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Abstract Detail


Conservation Biology

Olfelt, Joel P. [1], Rutschman, David [2], Kasmer, John [3].

Population Dynamics of Sedum integrifolium ssp. leedyi .

The dynamics of small, natural plant populations are not well understood, and long-term studies of them are rare, even though population fragmentation and isolation are common. We have been studying Leedy's roseroot (Sedum integrifolium ssp. leedyi) since 1997 with the goals of informing management decisions and developing mathematical models of the populations' dynamics. Leedy's roseroot is a federally threatened (USA) species with four known populations in southeastern Minnesota, and one in New York. We estimated yearly census sizes at the four Minnesota populations and measured plant size, sex ratios, seed set, and death rates from 21 to 55 permanently marked individuals in each of three of the populations. The probability of germination and survival to the seedling stage was estimated in 2005 from 473 seeds sown one year earlier in the three populations. We identified six demographic stages and estimated the probabilities of transitions among those stages. Our preliminary model is especially sensitive to variations in seed germination rates. Census sizes (N) were stable for the smallest population (average 174, SD = 11.5) and for each of the other populations were significantly higher in 2006 than in 1997 (P < 0.05) increasing from 278 to 388, 445 to 799, and 748 to 1012. The germination and survival to seedling rate was 0.02 percent, and death rates averaged from 9 to 23 percent per year (SD < 0.12). Yearly estimates of effective/actual population size ratios (Ne/N) fluctuated dramatically in the smallest and largest populations, ranging from approximately zero to 0.64, but were stable (0.61, SD 0.07) in the intermediately sized population. Our preliminary model identifies the stage from seed germination to seedling as critical, and our data demonstrate that the demographic parameters affecting the Ne/N of Leedy's roseroot populations can fluctuate dramatically while census sizes remain stable or increase.


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1 - Northeastern Illinois University, Biology, 5500 North St. Louis Avenue, Chicago, Illinois, 60625, USA
2 - Northeastern Illinois University, Mathematics, 5500 North St. Louis Avenue, Chicago, IL, 60625, USA
3 - Northeastern Illinois University, Biology, 5500 North St. Louis Avenue, Chicago, IL, 60625, USA

Keywords:
conservation
Staged model
Sedum
demography.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P65013
Abstract ID:1770


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