WAGENINGEN AGRICULTURAL UNIVERSITY PAPERS 98-2 (1998) The sections of Begonia including descriptions,key s and species lists (Studies inBegoniacea e VI) J. Doorenbos, M.S.M. Sosef &J.J.F.E . de Wilde Herbarium Vadense - Laboratory of Plant Taxonomy Wageningen Agricultural University P.O. Box 8010, 6700 ED Wageningen The Netherlands Date of publication 2-12-1998 Wageningen ^J Agricultural University The Netherlands 1998 Ys^ ..;vvo 1 -K'.! The sections of Begonia, including descriptions, keys and species lists / J. Doorenbos, M.S.M. Sosef &J.J.F.E . de Wilde ISBN 90-5782-007-2 NUGI 823 ISSN 0169-345X Distribution: Backhuys Publishers, P.O.Box 321, 2300 AH Leiden, The Netherlands. Telephone: +31-71-5170208 Fax:+31-71-5171856 E-mail: [email protected] All rights reserved Printed in The Netherlands BIBLIOTHEEK LANDBOUWUNIVERSITEIT WAGENINGEN Contents 1 Historical review 6 2 Goals of the present study 9 3 Methods 9 4 Character list 12 5 Keys 33 5.1 User-friendly keys 34 5.1.1 General user-friendly key to all sections 34 5.1.2 User-friendly key to the American sections 45 5.1.3 User-friendly key to the African sections 48 5.1.4 User-friendly key to the Asian sections 50 5.2 Analytical keys 52 5.2.1 General analytical key to all sections 52 5.2.2 Analytical key to the American sections 57 5.2.3 Analytical key to the African sections 60 5.2.4 Analytical key to the Asian sections 61 6 Taxonomie treatments 63 6.1 Generic description of Begonia 63 6.2 Alphabetical treatment of the sections 64 7 Species not attributable to any existing section 217 8 Relationships between the sections 220 8.1 Methods 220 8.2 Results and discussion 221 9 Alphabetical list of species 227 10 Acknowledgements 259 11 References 260 WageningenAgricultural UniversityPapers 98-2(1998) 1 Historical review The first description of a plant of what we now call Begonia to appear was Francisco Hernandez' Totocaxoxo coyollin' from Mexi­ co (1651). The second was 'Tsjeria-nariampuli' from Malabar described by Henricus van Rheede in 1689. Six years later Plumier described six species from the Caribbean Islands of the genus he was the first to name Begonia. Tournefort published these descriptions in 1700. For Linnaeus, who had never seen any material of it,Begonia was dubious. In his Species Plantarum of 1753 he reduced the six species of Plumier to one, which he gave the name Begonia obliqua. (All descriptions and pictures of Begonia published up to 1763 have been reproduced by Barkley,1968). The number of species known to the world expanded slowly. In 1791 Dryander, the first monographer of the genus, described 21 species and mentioned another 9 'species obscurae'. Fifty years later Steudel in the 2nd edition of his Nomenclator Botanicus listed 140 species names (and 36 synonyms). By that time it had become clear that Begonia was a large genus. As early as 1818 Robert Brown wrote 'the extensive genus Begonia, which it is perhaps expedient to divide'. The first to take this to heart was John Lindley, who in 1846 distinguished the genera Begonia with one placenta in each locule of the ovary, Diploclinium with two placentae per locule and Eupetalum with four tepals. Meanwhile, Gaudichaud had proposed the genus Mezierea (ignored by Lindley) for a species from Réunion. The author who went furthest in this direction was Klotzsch. In 1854 and 1855 he published the results of a meticulous study of a large and for the time representative collection of Begonia species. On the basis of this study he distinguished no less than 37 genera of Begoniaceae in addition to the four of Lindley and Gaudichaud. Although the great merit of Klotzsch' work was - and still is - generally recognized, subsequent authors have not followed his subdivision of the family. Alphonse de Candolle, who in 1864 published the second - and so far the last - monograph of the Begoniaceae, has only three genera: Mezierea with 3, Casparyawit h 23, and Begonia with 323 species (and 31 'species dubiae'). Mezierea is divided into 2, Casparya into 8, and Begonia into 61 sections, and of these 34 correspond to genera of Klotzsch. 6 WageningenAgricultural UniversityPapers 98-2 (1998) In 1894 Warburg reviewed the Begoniaceae for Engler's 'Natür­ liche Pflanzenfamilien'. He was the first to group the sections of Begonia according to continent and divided the genus, in which he included Casparya and Mezierea, into 12 African, 15 Asian, and 31 American sections, and 3 dubious ones, rejecting 17 of de Candolle's sections but adding 6ne w ones. In the second edition of Engler's monumental work, Irmscher (1925) greatly expanded Warburg's treatment but in general followed his taxonomy. Begoniai s divided into 12African , 16Asian , and 32 American sections, one section (Begoniastrum) with Asian as well as American representatives, and still 3 uncertain sections. Irmscher's subdivision and key have been used by most subsequent authors, sometimes including the printing errors (which Irmscher himself corrected in 1929, p. 93) and generally without observing the subsequent changes in Irmscher's own ideas. Meanwhile the number of species, put by Warburg at more than 400 and by Irmscher at more than 760, kept expanding, every collecting trip into territory rich in begonias revealing new ones. Repeatedly species were described that could not be fitted into one of the sections recognized by Irmscher. He himself had already written on the subject of genera within the Begoniaceae'Wen n man beginnt, einzelne morphologisch besonders abweichende Sektionen als Gattungen abzutrennen ... kommen schlieszlich noch andere mit gleichem Recht im Frage und man weiss nicht, wo man Halt machen soll' [When one starts to separate single morphologically aberrant sections as genera ... finally other ones should be considered similarly, and one does not know where to stop]. He must have realized that the same holds true for sections, only more so, for he is very reluctant to describe new sections himself. He proposes two new ones in 1929 and one more in 1939. In later papers he provisionally attaches aberrant species to the nearest section or leaves the classification undecided. In one of the latter cases (Irmscher, 1953: 95) he writes: 'doch sehe ich auch in diesem Falle von der Aufstellung einer neuen Gruppe zunächst ab, da ich z.Zt. mit der Neuordnung der bekannten Sektionen beschäftigt bin' [I refrain also in this case from the erection of a new group, as I am at the moment working on a rearrangement of the known sections]. It is unfortunate that he never published this rearrangement. We only know that he intended to have vegetative characters play a decisive role as well. In 1972 F.A. Barkley made an effort to classify all known species according to the sections of A. de Candolle and subsequent WageningenAgricultural UniversityPapers 98-2 (1998) authors. In the same year he published, together with A. Baranov, a list of all known sections of Begonia, their accepted names and synonyms together with a short description, where possible based on Irmscher (1925). In addition they recorded the type species of each section, and where this was not yet available, they indicated a lectotype species for accepted as well as rejected section names. Of both publications a revised edition appeared in 1974. The list of species had been much improved through collaboration with J. Golding. The list of sections could also have done with some revision, but except that the order of both authors had been reversed there were only minor changes. In 1986 The Begoniaceae' by Lyman B. Smith et al. appeared with a key to all known species, the great majority also pictured, as a rule by a photograph of the type specimen. The species list and relevant literature citations have been prepared with meticulous care by J. Golding and Ms CE. Karegeannes. This book will be an indispensable work of reference for years to come, but it does not mention sections. Probably because the contention "there are too many gaps in our knowledge to allow us to arrange the species of Begoniab y sections" (Smith & Schubert, 1946: 6) was still held to be valid. Be that as it may, when dealing with a genus the size of Begonia it is inevitable that one feels the need of a system to survey this multitude of species, preferably one which gives an insight into their natural relationships. As such the traditional grouping of species into sections presents itself and has been used, especially by authors whose work is only indirectly connected with taxonomy, e.g. Cuerrier et al. (anatomy) or Bouman & de Lange (seed micromorphology), who felt the need to discuss the variation they observed in relation to this classification. Until now, the list of species and sections of Baranov & Barkley (1974) has often been used, as it was the most recent, although it was in many ways unsatisfactory. In this way not only some of the inaccuracies of these authors are perpetuated, but the system on which it is largely based, that of Irmscher (1925), got a longer life than Irmscher himself would have wished. WageningenAgricultural UniversityPapers 98-2 (1998) 2 Goals of the present study In the course of their former work with Begonia, the present authors became convinced that grouping the species into sections is a useful way to get an insight into the existing variation within this extensive genus. It also became obvious, however, that the descriptions of the sections would have to be brought up-to-date and their delimitation in many cases to be revised. The purpose of the present study is to draw up an inventory of the sections of Begonia that have so far been proposed and to establish to what extent all known species can be fitted into these sections.