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Extramural Research

Grantee Research Project Results

Grantee Research Project Results

Cascades of Character Change and Speciation: A Study Using Populations of Threespine Stickleback, Gasterosteus Aculeatus, in Alaska

EPA Grant Number: U915010
Title: Cascades of Character Change and Speciation: A Study Using Populations of Threespine Stickleback, Gasterosteus Aculeatus, in Alaska
Investigators: Cresko, William A.
Institution: Clark University
EPA Project Officer: Jones, Brandon
Project Period: January 1, 1996 through January 1, 1999
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1996)
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems



The objectives of this research project are to: (1) use very recently derived populations of threespine stickleback to understand how micro-evolutionary processes can lead to the formation of new species.; (2) Specifically, my goal is to understand how selection can form associations between ecological, morphological, and mating behavior characters,; and also to(3) define the genetic background upon which the phenotypic divergence is occurring.


Stickleback populations exhibit extreme diversification in many morphological and behavioral characters, and many of these phenotypic characters also covary. Using both field and laboratory studies, I have been investigating how natural selection can maintain character associations within a single population, which contains two distinct sets of covarying characters. Using several divergent freshwater and anadromous populations, I also am also studying how sexual selection through mate choice can cause covariation between ecological, morphological, and reproductive characters. To do so, I am using both multiple mate choice experiments and digital editing of videotape images of male courtship behavior. I also have also been defining levels of neutral genetic divergence by gathering two types of molecular genetic data. Microsatellite allele frequencies are being used to investigate the role of genetic drift and gene flow in producing the population divergence, and mtDNA haplotypes allow me to infer how stickleback colonized Alaska. Lastly, I am producing a mathematical simulation model of cascades of character change leading to speciation.

Supplemental Keywords:

fellowship, threespine stickleback, Gasterosteus Aculeatus, diversification, phenotypic divergence, population, covariation, genetic divergence, allele, microsatellite, population divergence, speciation, Alaska.

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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