DOI: 10.5061/dryad.rv15dv46v
title: Asimina triloba georeferenced occurrence data and genetic data

description: Aim:  Predictions of species’ responses to accelerating global
 climate change require an understanding of historical range shifts.
 However, large-scale phylogeographic studies of Eastern North American
 understory plant taxa are relatively scarce. Here we employ ecological
 niche modelling and genetic analyses for inference of optimal pawpaw
 habitat in the past and future.  Location: Twenty-six states in
 the eastern United States Taxon: Asimina triloba (L.) Dunal (Annonaceae)
 Methods:  The present-day niche of Asimina triloba was modelled
 in Maxent using seven bioclimatic variables, elevation, and location data
 from field samples and herbarium specimens. To model historically optimal
 habitats, the present-day model was projected onto rasters of seven
 bioclimatic variables and elevation representing the last glacial maximum
 (~22,000 years before present [YBP]) and the mid-Holocene (~6,000 YBP).
 Predicted habitat suitability for 2070 was also modelled. Additionally, 62
 populations were genotyped with nine nuclear microsatellite loci and
 statistically analyzed. Levels and partitioning of genetic variation
 within and among populations were estimated within a geographic context.
 Results:  Models indicate that optimal habitat 22,000 YBP was
 severely restricted to now-submerged Gulf of Mexico and southeastern U.S.
 coastlines. By 2070 models suggest that optimal habitat will expand
 substantially northward relative to the present. Species-level genetic
 diversity (HE = 0.765) was high and genetic structure among populations
 was moderate (GST = 0.202). Structure indicates that there are two
 population clusters straddling the Appalachian Mountains. Main
 conclusions:  Models suggest that 22,000 YBP A. triloba was
 restricted to two major refugia in narrow bands of now-submerged habitat
 and one small inland refugium in southeastern Alabama and southwestern
 Georgia. Molecular data are consistent and suggest that the two eastern
 refugia expanded to give rise to the eastern cluster which is
 characterized by higher genetic diversity. The Texas/Louisiana refugium
 likely gave rise to populations in the western cluster, characterized by
 lower genetic diversity. 
description: <strong>Georeferenced Occurrence
 Data</strong> GPS coordinates were
 obtained from 82 naturally occurring populations throughout the United
 States as well as from 18 herbarium specimens collected after 1992
 (herbaria: DEK, ILLS, IND, KSP, MO, TROY and USF). Prior to 1992, the U.S.
 government scrambled GPS signals rendering them too inaccurate to be
 useful.  <strong>Genetic
 Data</strong> Leaf samples were
 collected from naturally occuring plants and snap-frozen in liquid
 nitrogen for transport to the University of Georgia. Frozen leaf tissue (~
 0.05 g) was ground to a powder and genomic DNA was extracted using a
 modified CTAB protocol (Doyle & Doyle, 1983). DNA quality and
 quantity were evaluated using a ND-1000 Nanodrop spectrophotometer. Nine
 nuclear microsatellite loci were amplified with markers developed by Lu et
 al. (2011). 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 in the reaction. PCR amplification was carried
 out in 12.5 mL reaction volumes consisting of 0.26 mM molecular grade
 ddH2O, 1 mM One Taq standard reaction buffer (New England Biolabs,
 Ipswich, MA), 0.7 mM MgCl solution (Sigma-Aldrich), 1 mM bovine serum
 albumin (Thermo-Fisher), 0.2 mM dNTP mix (New England Biolabs, Ipswich,
 MA), 0.04 mM CAG-tagged primer, 0.4 mM unlabeled primer, 0.36 mM universal
 fluorescently labelled CAG primer, 0.2 mM One Taq Hot Start DNA polymerase
 (New England Biolabs, Ipswich, MA), and 50 ng template DNA.
description: <strong>Genetic
 Data</strong> The dataset consists of
 codominant neutral nuclear markers.  Missing data is designated as
 "0".