E D I N B U R G H J O U R N A L O F B O T A N Y 65 (2): 161–347 (2008) 161 Ó Trustees of the Royal Botanic Garden Edinburgh (2008) doi:10.1017/S0960428608005106 A REVISION OF PARABOEA ( GESNERIACEAE) Z HAORAN X U 1 , yB. L. BURTT2 ,L.E.SKOG3 &D.J.MIDDLETON2 The genus Paraboea Ridl. (Gesneriaceae) is revised. It is found in Bangladesh, Bhutan, Burma, Cambodia, southern China, India (Assam), Indonesia (Sumatra, Java, Borneo, Sulawesi), Laos, Malaysia (Peninsular and Borneo), Philippines, Thailand and Vietnam, mostly from limestone habitats. Eighty-nine species and five varieties are recognised. Four new species and one new variety are described: Paraboea apiensis Z.R.Xu, Paraboea argentea Z.R.Xu, Paraboea graniticola Z.R.Xu, Paraboea paraprimuloides Z.R.Xu and Paraboea harroviana var. ovata Z.R.Xu. In addition two taxa are highlighted as possible new species but are not described here due to insufficient material. The treatment includes one new combination for a species, Paraboea harroviana (Craib) Z.R.Xu, one new combination for a variety, Paraboea schefferi var. ambigua (C.B.Clarke) Z.R.Xu, one new status for a variety, Paraboea rufescens var. tomentosa (Barnett) Z.R.Xu, and one new name, Paraboea primuloides Z.R.Xu. Fifty-one line drawings are included. A key is presented and all taxa are described. Preliminary conservation assessments are given. Keywords. Gesneriaceae, Paraboea, taxonomic revision. Introduction Paraboea (C.B.Clarke) Ridl. was first published by Clarke as a section, Didymo- carpus sect. Paraboea C.B.Clarke (1883), and was raised to generic level by Ridley (1905). Paraboea was distinguished from an allied genus, Boea Lam., by a carpo- logical character: valves of the capsule were straight in Paraboea, while those in Boea were twisted. A revision of Boea and allied genera by Burtt (1984) abandoned the above generic delimitation and circumscribed the two genera based on a difference in indumentum: an indumentum of simple straight hairs in Boea and an indumentum of interwoven arachnoid-like hairs in Paraboea. The revision fundamentally changed the content of the two genera, resulting in a relocation of the majority of species of Boea to Paraboea. Further discussion on generic delimitation in the Boea group (Boea, Paraboea and Trisepalum – including several other genera reduced to synonymy) can be found in Burtt (1984). This paper is a continuation of an earlier work on Paraboea (Xu & Burtt, 1991) in which several new taxa were described. It is based on an examination of a total of about 670 herbarium collections with more than 2000 sheets from herbaria all over 1 Sun Yatsen University, PO Box 971, Guangzhou 510275, China. E-mail: [email protected] 2 Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, Scotland, UK. 3 Department of Botany, NHB-166, Smithsonian Institution, Washington, DC 20560, USA. Downloaded from https://www.cambridge.org/core. Laurentian University Library, on 09 Mar 2019 at 19:54:31, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0960428608005106 162 ZHAORAN XU ET AL. the world. The purpose of this paper is to delimit the taxa, provide a key to identify them, provide a full synonymy, describe each taxon and provide conservation assessments of all taxa. What is now also needed is a thorough phylogenetic analysis of the genus to examine relationships between the species and the relationships of Paraboea to other genera, and indeed, whether Paraboea is a monophyletic group as we have assumed here. Preliminary molecular phylogenetic studies do suggest that Paraboea and Trisepalum together form a monophyletic group but as yet there is no resolution to whether the two genera are distinct or not (M. Mo¨ller, pers. comm.). However, this lack of a phylogenetic resolution does not need to delay the fundamental practice of taxonomy which is to delimit and describe species. Paraboea is found in southern China, northeastern India and the eastern Himalayas, Burma, Thailand, Cambodia, Laos, Vietnam, Malaysia, Philippines and Indonesia as far east as Sulawesi (Fig. 1). Much of this distribution coincides with a poor specimen collection density (Johns, 1995; Middleton, 2003). Consequently many of the taxa included in this revision are known from only one or very few specimens. This inevitably leads to decisions being based on insufficient information, and any use of this work must bear this in mind – there will almost certainly be taxa which we have misinterpreted. We hope, however, that this revision will encourage further exploration of the regions concerned and more targeted collecting of limestone areas where the majority of Paraboea species are found. But, for the time being, we have based our species concept on discontinuities in morphological characters and, where there is some doubt as to whether taxa should be recognised due to inadequate material, we have taken the geographical distributions into account. In addition it is very likely that there are many taxa yet to be discovered, particularly in underexplored limestone areas such as in Laos, Vietnam and Kalimantan. This paper has been completed in two distinct periods – the majority of the work was done before 1993 by the first author, under the supervision of the second and third authors, and it was then updated and extensively revised by the first and fourth authors in 2007. This work pattern will explain why not all recently collected material is included in the revision although all recently published taxa have been checked and incorporated into the work. Although we acknowledge that in an ideal world all of the recent material should have been included we believe that it is now important that this revision be published to provide a useful benchmark for further taxonomic study on this genus. We have, however, attempted to check the more recent material from particularly poorly known areas. In this work 89 species and five varieties of Paraboea are recognised, which include four new species, one new variety, one new combination for a species, one new combination for a variety, one new status for a variety and a new name. Morphology The genus is rather diverse in morphology, showing differences in habit, the indumentum, the inflorescence and the capsule. We have found inflorescence Downloaded from https://www.cambridge.org/core. Laurentian University Library, on 09 Mar 2019 at 19:54:31, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0960428608005106 AREVISIONOFPARABOEA 163 is Paraboea speciosa species. In each case the first number is the total number of species in the country or on the island (in Malesia) Paraboea 1. Distribution of . IG and the second numberquestionable is distributions the are counted number as of having endemic specimens found species in in those the areas (see same discussions region. under the Varieties relevant are species). included under species and species with additional not included as its provenance is unknown. The number given for northeastern India also includes Bhutan and Bangladesh. F Downloaded from https://www.cambridge.org/core. Laurentian University Library, on 09 Mar 2019 at 19:54:31, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0960428608005106 164 ZHAORAN XU ET AL. structure to be extremely important in identifying species and it will be interesting to see whether it proves to be phylogenetically informative once a molecular phylogeny of the group is available. Habit: Rosette vs. Cauline with extended internodes A rosulate habit (rosette-forming) means that the plants do not possess a stem and all the leaves are basal. A cauline habit means that the plants possess a stem with clear internodes. The rosulate habit and cauline habit may be confused with each other in vegetative growth, for a rosette may be formed by greatly reducing the length of internodes on the stem from the cauline habit. However, in association with inflorescence patterns this confusion may be clarified. A true rosette is generally associated with axillary cymes and the plant has a vegetative terminal bud that will continually grow to produce a polycarpic individual. Species with the cauline habit may also bear an inflorescence of axillary cymes and be polycarpic, but species with a terminal panicle never have a true rosette even though the stem may be very short. These individuals are monocarpic. Thus, a rosulate habit may not be qualitatively different from a cauline habit, but a rosette + axillary cyme is qualitatively different from cauline habit + terminal panicle. Leaf phyllotaxis: Opposite vs. Whorled vs. Alternate For the most part these three alternative leaf arrangements are clearly distinguish- able from each other. Opposite leaf arrangement is the most common in the genus and is associated with both terminal panicles and axillary cymes, and rosulate and cauline habits. Species with whorled leaves almost always have a terminal panicle with only two exceptions (Paraboea divaricata and P. elegans with subterminal cymes) and all these species occur only in tropical Malaysia and Indonesia. This group of species are also similar in habit, in flowers and in fruits. However, even though Paraboea divaricata and P. elegans have whorled leaves they have a similar habit, corolla, stamen and gynoecium to those species with a subterminal cymose inflorescence. Paraboea divaricata is closer to P. patens, and P. elegans to P. minor (see discussions under those species). Alternate leaf arrangement is uncommon in this genus. This leaf arrangement is more often associated with axillary cymes, although P. lancifolia has a terminal panicle. The three leaf arrangements have no intermediate types. Inflorescences: Terminal panicle vs.