Figure S1. Microsatellite data for alleles at each of the nine species-specific loci used for the manual identification of Ulmus pumila x U. rubrahybrid individuals.

Figure S2. Leaf phenotypes of Ulmus pumila and U. rubra (top) and their natural hybrids (bottom). Leaf phenotypes are a poor indicator of cross-type.

AppendixS1. A total of 152 allelesfrom 13 microsatellite loci detected in 280 putative Ulmus pumila individuals collected throughout the United Statesfrom cultivated material, herbarium specimen and eight naturalized populations.

Locus / 42 U. pumila specific allelesa / 66 U. rubra specific allelesb / 29 Shared alleles / 15 Other allelesc
UR123 / 239, 241, 243, 245, 247, 253,255, 259, 261, 263 / 246, 248, 251, 252, 254, 260, 262, 264 / - / -
UR138 / 224 / 238 / 226, 232, 234, 236, 240, 242, 244 / 197PWI, PSD, PIL, 220PUS
UR141 / 150, 156 / 154 / - / 162PUS
UR153 / 178, 187, 191, 197 / 184, 186, 189, 193, 194, 196, 199 / - / 202 PJN
UR158 / 175, 180, 187 / 184, 196, 200, 205 / - / 191PWI, PMM
UR159 / 249, 257, 279 / 236, 245 / - / 259PUS, PIL
UR173a / 137, 146 / 149, 156, 158, 160, 162, 164, 166, 168, 172, 174, 178 / - / 167PUS
UR175 / 216, 231, 233, 236 / - / 218, 220, 223, 225, 227, 229, 238 / 240PUS, PWI, PIL, PMM, PAB,
UR188a / 108 / 112, 114, 120, 122, 124, 125, 127, 129, 134, 136 / - / 110PUS, PCW
Ulmi1-98 / 122, 124, 128, 130, 134, 136 / 126, 143, 145, 146, 147, 148, 152, 154, 165 / - / 132PUS, PWI, 133 PUS,156PUS
Ulmi1-165 / 152, 153, 155, 160, 162, / 147, 157, 159, 161, 170, 182, 184, 186, / 163, 166, 172, 174, 176, 178, 180 / 158 PWI
Ulm-2 / 100 / 103, 106 / - / -
Ulm-3 / - / 144, 153, 156 / 159, 162, 165, 168, 171, 173, 176, 179 / 147PWI, PCW 191PUS

aU. pumilaalleles detected in the 86 accessions from East Asia(PEA; Appendix 1).

bAlleles specific to U. rubra (Zalapa et al. 2009) detected in the 60 U. pumila x U. rubra hybrids.

cAlleles not detected in U. pumila or U. rubra (superscript indicates the population(s) where each allele was detected; these populations are described in Table 1).