Environmental and reproductive factors influencing population size of the Illinois endangered species Camassia angusta (Wild Hyacinth)

Kevin M. Franken¹, Janice M. Coons¹, Henry R. Owen¹, Eric L. Smith², and John E. Ebinger^1
1 Department of Biological Sciences, Eastern Illinois University. ² Division of Natural Heritage, Illinois Department of Natural Resources.

Abstract

Wild hyacinth (Camassia angusta) is a perennial species native to mesic prairies of the midwestern and south central United States. In Illinois, the only extant population of this endangered species is in a small section of degraded black soil prairie along a railroad track right-of-way south of Elwin, Macon County. The objectives of this research were to determine the population status, seed production, and germination requirements of C. angusta of this population. The population was surveyed in June from 1990 to 2006 by counting the number of flowering wild hyacinth plants. A survey of other plant species present was conducted in 1999 to assess its quality. Seed production of C. angusta was estimated, and germination trials for seeds from the site were conducted. The population of C. angusta fluctuated significantly from 1990 to 2006 (28 to 168 plants). The site consisted of approximately ¾ native and ¼ introduced species. Prescribed spring burns and a construction equipment disturbance may be partially responsible for these fluctuations. A large percentage of undeveloped fruit, resulting in low seed production (< 3000), may be responsible for this population’s inability to increase consistently. In the laboratory, germination of wild hyacinth seeds was very low (8%). Future research efforts should take into account the results from this study in order to further develop management strategies.

Introduction

Wild hyacinth, Camassia angusta (Engelm. and Gray) Blankenship (Liliaceae), is a mesic prairie forb listed as endangered in IL and IN. Distributed throughout much of the south-central U.S., it also occurs in IA, KS, LA, MS, MO, OK, and TX. The only extant population in IL occurs along a 2 km railroad right-of-way south of Elwin, between agricultural fields and IL Route 51. Much of the community is degraded by fire suppression, woody species invasion, exotic taxa, and disturbances by construction and railroad activities. Threats to this species in IL make it important to understand its reproductive biology to improve management decisions. The objectives of this study were to: 1) determine the number of individual C. angusta plants at the site over 17 years; 2) determine what other plant species were present to assess the prairie quality prairie; 3) estimate the C. angusta seed production; 4) determine its germination requirements; and 5) determine the effects of burns and disturbances on the population.

Materials and methods

Surveys were conducted from 1990-2007 by counting the number of inflorescences. The population consisted of 7 colonies. Prescribed burns (Figures 1 and 2) were conducted in 1993, 1994, 1997, 1998, and 2000 between March 1 and April 15. In 1999, all observed vascular plant species were recorded. The height of each C. angusta inflorescence was measured, and the numbers of pedicels, flowers, and/or fruits/ plant were counted.

Sixty fruits of were collected from 18 plants. The number of seeds/fruit was counted and an estimate of total seed production was calculated. Three seed treatments were used: control, scarification, and stratification (5 replications; for a total of 50 seeds/treatment). Seeds were scarified by nicking the apex with a razor blade. Seeds receiving stratification were soaked in water overnight, placed in moist paper towels in a Ziploc^TM bag, and stored at 8^oC for 63 days.

Germination trials were conducted in Petri dishes on 2 layers of filter paper, wetted with 5 ml of dH₂O, and placed at 25^oC (16 hr-light/8 hr-dark; 47 µmol/m2/sec). Germinated seeds were counted daily for 40 days. Seeds that failed to germinate were tested for viability using 2,3,5-triphenyl tetrazolium chloride (TTC).

Results

The number of inflorescences of C. angusta fluctuated significantly (Table 1). In terms of the total number of inflorescences per year, the highest (169 plants) was in 2006, and the lowest (28 plants) was in 1994.

In 1999 this prairie consisted of 74 native and 27 introduced species (Table 2).

Approximately 25% of pedicels produced fruit. Fruits had an average of 7 seeds. An estimate of the total seed production of the population was <3000 (Table 3).

None of the control or scarified seeds germinated after 40 days. Germination of stratified seeds (8%) was significantly higher. TTC tests showed that 100% of the tested, un-germinated seeds were viable.
In seasons after a prescribed spring burn, 43% of colonies showed an increase in inflorescences, while 31% showed a decrease and 26% remained the same (Figure 3). After non-burn seasons, 42% of colonies showed an increase, 43% showed a decrease, and 15% remained the same.

The significant decrease from 1993 to 1994 may be due to a disturbance by construction equipment (Table 1). In the spring of 1994, equipment was driven over several of the colonies (1, 3, and 4), as evidenced in the reduction of flowering plants from 152 to 7.

Discussion

Competing vegetation may be affecting the population. Its presence along a railroad and agricultural cropland may subject it to periodic herbicide applications. IDOT has signs along the roadway that say “Prairie Do Not Mow or Spray,” but there is no such protection along the privately owned fields. There were 27 introduced species found in the area. Most of the competing plants overlie the C. angusta.
While fire positively affects flowering and reproduction of many prairie grasses, spring burns only stimulated a moderate decrease in the number of colonies that declined (43% to 31%) and did not change the number that an increased. Spring burns could stimulate wild hyacinth, but it also stimulates competition from exotic, cool season grasses.

The reduction of plants in colonies 1, 3, and 4 in 1994 is likely due to equipment damage. In 1994, IDOT ran trenching equipment over this area, causing very prominent crushing and trampling of vegetation.

Germination trials determined that scarification does not overcome seed dormancy, but stratification does increase it to a limited extent. Seeds that were stratified yielded 8% germination. A possible reason why it was so low might be inadequate stratification techniques, since seeds were viable. Higher percentages may be obtained by using lower or fluctuating temperatures, longer treatments, or different media.

<3000 seeds produced in 1999, together with low fruit set (only 25% of pedicels had fruit) and low germination (only 8%), puts this species in jeopardy of disappearing from IL. Other species grow over the C. angusta, which might make it difficult for pollinators. Factors after pollination also could influence its reproduction,

References

Cottrell, H. J. 1947. Tetrazolium salt as a seed germination indicator. Nature 159:748.

Herkert, J. R. and Ebinger, J. E. (ed.). 2002. Endangered and Threatened Species of Illinois: Status and Distribution. Volume 1 - Plants. Illinois Endangered Species Protection Board. Springfield, Illinois.
 

Indiana Department of Natural Resources. 2007. Endangered, threatened, rare, and extirpated plants of Indiana. http://www.in.gov/dnr/naturepr/endanger/etrplants.pdf, 29 December 2007. Indiana Dept. Natural Resources, Indianapolis, IN 46204.

Ohlenbusch, P. D. and D. C. Hartnett. 2000. Prescribed burning as a management practice. http://www.oznet.ksu.edu/library/crps12/1815.pdf, 23 January 2008. Kansas State University Agricultural Experiment Station and Cooperative Extension Service, publication L-815, Manhattan, KS 66506.

USDA, NRCS. 2007. The PLANTS Database (http://plants.usda.gov, 29 December 2007). National Plant Data Center, Baton Rouge, LA 70874.

Acknowledgements

The authors thank the Council on Faculty Research at Eastern Illinois University (EIU) and the Lewis Hanford Tiffany grant program in the Department of Biological Sciences at EIU for providing funds to support this study. Also, we thank the Illinois Department of Natural Resources for support through its Wildlife Preservation Fund. We acknowledge Michael Mason of the Illinois Department of Natural Resources and Ken Schaal of the Bluestem Prairie Nursery for their advice regarding stratification of C. angusta. Thanks also to Bob Szafoni of the Illinois Department of Natural Resources for conducting population surveys in 1993, 1994, and 1995 and to Carrie DuFrain (EIU student) for assistance with field collections in 1999. We thank Carol Baskin for the germination trial results of C. scilloides.