Chaowasku, T., A. Damthongdee, H. Jongsook, D.T. Ngo, H.T. Le, D.M. Tran & S. Suddee (2018). Enlarging the monotypic Monocarpieae (Annonaceae, Malmeoideae): recognition of a second genus from Vietnam informed by morphology and molecular phylogenetics. Candollea 73: 261–275. In English, English abstract. DOI: http://dx.doi.org/10.15553/c2018v732a11
Recent botanical expeditions in central Vietnam yielded an unknown species of Annonaceae that could not be confidently identified to subfamily, tribe, and genus. Preliminary BLAST® searches based on plastid data have suggested that this taxon is genetically closely-related to the following tribes of subfamily Malmeoideae: Malmeeae, Fenerivieae, Maasieae, Phoenicantheae, Dendrokingstonieae, Monocarpieae, and Miliuseae. Using representatives of Piptostigmateae, another tribe of Malmeoideae, as outgroups and including representatives of all other tribes of Malmeoideae, molecular phylogenetic analyses of seven combined plastid markers (rbcL, matK, ndhF, ycf1 exons; trnL intron; trnL-trnF, psbA-trnH intergenic spacers) inferred the enigmatic Vietnamese taxon as belonging to the monotypic tribe Monocarpieae. Detailed morphological comparisons between this taxon and its sister group, Monocarpia Miq., warranted the recognition of a second genus of Monocarpieae to accommodate our unknown taxon: Leoheo Chaowasku with a single species, Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le. The morphology of the new genus agrees well with the diagnostic traits of Monocarpieae, e.g., a percurrent tertiary venation of the leaves, a highly reduced number of carpels per flower, enlarged and lobed stigmas, multiple ovules/seeds per ovary/monocarp, considerably large monocarps with a hardened pericarp when dry, and spiniform ruminations of the endosperm. However, the new genus does not exhibit two characteristic features of Monocarpia: terminal inflorescences and generally distinct intramarginal leaf veins. In addition, the new genus possesses three autapomorphic characters: hairy domatia on the lower leaf surface, longitudinal ridges on the monocarp surface, and subsessile monocarps with a stout stipe. The tribe Monocarpieae is consequently enlarged to include the genus Leoheo. The enlarged Monocarpieae, along with the recently established monotypic tribe Phoenicantheae and two other related tribes, Dendrokingstonieae and Miliuseae, are discussed.
Received: November 4, 2017. Accepted: August 30, 2018. First published online: November 23, 2018.
Introduction
Annonaceae, a pantropical angiosperm family characteristic of lowland rainforests (e.g. Slik et al., 2003), comprise c. 2400 species classified in 109 genera (Guo et al., 2017; Chaowasku et al., 2018; Xue et al., 2018). A new classification has been recently proposed, subdividing the family into four subfamilies, viz., Anaxagoreoideae, Ambavioideae, Annonoideae, and Malmeoideae; with the last two subfamilies constituting the majority of generic and species diversity (Chatrou et al., 2012). Similar to the realigned subfamilies, tribal delimitations within Annonoideae and Malmeoideae have also been reconsidered. Malmeoideae have been classified into seven tribes, viz. Piptostigmateae, Malmeeae, Fenerivieae, Maasieae, Dendrokingstonieae, Monocarpieae, and Miliuseae. It is worthwhile to note that four (Fenerivieae, Maasieae, Dendrokingstonieae, and Monocarpieae) of the seven tribes are monotypic (Chatrou et al., 2012).
The evolutionary relationships within Malmeoideae are still poorly resolved, requiring further inclusion of DNA regions suitable to resolve deeper relationships. There is, however, one strongly supported clade composed predominantly of Asian-Pacific species, i.e. a clade of Dendrokingstonieae-Monocarpieae-Miliuseae (Chaowasku et al., 2014). Later Phoenicantheae, an additional monotypic tribe of Malmeoideae, has been proposed to accommodate the Sri Lankan endemic genus Phoenicanthus Alston formerly placed in Miliuseae because this genus has been shown to recover as the sister group of the Dendrokingstonieae-Monocarpieae-Miliuseae clade (Guo et al., 2017).
Recent field trips in central Vietnam (in Nam Đông and A Luoi Distr. of Thua Thien-Hue Prov.) resulted in the discovery of an unknown Annonaceae. This taxon is unique in possessing hairy domatia on the lower leaf surface, which is a rare character present only in a limited number of taxa in this family (Chaowasku et al., 2012a). Its percurrent tertiary venation of the leaves, reduced carpel number per flower, enlarged and lobed stigmas, and massive monocarps with a thick and hardened pericarp when dry point this taxon to be morphologically related to Dendrokingstonieae and Monocarpieae, two monotypic tribes of Malmeoideae (or the canangoid clade of subfamily Ambavioideae; Chaowasku et al., 2012b). The aims of this study are to (1) elucidate the phylogenetic position of the unknown Annonaceae from Vietnam and (2) determine its taxonomic status by detailed morphological investigations and comparisons with its phylogenetically most closely related taxa.
Material and methods
Taxon and character sampling
Twenty-four accessions comprise the ingroup, with representatives covering all currently accepted tribes of Malmeoideae except Piptostigmateae, viz. Malmeeae (3 accessions), Fenerivieae (1 accession), Maasieae (1 accession), Phoenicantheae (1 accession), Dendrokingstonieae (3 accessions), Monocarpieae (3 accessions), and Miliuseae (10 accessions). These tribes have been recently demonstrated to retrieve as a strongly supported monophyletic group (Guo et al., 2017; Xue et al., 2018). Two accessions of the unknown taxon from Vietnam collected in the same vicinity (Nam Đông Distr.: Chaowasku 129, CMUB; Chaowasku 165, CMUB) were included. Two species (Mwasumbia alba Couvreur & D.M. Johnson and Brieya fasciculata De Wild.) belonging to the tribe Piptostigmateae were assigned as outgroups. The above strategy of taxon sampling was adopted because preliminary nucleotide searches via BLAST® suggested that sequences of the unknown taxon from Vietnam were most similar to those of various species in several related tribes of Malmeoideae except Piptostigmateae, i.e. at least the first 80 sequences retrieved according to the E-value upon the BLAST® searches belonged to Malmeeae, Fenerivieae, Maasieae, Dendrokingstonieae, Monocarpieae, or Miliuseae; with a member of Monocarpieae retrieved as the first sequence in four of the seven plastid DNA markers selected. Every accession has sequences of six plastid DNA regions (rbcL, matK, ndhF exons; trnL intron; trnL-trnF, psbA-trnH intergenic spacers). Twenty-two of the 24 accessions of the ingroup have been sequenced for an additional plastid DNA region (ycf1 exon), but at least one species per tribe are represented by the ycf1 sequence. Previously published sequences were obtained from the following publications: Mols et al. (2004a, 2004b), Pirie et al. (2006, 2007), Su et al. (2008), Couvreur et al. (2009), Chaowasku et al. (2012a, 2013a, 2014, 2018), and Chatrou et al. (2012). Thirty-three sequences were newly generated in the present study. All information regarding voucher specimens and GenBank accession numbers are shown in Appendix I.
In total, 6975 nucleotide plus 10 indel characters were included. The simple method of Simmons & Ochoterena (2000) for indel coding was followed. More indel structures were observed in the aligned data matrix, but only the less homoplasious and non-autapomorphic ones were chosen. An inversion of 15-nucleotide stretch in the psbA-trnH intergenic spacer is present in roughly 40% of the accessions sequenced and was changed to its reverse-complement to be homologically comparable to the remaining sequences, following Pirie et al. (2006).
DNA extraction, amplification, and sequencing
DNA extraction was performed using the GF-1 Plant DNA extraction kit (Vivantis). A standard PCR protocol was followed throughout using the 5× Hot FirePol® Blend Master Mix with 10 mM MgCl2 (Solis BioDyne).The final reaction volume of 10 µl (1X) contained 0.2 µl of each primer (10 µM), 2 µl of 5× Hot FirePol® Blend Master Mix, and 1 µl of template DNA (average final DNA concentration = c. 5 ng/µl). The PCR programs used consist of 35 cycles, each with 95°C: 40 seconds, 53°C–65°C: 50 seconds (optimum annealing temperature depends on each primer pair; sometimes a touchdown approach was implemented by setting the initial annealing temperature at 65°C or 60°C, then decreasing the annealing temperature by 0.5°C every cycle until reaching 57°C or 53°C, respectively, and then continuing with these temperatures until the 35th cycle), 72°C: 1 min 20 seconds, with the initial denaturation for 15 min at 95°C and the final extension for 7.5 min at 72°C. The primer sequences for amplifying and sequencing all seven plastid regions were the same as those used in Chaowasku et al. (2012a). Amplicons were cleaned by the GF-1 AmbiClean kit (Vivantis), and then sequenced using the BigDye® Terminator v3.1 cycle sequencing kit chemistry (ThermoFisher Scientific).
Phylogenetic analyses
Sequences were edited using the Staden package [ http://staden.sourceforge.net] (Staden et al., 2000) and subsequently aligned by Multiple Sequence Comparison by Log-Expectation (MUSCLE; Edgar, 2004) in MEGA7 (Kumar et al., 2016). The alignment was then manually checked and re-aligned (if necessary) on the basis of homology assessment using the similarity criterion (Simmons, 2004). Parsimony analysis was performed in TNT v1.5 (Goloboff & Catalano, 2016). All characters were equally weighted and unordered. Incongruence among regions was evaluated by analyzing each region individually, to see if there was any significant conflict in clade support (Seelanan et al., 1997; Wiens, 1998). Multiple most parsimonious trees were generated by a heuristic search of the combined data, with 9000 replicates of random sequence addition, saving 10 trees per replicate, and using the tree bisection and reconnection (TBR) branch-swapping algorithm. Clade support was measured by symmetric resampling (SR), which is not affected by a distortion associated with some bootstrap and jackknife resampling analyses (Goloboff et al., 2003). A default change probability was used. Two hundred thousand replicates were run, each with four replicates of random sequence addition, saving four trees per replicate. A clade with SR ≥ 85%, 70–84%, or 50–69% was considered strongly, moderately, or weakly supported, respectively.
Maximum likelihood analysis was performed in IQ-TREE v1.6.1 (Nguyen et al., 2015) under partition models (Chernomor et al., 2016) implemented with the “-spp” command, whereas Bayesian Markov chain Monte Carlo (MCMC; Yang & Rannala, 1997) phylogenetic analysis was performed in MrBayes v3.2.3 (Ronquist et al., 2012) via the CIPRES Science Gateway v3.1 (Miller et al., 2010). The data matrix was divided into seven partitions based on DNA region identity (the trnL intron and the adjacent trnL-trnF spacer were combined as a single partition) plus a binary indel-coded partition. The most appropriate model of sequence evolution for each DNA partition was selected by Akaike Information Criterion (AIC; Akaike, 1974) scores, using FindModel [ http://www.hiv.lanl.gov/content/sequence/findmodel/findmodel.html] (Posada & Crandall, 1998). The General Time Reversible (GTR; Tavaré, 1986) nucleotide substitution model with a gamma distribution for among-site rate variation was selected for four partitions (rbcL, matK, ndhF, and ycf1), and the Hasegawa-Kishino-Yano (HKY; Hasegawa et al., 1985) substitution model with a gamma distribution for among-site rate variation was selected for the remaining two partitions (trnLF [= trnL intron + trnL-trnF intergenic spacer] and psbA-trnH).
In the maximum likelihood analysis, the model “JC2+FQ+ASC” was chosen by corrected AIC scores for the binary indel partition. Clade support was assessed by nonparametric bootstrap resampling method (BS; Felsenstein, 1985) with 2000 replicates. Similar to the discrimination of the SR values in the parsimony analysis, a clade with BS ≥ 85%, 70–84%, or 50–69% was considered strongly, moderately, or weakly supported, respectively.
In the Bayesian analysis, the “coding=variable” setting was selected for the binary indel partition, which was implemented with a simple F81-like model without a gamma distribution for among-site rate variation. Three independent analyses, each using four MCMC chains, were simultaneously run; each run was set for 10 million generations. The default prior settings were used except for the prior parameter of rate multiplier (“ratepr” [=variable]). The temperature parameter was set to 0.08. Trees and all parameter values were sampled every 1000th generation. Convergence was evaluated by checking the standard deviation of split frequencies of the runs with values < 0.01 interpreted as indicating a good convergence and by checking for adequate effective sample sizes (ESS > 200) using Tracer v1.6 (Rambaut et al., 2013). The initial 25% of all trees sampled were discarded as burn-in, and the 50% majorityrule consensus tree was generated from the remaining trees. A clade with posterior probabilities (PP) ≥ 0.95, 0.9–0.94, or 0.5–0.89 was considered strongly supported, weakly supported, or unsupported, respectively.
Morphology
The macromorphology of the unknown Annonaceae from Vietnam was studied from six herbarium specimens (dried and pickled material: HUAF collectors 2009-03-19-ND; Chaowasku 129, 130, 131, 165, 166; see below for more details). The relevant morphological information of related taxa were taken from literature (Huber, 1985; van Heusden, 1992; Kessler, 1993; Mols & Kessler, 2000a, 2000b, 2003; Mols et al., 2004a; Chaowasku et al., 2012b, 2013b, 2014; Turner, 2012) or derived from herbarium specimens for Phoenicanthus obliquus (Hook. f. & Thomson) Alston [Huber 515, 540, 565 (E); Huber 518, 577 (L)]. The indumentum terminology used follows Hewson (1988).
Results
The parsimony analysis resulted in eleven most parsimonious trees with 1302 steps. The consistency and retention indices (CI and RI) were 0.83 and 0.77, respectively. There was no strong topological conflict (SR ≥ 85%) in the analysis of each DNA region. Fig. 1 shows the Bayesian 50% majority-rule consensus tree, with posterior probabilities, maximum likelihood bootstrap values, and parsimony symmetric resampling values indicated.
The ingroup, comprising Malmeeae, Fenerivieae, Maasieae, Phoenicantheae, Dendrokingstonieae, Monocarpieae, and Miliuseae, was recovered as a maximally supported clade. The two accessions of the unknown taxon from Vietnam were retrieved as a maximally supported clade sister to another maximally supported clade consisting of three accessions in the genus Monocarpia. In the latter clade, M. euneura Miq. is the sister group of a strongly supported clade (PP 1, BS 100%, SR 99%) composed of two accessions of M. maingayi (Hook. f. & Thomson) I.M. Turner. Both Monocarpia and the unknown taxon from Vietnam constitute a strongly supported Monocarpieae clade (MON.; PP 1, BS 100%, SR 99%).The Monocarpieae clade is weakly to strongly supported (PP 0.98, BS < 60%, SR < 59%) as the sister group of an unsupported clade (PP 0.78, BS < 50%, SR < 50%) comprising the maximally supported Dendrokingstonieae (DEN.) and Miliuseae (MIL.) clades. A clade of Monocarpieae-Dendrokingstonieae-Miliuseae is the sister group of the Phoenicantheae lineage with strong support (PP 1, BS 100%, SR 99%). The Phoenicantheae-Monocarpieae-Dendrokingstonieae-Miliuseae clade then is the sister group of an unsupported clade (PP 0.53, BS < 50%, SR < 50%) consisting of a weakly to strongly supported Malmeeae clade (MAL.; PP 1, BS 68%, SR 57%) and a moderately to strongly supported clade (PP 0.95, BS 76%, SR 85%) composed of Fenerivieae and Maasieae lineages.
Discussion
Phylogenetic analyses strongly support the belonging of the unknown Vietnamese Annonaceae to Monocarpieae, sister to genus Monocarpia (Fig. 1). However, this taxon morphologically deviates from Monocarpia by two main features: 1) an absence of intramarginal leaf veins (Fig. 2C) and 2) axillary inflorescences (Fig. 3A). The intramarginal leaf veins (Fig. 2A) and terminal inflorescences (Fig. 3B) have been regarded as reliable diagnostic traits for Monocarpia (Turner, 2012). The absence of these features in the unknown taxon from Vietnam warrants its recognition as a distinct genus of Monocarpieae. In each Annonaceae genus, both terminal and axillary inflorescences seldom coexist (Koek-Noorman et al., 1990), e.g. in Miliusa Lesch. ex A. DC. (Chaowasku et al., 2013a) and Pseuduvaria Miq. (Saunders et al., 2004; Su et al., 2010), and either state has been previously shown to constitute a good character for generic delimitations (Chatrou et al., 2000).
Besides the above-mentioned crucial morphological differences, the unknown taxon from Vietnam exhibits longitudinal ridges on the monocarp surface (Fig. 2D), as well as domatia on the lower leaf surface, each composed of a tuft of aggregated hairs (Fig. 4A). These two characters have never been reported to occur in Monocarpia (Mols & Kessler, 2000b; Turner, 2012; Fig. 2B, 4B). Further, the monocarps of the unknown taxon from Vietnam are subsessile with a stout stipe (Fig. 2D), while those of Monocarpia are completely sessile (Fig. 2B; Mols & Kessler, 2000b; Turner, 2012). Other features of the Vietnamese new genus fit well with the diagnostic traits of Monocarpieae (van Heusden, 1992; Mols & Kessler, 2000b; Chaowasku et al., 2012b; Chatrou et al., 2012): enlarged stigmas (more or less peltate and lobed; Fig. 2H, 5J), a percurrent tertiary venation of the leaves (Fig. 2C, 6), a reduced carpel number to 3–4 per flower (Fig. 5A), multiple ovules per ovary (and hence seeds per monocarp) arranged in two rows, relatively large monocarps with a thick and hardened wall when dry (Fig. 2D, 5K), and spiniform endosperm ruminations (Fig. 5N). The tribe Monocarpieae is, therefore, enlarged to include the new genus from Vietnam.
Taxonomy
Leoheo Chaowasku, gen. nov.
Typus: Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le.
Medium-sized to large trees; indumentum of simple hairs; intramarginal leaf veins absent, tertiary leaf venation percurrent; inflorescences 1- or few-flowered, axillary; bracts present; flowers bisexual, both petal whorls of ± equal size; stamens 70–76, connective truncate and dilated, covering thecae; carpels 3–4 per flower, free in flower and fruit; stigmas ± peltate and lobed; ovules many and arranged in two rows, placentation lateral; monocarps subsessile, cylindrical, monocarp abscission basal, pericarp thick and hardened when dry; aril absent; endosperm ruminations spiniform.
Etymology. – The generic epithet Leoheo is from the local Vietnamese name of “Lèo Heo” for this plant and is designated as a masculine noun of nominative singular in third declension with genitive singular “Leoheonis”.
Notes. – The principal morphological differences between Leoheo and Monocarpia are highlighted in Table 1. Furthermore, in view of molecular phylogenetics, the genera Leoheo and Monocarpia each is characterizable not only by nucleotide substitutions, but also by an indel structure in the psbA-trnH intergenic spacer for Leoheo and another indel structure in the trnL-trnF intergenic spacer for Monocarpia. Although the other two species of Monocarpia, M. borneensis Mols & Kessler and M. kalimantanensis Kessler, have not been included in the present molecular phylogenetic analyses due to the failure in DNA amplification, their morphologies (e.g. Fig. 2A, 3B) substantially coincide with those of M. euneura Miq. and M. maingayi (Hook. f. & Thomson) I.M. Turner (Fig. 2B; Turner, 2012), hence we are convinced that such two missing species (both or any of them) will not retrieve as the sister group of Leoheo or the Leoheo-Monocarpia clade.
It is noteworthy that each of the axillary inflorescences of the genus Leoheo often contains leaf-like bract(s) at the top of peduncle (Fig. 3A, 6), probably this feature is a transition to the terminal inflorescences characteristic for the genus Monocarpia (Fig. 3B). The presence of domatia on the lower leaf surface is a rare phenomenon in Annonaceae. It occurs only in a limited number of genera and species, for examples, Annona L. (van den Bos et al., 1989), Dendrokingstonia Rauschert (Chaowasku et al., 2012b), Huberantha Chaowasku (Chaowasku et al., 2012a), Mitrephora (Blume) Hook. f. & Thomson (Weerasooriya & Saunders, 2010), and Tridimeris Baill. (Ortiz-Rodriguez et al., 2016). Of these genera, the hairy type of domatium similar to that of Leoheo (Fig. 4A) can be found in Annona, Huberantha, and Mitrephora (Chaowasku et al., 2012a).
The well-supported sister relationship of Fenerivieae and Maasieae is reported herein for the first time (Fig. 1). The two tribes share a number of features, e.g., axillary inflorescences, generally one ovule per ovary, and spiniform endosperm ruminations (Mols et al., 2008; Saunders et al., 2011). Their possible closest relationships were previously discussed (Schatz & Le Thomas, 1990; Saunders et al., 2011).
The tribes Phoenicantheae, Monocarpieae, Dendrokingstonieae, and Miliuseae constitute a strongly supported clade substantially composed of Asian-Pacific species. The fact that the Sri Lankan endemic tribe Phoenicantheae is the sister group of the remainder of this clade coupled with the restricted distribution of the tribes Monocarpieae and Dendrokingstonieae might have some biogeographic implication, especially on the geographic origin of Miliuseae, the most diverse tribe of Malmeoideae (Chatrou et al., 2012), but it is currently not possible to perform an in-depth biogeographic analysis because there are still unignorable phylogenetic uncertainties, especially the unsupported sister relationships of Dendrokingstonieae and Miliuseae, as well as of Malmeeae and a clade composed of Fenerivieae and Maasieae (Fig. 1). So far, no macromorphological features have yet been found to be synapomorphic for the Phoenicantheae-Monocarpieae-Dendrokingstonieae-Miliuseae clade. Nevertheless, some palynological correlations have been observed, i.e., any taxa of Malmeoideae recovered outside Miliuseae possess monosulcate pollen (Chaowasku et al., 2012b, 2014). Currently the pollen data of Phoenicanthus and Leoheo are unavailable, but they are anticipated to exhibit monosulcate pollen based on such correlations. In addition, it is worthwhile to note that Phoenicantheae, Monocarpieae, and Dendrokingstonieae all possess a highly reduced carpel number to 1–4 per flower (Huber, 1985; Chaowasku et al., 2012b). It is likely that the reduction in carpel number per flower is the ancestral trait of the Phoenicantheae-Monocarpieae-Dendrokingstonieae-Miliuseae clade. Table 2 compares the important macromorphological and pollen morphological characters of the amended Monocarpieae and the other three closely related tribes: Phoenicantheae, Dendrokingstonieae, and Miliuseae.
Monocarpia, the sister group of Leoheo, occurs in southern Thailand, Peninsular Malaysia, Sumatra, and Borneo (Turner, 2012); the shortest distance of the two genera is about 1300 km away. This disjunct distribution pattern is, however, not unprecedented. In Phaeanthus Hook. f. & Thomson (Malmeoideae, Miliuseae; Chatrou et al., 2012), P. vietnamensis Bân is the only species occurring in Indochinese Peninsula; the remaining species occur in southern Thailand Provinces bordering Malaysia (Gardner et al., 2015), Malay Peninsula to the Philippines and New Guinea (Mols & Kessler, 2000a). In Neo-uvaria Airy Shaw (Malmeoideae, Miliuseae; Chatrou et al., 2012), the recently described N. laosensis Tagane & Soulad. hitherto endemic to central Laos (Tagane et al., 2018) is the only species disjunctly occurring north of Peninsular Thailand and Malaysia, the nearest area where three other species of Neouvaria can be found (Chaowasku et al., 2011). Additionally, in Disepalum Hook. f. (Annonoideae, Annoneae; Chatrou et al., 2012) subg. Enicosanthellum (Bân) P.S. Li, D.C. Thomas & R.M.K. Saunders, a clade composed of two particular species: D.petelotii (Merr.) D.M. Johnson and D. plagioneurum (Diels) D.M. Johnson, both occurring in China and Vietnam (and Laos for the former; Johnson, 1989) is the sister group of D. pulchrum (King) J. Sinclair (Li et al., 2015, 2017) which can only be found in southern Thailand Provinces bordering Malaysia (Chamchumroon et al., 2017) and Malay Peninsula (Johnson, 1989). It is interesting to understand the plausible biogeographic scenarios and other biotic/abiotic factors shaping the mentioned disjunct distribution pattern within Southeast Asia.
Fig. 1.
50% majority-rule consensus phylogram derived from Bayesian inference of combined seven plastid DNA regions. Bayesian posterior probabilities (PP) indicated on the right; maximum likelihood bootstrap (BS) percentages in the middle; parsimony symmetric resampling (SR) percentages on the left [** denotes BS/SR < 50%]. DEN. = Dendrokingstonieae; MAL. = Malmeeae; MIL. = Miliuseae; MON. = Monocarpieae; PIP. = Piptostigmateae. Scale bar unit = substitutions per site.
Table 1.
Principal morphological differences between Leoheo Chaowasku and Monocarpia Miq.
Fig. 2.
A. Leaf of Monocarpia kalimantanensis Kessler, showing conspicuous intramarginal veins; B. Fruit of Monocarpia maingayi (Hook. f. & Thomson) I.M. Turner, showing monocarps without longitudinal ridges; C-H: Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le; C. Leaf without intramarginal veins; D. Fruit, showing monocarps with longitudinal ridges; E. Flowering branches; F. Dissected flower and young fruit; G. Dissected flower, showing detached stamens and stigmas; H. Flower, showing enlarged and irregularly lobed stigmas. [A: Sidiyasa et al. 3469, L; B: Gardner & Sidisunthorn ST0541a, L; C-D: Chaowasku 131, CMUB; E-H: HUAF collectors 2009-03-19-ND, CMUB] [Photos: A: Arbainsyah; B: S. Gardner & P. Sidisunthorn; C-H: D.T. Ngo]
Table 2.
Comparisons of important macromorphological and pollen morphological features of four closely related tribes in Malmeoideae.
Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le, spec. nova (Fig. 2C–H, 3A, 4A, 5–7).
Holotypus: Vietnam. Prov. Thua Thien-Hue: Nam Đông Distr., 19.III.2009, fl., HUAF collectors 2009-03-19-ND (CMUB!; iso-: G!, P!).
Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le differs from species of the genus Monocarpia Miq. by the lack of intramarginal leaf veins and by having axillary inflorescences, leaf domatia, longitudinal ridges on the monocarp surface, and subsessile monocarps with a stout stipe.
Medium-sized (to large) trees, 15–25(–30) m tall; young twigs puberulous with appressed hairs. Petiole 5–8 mm long, grooved on upper surface, both sides puberulous with appressed hairs; leaf blade elliptic, 9.1–22.8 × 3.1–6.5 cm, both surfaces glabrous, base cuneate, apex caudate-acuminate; midrib raised and puberulous with appressed hairs on lower surface, sunken (becoming less so toward apex) and puberulous with appressed and erect hairs (more sparsely so toward apex) on upper surface; secondary veins 11–12 per side, angle with midrib at middle part of leaf blade 40°–50°. Flower(s) in a 1- to 2-flowered axillary inflorescence, bisexual; peduncle 7–10 mm long (up to 17 mm long and 6–8 mm thick in fruit), indumentum puberulous-tomentose with erect hairs, bract(s) often leaf-like, placed at top of peduncle, often caducous; pedicel 2–2.5 cm long (6–7 mm thick in fruit), tomentose with erect hairs, bracts ovate, generally 2 per pedicel, one placed at ± midpoint of pedicel, another near pedicel base, often caducous. Sepals triangular-ovate, 8–11 × 7–8 mm, both surfaces and margin tomentose with erect hairs. Outer petals obovate, 5.8–6.2 × 1.8–2.1 cm, both surfaces and margin puberuloustomentose with erect hairs, apex obtuse-rounded; inner petals elliptic-obovate, 5.9–6.1 × 2–2.3 cm, indumentum similar to that of outer petals, apex obtuse. Torus volcano-shaped with a slightly sunken apex, glabrous. Stamens 70–76 per flower, c. 2 mm long, connective truncate, covering thecae. Carpels 3–4 per flower, 4.5–6 mm long; stigmas ± peltate and irregularly lobed (5–6 lobes); ovaries villous with appressed hairs; ovules 15–17 per ovary, lateral, biseriate. Monocarp(s) 1–4 per fruit, subsessile (with a stout stipe), cylindrical, 5.5–7.5 × 3–3.5 cm, pericarp c. 3 mm thick, hardened when dry, surface shallowly coarsely rugose-verrucose with 7–8 longitudinal ridges (some ridges running to only midpoint of monocarps, whereas some forming loops with others), indumentum short-tomentose (often more sparsely so or almost glabrous on ridges), apex not apiculate. Seeds 9–17 per monocarp, flattened-ellipsoid to flattened-ovoid, 1.7–2.1 × 1–1.2 cm, more flattened for in-between seeds, surface pitted and slightly rugose, raphe slightly raised with a slight groove in the middle, endosperm ruminations spiniform.
Etymology. – The specific epithet domatiophorus is a masculine adjective in first and second declensions, referring to “domatia” on the lower leaf surface.
Habitat and phenology. – Occurring in (edges of) evergreen forests, disturbed evergreen forests, or edges of secondary forests adjacent to the primary ones; on a steep hillside or near a stream at 270–350 m. Flowering material collected in March. Fruiting material collected in July.
Conservation status. – Leoheo domatiophorus grows in lowland rainforests of Nam Đông (where part of Bach Ma National Park is located) and A Luoi Districts of Thua Thien-Hue Province (Fig. 7), and has also been observed in the adjacent Quang Tri and Quang Nam Provinces as well. This habitat has been continuously destroyed for Acacia Mill. cultivation and other kinds of deforesting land use. Furthermore, only a small part of the habitat of L. domatiophorus is protected in the Bach Ma National Park. Due to its restricted range in threatened lowland rainforests of central Vietnam, the new species qualifies as “Vulnerable” [VU B2ab(iii)] using the IUCN Red List Categories and Criteria (IUCN, 2012).
Paratypi. – Vietnam. Prov. Thua Thien-Hue: Nam Đông Distr., 16°08′N 107°37′E, VII.2014, ster., Chaowasku 129 (CMUB); A Luoi Distr., 16 01′N 107°31′E, VII.2014, ster., Chaowasku 130 (CMUB); ibid. loco, VII.2014, fr., Chaowasku 131 (CMUB); Nam Đông Dister., 16°08′N 107°37′E, VII.2016, fr., Chaowasku 165 (CMUB); ibid. loco, VII.2016, ster., Chaowasku 166 (CMUB).
Fig. 3.
Inflorescence position of Leoheo Chaowasku (A) and Monocarpia Miq. (B). A. Axillary inflorescences/infructescences of Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le; B. Terminal inflorescence of Monocarpia kalimantanensis Kessler. [A: HUAF collectors 2009-03-19-ND, CMUB; B: Sidiyasa et al. 3469, L] [Photos: A: D.T. Ngo; B: Arbainsyah]
Fig. 4.
Lower leaf surface of Leoheo Chaowasku (A) and Monocarpia Miq. (B). A. Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le, with a hairy domatium; B. Monocarpia maingayi (Hook. f. & Thomson) I.M. Turner, without domatia. [A: Chaowasku 131, CMUB; B: Promchua 18, CMUB]
Fig. 5.
Reproductive organs of Leoheo domatiophorus Chaowasku, D.T. Ngo & H.T. Le: A. Flower with petals and stamens removed; B. Flower with petals, stamens, and carpels removed, back view, showing outer side of sepals; C. Same as (B), but on another side, showing a volcano-shaped torus and inner side of sepals; D. Inner side of an outer petal; E. Outer side of an outer petal; F. Inner side of an inner petal; G. Outer side of an inner petal; H. Stamen, abaxial side; I. Stamen, adaxial side; J. Carpels, showing enlarged and irregularly lobed stigmas; K. Fruit, showing longitudinal ridges on monocarp surface; L. Seed, lateral view, showing a raphe; M. Seed, lateral view, showing a pitted and slightly rugose surface; N. Cross section of a seed, showing spiniform endosperm ruminations. [A-J: HUAF collectors 2009-03-19-ND, CMUB; K: Chaowasku 131, CMUB; L-N: Chaowasku 165, CMUB] [Drawing: A. Damthongdee]
Acknowledgements
The first author would like to thank the Thailand Research Fund (TRG5880118) and IAPT Research Grants Program in Plant Systematics 2013 for financial support. Directors and curators of Edinburgh (E) and Leiden (L) herbaria kindly permitted the first author to study their material. Prapanth Iamwiriyakul is gratefully acknowledged for his invaluable advices on nomenclature of the new taxa. Daniel C. Thomas and Sven Buerki provided many useful comments and suggestions for the improvement of an earlier draft of this article. Arbainsyah, Simon Gardner, and Pindar Sidisunthorn kindly allowed us to use their beautiful photographs.
