Appendix 1.
List of herbarium specimens sampled. All specimens are located in the Brown University Herbarium (BRU), Providence, Rhode Island, USA.
| Species | Collection year | Location | Geographic coordinates | Accession no. |
| Artemisia biennis Willd. | 1889, 1892, 1900 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00021762, PBRU00021761, PBRU00021760 |
| Artemisia vulgaris L. | 2015 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00030884 |
| Artemisia vulgaris | 2015 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00030757 |
| Carex blanda Dewey | 2015 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00030890 |
| Carex muhlenbergii Kunth ex Boott | 1890, 1892 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00002532, PBRU00002539 |
| Cicuta bulbifera L. | 1895, 1895, 1895 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00024137, PBRU00024139, PBRU00024140 |
| Cicuta maculata Lam. | 1892 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00024154 |
| Daucus carota L. | 2015 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00030753 |
| Daucus carota | 2015 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00030886 |
| Erigeron annuus (L.) Pers. | 2015 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00030893 |
| Eurybia divaricata (L.) G. L. Nesom | 2015 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00030887 |
| Eurybia divaricata | 2015 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00030750 |
| Juncus acuminatus Michx. | 1893, 1893 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00011674, PBRU00011704 |
| Juncus articulatus L. | 1892 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00011715 |
| Juncus tenuis Willd. | 2015 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00030755 |
| Lactuca scariola L. | 1894, 1894, 1895 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00023243, PBRU00023246, PBRU00023250 |
| Lactuca L. sp. | 2015 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00030888 |
| Persicaria Mill. sp. | 2015 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00030892 |
| Plantago lanceolata L. | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00021069 | |
| Plantago major L. | 1892, 2015 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00020878, PBRU00030889 |
| Plantago major | 2015 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00030754 |
| Plantago media L. | 1890, 1892 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00020889, PBRU00020890 |
| Plantago patagonica Jacq. | 1892 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00021073 |
| Plantago rugelii Decne. | 1892, 2015 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00021094, PBRU00030747 |
| Plantago rugelii | 1892, 2015 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00021096, PBRU00030756 |
| Plantago L. sp. | 1890 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00021100 |
| Plantago sp. | 2015 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00030891 |
| Polygonum aviculare L. | 1893 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00018989 |
| Polygonum aviculare | 1899 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00018988 |
| Polygonum hydropiperoides Michx. | 1892, 1892 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00019119, PBRU00019122 |
| Polygonum lapathifolium L. | 1892, 1900 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00019145, PBRU00019142 |
| Polygonum lapathifolium | 1893 | Mashapaug Pond, Providence, RI, USA | 41°47′22.7″N, 71°26′06.2″W | PBRU00019151 |
| Sium cicutifolium Schrank | 1892 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00024281 |
| Solidago rugosa Mill. | 1892, 1892, 1916, 2015 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00023701, PBRU00023711, PBRU00023699, PBRU00030752 |
| Spartina alterniflora Loisel. | 1873, 1889, 2015 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00014271, PBRU00014264, PBRU00030751 |
| Symphyotrichum ericoides (L.) G. L. Nesom | 1916, 1916, 2015 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00022377, PBRU00022378, PBRU00030748 |
| Symphyotrichum laeve (L.) Á. Löve & D. Löve | 1871 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00022405 |
| Symphyotrichum lateriflorum (L.) Á. Löve & D. Löve | 1890 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00022081 |
| Symphyotrichum novae-angliae (L.) G. L. Nesom | 1916 | Block Island, New Shoreham, RI, USA | 41°09′30.9″N, 71°35′28.7″W | PBRU00022193 |
| Symphyotrichum tenuifolium (L.) G. L. Nesom | 1889 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00021988 |
| Verbena bracteata Lag. & Rodr. | 2015 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00030885 |
| Veronica arvensis L. | 1890, 1891, 1892 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00021128, PBRU00021133, PBRU00021124 |
| Veronica peregrina L. | 1892 | Cove Lands, Providence, RI, USA | 41°49′47.4″N, 71°24′41.9″W | PBRU00021163 |
| Viola blanda Willd. | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00015711 | |
| Viola cucullata Aiton | 1846 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00015784 |
| Viola sagittata Aiton | 1891 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00015922 |
| Viola L. sp. | 2015 | Seekonk River, Providence, RI, USA | 41°49′52.9″N, 71°22′45.0″W | PBRU00030749 |