Speciation in the Sea: Linking Evolutionary Processes to the Conservation of Biodiversity

EPA Grant Number: FP916314
Title: Speciation in the Sea: Linking Evolutionary Processes to the Conservation of Biodiversity
Investigators: McKitrick, Tanya R.
Institution: Stanford University
EPA Project Officer: Michaud, Jayne
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $111,688
RFA: STAR Graduate Fellowships (2004) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Aquatic Ecosystems , Fellowship - Aquatic Ecology and Ecosystems


The primary objective of this experiment is to assess the role of environmental gradients in facilitating both ecological and genetic divergence and ultimately the speciation process. By comparing the rate of genetic divergence to the strength of the environmental gradient, we can gain insight as to the varying types of evolutionary forces that affect populations on varying spatial scales. A better understanding of this fundamental evolutionary process may assist in identifying and managing habitats that maintain high levels of biodiversity.


I intend to apply a sympatric speciation model developed by Doebeli and Diekman (2003) to the intertidal barnacle, Balanus glandula (Darwin). I will use the principles outlined in the model to provide evidence for local adaptation, assortative mating, and hybrid incompatibility between distinct populations inhabiting an intertidal, estuarine, and latitudinal environmental gradient. I will argue that physiological tolerance is the ecological character undergoing disruptive selection and is sustaining their differentiation.

Local Adaptation and Reproductive Isolation

Experiment 1: Marker analysis will be used to demonstrate disruptive selection along the environmental gradients. The degree of genetic differentiation will demonstrate the degree to which populations are reproductively isolated.

Experiment 2: Transplant experiments both within and between habitats of distinct genetic types will be employed to determine if there is a fitness consequence of a particular genotype in a given habitat.

Experiment 3: I will genotype a subsample of initial recruits and survivors after a given time period. Thus, I will be able to determine whether pre-settlement behavior or post-settlement selection is creating the established populations.

Hybrid Incompatibility

Experiment 1: The purpose of this experiment is to determine if fitness differences exist between hybrid and parent genotypes when placed into the environmental gradient. Crosses within and between parental genotypes from each habitat will be created and transplanted into the field concurrently. Experimental animals will be placed into the field to measure fitness when exposed to the gradient.

If the predictions made by this model are congruent with my results, this project will provide a framework in which we can test other systems. By investigating three different environmental gradients on varying spatial scales, I expect to determine how strong selection must be to overcome the overwhelming effects of gene flow within the marine realm. In a conservation context, this method may be useful in identifying particular geographic areas that speciation may occur more rapidly and thus result in the generation of biodiversity if preserved.

Supplemental Keywords:

fellowship, speciation, sympatric speciation model, evolution, environmental gradient, barnacles, disruptive selection, biodiversity, genetic differentiation,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, Aquatic Ecosystem, Monitoring/Modeling, Ecology and Ecosystems, bioassessment, biodiversity, disruptive selection, environmental gradients, sympatric speciation model, aquatic ecosystems

Relevant Websites:

2004 STAR Graduate Fellowship Conference Poster (PDF, 1p., 164KB, about PDF)

Progress and Final Reports:

  • 2004
  • 2005
  • Final