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

Discovery of Ipomoea species in America
Inevitably the first species of Ipomoea to be recognized and catalogued from the New World were species of economic importance (I. batatas), of horticultural value (I. alba, I. indica, I. nil, I. purpurea), or were widespread conspicuous species of accessible habitats, such as I. pes-caprae, or I. violacea, which grow on seashores. All were known to pre-Linnean botanists and featured in Species Plantarum and other near contemporary works.
Geographically, the first region from where a reasonably comprehensive inventory of Ipomoea emerged was the eastern United States. Nearly all the localized species from this area had been found and described by around 1800, including species like I. pandurata, I. lacunosa and I. macrorhiza. The United States Southwest had to wait until the 1850s after the United States-Mexican war. It was only then that species from this region were discovered, principally by Wright, Lindheimer and Torrey. Most were described a quarter of a century later by Gray (1878, 1886) including I. leptophylla, I. tenuiloba, I. barbatisepala, I. lindheimeri and I. cardiophylla. After the mid 19^th century there was little new to discover in the United States, and most (but not all) described novelties were ephemeral, being shown subsequently to be conspecific with earlier species.
The Caribbean had been one of the earliest regions of botanical exploration and many of its endemic species including Ipomoea ternata, I. tenuifolia, I. repanda, I. digitata, I. clausa and I. desrousseauxii were discovered in the 18^th century, as both Jamaica and Hispaniola were visited by botanists from different European countries. Cuba was somewhat different. Although Humboldt and Bonpland visited Cuba, they did not find any of its endemic species. A few were discovered by Sagra in the 1840s, but it was only in the 1860s that the rich diversity of Ipomoea in Cuba became known after Grisebach (1862a, 1866) wrote up the many new species found by Charles Wright (the same Wright who had been active in the United States Southwest). In the years after 1870 there was a slow increment of new species from the Caribbean culminating in the collections of Eric Ekman on Cuba (I. baliocalda, I. erosa) and on Hispaniola (I. luteoviridis), although many of his supposed novelties described by Urban (1924a and passim) have proved to be synonyms of other species. The occasional new species has been found since but the inventory of Caribbean Ipomoea is now largely complete.
There were collections from Mexico in the Spanish colonial era but those of Sessé and Moçiño were not published until a hundred years later. Nevertheless, seeds sent to Spain by them and by Née were cultivated in Madrid enabling Cavanilles to describe several attractive and interesting Mexican species including Ipomoea tricolor, I. stans and I. bracteata at the end of the 18^th century. The expedition of Humboldt and Bonpland constituted the next step forward in revealing the wealth of Mexican Ipomoea. Ipomoea cholulensis, I. suffulta and I. hastigera were amongst their discoveries, as was I. arborescens, the first tree Ipomoea to be described. During the first half of the 19^th century Mairet, Andrieux, Hartweg and others added to the list of species known from Mexico, but the most important advance came with the collections of Galeotti, which greatly increased the number of known species. His discoveries were published in 1845 and included many well-known Mexican species such as I. lindenii, I. minutiflora, I. chenopodiifolia, I. pauciflora, I. suaveolens and I. proxima (Martens and Galeotti 1845).
After 1845 there was a lull in the discovery of new Mexican species for almost fifty years. However, the end of the 19^th century proved to be a golden age for botanical exploration in Mexico thanks to a series of collectors mostly from the United States, especially Palmer, Pringle, Purpus, Nelson and Brandegee, and the Mexican-Italian Casiano Conzatti. The number of recognized species doubled during this era. However, these collections did not exhaust the riches of Mexican Ipomoea and the 20^th century has seen the regular discovery of new species by collectors from both Mexico and the United States, notably H.S. Gentry, G.B. Hinton and Rogers McVaugh from the United States and the Japanese-Mexican Eizi Matuda. This trend has continued into the new century with at least eight new species described since 2000. It is too early to say whether this trend is ending but it is perhaps significant that rather few new Mexican species has been found during the course of our studies in Ipomoea.
It was mostly during the 20^th century that the Ipomoea flora of Central America was discovered and described. Although not as rich as the Mexican flora, there has been a steady increment of new species since the middle of the century including I. chiriquensis from Panama, I. magniflora from Costa Rica, I. riparum from Honduras, I. heterodoxa from Belize and I. steerei from Yucatán, mostly found by North American collectors. However, the inventory of species seems to be nearly complete, since, as with the Caribbean, nothing new has been reported since the turn of the 21^st century.
The earliest collections from South America of any importance were made by Ruiz and Pavón in Peru at the end of the 18^th century. They noted surprisingly few new species of Ipomoea but amongst them were I. ramosissima. Of far greater importance was the expedition of Humboldt and Bonpland. Having found new species in Mexico they went on to find a series of new species in the northern Andes including I. discolor and I. parasitica in Venezuela, I. capillacea in Colombia and I. abutiloides in Ecuador.
Essentially little more was discovered or described from the Andean region for well over a century apart from a few species from Venezuela (Pittier 1927, 1931), a few from Peru by Weberbauer (Ooststroom 1933), two from Bolivia (Rusby 1896, 1899) and a couple from Argentina (Grisebach 1879, Kuntze 1891).
This situation only changed after the Second World War initially as a result of O’Donell’s short career (O’Donell 1941 and passim). He significantly increased our knowledge of species in the southern Andes, describing at least six new species from Argentina (Ipomoea jujuyensis, I. rubriflora, I. lilloana, I. oranensis etc.) as novelties, two from Bolivia (I. tarijensis, I. suburceolata), two from Peru (I. velardei, I. peruviana), three from Colombia (I. colombiana, I. killipiana and I. reticulata) and one from Venezuela (I. pittieri); these all still recognised. Fieldwork by Danish botanists led to the discovery and description of three new species from Ecuador by Dan Austin. The diversity in Bolivia was, however, only revealed recently (Wood et al. 2015, 2018, Wood and Scotland 2017b), with the description of 21 new species, mostly Andean which took the total number of Ipomoea species known from that country to 109, thus putting it in third place after Brazil and Mexico for the total number of Ipomoea species recorded.
The 19^th century, in contrast, was a golden age for plant discovery in Brazil, mostly under the stimulus of the production of Martius’ Flora Brasiliensis. The roll call of collectors finding new species of Ipomoea in Brazil is composed of most famous plant collectors in Brazil in the 19^th century. They include the Germans Martius, Riedel and Sellow, the Brazilians Vellozo and Silva Manso, Blanchet and Glaziou from France, Regnell from Sweden, Gardner, Spruce and Burchell from Britain and Pohl from Austria, their achievement commemorated in species such as I. burchellii, I. regnellii, I. blanchetii, I. spruceana and I. pohlii, all still recognized Brazilian species. The result was that by about 1870 our knowledge of Ipomoea was greater in Brazil than elsewhere in South America.
After the publication of Flora Brasiliensis (Meisner 1869), there was lull in the process of discovery in Brazil, which did not really pick up again for more than a hundred years. It has only been since the 1980s that significant numbers of new species have been found and described from Brazil (Austin 1981, Simão-Bianchini and Pirani 2005 Ferreira and Miotto 2011, Vasconcelas et al. 2016, Wood et al. 2017a,d, Wood and Scotland 2017a,b). It is clear that Brazil is the richest country in South America for Ipomoea but it remains the least explored and it is the only country in the Americas from where we would expect significant numbers of new species to emerge.
As in other aspects of its history, Paraguay (and neighbouring parts of Argentina) has followed a somewhat different trajectory. Until the 1870s, the flora of this region was essentially unknown. Then came a publication by Parodi (1877) listing around 15 species of Ipomoea but in the absence of associated specimens, these names cannot mostly be linked to recognized names. Expeditions by Morong and Balansa began to reveal the diversity of Ipomoea in Paraguay, but it was a long-term Swiss resident, Emile Hassler, and Teodoro Rojas, the Paraguayan curator of his herbarium, who really discovered the Paraguayan flora and revealed the number of Ipomoea species in the country. Between them they added some 20 recognised species, all of which are endemic to the region, some extending into nearby parts of Argentina. Those species that were not recognized by Hassler himself were described subsequently by Carlos O’Donell (1948a, 1950b, 1953a), together with a number of species from Misiones and Corrientes provinces in neighbouring Argentina.