A foundation monograph of Ipomoea (Convolvulaceae) in the New World

Materials and methods
Specimens
This monograph is based fundamentally on the study of herbarium specimens of Ipomoea informed by observations from morphology and molecular sequence data, fieldwork, photographs and information from literature and individual contacts throughout the Americas.
We have depended heavily on herbarium collections at Kew (K) and the Natural History Museum in London (BM), which together with material at Oxford (OXF) have formed the basis of our study. We have visited various European herbaria including Edinburgh (E), Leyden (L), Paris (P), Madrid (MA) and Stockholm (S) to view their collections of Ipomoea. During the course of visits to the United States we have seen material at (GH) and (A) at Harvard, the New York Botanical Garden (NY), the Smithsonian Institution in Washington (US), the Field Museum (F), Missouri Botanical Garden (MO) and Arizona University (ARIZ), including extensive material from Fairchild in Florida (FTG). Within Latin America, visits have been made to see herbarium collections in Cuba (HACB, HAJB), Mexico (IEB, MEXU), Ecuador (Q, QAP, QCA, QCNE, GUAY, LOJA), Peru (CIP, CUZ, USM), Bolivia (BOLV, HSB, LPB, USZ), Paraguay (FCQ, PY, SCP), Argentina (CTES, LIL) and Brazil (CEN, CPAP, HUEFS, IPA, JPB, MBM, PEUFR, R, RB, SP, UB). Help received from individuals in all these institutions is detailed in the acknowledgements at the end of this monograph. We have also received important loans of material from most of these institutions as well as from G and GOET. Photographs of herbarium specimens have also been a valuable source of information. The most important have been the images of types available through Jstor (www.jstor.org), but the websites of CRIA (splink.cria.org.br) and Reflora (reflora.jbrj.gov.br) and those associated with herbaria, including ARIZ (SEInet; swbiodiversity.org), B, BR, C, COL, E, F, MO, NY, P, PMA, US and W have all provided valuable information. We have also been sent images of important material from Geneva (G), Turin (TO), St Petersburg (LE), Vienna (W), Göttingen (GOET), Rancho Santa Ana (RSA), Montevideo (MVM) and Cambridge University (CGE). All cited acronyms are in accordance with the Index Herbariorum (http://sweetgum.nybg.org/science/ih/).
Much of the material we have been loaned has been type material or old or rare specimens and this has had important limitations on our ability to provide complete and accurate descriptions. In particular, details of the habit of many species is missing and can only be inferred. Flower colour has often been lost or modified during the drying process. It is often impossible, or at least undesirable, to dissect corollas, where only one or two are present pasted to the sheet and fragile in nature. Finally, it must be emphasized that the fruit of many species is unknown.
It is important to stress that herbarium specimens are not only a source of basic taxonomic information and an indispensable tool for species delimitation but also an essential resource for phylogenetic, ecological and other information. We have been able to use specimens for DNA sequencing, even from collections over a hundred years old, if they have been rapidly dried and retain their natural colouring. More recent, heat-dried specimens nearly always yield high-quality DNA, but there are striking exceptions, such as specimens of Ipomoea chondrosepala, which have mostly resisted repeated attempts to extract DNA. Specimen labels are another invaluable source of data. They can provide information that is not apparent from the specimen, such as flower colour, habit and size. Label information can also contain information about the general and specific habitat of the plant and can provide important facts about flowering patterns and ecology. We have used all available information of this kind to inform our descriptions and notes.