U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Main content area

Population genetic structure and fitness of Daphnia pulicaria across a pH gradient in three North American lakes

Billy W. Culver, Francisco Acosta
Hydrobiologia 2018 v.805 no.1 pp. 325-338
Daphnia, anthropogenic activities, genetic distance, genetic variation, genotyping, lakes, microsatellite repeats, models, pH, survival rate
Understanding the evolutionary response of organisms to environmental gradients is important in light of increasing anthropogenic changes to our environment. In this study, we use ecological genetic tools to determine local adaptation of the model organism, Daphnia pulicaria, across a pH gradient in three North American lakes. We predicted that there would be genetic differentiation and local adaptation among the three populations of D. pulicaria. To assess the degree of genetic differentiation, we genotyped individual D. pulicaria using 15 microsatellite loci across the three populations and performed a STRUCTURE analysis corroborated with PCA based upon Nei’s genetic distance and multiple F ₛₜ comparisons. To test for signatures of local adaptation, a survivorship experiment across a pH gradient under common-garden conditions was performed. We determined that each of the three populations was genetically differentiated from one another, with Hill and Madison Lake populations of D. pulicaria being more similar to each other than that of the Frenchman Lake population. The results of the survivorship experiment showed a signal of local adaptation, with Frenchman Lake showing higher survivorship at lower pH [~6.5] when compared to Hill and Madison populations, while both Hill and Madison had higher survivorship at higher pH [7.9 and 8.6, respectively] when compared to the Frenchman population.