The Ecology and Evolution of an Exotic Estuarine Plant, Spartina Alterniflora LoiselEPA Grant Number: U915802
Title: The Ecology and Evolution of an Exotic Estuarine Plant, Spartina Alterniflora Loisel
Investigators: Davis, Heather G.
Institution: University of California - Davis
EPA Project Officer: Packard, Benjamin H
Project Period: August 1, 2000 through August 1, 2003
Project Amount: $87,441
RFA: STAR Graduate Fellowships (2000) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems
The goal of this research project is to investigate three general questions of exotic species research with a perennial, estuarine plant, Spartina alterniflora, invading the Pacific coast of North America: (1) What intrinsic and extrinsic ecological factors might influence the rate of growth of the invading population? (2) What genetic adaptations in the invading population have occurred in response due both to rapid population growth and to a novel environmental context? and (3) What are the potential consequences of adaptation to subsequent population expansion?
Experiment 1: What are the effects of population density and demographic parameters on seedset and germination success? This experiment will utilize hierarchical modeling (logit model and analysis of variance) to determine the effects of density and location, a multiple linear regression to summarize and model relations between the predictor variables to seedset and germination, and path analysis to examine the pattern of direct and indirect effects. Inflorescences were collected from 10 individuals per meadow (high density), and 10 "isolate" (low density) 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.
Experiment 2: What life history traits (time to first reproduction, selfing ability, reproductive effort, survival probability after reproduction, and reproductive versus biomass allocation) are different, under greenhouse conditions, between an invasive population and genets from a wide range along the native distribution? Twenty maternal genotypes are represented per treatment by four siblings. To acquire data on the timing of inflorescence receptivity and selfing ability, timing of inflorescence emergence is recorded, and inflorescences are bagged. Two inflorescences are chosen at random for each plant (subsample) and the total number of florets and seeds are counted. Seeds will then be subjected to a germination trial.
Experiments in early stages: (1) Is seedset limited by an Allee effect of outcross pollen limitation, genetic relatedness, or an interaction of these effects? Each of the three locations will be visited during the emergence of inflorescences with three treatments: (a) pollen augmentation by an inflorescence from the same individual; (b) pollen augmentation by an individual from a different site; and (c) unmanipulated control inflorescences. Distance to nearest upwind neighbor and number of inflorescences on each individual will be covariates. Traits will be compared with a fixed effects, nested, analysis of covariance. (2) Have evolutionary changes occurred in the population of Spartina alterniflora in Willapa Bay, Washington? To determine the extent of loss of self-incompatibility and changes to other life history traits in situ, a chronosequence of cohorts on greenhouse grown plants will be compared. The treatment effect of age of maternal plant will be analyzed using a fixed model nested multiple analysis of variance.
The study of the interaction of biology and life history evolution of an invading organism with the ecology of the recipient community provides an opportunity to address the consequences to subsequent population expansion.