THAI FOR. BULL. (BOT.) 41: 145–156. 2013. Is it really worthwhile revising the same fl ora repeatedly? A case study in Thai Orchidaceae HENRIK Æ. PEDERSEN1 ABSTRACT. For many purposes, scientifi c Floras (dealing with one, several or all plant families on a national or regional scale) are the most intensively used surveys and identifi cation tools for species of vascular plants. Flora of Thailand will be the fi rst real stan- dard Flora to cover all families of fl owering plants in Thailand. Nevertheless, the Thai representatives of a number of plant groups have undergone one or more revisions previously. Is it worthwhile revising such groups again for Flora of Thailand – and would it even make sense to start thinking of a second edition? To throw some light on this, I compared three successive revisions of the or- chid subfamily Orchidoideae in Thailand (published in 1958–1964, 1977–1978 and 2011, respectively). The series of revisions ex- hibited a progressive increase in the net number of accepted taxa. The relative increase was highest from the fi rst to the second revi- sion, but still substantial from the second to the third. The net results obscured an even higher number of changes (additions end exclusions of taxa) that partly neutralized each other – and other changes were in themselves neutral in relation to the net number of taxa accepted. Classifi cation at species level, but not at genus level, tended to stabilize over time. Altogether, the results demonstrate that both the second and the third revision were worthwhile indeed, as each of them provided comprehensive changes (arguably improvements) compared to the latest previous revision. KEY WORDS: Flora of Thailand; fl oristics; Orchidoideae; taxonomy. INTRODUCTION For example, the yet unfi nished Flora of Thailand will be the fi rst real standard Flora to cover all Many facets of biodiversity conservation families of fl owering plants in Thailand. require the application of taxonomic knowledge, especially at species level (e.g. Schuiteman & de Although the critical treatments in Flora of Vogel, 2003; Mace, 2004). As far as vascular plants Thailand constitute the fi rst true revision of many are concerned, such knowledge is mainly established genera (and even families) in a Thai context, the through revisions (including monographs and Thai representatives of a number of plant groups critical treatments in scientifi c Floras). For many have undergone one or more revisions previously. purposes, national and regional fl ora handbooks In a time when rapidly changing land use in (dealing with one, several or all plant families in Thailand and other parts of tropical Asia threatens the area concerned) are the most intensively used plant diversity and reduces the time that we have surveys and identifi cation tools (e.g. Funk, 2006). left to document it (e.g. Webb et al., 2010), is it The most thorough and comprehensive fl ora really worthwhile revising these groups again for handbooks in each region are usually called Flora of Thailand – and would it make any sense at “standard Floras”. Especially in those parts of the all to start thinking of a second edition of this western world that have been fl oristically explored national standard Flora? for several centuries, a succession of standard In order to assess the degree of scientifi c Floras have been published for each area – see, for relevancy of repeated revisions of the same fl ora, I example, Eriksson’s (2004) historical survey of performed a case study of the orchid subfamily Flora writing in the Nordic region. In the generally Orchidoideae in Thailand. This was done by com- late-explored tropics, on the other hand, repeated paring the taxonomic content of three subsequent revision of the same Flora is much less pronounced. revisions of this group (published in 1958–1964, 1 Herbarium, Botanical Garden, Natural History Museum of Denmark, University of Copenhagen, Øster Farimagsgade 2C, DK-1353 Copenhagen K, Denmark. e-mail: [email protected] SW 6585-P145-156-PC6.indd 145 7/11/2556 0:06:00 146 THAI FOREST BULLETIN (BOTANY) 41 1977–1978 and 2011, respectively). I primarily • Complex changes that overlap between two focused on exploring changes at species level, or more of the above categories. whereas changes at the genus level, which is For each pair of revisions, Sørensen’s (1948) generally considered less critical in a fl ora context, index of similarity was calculated (at species and was only given secondary attention. Already from genus level, respectively) as: ISS = [c / 0.5(A + B)] the beginning, it was my belief that the signals × 100%, where c is the number of taxon names from my case study could, to some extent, give an common to both revisions, whereas A and B are the impression of the scientifi c relevancy of repeated total numbers of taxon names recognized in the early revisions of other groups of vascular plants, not only and the late revision, respectively. In comparison in Thailand but also on a wider geographic scale. to Jaccard’s original index of similarity (ISJ = [c / (A + B - c)] × 100%), Sørensen’s index expresses METHODS the actually measured coinciding taxon occurrences against the maximally possible ones. As noted by The Thai representatives of the Orchidoideae Mueller-Dombois & Ellenberg (1974), this may be (as circumscribed by Pridgeon et al., 2001–2003), mathematically more satisfactory, as it includes a have been revised thrice. The fi rst revision was statistical probability term. In order to visualize the published in “The Orchids of Thailand: a relationships between the three revisions at species Preliminary List” (Seidenfaden & Smitinand, and genus level, respectively, two cluster analyses 1958–1964; the Orchidoideae were mainly treated employing the IS values were performed. The in part I from 1958, but a few emendations appeared S dendrograms were constructed in NTSYSpc 2.0 in part IV(2) from 1964). The second revision (Rohlf, 1998) by means of the unweighted pair- appeared in parts V and VI of “Orchid Genera in group method using arithmetic averages (UPGMA) Thailand” (Seidenfaden, 1977, 1978), and the third algorithm (Legendre & Legendre, 1983). revision was recently published in “Flora of Thailand” (Pedersen et al., 2011). In the present study, the fi rst and the second revision were compared at species RESULTS and genus level, as were the second and the third Changes at species level from fi rst to second revision – to map all changes according to the revision following categories: • Species or genera added from the early to From the fi rst to the second revision, nine the late revision. Additions include: taxa described species were described as new based on material as new based on material from Thailand; new from Thailand (Table 1), and additionally 43 species national records; taxa revived from the synonymy were added as new national records (Table 2). of other taxa occurring in Thailand. On the negative side, fi ve species were reduced • Species or genera excluded from the early to taxonomic synonyms of species names already to the late revision. Exclusions include: taxa applied to other material from Thailand (Table 3). reduced to heterotypic synonyms of names already Similarly, nine species that were accepted as applied to other material from Thailand; taxa that members of the Thai fl ora in the fi rst revision were were accepted as members of the Thai fl ora in the excluded in the second revision, as they were early revision, but excluded in the late revision, as considered to represent misidentifi cations (Table 4). they were considered to represent misidentifi cations. Finally, a number of neutral changes occurred • Changes neutral to the selection of Thai from the fi rst to the second revision. Thus, 16 species species or genera recognized in the early and the were recognized in both revisions, but under different late revision, but changing the names under which names. In 14 cases, the change of name refl ected a some of them are treated. Neutral changes include: change in taxonomic synonymy (Table 5), whereas nomenclatural corrections; emendations refl ecting in the other two cases it refl ected a change in adjustments in taxonomic synonymy (not involv- generic recognition or delimitation (Table 6). ing other taxa occurring in Thailand); emendations refl ecting adjustments in generic recognition or delimitation. SW 6585-P145-156-PC6.indd 146 7/11/2556 0:06:27 IS IT REALLY WORTHWHILE REVISING THE SAME FLORA REPEATEDLY? A CASE STUDY IN THAI ORCHIDACEAE (H. Æ. PEDERSEN) 147 Table. 1. Survey of species of Thai Orchidoideae added from one revision to the next, I. Species described as new based on material from Thailand. Species added from fi rst to second revision Cheirostylis didymacantha Seidenf. Cheirostylis thailandica Seidenf. Goodyera thailandica Seidenf. Habenaria falcatopetala Seidenf. Habenaria longitheca Seidenf. Habenaria thailandica Seidenf. Pecteilis sagarikii Seidenf. Peristylus kerrii Seidenf. Zeuxine grandis Seidenf. Species added from second to third revision Amitostigma thailandicum Seidenf. & Thaithong Brachycorythis neglecta H.A. Pedersen Corybas ecarinatus Anker & Seidenf. Habenaria anomalifl ora Kurzweil & Chantanaorr. Habenaria hastata Seidenf. Hetaeria armata Ormerod & H.A. Pedersen Hetaeria youngsayei Ormerod Peristylus carnosipetalus Kurzweil Peristylus phuwuaensis Kurzweil Peristylus rigidus Kurzweil Platanthera angustilabris Seidenf. Sirindhornia mirabilis H.A. Pedersen & Suksathan Sirindhornia pulchella H.A. Pedersen & Indham. Table 2. Survey of species of Thai Orchidoideae added from one revision to the next, II. Species added as new records for Thailand. Species added from fi rst to second revision Anoectochilus abbreviatus (Lindl.) Seidenf. Anoectochilus lanceolatus Lindl. Anoectochilus roxburghii (Wall.) Lindl. Cheirostylis spathulata J.J.Sm. Cheirostylis yunnanensis Rolfe Cystorchis aphylla Ridl. Dicerostylis lanceolata Blume Erythrodes blumei (Lindl.) Schltr. Erythrodes herpysmoides (King & Pantl.) Schltr. Goodyera fumata Thwaites Goodyera schlechtendaliana Rchb.f. Habenaria acuifera Wall. ex Lindl. Habenaria austrosinensis Tang & F.T.