Systematics and evolution of Xanthophyllum (Polygalaceae) BY R. van der Meijden E. J. BRILL / LEIDEN UNIVERSITY PRESS LEIDEN 1982 This book can be cited as: MEIJDEN, R. VAN DER. 1982. Systematics and evolution of Xanthophyllum (Polygalaceae). E. J. Brill/Leiden University Press (Leiden Botanical Series, vol. 7). 159 pp., 22 figs. In the Leiden Botanical Series will be published papers of a monographic nature from the entire field of botany (including its history, bibliography, and biography) which by their length (100 printed pages or more) are unsuitable for publication in journals. Information can be obtained from the editors, Rijksherbarium, Schelpenkade 6, Leiden, The Netherlands. World distributor for publications of the Universitaire Pers, Leiden: E. J. Brill, Postbus 9000, 2300 PA Leiden, The Netherlands. ISBN 90 04 06594 6 Copyright 1982 by E. J. Brill, Leiden, The Netherlands All rights reserved. No part of this book may be reproduced or translated in any form, by print, photoprint, microfilm, microfiche or any other means without written permission from the publisher PRINTED IN THE NETHERLANDS Contents Summary vi Introduction vii Acknowledgements vii GENERAL PART 1. Notes onmorphology and discussion on evolution of characters 1 1.1. Growth of twigs 1 1.2. Phyllotaxis 2 1.3. Stipules or pseudostipules; nodal and foliar glands 2 1.4. Axillary buds 4 1.5. Venation 5 1.6. Idioblasts 7 1.7. Inflorescence 7 1.8. Ontogeny of the flower 8 1.8.1. Initial development 8 1.8.2. Retardation of median abaxial petal 12 1.9. Full-grown flowers 12 1.9.1. Petals 12 1.9.2. Stamens 14 1.9.3. Anthers 14 1.10. Remarks on flower biology 15 1.11. Ovary 16 1.12. Stigma 20 1.13. Fruit 20 1.14. Seed 21 1.14.1. Testa 21 1.14.2. Development of embryo 23 1.14.3. Morphology of embryo 26 1.15. Seedlings 28 1.16. Literature 29 2. Phylogeny of Xanthophyllum 30 2.1. Affinities of the Polygalaceae with other families 30 2.2. Position of Xanthophyllum in the Polygalaceae 32 2.3. relation of 32 Phylogenetic Xanthophyllum groups 2.3.1. The problem of Xanthophyllumfragrans: an old allopolyploidspecies? 35 2.3.2. The position of Xanthophyllumramiflorum:: another allopolyploid species? 36 2.4. Evolution at species level 37 2.5. Reflections 37 2.6. Literature 37 3. Classification 38 4. Habitat, distribution,dispersal,plant-geography 41 4.1. Habitat 41 4.2. Distribution 41 4.3. Dispersal 44 4.4. Discussion: migration from the East 44 4.5. Literature 46 SPECIAL PART Notes on the key and the descriptions 47 Key to the species 51 Xanthophyllum 6O Index to taxonomic names 157 V Summary The work the first of all of present comprises revision species Xanthophyllum; 93 spe- cies (22 new) have been distinguished with 5 subspecies (1 new) and 2 varieties (both new). Seven subgenera are proposed (4 new) of which one has been divided into 2 sections and 2 subsections. Keys to all taxa have been included. In the General Part the (sub)generic and (sub)sectional characters are discussed separately in order to find arguments regarding the direction of the evolution of those characters the of in ‘Hennigian’ way reasoning. From this it has been concluded that the Polygalaceae are derived from the Malpighiaceae- Vochysiaceae- -Trigoniaceae-complex and secondly that Xanthophyllum belongs to a of the derived tribe Polygalaceae (and not to a separate family Xanthophyllaceae ). The lack of information on the genomes of the species appeared to be a serious problem in the of reconstruction the evolution within Xanthophyllum: one subgenus with ‘gigas’-charac- old that ters may represent an allopolyploid hybrid; it is suggested hybridization may have been the evolution of the two endemic to important in genus. Although only species, N. Queensland, do not occur in Malesia-Southeast Asia, it is shown that Australia must have been the centre of origin of the genus. The fact that Wallace’sLine is still respected by all is indication that West Malesia is of species regarded as an a secondary centre speciation. vi Introduction to for The genus Xanthophyllum was the last one be done the revision of the Polygala- ceae for Flora Malesiana. Because it had never been revised before, covered only a restrict- and would number of undescribed the non-Malesian ed area, probably comprise a species, The of undescribed than species were included. number species appeared to be greater ex- pected: I described 37 new species (of which 22 in the present paper), being 40 %of the total number of accepted species. The major reason for the high number of new species is the fact that many (17) have been discovered only after (1957—)1961. Also the superficial similarity of the collections must have played a role, as well as the fact that the species are economically of no known use. After with the became succeeding in combining the flowering fruiting collections, it ap- that the of rather well-defined The parent genus comprised a number infrageneric groups. renewed interest in methods for the reconstruction of evolution induced me to try the 'Hennigian' method (hitherto mainly used in systematics of animal groups) on a group of flowering plants, also in the hope of helping to bring back the discussion to the practical work. Characters ofthe wood will be described in a separate paper(Peletier-Bridgwater & Baas, 1982). Pollen morphologically Xanthophyllum differs hardly from other Polygalaceae. A survey of the pollen morphology will be published separately. ACKNOWLEDGEMENTS This study could not have been made without the generosity of the following herbaria, which their collections at kindly put (c. 14,000 sheets) my disposal: Ann Arbor (AFS), Berkeley (UC), Bogor (BO), Brisbane (BRI), Bruxelles (BR), Cambridge, Mass. (A), Copen- hagen (C), Edinburgh (E), Firenze (FI), Geneve (G), Kepong (KEP), Kew (K), Kuching (SAR), Kyoto (KYO), Leiden (L), London (BM), Melbourne (MEL), Munchen (M), New York (NY), Paris (P), Sandakan (SAN), Singapore (SING), Utrecht (U), Wageningen (WAG), Wien (W), Wroclaw (WRSL), Zurich (Z). I am much indebted to Dr. R.C. Bakhuizen van den Brink for rendering the diagnoses in Latin. I want to express my thanks to Dr. F.S.P. Ng (Forest Research Institute, Kepong, Malaya) for the stimulating correspondence. vii General part 1. Notes on morphology and discussion on evolution of characters In Xanthophyllum I distinguish eight groups of species which I think to be monophyle- tic. These groups are: group 1 (subgenus 5. Brunophyllum, 5 species) group 2 (subgenus 7.Macintyria, 1 species) group 3 (subgenus 6. Grandiflorum, 1 species) 5 group 4 (subgenus 3. Triadelphum, species) group 5 (subgenus 2. Coriaceum, 1 species) group 6 (subgenus 4. Exsertum, 3 species) 7(subgenus 1. Xanthophyllum, section 1. Xanthophyllum 16 species) group , group 8 (subgenus 1. Xanthophyllum, section 2. Eystathes, 61 species) Sometimes I will refer to the subsections: group 8a (subsection Jakkia; 47 species), group to of within 8b (subsection Eystathes; 14 species), or groups species subsection Jakkia. In this chapter I will try to compare the subgenera and sections in their separate charac- ters, and often also to compare these characters with those of other genera of the family. For brevity I will avoid the terms 'subgenus' and '(sub)section' in this chapter, as well as the of those will be referred the word and their names taxa; they to by 'group' group-num- ber as indicated above. (The group-numbers have no (hidden) meaning at all. Not wanting the chosen linear of the I each to give more weight to sequence subgenera, gave group a number which differs from that in the linear sequence.) The aim of the discussions is to find for each character arguments to make hypotheses on the transformation-seriesof that character for the find for the relations eight groups, i.e., to arguments phylogenetic be- tween these will for of the of groups. I use practical reasons some terminology Hennig (1966); this is based on a Darwinistic view on evolution. In that terminology the change of in a character a monophyletic group of organisms is called a transformation. The character- from which transformation state a starts is called plesiomorphous, the derived character- of such state a transformation is called apomorphous. These concepts are more or less syn- to the words in onymous 'primitive', resp. 'derived', but those words are ambiguous at least literature. will that often these be (botanical) It appear quite concepts cannot applied be- cause oflack of evidence or of knowledge of the specific character. 1.1. Growth of twigs The twigs of all species elongate in flushes. In each twig of a growing period the terminal bud becomes aborted and one of the axillary buds of the nearest leaf will produce the new shoot after The a resting period. internode with the aborted terminal bud at its end usually further grows for a short period; later, when the next shoot has developed, the aborted ter- of former minal bud the season is visible at the end of a short, slender part of last season's twig pressed against the basal part of the new twig. Very rarely the terminalbud produces shoot addition the the axil of the leaf a new in to one developed in upper (seen once), or forms an inflorescence (seen a few times in different species). 1 Discussion — Sympodial growth has not been reported for any other genusof the Poly- from related families. Also the which galaceae, nor is it known to me considering way in convinced that character of all the sympodial structure arises, I am it is a synapomorphous groups ofXanthophyllum. 1.2. Phyllotaxis One of the difficulties met with when examining the phyllotaxis in Xanthophyllum is the fact that the shoots so often produce only a few leaves, a fact already noted by Raci- borski he for 36.