Evolutionary relationships in Thunbergioideae and other early branching lineages of Acanthac e a e Agneta Julia Borg Evolutionary relationships in Thunbergioideae and other early branching lineages of Acanthaceae Agneta Julia Borg ©Agneta Julia Borg, Stockholm 2012 Cover illustration: From top left, Mendoncia retusa, Thunbergia convolvulifolia , Pseudocalyx saccatus, Crossandra strobilifera, Avicennia bicolor, Elytraria marginata. Photos: Agneta Julia Borg and Jürg Schönenberger. ISBN 978-91-7447-445-9 Printed in Sweden by Universitetsservice US-AB, Stockholm 2012 Distributor: Department of Botany, Stockholm University Academic dissertation for the degree of Doctor of Philosophy in Plant Sys- tematics presented at Stockholm University 2012 Abstract Borg, A.J. 2012. Evolutionary relationships in Thunbergioideae and other early branching lineages of Acanthaceae. Acanthaceae as circumscribed today consists of the three subfamilies Acan- thoideae (Acanthaceae sensu stricto), Thunbergioideae and Nelsonioideae, plus the genus Avicennia. Due to the morphological dissimilarities of Thun- bergioideae and Nelsonioideae, the delimitation of the family has been con- troversial. The mangrove genus Avicennia was only recently associated with Acanthaceae for the first time, based on molecular evidence, but without morphological support. In this thesis, phylogenetic analyses of nuclear and chloroplast DNA sequences were used to test the monophyly and exact posi- tions of Thunbergioideae and Nelsonioideae, and to infer detailed phyloge- netic relationships within these subfamilies and among major lineages of Acanthaceae. Floral structure and development were comparatively studied in Avicennia and other Acanthaceae using scanning electron microscopy and stereo microscopy. Phylogenetic analyses strongly support monophyly of Thunbergioideae and Nelsonioideae, and place the latter clade with strong support as sister to all other plants treated as Acanthaceae. Thunbergioideae and Avicennia are moderately supported as sister taxa, and together they are sister to Acanthoideae. The general morphology of Avicennia can be easily accommodated in the Acanthaceae, and three synapomorphies support the suggested sister group relationship of Avicennia and Thunbergioideae: (1) collateral ovule arrangement, (2) vertical orientation of ovule curvature, and (3) an exposed nucellus that is contiguous with the ovary wall. Within Thun- bergioideae and Nelsonioideae, support values for major lineages are gener- ally high. With some exceptions, the constituent genera are supported as monophyletic. Evolutionary relationships among and within genera are dis- cussed in a morphological and biogeographical context. Preface This thesis is based on the following papers, referred to in the text by their Roman numerals. I Borg, A.J., Schönenberger, J., and McDade, L.A. 2008. Mo- lecular phylogenetics and morphological evolution of Thun- bergioideae (Acanthaceae). Taxon 57: 811-822. II Borg, A.J., and Schönenberger, J. 2011. Comparative floral development and structure of the black mangrove genus Avi- cennia L. and related taxa in the Acanthaceae. International Journal of Plant Sciences 172: 330-344. III McDade, L.A., Daniel, T.F., Kiel, C.A., and Borg, A.J. Phy- logenetic placement, delineation, and relationships among genera of the enigmatic Nelsonioideae (Lamiales: Acanthace- ae). Accepted by Taxon. IV Borg, A.J., and Schönenberger, J. Phylogenetic relationships in Acanthaceae based on nuclear and chloroplast sequences with particular focus on the Thunbergioideae. Manuscript. Published papers are reproduced with permission from the publishers. Papers I, II and IV were written by AJB with comments and suggestions from the co-authors. The papers were planned in collaboration with the co- authors. AJB has generated all sequences for Paper I, and all new sequences for Paper IV, and is responsible for the phylogenetic analyses in these pa- pers. AJB has conducted the morphological analyses for Paper II in coopera- tion with the co-author. AJB took part in the preparation, laboratory work and writing of the manuscript of Paper III. Contents Introduction 11 Aims 15 Materials and methods 15 Results and discussion 17 Concluding remarks 21 Svensk sammanfattning (Swedish summary) 22 Acknowledgements 25 Literature cited 26 INTRODUCTION The flowering plant family Acanthaceae (Lamiales) consist of more than 4000 predominantly tropical and subtropical species. The vast majority of these belong to the subfamily Acanthoideae (sensu Scot- land & Vollesen 2000). Acanthoideae are characterized by having explosively dehiscent capsules with the few seeds borne on hook-like outgrowths of the funiculus, called retinacula. Retinacula are synapo- morphic for the subfamily, and Acanthoideae constitute a clearly de- fined and recognized group. In addition to these “core” Acanthaceae, two small lineages, the Thunbergioideae and Nelsonioideae sensu Scotland & Vollesen (2000), have traditionally been associated with Acanthaceae, though their markedly different morphology has resulted in various suggestions on how to classify these groups. Several au- thors have treated them outside Acanthaceae, and in some cases as distinct families (e.g. van Tieghem, 1908; Bremekamp, 1953; Dahlgren, 1980; Cronquist, 1981). In more recent years, the close rela- tionship of thunbergioids and nelsonioids with core Acanthaceae has gained wide support from both molecular and morphological studies, although molecular studies have not included more than a few repre- sentatives of the two former subfamilies (e.g. Hedrén & al., 1995; McDade & Moody, 1999; Schönenberger & Endress 1998). More sur- prisingly, a molecular study by Schwarzbach & McDade (2002) showed that the black mangrove genus Avicennia, usually treated ei- ther as a family of its own in Lamiales, or within Verbenaceae, most likely belong in Acanthaceae. Thunbergioideae The Thunbergioideae comprise five genera, the largest of which, Thunbergia, contains about 100 species restricted to tropical and sub- tropical regions of Africa, Madagascar, Asia, and Australia (Fig. 1). The second largest genus, Mendoncia (~60 species), is most diverse in Central and South America with some African representatives and a few species native to Madagascar (Fig. 1I). The remaining genera are Pseudocalyx with currently 7 species in Africa and Madagascar, mon- otypic Anomacanthus in tropical Africa, and monotypic Meyenia in India and Sri Lanka. The subfamily is characterized by a predominant- ly twining habit, enlarged prophylls (sensu Endress 2010), and a re- duced calyx (Fig. 1). Furthermore, Thunbergioideae lack the retinacu- late fruits found in Acanthoideae. Flowers are often showy, and sever- al Thunbergia species are cultivated as ornamentals. Particularly Thunbergia, but also Mendoncia, display a diversity of flower shapes 11 Fig. 1. Characteristics of Thunbergioideae, Avicennia, and Nelsonioideae. A-C, habitat; A, tropical forest clearance (e.g. Thunbergia convolvulifolia in Thunbergioideae); B, sunny space in rainforest near running water (e.g. Mendoncia retusa in Thunbergioideae); C, tropical coastal intertidal region (Avicennia). D-G, habit; D, small erect shrub (e.g. T. usambarica); twining around other plants (e.g. M. retusa); F, tree (A. bicolor); G, erect herb (E. imbricata in Nelsonioideae). H-K, flower morphology; H, corolla tube partially covered by prophylls, T. natalensis; I, corolla almost completely covered by prophylls, M. retusa; J, A. bicolor; K, E. imbricata. L-O, fruit types; L, immature capsule with persistent reduced calyx (T. convolvuli- folia); M, drupe with persistent annular calyx and persistent prophylls (M. retusa); N, vivip- arous, leathery capsules (A. marina); O, dehisced capsule (Staurogyne merguensis Kuntze, Larsen & al. 44309, AAU). P-T, pollination syndromes and floral features; P, bee pollination 12 syndrome (T. grandiflora); Q, hawkmoth-pollination syndrome (T. guerkeana, Bally 14996, K); R, bird pollination syndrome (T. mysorensis); S, close-up of thecal awns (T. mysorensis); T, bristled anthers (M. retusa). and colors, reflecting adaptation to a variety of pollinators, including bees (e.g. in T. grandiflora, Faegri & van der Pijl, 1966; Fig. 1P), moths (T. guerkeana, Schönenberger, 1999; Fig. 1Q), birds (e.g. T. mysorensis, T. coccinea, Schönenberger, 1999; M. velloziana, Buzato & al. 2000, Snow & Teixeira 1982; Fig. 1R, S) and possibly even bats (Mendoncia, Vogel & al. 2004; M. bivalvis, M. glabra, Hequet, 2003.) There are no existing subgeneric classifications for Mendoncia or Pseudocalyx (but see Profice, 1988, for Mendoncia in Brazil). More attention has been directed towards Thunbergia. Lindau (1893) subdi- vided Thunbergia into four sections based on morphology and ar- rangement of flowers. Bremekamp (1955) revised and extended Lindau’s subdivision and proposed eight subgenera. His classification largely concurs with a recent study of floral development and structure in Thunbergia by Schönenberger (1999). Avicennia The black mangrove genus Avicennia consists of around 8 species of trees which grow in the intertidal zone of coastal mangrove forests, ranging widely throughout tropical and warm temperate regions of the world (Tomlinson, 1995; Fig. 1C, F, J, N). Avicennia has always pre- sented a problem to systematists. Like other mangroves, Avicennia exhibits a number of conspicuous adaptations to the mangrove habitat of which they are an important constituent. These include specialized erect, lateral roots developed as pneumatophores,