Problem in the generic delimitation between Alseodaphne , Dehaasia and Nothaphoebe ( Lauraceae ) in Borneo

Alseodaphne, Dehaasia and Nothaphoebe are, morphologically, three closely related genera belonging to the Persea subgroup of the Lauraceae. A total of 214 binomials of the three genera have been published by various authors (International Plant Names Index, March 2007), of which 44 have been attributed to species occurring in Borneo. In revising the Lauraceae for the Tree Flora of Sabah and Sarawak Project, we recognize 40 distinct species (i.e., Alseodaphne 11; Dehaasia 16; and Nothaphoebe 13) for Sabah and Sarawak. These include 34 previously known and 6 undescribed species. Despite many attempts by various authors (Rohwer 1993, 2000, Van der Werff & Richter 1996, Van der Werff 2001) to clarify the generic delimitation between these three genera, to date there remains to be no satisfactory solution. In the absence of a well-accepted generic delimitation and classification within the Lauraceae as a whole, and for the purpose of preparing revision of the Lauraceae for the Tree Flora of Sabah and Sarawak, we have opted for recognising Alseodaphne, Dehaasia and Nothaphoebe as distinct genera. The distinguishing morphological characters of these three genera, based on specimens from Borneo (Sabah and Sarawak, in particular) are presented.


INTRODUCTION
The Lauraceae is one of the largest and important families of trees and shrubs throughout tropical and subtropical forests.About 2 500 -3 000 species in 50 genera estimated worldwide consist of many species that are important ecologically and economically (Kostermans 1957, Hutchinson 1964, Burkill 1966, Rohwer 1993, Van der Werff & Richter 1996).
Based on literature dating back to Blume (1825), about 287 species in 16 genera of the Lauraceae have been reported for Borneo.All these 16 genera are represented in Sabah and Sarawak.At local level, the revision of the Lauraceae for Sabah and Sarawak is still on-going.To date, we recognise 208 species in 16 genera of Lauraceae in Sabah and Sarawak, of which 11 represent undescribed new species.
In the absence of a well-accepted suprageneric classification and generic delimitation for the Lauraceae as a whole, botanists involved in the revision of the Lauraceae for the Tree Flora of Sabah and Sarawak volume, have adopted the generic delimitation as proposed by Van der Werff (2001), except for the inclusion of Nothaphoebe within Alseodaphne.
Alseodaphne, Dehaasia and Nothaphoebe are morphologically closely similar genera belonging to the Persea subgroup of the Ocotea group of the Lauraceae.Other genera occurring in Borneo that have been placed in the same subgroup include Persea, Phoebe Nees and Caryodaphnosis Airy Shaw (Rohwer 1993).
The genus Alseodaphne was established by Nees (1831) with A. semecarpifolia Nees as the type species.Since then, a total of 98 binomials have been published by various authors (International Plant Names Index 2007).Of these, 11 apply to species occurring in Borneo (Kostermans 1973a).The present study discovered three more entities representing undescribed taxa from Sabah and Sarawak (Yahud et al. in prep.).
Dehaasia was first described by Blume (1836) with D. microcarpa Blume (i.e., synonym for D. incrassata (Jack) Kosterm.) as the type species (Kostermans 1973b).A total of 52 binomials have been published for the genus (International Plant Names Index 2007).Of these, seven were attributed to species occurring in Borneo while other species listed in International Plant Names Index (2007) were without indication that the species occurred in Borneo.Kostermans (1973b) recognised 35 species in the genus, distributed from China to New Guinea.Of these, 14 were reported from Borneo.In the present study (Yahud & -7)   As has been adequately discussed by Rohwer (1993Rohwer ( , 2000)), Van der Werff (2001) and Li et al. (2004), hitherto, the suprageneric classification as well as the generic delimitation within the Lauraceae are largely remain unresolved.Some of the main reasons for this problem are the lack of recent and up-to-date revisions and/or monographs of most of the known genera and that classification based mainly on morphological and anatomical evidence is generally inconclusive and unsatisfactory.The problem is compounded further by the fact that only a few genera have been subjected to molecular studies (e.g., Chanderbali et al. 2001, Li et al. 2004).
This paper is a first report following from a study undertaken by the authors as part of the revision of Lauraceae for the Tree Flora of Sabah and Sarawak Project (Julia et al. in prep., Yahud & Soepadmo in prep., Yahud et al. in prep.).Its main goal is to highlight the readily observed morphological characters which may be used to distinguish and identify species of Alseodaphne, Dehaasia and Nothaphoebe occurring in Sabah and Sarawak.

MATERIAL AND METHODS
A total of about 1 500 herbarium specimens of Alseodaphne, Dehaasia and Nothaphoebe collected from Borneo (particularly in Sabah and Sarawak) and its adjacent islands were investigated at the herbaria of the Forest Research Institute Malaysia (KEP), Forest Research Centre, Sandakan, Sabah (SAN), Sabah Parks (KNP), Forest Research Centre, Kuching, Sarawak (SAR), Singapore Botanical Garden (SING), Herbarium Bogoriense (BO) and the Philippines National Herbarium (PNH).Digital images of type specimens were obtained from the websites made available online by The National Herbarium of the Netherlands, University of Leiden Branch (L), The New York Botanical Gardens (NY) and The Royal Botanic Gardens Kew (K).Additional flowering and fruiting specimens were occasionally obtained from the field in Sabah and Sarawak.

Comparative morphology of Alseodaphne, Dehaasia and Nothaphoebe in Borneo
We selected vegetative and reproductive characters which were comparable and readily observable on the herbarium specimens (Table 1).
Table 1 shows that none of the selected vegetative characters can be used conclusively to distinguish the three genera.On the other hand, a number of characters of the petiole, inflorescence, flower and fruit can, in combination, be utilized to large extent to segregate the three genera.In the past, one or more of the characters mentioned in Table 1 were used by previous authors to identify or distinguish these three genera (e.g., leaves arrangement, colour of lower surface, lateral flowers of terminal cymes, perianth lobes, glands, number of anther locules, arrangement of pollen sacs, filament staminodes, receptacle, fruits and fruit pedicels).Sometimes these characters were used to classify the genera into subfamilies in Lauraceae; in addition, like many authors before, we are still using more or less similar characters of the inflorescences and fruits to distinguish these genera.Nevertheless, additional characters that we find useful to distinguish Alseodaphne, Dehaasia and Nothaphoebe include: 1) the number of flowers per inflorescence; 2) relative length of inflorescence compared to the length of leaves; 3) length of proximal rachis (axis) before the first branching; and 4) the number of flowers on the distal part of inflorescence.At this stage and for the revision of these three genera for the Tree Flora of Sabah and Sarawak, we tried to use as many characters as possible to distinguish these genera; however, since we only look at Borneo specimens, variation in the characters across these three genera are possible particularly when one study the genera worldwide.

Morphological similarity and differences between the three genera
Based on our experience dealing with specimens from Borneo, particularly those collected from Sabah and Sarawak, the characters presented in Table 1 can be used to distinguish Alseodaphne, Dehaasia and Nothaphoebe with some degree of certainty; however, since the differences are mainly based on inflorescences and fruits characters, identification of sterile materials are still quite impossible unless one is familiar with all the species in the genera.Similarity -All three genera normally have non-perulate terminal vegetative buds.The leaves are pinnately veined and usually crowded at the end of the upright twig.The texture of the leaf blade varies between species across the three genera even though species of Nothaphoebe generally have smaller and thinner leaf blade compared to those of Alseodaphne and Dehaasia.All three genera have a thyrso-paniculate inflorescence known as Type II by Van der Werff (2001); bisexual and trimerous flowers with 6 perianth lobes arranged in 2 whorls (with the lobes of the outer whorl are smaller than or equal to that of the inner ones), 9 fertile stamens arranged in 3 whorls, 3 staminodes, and ovary seated on a flat or shallow hypanthium (receptacle); and the fruit is 'unprotected', subtended only by a shallow saucer-shaped or flat receptacle.
Differences -Data presented in Table 1 suggest that, except for the number of anther locules (4 vs 2), Alseodaphne is more similar to Dehaasia than to Nothaphoebe.This finding is conform with the suggestion made by Rohwer (1993) but contradicts Van der Werff's (2001) proposal in which Nothaphoebe is treated as a synonym of Alseodaphne.
For the purpose of identifying the genera/species occurring in Borneo (Sabah and Sarawak in particular), the comparative morphological data presented in this paper suggest that the three genera can be distinguished as follows: Nothaphoebe differs from both Alseodaphne and Dehaasia in its rounded or adaxially only indistinctly channelled petiole; many-flowered inflorescence with shorter proximal axis, distal part with 3 -5 flowers, filament of fertile stamen very short or absent, more or less sessile staminodes, woody fruit-receptacle with smaller persisting perianth lobes, woody and not or only slightly thickened brown or pale brown fruit-pedicel.
Most species of Alseodaphne can be distinguished from that of Dehaasia by combination of the following characters: lateral flowers of terminal cymes non-opposite (vs strictly opposite); anther 4-locular (vs mostly 2-locular), except in Alseodaphne oblanceolata with 2-locular anther; fruiting receptacle mostly shallow saucer-shaped (vs mostly flat), except in Alseodaphne borneensis with flat receptacle.In the case whereby one odd character is observed, combinations of majority of the characters take precedence over the single character.

CONCLUSION
As discussed above, Alseodaphne, Dehaasia and Nothaphoebe can be distinguished by a combination of characters.To certain extent, some of these characters are rather qualitative and argumentative, nevertheless for the above and more pressing practical reasons, botanists involved in the revision of the Lauraceae for the Tree Flora of Sabah and Sarawak have, with a minor exception, adopted the generic delimitation as proposed by Van der Werff (2001).In this context, we have opted to recognize Alseodaphne, Dehaasia and Nothaphoebe as three distinct genera.
the end of twig, sometimes not crowded Crowded at the end of twig or rarely not crowded Loosely or closely crowded at the end of inflorescence compared to leaves Usually longer, rarely shorter or as long as leaves Shorter or as long as leaves Usually shorter than leaves or rarely longer than leaves (N.heterophylla) length of proximal rachis (axis) before 1st branching (cm) 2-15 (1-)2-10(-11.5)0.5 -5, rarely 11 (N.heterophylla) number of flowers on the distal part of perianth lobes Usually smaller or almost equal, rarely larger than the inner ones Smaller or almost equal as the inner ones Slightly smaller than the inner ones 3rd whorls with a pair of glands above each other, rarely side by side Side by side In 2 pairs above each other shape Ovoid or oblong Ovoid, obovoid, oblong or rounded Oblong or obovoid, rarely ovoid Filaments relative length Usually shorter, sometimes longer or as long as anthers Usually longer, sometimes shorter or as long Usually shorter than anther or anther sessile, rarely or ellipsoid length of style compared to ovary Usually shorter, sometimes longer or as long Longer or shorter than ovary Usually longer, sometimes shorter or as Soepadmo in prep.)we recognise 16 species in Sabah and Sarawak, including two new species.The genus Nothaphoebe was established byBlume (1851)  with N. umbelliflora (Blume) Blume (basionym: Ocotea umbelliflora Blume) as the type species.A total of 45 binomials have been published (International Plant Names Index 2007), of which only two apply to species found in Borneo.Present revision(Julia  et al. in prep.)recognises 13 species in Sabah and Sarawak including four new species to be described.

Table 1
Comparison between Alseodaphne, Dehaasia and Nothaphoebe based on readily observable vegetative and reproductive characters.