PARENT SESSION
Oral Session #39: Invasions: Effects of invaders -- Aquatic, marsh, riparian. Presiding: C. Kolar.
Wednesday, August 8, 2001. 8:00 AM to 11:45 AM. Madison Ballroom C.
The interaction of the ecology and evolution of an exotic estuarine plant, Spartina alterniflora Loisel.
Davis, Heather1, Taylor, Caz1, Civille, Janie1, 1
ABSTRACT- We consider the interactions of the biology and life history evolution of an invading organism, with the ecology of the recipient community using a perennial estuarine plant, Spartina alterniflora Loisel (Smooth cordgrass). A small founding population introduced to Willapa Bay, Washington, has propagated for almost a century to produce clones of greatly differing age and growth conditions. What are the potential consequences of life history adaptation and intrinsic ecological factors, including Allee effects due to pollen limitation and self-incompatibility, to subsequent population expansion? There are indications that this invasive population has an increased ability to self-pollinate and to mate with close relatives (in progress). We collected inflorescences from ten individuals per meadow, and ten 'isolate' clones at five locations around Willapa Bay (N=100). The variables are: diameter of isolate clones, height, density of stems and inflorescences, substrate, leaf nitrogen, proximity to and density of conspecifics, seedset and germination success and accessions grown from collected seed will be screened for self-compatibility. A multiple linear regression will predict the reproductive success of individuals and a path analysis will assess direct and indirect effects on fertility. Preliminary data analyses suggest severe pollen limitation for isolate clones, as indicated by greatly reduced or non-existent seedset, and abiotic restrictions on seedset acting on meadow clones. There are also indications that the location with the oldest individuals is limited by genetic incompatibility of available pollen.
KEY WORDS: invasive plant, pollen limitation, population growth, Spartina alterniflora