PARENT SESSION
Oral Session #67: Metapopulations, fragmented landscapes, and patch dynamics. Presiding: C. Kraft.
Thursday, August 9, 2001. 1:00 PM to 4:30 PM. Hall of Ideas F.
Patterns of extinction and colonization in wild sunflower populations.
Alexander, Helen1, Cummings, Charity 1, 1
ABSTRACT- Studies on many spatial scales are needed to understand patterns of plant abundance. Our past work on the wild annual sunflower, Helianthus annuus, has emphasized research on local populations; we now also have two years of data on the abundance of sunflowers in 81 m increments along both sides of a 47.3 km road in northeastern Kansas. Of the 586 roadside units studied, 49% had sunflowers present in 1999 and 44% were occupied in 2000; the average number of flowering plants per roadside interval was more than two-fold higher in 2000. Considerable extinction and colonization occurred; of the 287 occupied sites in 1999, 34% lacked flowering plants in 2000. Local populations that went extinct from 1999 to 2000 had significantly fewer plants in 1999 than 1999 populations that were also present in 2000. 22% of the 299 sites without flowering plants in 1999 had sunflowers present in 2000. Our long-term goal is to continue these roadside surveys for many years and integrate these data with our local population studies, research on seed bank longevity, and observations on disturbance.
KEY WORDS: sunflower, Helianthus annuus, metapopulation, extinction/colonization