, sometimes in habitats that are now obviously unfavorable.

Light levels, soil moisture, soil pH, nutrient levels (van Kley 1988) and habitat (Makholm 1986) vary widely between dwarf lake iris sites. The lowgrowth areas of upper beach, dunes and dolomite ledges provide the high light and low litter habitat which is favored by I. lacustris (Makholm 1986). Northern wet-mesic forests and boreal forest habitats also support populations, but such are apparently less suitable. Within these forests, I. lacustris is typically found in association with white cedar trees

(Makholm 1986, Planisek 1983, Guire and Voss 1963). Light levels vary between full sun and nearly complete shade in this array of habitats, but only individuals in semi-open edge habitats typically flower (Crispin and Penskar 1990). Plants are usually found in sfibilized sand or sand/gravel areas (Makholm 1986) with shallow soils, where competition from other plants is minimal (van Kley 1988).

In Ontario, Stebbins (1935) found the plant very abundant in damp woods and open places along the west shore of the Bruce Peninsula.

In Wisconsin, I. lacustris occurs in the Door Peninsula (Door and Brown Counties). Historic Milwaukee County populations have been extirpated (Makholm 1986). Trick and Fewless (1984) found the plant occupying small openings within a canopy of Thuja occidentalis in Wisconsin. Typically, Iris lacustris is known from sites within two miles of the shoreline and 140 or more feet above the current Lake Michigan water level. Soil pH at these sites ranges from 6.9 to 8.0 (Makholm 1986). Iris lacustris occurs at two preserves owned by The Nature Conservancy in Door County, Wisconsin: Mink River and Jackson Harbor Ridges Preserves (Braker pers. comm.). Plants occur in thick carpets at these sites in the transition zone between boreal forest and open beaches. Associates include Maianthemum canadense, Cornus canadensis, Smilacina stellata, Abies balsamifera, Juniperus horizontalis, Arabis lyrata, Polygala pucifolia, Zygadenus glauca, Equisetum sp., Mitella nuda, vaccinium sp., Arctostaphylos uva-ursi, Aquilegia canadensis and Clintonia sp. (Braker pers. comm.).

Van Kley (1988) observed that only mature Thuja occidentalis and Abies balsamea were routinely associated with Iris lacustris in Michigan. Additional associates in the overstory include Populus tremuloides and Picea SPP- (Crispin and Penskar 1990). Ground-layer associates include Arctostaphylos uva-ursi, Primula mistassinica, Cypripedium calceolus, Polygala paucifolia, smilacina stellata, Castilleja coccinea and Carex eburnea (Crispin and Penskar 1990). Associated shrubs include Shepherdia canadensia, Juniperus communis, Cornus stolonifera and Potentilla fruticosa. In Michigan, I. lacustris grows,to its greatest abundance in three general areas (the Garden Peninsula, southeastern Presque Island and Cheboygan/Emmet Counties) where it occurs almost continuously for several miles of lakeshore (Crispin and Penskar 1990). Inland sites (as discussed by Guire and Voss (1963) ] occur in a sparse pine woods on a rocky plain (2 miles inland), a gravel ridge among aspens (14 miles inland), and a calcareous bank along a river (10 miles inland).

>==2000 BIOLOGY-ECOLOGY

Planisek (1983) described the annual growth of Iris lacustris as follows:

In another study in Michigan, van Kley (1988) found flowering plants in sunny, open areas as early as May 12th. Flowers typically opened in the morning and withered by the afternoon of the second or third day. Some flowers occasionally were opened in the afternoon or evening. Plants have been observed flowering in September and October (Dykes 1510). Capsules are formed shortly after flowering and last roughly seven to ten days. Mature capsules dry and dehisce into three sections during mid-July through midAugust (Makholm 1986). The timing of particular events such as flower emergence and fruit production varies with local conditions (Makholm 1986).

Vegetative growth occurs largely during the mid to late summer. Plants that produced unsuccessful flowers (did not form fruits) frequently produce one or two additional vegetative shoots the following year (Makholm 1986). Old tubers will occasionally produce side shoots which can f orm at any time during the growing season. This production of extra shoots serves to fill in empty spaces within the colony. Following f lowering, new tubers are produced at the base of the shoots and begin to thicken. Shoots for the upcoming year are formed shortly thereafter (Makholm 1986). The growing season ends typically in September or early October.

Makholm (1986) found that the distribution of I. lacustris depends largely upon the availability of light. In the darkest habitats, the species is found where larger sun flecks reach the forest floor. The optimal light conditions, however, occur in conditions where 50% of the light comes from open sky and the other half from side-lighting. In such situations, Iris leaves are situated with a flat vertical surface at a 90 degree angle from the forest edge. In high light levels shoots grow fully -erect, with all or most of the population growing parallel to each other at right angles to the edge of the forest. In dark sites within Thuja forests, proportionately more light comes from overhead rather than side light. In such situations, Iris shoots are tilted away from a fully upright position and may drape prostrate to- the ground (Makholm 1986).

Limitations of the breeding system appear to be the major reason for the rarity of this species. Severe bottlenecks occur in several portions of the sexual cycle: pollination, seed dispersal and seedling establishment (van Kley 1988). According to Makholm (1986) dispersal appears to be the limiting factor in the life history of I. lacustris. Historically, a major dispersal factor may have been the rise and fall of the Glacial Great Lakes and glacial meltwater. Conditions for such dispersal apparently no longer exist or have been greatly subdued. Data obtained by Makholm (1986) suggest a strong bias against seedling establishment and survival in habitats with a continuous litter layer. Colonies that occur in mature Thuja forests appear to maintain themselves solely through vegetative reproduction.

Although pollination via pollen vector is believed to be essential in this species (Planisek i983), no insects with pollen have been observed visiting these flowers (Planisek 1983, van Kley 1988). Van Kley (1988) did, however, observe several bees and flies visiting the flowers but either observed no pollen on the insects, or was unable to catch them.

Planisek (1983) reported that the dwarf lake iris is not apomictic or autogamous (i.e., no seed set was reported without pollination or without the presence of pollinator vectors, respectively). The species, however, was found to be self-compatible. Planisek (1983) found that selfed flowers typically set more fruit than out-crossed ones (85% and 71-t fruit set, respectively). Similar tests by van Kley (1988) yielded 90% fruit set through self-pollination and 70% from outcrossing during the peak flower period. Tests conducted toward the end of the flower ng period showed markedly lower fruit set (30% fruit set) for both groups (van Kley 1988).

Planisek (1983) found that fruit set within the species was low (3% of growing tips produced fruits), with fruits unevenly distributed over the plant's range. Although the number and dens ty of flowers correlated well with growing-tip density, fruit set did not. Van Kley (1988) however, disagreed with the results reached by Planisek, showing a correlation between the number of flowers and fruit set. In Michigan, seed set within a fruit was found to average roughly half the potential with respect to available ovules (Planisek 1983). This was not bel eved to be a result of pollen scarcity.

Predators of I. lacustris seeds have been noted. Makholm (1986) observed an unknown insect larvae devouring the contents of the Iris fruit and suggested that it may, as an adult, play a role in pollination. Apparently chipmunks have also been observed devouring Iris seeds. other small rodents (mice, etc.) may be additional predators of seeds. On vegetative portions of the plants, Makholm (1986) observed small herbivory injuries thought to be caused by landsnails (Triodopsis multilineata) and slugs.

Ants are believed to be the primary dispersal agents in dwarf lake iris seeds. Ants are apparently attracted to seeds by structures occurring on them that resemble eliasomes (small fat bodies which serve as a food source for ants). Seeds are consequently carried . back to the ant mounds (Planisek 1983). Several species of ants apparently act as dispersal agents. Although dispersal by ants may help colonize areas adjacent to existing sites, it does not enable Iris lacustris to colonize suitable areas several kilometers away (van Kley 1988).

Van Kley (1988) suggested that seed germination is low in this species; only 5 of 192 plots visited during his study yielded seedlings. When germination does occur, it-usually happens from late May to early July (Makholm 1986). Apparently, seeds must overwinter at least one year before germination can take place. Makholm (1986) suggested that it may be the soggy spring weather rather than the cold of winter that release seeds from dormancy, since there is no absolute requirement for a cold treatment in the genus Iris.

Most reproduction within the species is believed to be vegetative. The species can rapidly clone and spread in open areas possessing dry, calcareous substrates (Crispin and Penskar 1990). Dispersal in lake waters by means of floating rhizomes is believed to be a major factor in long-distance dispersal.

Significant correlations between light levels and both absolute numbers of blooms and bloom/shoot ratio have been found in Michigan (van Kley 1988). Fruit set was also higher in open locations (van Kley 1988). Although this may be true in times of adequate moisture, Morgan (pers. comm.) found that plants in partial or full shade fared much better than those in full sunlight during periods of drought.

significant negative correlations have been found between soil depth and 1) the bloom to shoot ratio, 2) total number of blooms, 3) light levels, and 4) numbers of fruit (van Kley 1988).

>== 2000 EO-QUAL-DET

This field is designed to help the field worker determine the quality (A=excellent, B--good, C--marginal, D=poor) of an occurrence of this element. These ranks are based on size and productivity of the population, vitality and vigor of the individuals within the population, and size and quality of the habitat in which the element occurs. Headings (habitat, population size and vigor) should be considered separately in determining overall quality of the element occurrence.

>== 3000 THREATS

Development along the shorelines of the Great Lakes poses the greatest threat to the habitat of the dwarf lake iris and, consequently, to the iris itself (Ewert pers. comm., USFWS 1988a, USFWS 1988b, van Kley 1988). Other threats include road widening, chemical spraying, salting of road.4, off-road vehicle use (USFWS 1988b) and trampling (Ewert pers. comm.). Natural plant succession has also reduced habitat for this species (USFWS 1988b, van Kley 1988). Although sensitive to mechanical disturbance, I. lacustris is able to readily repopulate disturbed areas if populations occur nearby (Crispin and Penskar 1990).

Drought appears to have had a major negative impact on dwarf lake iris populations. Van Kley (1988) observed dead and dying rhizomes and plants during the 1988 drought in Michigan, with no signs of dormancy in any individuals, other forms of mortality, damage or predation were seldom observed by van Kley (1988).

>== 3500 LAND-PROT-SPECS

Protection must include old dune habitat along the Great Lakes shoreline where ope@ canopy, shallow soil, lightly vegetated habitats necessary for this species exist. Habitats of extensive area need protection in order to ensure natural disturbance regimes (tree windfall,, etc.) and the long-term viability of extant populations. Protection from excessive disturbance, pesticide.application and other destructive forces are essential. current development of the shorelines threatens the continued viability' of this species and should be checked in areas of high importance. Adequate buffer lands must surround populations slated for protection.

>== 4000 RECOVERY-POT

Presently, one site is protected on federal land, while several other populations are protected on state lands (USFWS 1988a) as well as two preserves owned by The Nature Conservancy in Michigan (Ewert pers. comm.).

Recovery potential appears excellent if enough habitat is protected. Since this species thrives in shallow toil sites where physical disturbance is common (ice jams, wind erosion, etc.), it should do nicely where habitat has been altered by human impact. In fact, van Kley (1988) observed numerous plants growing in old field situations. once established,, and in the absence of significant competition, individual plants tend to reproduce aggressively via branching of the rhizome (van Kley 1988).

Apparently, this species has been cultivated for many years (Litzow 1978), so artificial propagation and maintenance of the species can be accomplished, if and when the situation arises.

>== 5000 BIOL-MONIT-NEEDS

A simple survey of the precise extent of all the known populations is needed in Michigan (Penskar pers. comm.) and perhaps, elsewhere. In the compilation of data,, the Iris lacustris Recovery Team found that this information was missing for many of the sites. Since precise individual counts are nearly impossible to make, aerial coverage estimates are the best predictors of population size.

Monitoring with respect to habitat (canopy closure, disturbance, etc.) and population dynamics (proportion of flowering and fruiting individuals, recruitment, etc.) are additional needs.

>= 5200 BIOL-MONIT-PROCS

Monitoring of I. lacustris populations is not simple due primarily to the difficulty in determining what constitutes an individual or a population. The Iris lacustris Recovery Team has ranked populations based on aerial coverage in order to arrive at estimates of population size. Counts of flowering and fruiting stalks should be considered for long-term monitoring as an indicator of frequency and success of sexual reproduction within a given population. For a discussion of an appropriate monitoring methodology see those utilized in Michigan by Ewert or contact him at the address listed below.

>== 5400 BIOL-MONIT-PROGS

Monitoring programs have been established for Iris lacustris on two preserves in Michigan owned by The Nature Conservancy (Ewert pers. comm.). At Grass Bay Preserve, 24 permanent plots (each 70.7 cm X 70.7 cm = 0.5 square meters) have been established in the center of each preserve to count the number of flowers and vegetative stems. This provides baseline data on the number of plants within each preserve and some information of population changes under different light and soil moisture conditions over time. Data concerning

canopy cover, associated species, light levels, litter depth, fruit production and soil depth is also collected. Contact: Dave Ewert, Director of Stewardship, Michigan Field Office, The Nature Conservancy, 2840 E. Grand River, Suite 5, East Lansing, MI 48823. Telephone No. (517) 332-1741.

At Presque Isle Harbor Preserve in Michigan, The Mature Conservancy has contracted with the State of Michigan to evaluate the response of I. lacustris to marina development (Ewert pers. comm.). Similar procedures and plot size are used to gather information concerning associated species, canopy cover, litter depth,, number of Iris stems, flowers and fruits. Data from both sites is available upon request. Contact: Dave Bwert at the above address or Mike Penskar, Botanist, Michigan Natural Features Inventory, Mason Bldg., 5th Floor, Box 30028, Lansing, MI 48909. Telephone No. (517) 3731552.

The Wisconsin Field Office of The Nature Conservancy recently began a monitoring program for I. lacustris at the two preserves where it occurs (Braker pers. comm.). Started in 1989, the monitoring program is very similar to that established for the species in Michigan by Ewert. Permanent plots, in which the numbers of total plants and flowering plants were counted, have been established at the Mink River and Jackson Harbor Ridges Preserves. Monitoring will take place once every year for the first three or four years, then slow to a rate of once every three or four years. Contact: Nancy Braker, Director of Stewardship and Registry, Wisconsin Field Office, The Mature Conservancy, 1045 E. Dayton Street, Rm. 209,,Madison, WI 53703. Telephone No (608) 251-8140.

>== 6010 RSRCH-NEEDS-COMM

The overall genetic variability of this species must be known if this species is to benefit fully from any future management practices. This information will aid in understanding the factors involved in its past and present life history and distribution patterns. In addition, such information may provide crucial insight into the importance of vegetative and sexual reproduction in this species.

Research also needs to identify the active pollinators of this plant. At present, pollen dispersers are largely unknown for the species. Proper management in the future must ensure that pollination vectors and associated habitat are protected along with the plant.

Apparently there is no reliable information on under what instances and conditions Iris lacustris seeds germinate. Van Kley (1988) recently achieved no germination success when he planted 100 seeds. No tests, however, were conducted to attempt germination enhancement. Van Kley (1988) also mentioned that it is unknown how long Iris seeds can remain viable within a seed bank. Such information is essential in order to understand the long-term survivability of the species.

Research must also determine the exact size of the remaining populations of dwarf lake iris. Van Kley (1988) alluded to the fact that sizable areas away from nearby roads have never been checked for the presence of this species. An accurate assessment of the population size must be known if proper management and protection is to be offered.

>= 6410 RSRCH-PROGS-COMM

The Federal Recovery Team for Iris lacustris is currently preparing a recovery plan for the species. This report will identify the primary management needs for the species. Contact: Mike P6nskar, Botanist, Michigan Natural Heritage Program, 2840 E. Grand River, Suite 5, East Lansing, MI 48823. Telephone No. (517) 332-1741.

Morgan (pers. comm.) stated that he is in the fifth year of a lo ng-term study on the, reproductive biology of Iris lacustris at a site in Brown County, Wisconsin. Forty permanent quadrats have been established in areas ranging from full sun to full shade. Currently, the numbers of vegetative ramets, ramets producing flowers, flowers producing fruit, and fruit ' reaching maturity are determined at each quadrat. The amount of sunlight received by plants is being analyzed in order to determine its effect under different weather conditions. Contact: Dr. Mike Morgan,, College of Environmental Science, University of Wisconsin-Green Bay,, Green Bay, WI 54311-7001. Telephone No. (414) 465-2265.

This year, James P. Moore, a graduate student of Dr. Mike Morgan, will begin study on the effects of competition by large-leaved asters on Iris lacustris. These asters have been known to crowd out populations- of I. lacustris. Contact: James P. Moore, College of Environmental Science, University of Wisconsin-Green Bay, Green Bay, WI 54311-7001. Telephone No. (414) 4652265.

>== 7010 MGMT-NEEDS-COMM

Management of the sites to reduce competition from other plants is a need for the species (USFWS 1988). Ewert (pers. comm.) stated that, although shading by encroaching vegetation is a potential problem, it is not a serious threat if enough wind-throw of sand is occurring. Management should consider.the maintenance or creation of partial opening of closed canopies in order to enhance habitat of existing populations (Penskar pers. comm., Makholm 1986).

Makholm (1986) suggested. the following management considerations: (1) halting the successional development of deciduous forest in the vicinity of Iris populations through the removal of saplings and seedlings, (2) paths and trails should be maintained as they apparently provide openings within the forest, (3) continue the practice of selective logging in areas that possess Iris populations, and (4) protection of populations on private lands via landowner contacts or acquisition.

The transplanting of Iris to historic sites has also been considered (USFWS 1988, Makholm 1986). Van Kley (1988) suggested that transplanting of rhizomes could overcome the minimal dispersal rate of this species. The genetics of each population should be determined prior to undertaking this practice so that human intervention will minimally impact the genetic integrity of the species.

According to Ewert (pers. comm.), management needs also include the production of adequate preserve designs to allow for fluctuating water levels and other threats. Van Kley (1988) and Ewert (pers. comm.) stated that management cannot improve the prospect for this species unless shoreline development, the primary threat, is halted.

>= 7400 MGMT-PROCS

The Federal Recovery Team for Iris lacustris is currently compiling information and prioritizing recovery actions with respect to management, but procedures have not yet been finalized (Penskar pers. comm.).

Fire management is not considered to be a viable option in maintaining open dune areas inhabited by Iris lacustris (Morgan pers. comm.). Since this species possesses fleshy rhizomes near or at the surface of the ground, they would be susceptible to fire. In addition, large-leaved aster clones which are known to out-compete I. lacustris clones for resources, have rhizomes deeper in the soil. As a consequence, the asters would benefit greater from prescribed burning than would I. lacustris (Morgan pers. comm.).

Generally, large open areas within the dune ecosystem tend to remain open due to frequent wind-fall of large trees along the perimeter of the open areas. Shallow root systems, sand substrates and increased wind velocity make this a common occurrence. Consequently,, active management in maintaining the openings is probably not needed. In smaller openings where wind-fall is not prominent, brush or tree cutting pay have to be implemented to enhance the viability of a population (Morgan pers. comm.).

The Michigan Chapter of The Nature Conservancy manages for the specie ' s by keeping trails away from I. lacustris populations as mudh,as possible (Ewert pers. obs.). Otherwise, no management is being conducted.

>== 8000 SUM-STEW-NEEDS

Habitat and population dynamics at I. lacustris sites need to be monitored in order to determine long-term survival probabilities at such sites. A survey to determine the exact size of extant populations is also needed. Research needs include work on determining the genetic variability within the species, identification of pollinators, seed germination requirements and a survey to find all extant sites. Management needs include the maintenance of open canopies, restriction of development of old dune habitats, and protection of populations on private lands. The production of adequate preserve designs to account for threats, I. lacustris and pollinator needs, and habitat management practices is also imperative.

>= 9000 BIBLIOGRAPHY

Alverson, W. 1981. Bull. Botanical Club of Wisconsin 13(3): supplement.

Atwood, W. H. 1933. The lake iris and its differentiation from cristata. Bull. Am. Iris Soc. 47: 78-79.

Braker, H. 1990. Director of Stewardship and Registry, Wisconsin Field Office. Personal communication with Wayne Ostlie, MRO, The Nature Conservancy.

Braun, E. L. 1967. The vascular flora of Ohio. I. The monocotyledonae (cattails to orchids). Ohio State University Press, Columbus. 464 pp.

Crispin, S. and M. Penskar. 1990. Iris lacustris. Unpublished abstracts, Michigan Natural Features Inventory, Endangered Species Manual. 3 pp.

Ewert, D. 1989. Land Steward, Michigan Field Office, The Nature Conservancy. Personal communication: ESA questionnaire for Iris lacustris. 3 pp.

Foster, R. C. 1937. A cytotaxonomic survey of the North American species of Iris. Contr. Gray Herb. 119. 82 pp-.

Guire, K. E. and E. G. Voss. 1963. Distributions of distinctive shoreline plants in the Great Lakes region. Mich. Bot. 2: 99-114.

Litzow, M. 1978. Iris lacustris Nutt: Summary of the literature by Margaret Litzow. Unpublished report to the Minnesota Landscape Arboretum, Chanhassen, MN. 6 pp.

Makholm, M. M. 1986 Ecology and management of Iris lacustris in Wisconsin. M.S. thesis, Univer@ity of Wisconsin, Madison. 122 pp.

Morgan, M. 1990. Professor of Botany, University of Wisconsin, Green Bay. Personal communication with Wayne Ostlie, MRO, The Nature Conservancy.

Penskar, M. 1990. Botanist, Michigan Natural Features Inventory. Personal communication: ESA questionnaire for Iris lacustris. 3 pp.

Planisek, S. L. 1983. The breeding system, fecundity. and dispersal of Iris lacustris. Mich. Bot. 22: 93-102.

Randall, C. 1978. Four threatened plants of the Great Lakes shorelines. Michigan Department of Natural Resources report, Lansing. 6 pp.

Rees, M. D. 1988. Final listing rules-approved for 25 species. Endangered Species Tech. Bull. 13(9-10): 3-5.

Stebbins, G.L. 1935. Some observations on the flora of the Bruce Peninsula, Ontario. Rhodora 37: 63-74.

Trick, J. A. and G. Fewless. 1984. A new station for dwarf lake iris (Iris lacustris) in Wisconsin. Mich. Bot. 23: 68.

USFWS. 1988. Habitat loss threatens two Midwestern plants. Endangered Species Tech. Bull. 13(l): 1.

van Kley, J. E. 1988. Habitat and ecology of Iris lacustris (the dwarf lake iris). Unpublished M.S. thesis, Central Michigan University, Mount Pleasant. 82 pp.

Waller, A. E. 1931. The native Iris of Ohio and bordering territory. Ohio J. Sci. 31: 29-43.

Wisconsin Natural Heritage Program (WI NHP). 1990. Database records for Iris lacustris. 76 pp.

>== 9990 UPDATE

[YY-MM-DD]

>= 9999 END