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

Keywords
America, Batatas, Convolvulaceae, distribution, illustrations, keys, lectotypification, monograph, morning glory, new taxa, Pharbitis, Quamoclit, revision, storage roots, sweet potato, synonymy
Introduction
This monograph of Ipomoea L. in the New World follows on from our monograph of Convolvulus (Wood et al. 2015). Ipomoea, as here interpreted, is a large pantropical genus of about 800 species. We have studied the genus worldwide and supporting papers (Wood et al. 2015, 2016a, 2016b, 2017a, 2017b, 2017c, 2017d, 2018; Wood and Scotland 2017a, 2017b, 2017c; Muñoz-Rodríguez et al. 2018, 2019) reflect this comprehensive overview, but for pragmatic reasons this monograph treats in detail only those species recorded from the New World (i.e. the American continent and associated islands including Easter Island, the Galapagos Islands and Hawaii in the Pacific together with Bermuda, Bahamas and the Caribbean Islands on the Atlantic side).
We have developed the ‘foundation monograph’ concept at Oxford as an approach to overhauling the taxonomy of species-rich groups of tropical plants since many of these groups have never been studied across their entire geographical distribution as a consequence of the pragmatic and local nature of much taxonomy. Inevitably, these groups contain undiscovered species, high levels of undetected synonymy, and identification keys are absent or limited. A major challenge in monographing these groups is the size of the task given the number of species, their global distribution and extensive synonymy, the large and increasing number of specimens, the numerous and dispersed herbaria where specimens are housed and an extensive, scattered and often obscure literature. Our approach seeks to focus on those tasks that are tractable and can offer the maximum improvement in taxonomic knowledge in a given period of time. It is novel in the sense that we combine standard taxonomic techniques with the use of online digital images and molecular sequence data to focus on species level taxonomic problems across the entire distribution range of individual species. A detailed account of our approach is available in Muñoz-Rodríguez et al. (2019).
Although there are some problems of species delimitation in Ipomoea, particularly in Clade A (Figure 1; Muñoz-Rodríguez et al. 2019), we have been able to provide descriptions of all accepted species in New World Ipomoea, identify types and provide outline details of distribution and ecology for nearly all taxa. We have described six further new species and provided a complete synonymy, keys, illustrations and notes to facilitate identification as well as to highlight infraspecific variation and areas of taxonomic uncertainty. To avoid unnecessary redundancy authorities are not provided for taxa mentioned in the introductory section and notes, as these are all provided in the taxonomic account. Exceptions are made for first occurrence of taxa which do not feature in the taxonomic account or in situations where authorities are needed to distinguish between different applications of the same name.