Seed Scarification Techniques in Silver Leaf Lupine Alyssa Koomas Abstract A major problem affecting the populations of the endangered mission blue butterfly of the northern coast of California is the declining numbers of its host plant the silver leaf lupine Lupinus albifrons due to competition with non native species An attempt to ensure the restoration of populations of L albifrons through germination in greenhouses and subsequent transplantation was initiated in 1984 and has continued to date within the Golden Gate National Recreation Area GGNRA This work analyzes the germination rates necessary expertise and time efficiency of three different scarification techniques applied to rupture the seed coat and induce germination in a greenhouse setting The three scarification techniques applied were 1 manual nicking with a razor blade near the attachment point 2 an acid bath in concentrated sulfuric acid for 30 minutes and 3 scarification by agitation between two pieces of sandpaper for 5 minutes Sample sizes of 98 seeds were studied at three different greenhouses in GGNRA California The experiment was controlled for soil composition and sowing procedure The data provided no conclusive evidence for determining the most successful treatment for increasing L albifrons germination rates There was no significant difference between the germination rates of the three scarification treatments including the control but there was a strong difference in the rates of imbibition The success of the control provides an impetus for further studies regarding the need for scarification on lupine seeds Among the three scarification treatments manual nicking had the highest imbibition rate had the lowest cost and was the most time efficient The significance of these results will aid in the restoration of L albifrons to its native habitat and encourage increased populations of the mission blue butterfly Introduction The threat of extinction for native species of North America has been a pressing issue since the time of European colonization with the unchecked dominance of invasive species from across Europe It is only in the past few decades that the environmental advantage of restoring native ecosystems has been recognized and the large task of restoration been undertaken Mackay 1995 2001 One such threatened species the mission blue butterfly Plebejus icarioides missionensis native to the coast of northern California has been federally listed as endangered since 1976 Elliott 2003 pers comm The population decline of this tiny blue butterfly is principally attributed to the loss of its host plant the shrub like silver leaf lupine Lupinus albifrons ssp collinus La Pierre 1998 Figure 1 Mission blue butterfly with L albifrons The mission blue butterfly Figure 1 relies on one of three species of lupine to lay its eggs and for nourishment of larvae Arnold 1994 Due to a decline in numbers resulting from a loss of habitat restoration of lupine to its native ecosystem is necessary in order to increase butterfly populations In 1984 a recovery plan drawn up by the U S Fish and Wildlife Service USFWS outlined the need to protect mission blue habitat and to repair habitat damaged by urbanization off highway vehicle traffic and invasion by exotic non native plants Arnold 1987 This recovery plan advocates the restoration of the native habitat of the mission blue butterfly by planting high numbers of native species of lupine including L albifrons Due to development and construction what is left of the native habitat of the mission blue butterfly is mainly the area that comprises the Golden Gate National Recreation Area GGNRA Within this protected area the survival of the silver leaf lupine is impeded by non native species and seed predation This competitive environment has provided an impetus for the development of new methods to reestablish the lupine habitat To decrease seed predation biologists at GGNRA in the past have collected lupine seeds in the field germinated them in greenhouses and later transplanted them back to the field once they have grown to a substantial height Setty 2003 pers comm But low greenhouse germination yields have called for an inquiry into better methods for seed germination of the silver leaf lupine Past studies have been done with seeds of other classes of Lupinus to increase germination rates Kaye 2001 but there is no information on studies of L albifrons Of the techniques applied to bush lupine L sulphureus which included a variety of scarification and temperature treatments the method which produced the highest percentage of germination was nicking the seed coat with a razor blade before sowing Kaye 2001 Scarification techniques such as nicking or the use of sandpaper are meant to simulate the scarification of the seed coat that would occur in the natural habitat of the coastal sand dunes Setty 2002 pers comm A comprehensive experiment that specifically studies different scarification methods and the correlating germination percentages for silver leaf lupine seeds will facilitate lupine restoration and in turn the restoration of mission blue butterfly populations The objective of this research was to determine a scarification technique that would produce the highest yield of germination for the silver leaf lupine in the GGNRA Three different scarification methods were tested manual nicking acid bath washing Simms 2002 and sandpapering Natoli 2003 While recording imbibition and germination rates other factors were noted including time efficiency of each treatment and necessary expertise Based upon past studies of different classes of lupine Sholars 2002 my hypothesis was that nicking seeds near the attachment point would produce the highest percentage of seed germination but would also be the most labor intensive To determine the scarification technique that is best for the entire GGNRA treated seeds were sown in three different greenhouses throughout the Recreation Area This study thus yields results for germination that can be compared across greenhouses to determine the method that is best overall or that is particularly best for a specific greenhouse This technique can then be the basis for more efficient restoration projects of the silver leaf lupine at all greenhouses in GGNRA Methods All L albifrons LUAL seeds used in this experiment were purchased by the GGNRA from S S Seeds collected from Los Alamos California The effects of scarification were examined with three different
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