Flora of Bokor National Park V: Two new species of Machilus (Lauraceae), M. bokorensis and M. brevipaniculata

Abstract Two new species, Machilus bokorensis Yahara & Tagane and Machilus brevipaniculata Yahara & Tagane (Lauraceae) are described from Bokor National Park, Cambodia with their illustrations and DNA barcodes of the two plastid regions of rbcL and matK and the nuclear region of ITS.


Introduction
Lauraceae is a large family containing 54 genera and 2500-3500 species distributed from tropical to temperate areas in the world (Rohwer 1993). In Southeast Asia, species of Lauraceae are found from lowlands to high elevations, and are often dominant components of tropical and subtropical evergreen forests. Th us, some eff orts have been made to elucidate species taxonomy of Lauraceae in Southeast Asia (e.g., Lecomte 1914;Liou 1934;Kostermans 1974Kostermans , 1988Kochummen 1989), including regional revisions for Beilschmiedia of Borneo (Nishida 2008), Cinnamomum of Borneo (Wuu-Kuang et al. 2011), Cryptocarya of Th ailand and Indochina (de Kok et al. 2015) and Litsea of Th ailand (Ngernsaengsuruay et al. 2011). However, no volumes on Lauraceae have been published in Flore du Cambodge du Laos et du Vietnam, Flora Malesiana, or Flora of Th ailand. Th us, species of Lauraceae still remain diffi cult to identify in many areas of Southeast Asia.
Th e genus Machilus Nees is a member of the monophyletic Persea group consisting of Alseodaphne Nees, Apollonias Nees, Dehaasia Blume, Machilus, Nothaphoebe Blume, Persea Mill., and Phoebe Nees (Rohwer et al. 2009;Li et al. 2011). Although Kostermans (1990) merged Machilus into Persea, recent molecular evidence showed that Persea of the New World may be polyphyletic and Machilus of Asia is well diff erentiated from the two clades including the majority of the Neotropical Persea species (Rohwer et al. 2009;Li et al. 2011). Machilus comprises about 100 species in tropical and subtropical S and SE Asia (Wei and van der Werff 2008 (Hô 1999), three species from Laos (Newman et al. 2007), eight species from Malaysia (treated as Persea, Kochummen 1989), and 82 species from China (Wei and van der Werff 2008). In Cambodia, only one species, Machilus odoratissima Nees, has been reported based on specimens (Lecomte 1914;Liou 1934;Phon 2000); three additional species, M. gamblei King ex Hook.f., M. salicina Hance, and M. velutina, were recorded from Cambodia in Flora of China (Wei and van der Werff 2008), but we could not fi nd any specimens supporting those records.
During our fi eld surveys of vascular plants in Bokor National Park, Kampot Province, Southern Cambodia conducted from 2011 to 2013, we collected fi ve species of the genus Machilus among which two fertile species which diff er from all known congeners.

Morphological observations
We have made morphological observations on the specimens that we had collected in Bokor National Park, Cambodia. We have surveyed the diagnostic features of all the known species in Cambodia and its neighboring regions by the means of a thorough literature review and by morphological observations of the dry specimens, kept in the herbaria BKF, BO, FU, HN, K, KYO, L, MBK, P, RAF, SAR and VNM and specimen images available on the web [e.g. JSTOR Global Plants (https://plants.jstor.org/)].

Machilus bokorensis
Ohter Preliminary conservation assessment. Machilus bokorensis is commonly found in higher elevations in Mt. Bokor. Since many mature individuals were found in the protected areas, we suggest the status for this species as Least Concern (LC) according to IUCN Red List criteria (IUCN 2012).
Note. Among fi ve species we collected in Mt. Bokor, this species is most common and agrees with the description of "M. odoratissima" in the key of Liou (1934) who recorded "M. odoratissima" from Nord de Kampot, corresponding to Mt. Bokor. Th us, we consider that this species is "M. odoratissima" recorded by Liou (1934), although we could not examine the specimen of Poilane 14625 (P) cited by Liou (1934) because it is currently on loan. In Indo-china, Machilus plants similar to this species have been identifi ed as M. odoratissima for a long time (Lecomte 1914;Liou 1934;Phon 2000). However, M. bokorensis is distinct from M. odoratissima distributed in Nepal, E Himalaya, Assam-Burma in sericeous infl orescence rachis (vs. glabrous in M. odoratissima; Pendry 2012), perianth lobes pubescent on both surfaces (vs. outside almost glabrous), ca. 1 mm staminodes (vs. ca. 2 mm), and blackish grey twigs (vs. reddish). In Cambodia, we collected sterile specimens of Machilus spp. morphologically similar to M. bokorensis in Central Cardamon and Seima protection forests but those are morphologically distinguishable and not sister to M. bokorensis in our unpublished phylogenetic tree constructed by rbcL, matK and ITS sequences. "M. odoratissima" is recorded from Mulu-prey, Preah Vihear (Lecomte 1914). Th e specimens from Mulu-prey (Harmand s.n., P) are, however, diff erent from M. bokorensis in having naked terminal buds and scalariform tertiary veins. Lecomte (1914) and Liou (1934) recorded "M. odoratissima" also from Laos and Vietnam, but we have not found specimens from Laos and Vietnam identical with M. odoratissima. As far as we know, M. odoratissima is not distributed in Cambodia, Laos, Th ailand and Vietnam. Th e relationship between M. bokorensis and the specimens of Mulu-prey, Laos and Vietnam remains to be further examined. At present, we consider that M. bokorensis is endemic to Bokor, Cambodia. According to our unpublished ITS tree, this species is sister to Machilus rimosa (Blume) Blume distributed in Indonesia, but distinct from M. rimosa in thickly leathery leaves densely foveolate on both sides (vs. thinner leaves not densely foveolate in M. rimosa) and perianths larger (6.8-7 mm long vs. ca. 3.5 mm long). Diagnosis. Similar to M. kingii Hook.f. in leaf shape and size, and short panicles less than 5.5 cm long, but distinct from M. kingii by its naked bud (vs. bud covered with scales in M. kingii), lamina foveolate on both surfaces (vs. obscure on lower surface), fewer fl owers per panicle (3-5 vs. 4-9), and smaller perianth lobes (2 mm vs. 3-3.5 mm long).
Distribution. Cambodia. Known only from the lowland of Bokor National Park. Habitat and ecology. Th is species was found in evergreen forest at the foot of Mt. Bokor. Flowering specimens were collected in December.
Preliminary conservation assessment. Critically endangered (CR) (IUCN 2012). We collected only one fl owering individual of this species at alt. 65 m during 7 fi eld surveys on the southern slope and top plateau of Mt. Bokor (Tagane et al. 2015). Further botanical inventories might enable us to fi nd more individuals, but it seems to be a rare species. Considering the fact that the forest is almost cleared in the foot of Mt. Bokor (below 100 m in particular), we believe that this species should be considered critically endangered.
Note. Th is species is distinct in having naked terminal buds and panicles having frondose bracts subtending secondary paniculate axes, while most of Machilus species have scaly terminal buds and panicles without frondose bracts. According to our unpublished ITS tree, this species is sister to Machilus coriacea A.Chev. endemic to southern Vietnam, but can be readily distinguished from the latter by the two above mentioned traits and also in having glabrous leaves (vs. densely hairy beneath when young in M. coriacea).