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

Subspecies
The concept of a subspecies is retained for taxa which are morphologically distinct throughout most of their range but whose characters overlap in regions where the ranges of the two taxa meet. We accept that some species recognized in the following account could have been treated as subspecies of a closely related species, but in many cases, the number of specimens seen is so few that it would be premature to make this decision. Subspecific status is, therefore, reserved pragmatically for taxa of which we have seen many examples. Subspecies are keyed out when there are three more recognized subspecies for a particular species.
Variety
Apart from subspecies, other infraspecific categories are not formally recognized in this account with the exception of two varieties. Most varieties, formas and subformas recognized by previous authors have little value and often do little more than recognize minor variations of corolla colour, indumentum or leaf shape. Some varieties, however, have long been recognized and, where these are historically significant or readily recognized, we have drawn attention to them in the notes that follow the species descriptions and made comments about their distinctive characters and distribution. We accept that some readers may wish to continue recognizing and using these varietal names. We understand varieties as morphologically distinct populations that occur sporadically over part or all of the range of a species. Although varieties may be restricted to a specific area they do not occupy a distinct geographical region with populations overlapping with those from another distinct geographical area. Sporadic occurrence is an important criterion in the recognition of varietal, rather than subspecific status.
Structure of the monograph
In the following taxonomic account species are arranged in a linear order, reflecting phylogenetic relationships as far as is possible (Muñoz-Rodríguez et al. 2019). The 605 nuclear regions we sequenced provided an overall framework for the major clades we recognise but as the number of sequenced species was relatively small, this provided information on the placement of only about 140 species from the Americas into major clades. We have added to this analysis with information from chloroplast sequences and ITS, thus increasing the coverage to well over half the American species. Where there were differences between nuclear and chloroplast results we generally followed the nuclear data because of the larger data set and the support it gave for major clades. In cases of incongruence (Ipomoea parasitica, for example) we considered the size and increased support offered by the NGS nuclear data to be more reliable than ITS (Muñoz-Rodríguez et al. 2019). The order of species was then expanded based on obvious morphological similarities, thus all species in the Quamoclit Clade were grouped together as were all the inferred relatives of I. malvaeoides, even though we had not obtained sequences for some species in these groups. There remained a residue of species (± 40) whose placement was somewhat arbitrary as it was based on uncertain interpretation of morphological characters. Only five species are included at the end of the treatment as we were unable to suggest any likely placement.
The process described above was not always straightforward as the resolution of some parts of the phylogeny is poor, particularly in Clade A (Figure 1, Muñoz-Rodríguez et al. 2019). Nevertheless we are confident that the order of species presented in this monograph is a reasonable approximation reflecting the phylogenetic history of Ipomoea (Muñoz-Rodríguez et al. 2019).
The accepted names of species and subspecies are given in bold italics, followed by their author and place of publication. Where a recognized taxon is based on a nomenclatural combination, the basionym is given in plain italics immediately following the accepted names. This is followed in chronological order by any other names based on the same basionym. Heterotypic synonyms are then listed in chronological order of their basionym, each followed by subsequent combinations based on each basionym. Finally any commonly used name misapplied to the species is listed but only very common misapplications are cited. Authorities are not cited in the notes and other discussion sections for taxa that are treated in the monograph unless needed to clarify some typification or nomenclatural issue.
Types are cited for all listed taxa. The location of all types is indicated by the appropriate acronym following Index Herbariorum (http://sweetgum.nybg.org/science/ih/), the only exception being CIP (Centro Internacional de La Papa at Lima), whose herbarium is not included in Index Herbariorum but does contain some types. We have tried to indicate the holotype (or lectotype) in each case and we have seen all holotypes and lectotypes unless indicated with n.v. (not seen). We have not necessarily seen all isotypes but have listed herbaria where they are reported to be present. The list of isotypes may not be complete in every case and we have uncovered numerous isotypes during the course of our visits to different herbaria. Many more are likely to be found in herbaria we have not visited. We have designated lectotypes in many cases where no holotype existed or where it was ambiguous. It is hoped this will help achieve nomenclatural stability.
Descriptions all follow the same sequence and should be comparable although some details (fruits and seeds for example) are not always known. Subspecies are treated diagnostically following the main species description. With two exceptions varieties are not formally accepted and are included within the synonymy of individual species. However, those varieties we consider particularly significant are highlighted in bold in the notes that follow each species and we indicate what their distinctive characteristics are.
References are provided to illustrations after the descriptive text. These include all illustrations in the present work and selected illustrations from other publications. We have only selected illustrations from relatively recent publications with an emphasis on those from publications related to the Americas. However, we have included references to Bosser and Heine’s (2000) Flora of the Mascarenes and Deroin’s (2001) Flore de Madagascar 2001, although these works are not American, The two floras have illustrations of outstanding quality, showing most of the widespread species and including details which are not shown in other drawings. Systematic references to photographs have not been made. These are increasingly available on websites such as Tropicos, Reflora, SEInet and those of individual herbaria and on the websites of individual research workers.
Geographical information is provided country by country. Continental countries are ordered from south to north as follows: Eastern non-Andean, South America: Uruguay, Argentina, Paraguay, French Guiana, Surinam, Guyana; Western South America northwards, Chile north to Venezuela and then northwards from Panama to Canada. The islands are ordered from Bermuda to Bahamas, Turks and Caicos, Cuba, Cayman Islands and Jamaica, then from Haiti in an arc east and south to Trinidad, with the Netherlands Group at the end. Hawaii is placed in final position. Although apparently rather eccentric, this order ensures to a very large extent that plants whose range extends into adjacent countries or along mountain or island chains are arranged into logical distribution patterns.
Citations of occurrence are provided for all countries and, where possible, for major areas (states, provinces or departments), highlighted in bold face, in the larger countries. All South American countries except Uruguay and the Guianas are treated as “large countries”, together with Mexico, the United States and Canada. Major areas within larger countries are arranged alphabetically. The small Caribbean islands are treated as “major areas” of the Lesser Antilles. Citations are based on specimens seen or, in a few cases, identified by an established authority who is known to have understood the species well. Records from checklists and, especially data bases without images, have not been used as they contain many errors (Goodwin et al. 2015) and, if included, are indicated with the word fide. As a general rule at least one specimen is cited for every country and major area in larger countries. The purpose of the citations is to provide evidence of the presence of a species in a particular territory, not to provide a complete list of specimens seen, but in the case of rarer species, all specimens we have seen may be cited. If a user of this monograph wishes to confirm a record this can be traced through the cited herbarium. Photographs of many but not all cited specimens are available on line through the web sites of the relevant herbaria. Many individual records can also be traced through our project website “www.ipomoeaproject.org”.
Ecological information is included within distributional information. Our knowledge of the ecology of individual species varies from zero to good. It is particularly poor in cases of very localized species. Many of the widespread species occur as garden escapes, weeds or adventives in and around settlements and by roads. The only Ipomoea species reported to be invasive is I. aquatica and that only in Florida and Cuba. No troublesome weed of cultivation has been noted.
Explanations for lectotypifications are provided separately from other notes. In cases where no explanation is provided, it should be assumed that the most complete specimen seen and cited by the original author was chosen.
Notes are mostly related to taxonomic issues. They often summarise distinctive characteristics of a species and indicate how it can be distinguished from other species with which it is often confused. Some information has been given about traditional and economic uses but this has not been a focus of attention in this monograph.