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Asimina triloba genetic data

Citation

Trapnell, Dorset; Wyatt, Graham; Hamrick, Jim (2021), Asimina triloba genetic data, Dryad, Dataset, https://doi.org/10.5061/dryad.5x69p8d3g

Abstract

Dispersal and colonization are among the most important ecological processes for species persistence as they allow species to track changing environmental conditions. During the last glacial maximum (LGM), many cold-intolerant Northern Hemisphere plants retreated to southern glacial refugia. During subsequent warming periods, these species expanded their ranges northward. Interestingly, some tree species with limited seed dispersal migrated considerable distances after the LGM ~19,000 year before present (YBP). It has been hypothesized that indigenous peoples may have dispersed valued species, in some cases beyond the southern limits of the Laurentide Ice Sheet. To investigate this question we employed a molecular genetics approach on a widespread North American understory tree species whose fruit was valued by indigenous peoples. Twenty putative anthropogenic (near pre-Columbian habitations) and 62 wild populations of Asimina triloba (pawpaw), which produces the largest edible fruit of any North American tree, were genetically assayed with nine microsatellite loci.

Putative anthropogenic populations were characterized by reduced genetic diversity and greater excess heterozygosity relative to wild populations. Anthropogenic populations in regions that were glaciated during the LGM had profiles consistent with founder effects and reduced gene flow, and shared rare alleles with wild populations hundreds of kilometers away (mean = 723.1 km). Some of the most compelling evidence for human-mediated dispersal is that putative anthropogenic and wild populations sharing rare alleles were separated by significantly greater distances (mean = 695.3 km) than wild populations sharing rare alleles (mean = 607.1 km; p = 0.014). Collectively the genetic data suggest that long-distance dispersal played an important role in the distribution of pawpaw and is consistent with the hypothesized role of indigenous peoples.

Methods

Genomic DNA was extracted from frozen leaf tissue (~ 0.05 g) using a modified CTAB protocol (Doyle & Doyle, 1983) and DNA quality and quantity were evaluated using an ND-1000 Nanodrop® spectrophotometer. Nine nuclear microsatellite loci (Lu et al., 2011; Table S2) were PCR amplified in 12.5 µL reaction volumes containing 3.25 µL molecular grade ddH2O, 2.5 µL 5X One Taq® standard reaction buffer (New England Biolabs, Ipswich, MA), 0.35 µL 25 mM MgCl solution (Sigma-Aldrich), 1.25 µL 10X (1 mg/mL) bovine serum albumin (Thermo-Fisher), 1 µL 2.5 mM dNTP mix (New England Biolabs, Ipswich, MA), 1 µL primer mix (0.5 µM CAG-labeled primer and 5 µM unlabeled primer), 0.45 µL 10 µM universal dye-labeled primer, 0.2 µL One Taq® Hot Start DNA polymerase (New England Biolabs, Ipswich, MA), and 2.5 µL of diluted template DNA (20 ng/µL). A 3-primer PCR protocol was used whereby a CAG-tag sequence (Hauswaldt & Glenn, 2003) was added to the 5’ end of one primer and a third fluorescently labeled (FAM, HEX, or NED) primer identical to the CAG-tag was included.

Usage Notes

Missing data is indicated by "0"

Funding

University of Georgia, Award: Office of the Vice President for Research