Publication Date

1992

Document Type

Dissertation/Thesis

First Advisor

Scheiner, Samuel M., 1956-

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences

LCSH

Coreopsis lanceolata L; Seeds--Ecology; Compositae; Coreopsis

Abstract

Various aspects of the seed ecology of Coreopsis lanceolata L. (Asteraceae) were examined in order to examine seed viability, survival, germination, abundance, and local distribution. The studies were carried out on three populations of lanceolata in northeast Indiana and southwest Michigan, USA. The first study examined the physical and physiological factors that control germination. Germination rates were greatest at 25 C and 12 h light/dark cycles. Germination rates were not affected by cold temperatures (15 C) or freezing. Seeds subjected to 5 C entered an induced dormancy that could not be broken by subsequent warmer temperatures, light/dark cycles, or freezing temperatures. This study is the first documentation of induced dormancy. The induced dormancy in Cj. lanceolata may be a mechanism for spreading the risk of recruitment. The second study examined the effects of seed size on seed survival and germination. Collected seeds were tested for within and between population, and individual seed mass variation. Seed mass variation was 29-fold (range 0.111 to 3.210 mg), almost twice as high as previously reported in other species. For seeds buried in soil flats, larger seeds had greater viability, deeper emergence depths, and higher emergence rates. After a one-year burial in nylon bags in the field, larger seeds had higher recovery and viability rates but lower germination rates. The lower germination rates of large seeds after a one-year burial may be due to a dormancy state. This study is the first to test seeds previously buried and recovered for survival, viability, and germination. Seed size variation may be maintained by the differential dormancy and germination which results in a spreading of the risk of recruitment. The third study examined the relative importance of three common types of seed predators. In two populations of Coreopsis lanceolata in southwest Michigan the rate of seed losses was determined for three common types of seed predators: arthropods, rodents, and birds. In this study predator specific seed losses were measured for a wider range of seed predator types than previous studies. The experiment used five different treatments (ANT, RODENT, BIRD, CONTROL, and ALL). Seeds were placed in petri dishes in the field with various cages and heights to exclude the other predator types. The overall removal rate was 17.3% per day. The ALL and BIRD treatments had the most seeds removed, a combined average of 2.20 seeds per day; the RODENT, CONTROL, and ANT treatments had fewer seeds removed, a combined average of 1.12 seeds per day. Thus, the inclusion of birds as a source of seed loss is important for an accurate estimation of predation rates.

Comments

Includes bibliographical references (pages 51-58)

Extent

vi, 59 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

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