Date of Award

Fall 2018

Degree Type

Honors Project

School

College of Liberal Arts

First Advisor

Leif Hembre

Abstract

A paleoecological approach allows for the study of genetic change in populations over longer periods of time than would be possible if one were sampling populations from year to year. Daphnia and other cladoceran zooplankton are amenable to this type of study because they produce diapausing embryos (ephippial eggs) when they sexually reproduce, and these resting eggs can remain viable for decades to centuries in lake sediments. This study uses paleoecological methods as well as a new methodology for ephippial DNA extraction and amplification to assay for genetic variation in ephippial eggs obtained from sediments of varying ages from Square Lake (Washington County, MN). Using this new methodology was successful and it was possible to extract 22 ephippial embryos and test 12 different loci for each one. Starting in 1981, Square Lake was annually stocked with rainbow trout, a selective predator on Daphnia pulicaria, by the Minnesota Department of Natural Resources (MDNR). Eggs extracted from the sediment cores of this lake were screened for 15 loci and genotyped by capillary electrophoresis and of those, 12 loci amplified and 11 were polymorphic. Genetic analyses of the ephippial eggs deposited before and after the advent of the trout stocking program indicates that the pre-1981 (1930-1977) individuals have higher allelic diversity than the those assayed from recently deposited sediments (2015 dredge sample). In addition, there were relatively few alleles in common between the resting eggs assayed from the two time periods. It is possible to use this methodology and resulting data at Hamline University to conduct further research on the topic of Daphnia pulicaria population genetics as it produces data with resolution and also replicability.

dc_type

text

dc_publisher

DigitalCommons@Hamline

dc_format

application/pdf

dc_source

Departmental Honors Projects

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