The Odonata of Binyo Penyilam, a unique tropical wetland area in Bintulu Division, Sarawak, Malaysia

Historically there has been very little collecting of Odonata (dragonflies and damselflies) in Sarawak’s Bintulu Division. A few records had been published prior to 2007 (Laidlaw 1915; Laidlaw 1920; Hincks 1930), with a total of just 14 species recorded from the entire division. A number of publications dealing with Odonata and including records from locations in Bintulu Division have appeared from 2007 onwards (Dow et al. 2007; Dow 2008; Dow & Hämäläinen 2008; Dow & Reels 2010). A large part of Bintulu Division is now included in the Sarawak Planted Forest Project (SPFP), formerly known as the Planted Forest Zone. Here we present records of Odonata from the Binyo Penyilam Conservation Area (BPCA), a wetland area within the SPFP. The SPFP (Image 1) lies within a gently rolling landscape, situated northwest of a series of high, parallel ridges that separate it from the Rejang River basin. It covers 490,000ha, of which 150,000ha have been identified as being suitable for the establishment of forest plantations. 220,000ha are being retained as natural forest and managed as reserves of various types. The balance of 120,000ha is Native Customary Rights land. In the long term at least half of the entire area will remain as natural forest, with two thirds of this protected. OPEN ACCESS | FREE DOWNLOAD JoTT CommuniCation 2(13): 1349-1358

A variety of vegetation types can be found within the area, including lowland mixed dipterocarp forest, peat swamps, limestone associations and kerangas forest, as well as Acacia mangium plantation. The SPFP Conservation Department has been conducting plant inventories together with international and local partners in Bintulu division, which had been poorly known floristically.
The BPCA (Image 1) is situated in the eastern central SPFP, and consists of kerangas forest, peat dome forest and peat swamp "lakes", and has a total area of 15,300ha. It is a mosaic of partially disturbed and original swamp forest that has developed over a deep inland basin. Details of vertebrate groups found in the BPCA can be found in Stuebing et al. (2007). The vegetation of the BPCA is mainly influenced by the permanently and semipermanently flooded nature of the area. The poor drainage of the area has led to the formation of an unusual type of peat dome forest, creating unique padang communities of stunted trees and grasses and black water lakes. Within the permanently flooded area there are peat dome forests of Alan (Shorea albida) and Ramin (Gonystylus bancanus and G. maingayi). Some small clumps of higher ground surrounded by the swamps and small lakes are mostly dominated by dipterocarps and gymnosperm species.
About 150 species of ferns and fern-allies and flowering plants have been collected and identified in the BPCA to-date (Demies et al. 2006). Trees and shrubs are well represented by 67 species, orchids with 25 species, ferns and fern-allies with 15 species. Four palm species and two species from the Cyperaceae, a grass family, have been found. The Araceae (aroids) is represented by five species, and at least five climber species have been found. Elements of the deep peat swamp flora (i.e. species that only grow on peat domes) are represented by two species of Gonystylus, one from the Bombaxaceae, one aroid and two Pandanus species. Padang communities are dominated by grasses such as Cyperaceae, and carnivorous plants such as Nepenthes. Nepenthes species are rich in the marsh areas and around the lakes, seven species have been recorded (Unggang 2007), of which N. bicalcarata and N. albomarginata are Bornean endemics. Another unusual plant of the BPCA is a fern, Trichomanes singaporeanum, that until recently had only been found growing on mountain ridges.
Sampling of Odonata has been conducted in most of the habitat types stated above except the lake areas, but only a small part of Binyo Penyilam has been sampled to-date. Sixty-one species of Odonata have been found in the area so far. This total is certain to rise with further sampling, but already includes a relatively high proportion of species that can be considered as rare and/or poorly known, and several first records for Sarawak and, in some cases, Borneo.

MATeRIAl AnD MeThODS
To-date only sampling of adult Odonata has taken place within Binyo Penyilam. Collecting has been conducted using hand-held nets, and has taken place on foot, or when this was not possible, from boats. Collecting was carried out on 8-11 March in 2006, and on 26 -29 January and 5-10 October in 2008. At each location sampled the aim was to collect at least one specimen of each species present. In cases where species are difficult to distinguish in the field, or of particular interest, an effort was made to take longer series of specimens. However, many adult odonates are difficult to capture, hence not every species encountered was successfully collected. Conversely, little effort was made to capture more than a single voucher specimen for common and widely distributed species that are easily identified in the field. Most of the material collected is currently held in the Image 2. Map of the sampling area.
collection of the first author, with duplicates to be placed in the Sarawak Forest Research Centre.
collecting was carried out at the locations listed below: (1 ; the upstream part to the furthest point sampled flows through disturbed low pH swamp forest (Image 5). Sampling has been conducted between the locations marked as "Field Station" and "Upstream" in Image 2.
(2) Swamp forest (Image 6) around the Sg. Penyilam and small hillocks arising from the swamp. Sampling was carried out at a number of individual sites along the Sg. Penyilam.
(3) Open flooded areas at the landward margins of the large Pandanus andersonii areas in the lower part of the Sg. Penyilam.
(5) A tributary to the Sg. Binyo, upstream and on the opposite shore to the Sg. Penyilam, in disturbed forest, marked as "Location 5" in Image 2.
(7) At the SPFP Conservation Department field station, "Field Station" in Image 2.
(8) Rumah Joseph, an Iban longhouse on the Sg. Binyo, close to the mouth of Sg. Penyilam.

ReSUlTS
The following is a list of all species collected at Binyo Penyilam to-date. For each species a list of material, brief notes and a list of locations where they were collected are given. The family level taxonomy used here follows that in Orr (2003).

calopterygidae
(i) Vestalis amabilis Lieftinck, 1965 -In March 2006 when the Sg. Penyilam still ran clear this species was common on the upstream part, but on subsequent visits it was much scarcer; it is unclear whether this is the result of the increased turbidity or of natural population fluctuations, or of some other factor not apparent to the authors. In Sarawak this species is most often encountered on streams in swamp forest or kerangas areas. Locations 1, 2: 11 males, 1 female, 8-11.iii.2006; 4 males, 27-28.i.2008; 1 male, 6.x.2008.
(ii) Elattoneura longispina Lieftinck, 1937 -This species, remarkable for the structure of its anal appendages, has not been recorded from Sarawak previously. It is otherwise known from north-west and south-east Kalimantan and Belitung (formerly Billiton) island (Lieftinck 1954). It occurs very locally in swamp forest at Binyo Penyilam, and has also been found at another location in Bintulu Division. It has yet to be found (iv) Amphicnemis sp. cf. dactylostyla Lieftinck, 1953 -This problematic form is commoner at Binyo Penyilam than the last species, and appears to be distributed across Sarawak from the west to Loagan Bunut National Park in the north-east. It is clearly closely allied to dactylostyla, but determination of its true status will have to await a revision of the genus in Borneo. It is also closely related to A. martini Ris, 1911, but appears to be distinct from that species, which in Sarawak has only been found recently in Gunung Mulu National Park. All records of A. martini in Sarawak from west of Gunung Mulu National Park appear to actually refer to this form/species. It is usually, but not always, found in peatswamp forest; like the last species it is very local in its occurrence at Binyo Penyilam. Location 2: 5 males, 3 females, 9-10.iii.2006; 4 males, 11 females, 27-28.iii.2008. (v) Amphicnemis sp. cf. gracilis Krüger, 1898 -An even more problematic form than the last; it has similarities with A. gracilis, A. billitonis Lieftinck, 1940 andA. wallacii Selys, 1863. Although in the structure of its terminal appendages the male is most similar to A. gracilis, it is possible that it and forms found further east in Sarawak are all merely local variants of A. wallacii. Abundant in swamp at Binyo Penyilam and known from other locations in Bintulu Division. Location 2: 3 males, 2 females, 8-10. iii.2006; 14 males, 13 females, 27-28.i.2008; 2 males, 3 females, 8.x.2008. (vi) Archibasis incisura Lieftinck, 1949 -This is not generally a common species in Sarawak, but appears to be quite abundant on the Sg. Penyilam, and may favour low pH forest streams. Locations 1, 5: 2 males, 1 female, 9.iii.2006; 6 males, 2 females, 26-29.i.2008; 7 males, 5-9.x.2008. (vii) Archibasis melanocyana (Selys, 1877) -In the authors experience this is not a common species in Sarawak, although it is common in Brunei (Orr 2001), but it is sometimes abundant on the Sg. Penyilam. Locations 1, 3, 4 (two females were taken at a pool at this location): 20 males, 4 females, 9-11.iii.2006; 5 males, 26-29.i.2008. (viii) Archibasis tenella Lieftinck, 1949 -This species is normally commoner than the preceding two in Sarawak, and occurs on a larger range of stream types; however at Binyo Penyilam only a single teneral (freshly emerged) specimen has been collected.  (Dow & Reels 2008). However it has been recorded in Brunei (Orr 2001) and is easily overlooked on account of its small size, so is likely to be under-recorded in Sarawak. (xiii) Pseudagrion coomansi Lieftinck, 1937 -apart from one old and questionable record of a female (Lieftinck 1954) this is the first record of this species from East Malaysia. It is moderately common in the open marshland at Binyo Penyilam, where it is found flying over black water pools. Location 4: 4 males, 1 female, 10.iii.2006; 3 males, 7.x.2008.

Platycnemididae
(i) Copera vittata (Selys, 1863) -This is a widespread species in tropical and subtropical Asia, with a confusing variety of named subspecies, and still more unnamed forms. The typical form in Borneo has red legs, but a form with yellowish legs exists in western Sarawak, a form with black legs exists in Brunei (Orr 2001(Orr , 2003) and a form with yellow and black legs is found in Bintulu Division. The determination of the true status of these forms awaits a thorough revision of the genus. Locations 2, 5: 1 female, 11.iii.2006; 1 male, 9.x.2008.
(iii) Macrogomphus parallelogramma albardae (Selys, 1878) -This species has not previously been recorded from Sarawak, it appeared to be moderately common on the Sg. Penyilam in March 2006, but has not been found there subsequently. One male was captured while foraging at the streams edge at dusk; records of crepuscular (dusk and evening) flight in this family are scarce; but the first author has subsequently observed similar behaviour from this species at Bukit Sarang (also in Bintulu Division). Wilson (2008) recorded crepuscular activity in Orientogomphus minor (Laidlaw, 1931) in Thailand, so perhaps dusk and evening flight in the Gomphidae is more common than has been supposed. Location 1: 3 males, 1 female, 8-11.iii.2006. (iv) Macrogomphus quadratus (Selys, 1878) -A distinctively marked species, the commonest of its genus in Sarawak, found on a variety of forest streams. Location 1: 3 males, 9-11.iii.2006; 4 males, 28-29.i.2008. (v) Merogomphus femoralis Laidlaw, 1931 -This is the first record of a Merogomphus species from Borneo; the Sg. Penyilam remains the only site known on the island for the genus. M. femoralis was previously only known from the holotype, taken in west Malaysia, but a photographic record probably of this species was recently made in Singapore (Cheong et al. 2009). Location 1: 3 males, 1 female, 9-11.iii.2006; 2 males, 6.x.2008. (vi) Microgomphus sp. -A single teneral female was collected on the Sg. Penyilam. The only species of the genus so far recorded from Borneo is M. chelifer (Selys, 1858), but as the adults of Microgomphus species are very elusive, there could well be additional species present on the island. As the specimen is in poor condition, it is not possible to come to any firm conclusion regarding its status. Location 1: 1 female, 11.iii.2006.

Aeshnidae
(i) Gynacantha basiguttata Selys, 1882 -Likely to be quite common in Sarawak, but not many records have been made in the state to-date. The single specimen collected at Binyo Penyilam was foraging during rain in the late afternoon. Location 7: 1 male, 7.x.2008.

corduliidae
(i) Hemicordulia tenera Lieftinck, 1930 -A fast flying species, in Sarawak seemingly confined to swampy forest areas and very local in occurrence. Sometimes quite common on the Sg. Penyilam where males patrol sections of the stream. Location 1: 2 males, 9-10.iii.2006; 3 males, 5-8.x.2009. (ii) Macromia arachnomima Lieftinck, 1953 -The exuviae of the distinctive long legged larvae of this species were found in large numbers on the Sg. Penyilam in January 2008. All records from Sarawak are of larvae or exuviae, with the first record of the species in the state being made at Gunung Mulu National Park earlier in January 2008 (Dow & Reels 2009). Location 1.

Elattoneura aurantiaca
Currently only three sites are known in Sarawak for this species (BPCA, Bukit Sarang, also in Bintulu division, and a site near Kuching); none of these is totally protected at the time of writing.

Elattoneura longispina
The only other site known for this species in Sarawak is Bukit Sarang.

Mortonagrion falcatum
Currently known from only two sites in Sarawak (BPCA and Gunung Mulu National Park).

Mortonagrion new species
Although this species is widespread in Sarawak, it is not known outside the state and is only known from one totally protected area (Loagan Bunut National Park); several of the known sites in Kuching and Samarahan divisions are likely to be lost in the near future.

DIScUSSIOn
As a large area consisting mainly of low pH swamp forest (albeit disturbed) mixed with naturally open habitats, Binyo Penyilam is an exceptionally interesting area for Odonata in Sarawak. A number of the habitats at Binyo Penyilam are unusual and may not be represented in totally protected areas in Sarawak. Low pH swamp forest is relatively poorly represented in Sarawak's currently gazetted protected areas (compared, for instance, to hillside mixed dipterocarp forest), but provides a habitat for a number of specialist species. Natural open habitats are scarce in Sarawak, and the open marsh areas at Binyo Penyilam appear to offer suitable habitat for some species not found elsewhere in the state.
At least seven species (Libellago orri, Elattoneura longispina, Pseudagrion coomansi, Macrogomphus parallelogramma albardae, Merogomphus femoralis, Brachygona puella and Chalybeothemis fluviatilis) not definitely recorded in Sarawak prior to 2006 have been found at Binyo Penyilam, a high number for a single area; four of these species have still not been found elsewhere in the state (P. coomansi, M. femoralis, B. puella and C. fluviatilis). The Sg. Penyilam remains the only known site for a Merogomphus species on Borneo. Two other species collected in this area have not been recorded anywhere else in Sarawak for decades, these are the apparently very rare Nannophyopsis chalcosoma and Raphismia inermis.
Because of under-sampling it is generally difficult to assess the conservation status of Odonata in south-east Asia. However 16 of the species found at Binyo Penyilam can be considered to be of potential conservation concern, at least within Sarawak. These species are listed in Table  1, together with a brief justification for their inclusion.
A number of the species listed in Table 1 (Mortonagrion falcatum, Ictinogomphus acutus, Hemicordulia tenera, Chalybeothemis fluviatilis, Nannophyopsis chalcosoma, Rhyothemis pygmaea, Tramea phaeoneura) have also been recorded in Brunei, but all are very localised there and in many cases their habitats are at risk (Orr 2001;pers. comm.).
Odonate diversity in lowland swamp and marshland habitats in Borneo is not as high as in mixed dipterocarp forest (Orr 2006). That said, diversity at Binyo Penyilam is relatively high, with 61 species from 11 families of Odonata recorded. Most of the collecting effort to-date has been concentrated on the Sg. Penyilam, or in the open marshland; relatively little time has been spent within the swamp forest areas, it is likely that more collecting here would result in a significant increase in the number of species recorded in the area. The lakes present in the area, not sampled for Odonata yet, are also likely to yield additional species.