Olfelt, Joel P. .
Population dynamics of Sedum integrifolium ssp. leedyi.
The dynamics of small, natural plant populations are not well understood, and long-term studies are rare, even though population fragmentation and isolation are common. Studies of small, isolated plant populations, such as Sedum integrifolium ssp. leedyi, a federally threatened (USA) plant species, have the potential to yield insights into the dynamics of natural plant populations and to inform management decisions for them. I estimated demographic parameters in three southeastern Minnesota S. integrifolium ssp. leedyi populations over six growing seasons between 1997 and 2003 to test for trends in population growth rates and to establish baseline population characteristics. In each season I censused plants and recorded flowering rates. Beginning in 1997 I permanently marked a total of 117 individuals, using them to estimate sex ratios, seed set, and death rates. Census sizes (N) were higher for each population in 2003 than in 1997 (P < 0.05) increasing from 278 to 384, 445 to 786, and 748 to 1272 in the smallest, medium, and largest population over the six years. Death rates averaged 7 to 32 percent per year. Estimates of effective population size (Ne/N) fluctuated dramatically in the smallest and largest populations, ranging from approximately zero to < 0.64, but were relatively stable (0.63, Standard Deviation 0.06) in the intermediately sized population. The data suggest that the largest population may be recovering from a bottleneck, and that the smallest population may be unstable. The results reinforce the idea, based on animal population studies, that more than several years’ worth of data are necessary to obtain a sound understanding of population dynamics.
1 - Northeastern Illinois University, Biology, 5500 North St. Louis Avenue, Chicago, Illinois, 60625-4699, USA
Effective Population Size
Presentation Type: Poster
Location: Special Event Center (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 12:30 PM