title: A resurrection experiment finds evidence of both reduced genetic diversity and potential adaptive evolution in the agricultural weed Ipomoea purpurea.
abstract: Despite the negative economic and ecological impact of weeds, relatively little is known about the evolutionary mechanisms that influence their persistence in agricultural fields. Here, we use a resurrection approach to examine the potential for genotypic and phenotypic evolution in Ipomoea purpurea, an agricultural weed that is resistant to glyphosate, the most widely used herbicide in current-day agriculture. We found striking reductions in allelic diversity between cohorts sampled nine years apart (2003 vs. 2012), suggesting that populations of this species sampled from agricultural fields have experienced genetic bottleneck events that have led to lower neutral genetic diversity. Heterozygosity excess tests indicate that these bottlenecks may have occurred prior to 2003. A greenhouse assay of individuals sampled from the field as seed found that populations of this species, on average, exhibited modest increases in herbicide resistance over time. However, populations differed significantly between sampling years for resistance: some populations maintained high resistance between the sampling years whereas others exhibited increased or decreased resistance. Our results show that populations of this noxious weed, capable of adapting to strong selection imparted by herbicide application, may lose genetic variation as a result of this or other environmental factors. We probably uncovered only modest increases in resistance on average between sampling cohorts due to a strong and previously identified fitness cost of resistance in this species, along with the potential that nonresistant migrants germinate from the seed bank.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Michigan, 2059 Kraus Natural Science Building, 830 North University, Ann Arbor, MI, 48109, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Kuester
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Michigan, 2059 Kraus Natural Science Building, 830 North University, Ann Arbor, MI, 48109, USA.
authors.forename: Ariana
authors.initials: A
authors.lastname: Wilson
authors.affiliation: Plant Biology Department, University of Georgia, 2502 Plant Sciences Building, 120 Carlton Street, Athens, GA, 30602, USA.
authors.forename: Shu-Mei
authors.initials: SM
authors.lastname: Chang
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Michigan, 2059 Kraus Natural Science Building, 830 North University, Ann Arbor, MI, 48109, USA. rsbaucom@umich.edu.
authors.forename: Regina S
authors.initials: RS
authors.lastname: Baucom
mesh_terms: D000383:Agriculture; D018556:Crops, Agricultural; D019143:Evolution, Molecular; D014644:Genetic Variation; D005828:Genetics, Population; D053209:Herbicide Resistance / Q000235:genetics*; D027741:Ipomoea / Q000235:genetics*; D009657:North Carolina; D057685:Plant Weeds / Q000235:genetics*; D013022:South Carolina; D013714:Tennessee
keywords: agriculture; allelic diversity; genetic drift; selection; temporal evolution