Notes on the taxonomy and distribution of two endemic and threatened dipterocarp trees from the Western Ghats of Kerala , India

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2 6 D e c em b e r 2 0 1 7 | V o l . 9 | N o . 1 2 | P p . 1 1 0 3 3 -1 1 0 3 9 1 0 . 1 1 6 0 9 / j o tt . 3 6 2 8 . 9 . 1 2 . 1 1 0 3 3 -1 1 0 3 9 T h r e a tt e n e d T a x a The genus Hopea Roxb., one of the economically and ecologically dominant genera, belongs to the family Dipterocarpaceae and comprises around 102 species mostly of Indo-malayan in distribution (Mabberley 2008). The genus is widely used in timber and plywood industries, construction purposes include planking, floor boards, shipbuilding, masts and spars, dug-outs and heavy packing cases (Pearson & Brown 1932). The hard solid resin, commonly called rock dammar, derived from Hopea species is used as varnish and anti-corrosive coating in boat making and handicrafts (Shiva & Jantan 1998). In India, the genus is represented by 11 species distributed in evergreen forests of the Western Ghats and northeastern India (Janardhanan 1993). Nine species have been reported from the Western Ghats (Nayar et al. 2014) of which seven are highly threatened and endemic to Kerala (Sasidharan 2004). The level of endemism suggests the Western Ghats as one of the centres for evolution and diversification of Hopea. The narrow endemic Hopea canarensis Hole was relocated from some patch of Kudremukh region after a lapse of about 80 years (Ravikumar & Goraya 1999) and is also reported from Bhagavathi Valley region of Karnataka (Kumar & Kaveriappa 1999). Similarly, Hopea jacobi C.E.C. Fisch. has not been collected from its type locality or any other place in the recent past. Hence, this species is presumed to be extinct (Shetty et al. 2002), whereas other species like Hopea parviflora Bedd. and Hopea ponga (Dennst.) Mabb. are widely distributed in the southern part of the Western Ghats (Pascal 1988). Hopea glabra and Hopea utilis are two little known highly threatened dipterocarp trees found in evergreen forests of the Western Ghats. Earlier herbarium Abstract: Hopea glabra Wight & Arn. and Hopea utilis (Bedd.) Bole are two little-known highly threatened endemic dipterocarps distributed in evergreen forests of the Western Ghats. Although literature surveys and herbarium records show occurrence of these species in different forest areas of Kerala, the present study could locate Hopea glabra from the Silent Valley National Park and Hopea utilis from Shankili forests in Kulathupuza range, enabling the portrayal of current distribution, basic ecology covering phenology, species association, regeneration and conservation status along with taxonomic notes.
Keywords: Conservation, Dipterocarpaceae, evergreen forest, Hopea glabra, H. utilis, threatened species. collection records and literature surveys indicate that these two species occur only in the southern part of the Western Ghats and in the present study the current distribution, basic ecology and conservation status along with taxonomic notes are provided.

Material and Methods
Frequent field surveys were carried out during the period from 2013-2016 in Kerala part of the Western Ghats and specimens of Hopea glabra and Hopea utilis were collected, identified using relevant literature (Gamble 1915;Saldanha 1984;Janardhanan 1993;Sasidharan 2004) and also compared with specimens from different herbaria (BSI, CALI, DD, E, FRLH, HIFP, K, MH). All voucher specimens are deposited in the herbarium of the Kerala Forest Research Institute (KFRI).

Results and Discussion
The descriptions of the species with notes on their distribution, phenology, ecological aspects, details of specimens examined and conservation status along with colour photographs to facilitate accurate identification are given below.
Flowering: January-March Fruiting: April-July Distribution: Endemic to the Western Ghats; herbarium records show that the species is distributed in Trannikudy areas in Idukki, backwaters of Kollam, Thannithode in Pathanamthitta and Silent Valley dam site. In the present survey, however, we could collect this species only from the dam site in Silent Valley National Park.
Ecology: This species is growing mainly along the sides of streams in evergreen forests at an altitude of 900m and the associated species are mainly Hydnocarpus pentandra (Buch.   (Saldanha 1984;Janardhanan 1993). Anilkumar et al. (2005) in the flora of Pathanamthitta mentioned its distribution in Thannithode area, but we couldn't locate the same from that particular locality. Only a few trees were found along the riverside of Kunthipuzha, near the dam site. This species is treated as an unresolved name in the Plant list (www.plantlist.org) and but Hopea glabra Wight & Arn. is a well resolved species, closely related to Hopea canarensis and Hopea racophloea according to matK and trnL-trnF intergenic spacer DNA sequence data (Sanil et al. in preparation). This species differs from Hopea racophloea in the larger number of veins and the absence of domatia, glabrous calyx lobes and reduced fruit wings, and from Hopea canarensis by their reduced leaf size, acute leaf base, absence of domatia and reduced fruit wings. (Image 2; Fig. 2 A medium-sized tree with a straight clear bole of 16-30 m and a girth of 1.3-1.9 m. Bark smooth, pale brown, often with greyish patches; young shoots pubescent, branches and branchlets terete. Leaves 11.5-17.5 x 3-5 cm, simple, alternate, linear-lanceolate, rounded or acutely attenuate at base, obtuse or subacute at apex, entire or slightly undulate; lateral nerves 10-12 pairs, oblique, tertiary nerves parallel, prominent on both surfaces, their axils often glandular; petioles about 1.2cm long; stipule minute, deciduous. Panicles racemes, solitary or fascicled. Flowers yellowish-white, shortly pedicelled, 6-8 mm. Calyx lobes slightly connate at base, snowy white outside, two outer ones slightly longer, ovate, more or less obtuse, thickened, three inner suborbicular, often mucronate, thin along the margin. Petals 5, yellowish-white, oblong, obtuse, entire or crenulate at apex, pubescent. Stamens 15, adnate to corolla base, filaments dilated at base, subulate, anther suborbicular, extended by the apicular awn, which is three times the length of the anther. Ovary ovate, superior, pubescent, three-loculed; ovules two in each locule; style short, cylindrical; stigmas thick. Fruit belly globose, apiculate, 2.5cm in diameter, enclosed at the base of the thickened and accrescent sepals which attain 2.5cm in length and spread horizontally.
Flowering: April-June Fruiting: July-September Distribution and status: Endemic to southern Western Ghats, it is assessed as Endangered on the IUCN Red List (Ashton 1998b) Ecology: The species is highly restricted to hill slopes close to streams and rivers in the West coast tropical evergreen and semi evergreen forests of Tamil Nadu (Tirunelveli) and Kerala. Presently, only one population is located in the Kulathupuzha forest range in Thiruvananthapuram forest Division. Only four mature trees were found along the banks of Shankili River at an altitude of 400m. The associated species   (KFRI 1978;FAO 1985;Sasidharan 2004). Most of these have the flagship tree-species-architecture of the low elevation evergreen forests and distribution has broken down into due to selective logging in the past. According to Pascal (1988) and Meher-Homji (1979, 1996 the dipterocarps dominant lowland evergreen vegetation formations are the most depleted forest type in the southwestern coast of peninsular India owing to increasing human density and occupation. The current study reveals that limited population, less number of mature individuals, irregularity along with sparse flowering, low fruit setting, heavy immature fruit falls, recalcitrant nature of seeds, poor regeneration and survival make it rare. Sasidharan (2017) reported that most of the dipterocarps, viz., Hopea erosa, Hopea jacobi, Hopea racophloea and Vateria macrocarpa, are only known from limited localities and their high degree of habitat specificity make them rare. Similarly, Swarupanandan et al. (2013) studied population biology of Dipterocarpus and also supported the habitat specificity of this group. According to Stiling (2011) the species that exhibit high degree of habitat specificity are prone to extinction. In order to maintain a viable population there should be a minimum number of mature individuals in a particular population. Many Indian dipterocarps fail to attain this minimum number (Kumar & Kaveriappa 1999;present observation), which in turn result in loss of genetic diversity through inbreeding depression (Swarupanandan et al. 2013). Moreover, some of the Malesian dipterocarps show reproductive constraints like flowering irregularities (Appanah 1993). The infrequency of reproductive incompatibility and embryonic mortality are the main reasons for low fruit set and heavy fruit falls respectively (Chan 1981;Swarupanandan et al. 2013).
Generally, seeds of Hopea are recalcitrant and shortlived in nature and they will germinate immediately after attaining maturity (Sasaki 1980;Yap 1981). These seeds, however, are mature during the monsoon season and may have a chance to be swept away. Regeneration and survival status of dipterocarps are comparatively low (Sukesh & Chandrashekar 2011). The present observation shows that Hopea glabra and Hopea utilis exhibited comparatively lesser regeneration and seedling survival among genus Hopea in Kerala. Hence, urgent attention is required to understand population structure, pattern of genetic variation, and developing propagation protocols for planning immediate restoration practices. As a first step towards this, we have collected a few seeds of Hopea utilis from Shankili forests. Seedlings were raised in the nursery, kept in a mist chamber for four to five weeks and planted at the KFRI Arboretum at Peechi.