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

Author:
Culver, Billy W., Acosta, Francisco
Source:
Hydrobiologia 2018 v.805 no.1 pp. 325-338
ISSN:
0018-8158
Subject:
Daphnia, anthropogenic activities, genetic distance, genetic variation, genotyping, lakes, microsatellite repeats, models, pH, survival rate
Abstract:
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.