Adolfo Cordero Odonata Rivera in (ed) Bornean 2006 tropical rain forest formations 51 Forests and Dragonflies. Fourth WDA International Symposium of Odonatology, Pontevedra (Spain), July 2005, pp. 51-78. Pensoft Publishers Sofia Moscow Odonata in Bornean tropical rain forest formations: diversity, endemicity and implications for conservation management A. G. Orr School of Australian Environmental Studies, Griffith University, Nathan, Q 4111, Australia ABSTRACT The island of Borneo was originally almost completely covered by closed canopy tropical rainforest. Owing to an aseasonal, hot, perhumid climate and high rainfall, forests were well supplied with streams and standing water. Consequently the rich, largely endemic odonate fauna must have evolved in association with these forests, and non-forest species, common today in disturbed land, must formerly have been rare opportunists in forest gaps or localised lacustrine species. It is estimated that at least 70 % of the fauna is presently confined to forest habitats and probably depends on forest for its survival. This study relates odonate distribution to a mosaic of complex tropical rain forest formations in Brunei. The tiny sultanate of Brunei still enjoys about 80% forest cover, representative of all the seven major formations found on the island and a great many of the 30+ sub-formations, and results from a nation-wide survey of odonates from most habitats are considered to be broadly applicable to the entire island of Borneo and many other parts of equatorial south-east Asia. Greatest odonate diversity, both a and b, and greatest endemicity, is found in the primary lowland mixed dipterocarp forests, especially those growing in highly dissected landscapes such as occur at the KBFSC, at the edges of the central uplands. High diversity and endemicity is also found in swamp forest, especially freshwater swamp, with certain endangered peat swamp formations also important. The highly vulnerable kerangas forest harbours fewer species, none uniquely, and the mangrove fauna is still more depauperate, with only a single wide-ranging specialist restricted to this habitat.
52 A. G. Orr Secondary dipterocarp forest is certainly less rich in odonates than primary forest, but lack of sites for parallel comparisons makes it difficult at present to state how serious this effect is. These results emphasise the importance of conserving a wide range of primary forest formations to achieve satisfactory odonate conservation, a strategy congruent with the conservation of charismatic land-based vertebrates and forest peoples. INTRODUCTION The ecology of tropical forest Odonata is one of the most significant gaps in our knowledge of the biology of the order. It is well known that, globally, many more odonates occur in tropical ecosystems than in all others combined, and that a probable majority of species are forest dwellers dependent on forests for their survival. At present however, we can neither quantify nor explain this phenomenon. Even in Corbet s (1999) encyclopaedic review of odonate biology, there are few direct references to the topic, indicative of a dearth of published work. Furtado (1969), in a definitive study of Malaysian dragonfly biotopes and habitat requirements, virtually ignores the surrounding forest in his habitat characterisations, suggestive of an intellectual demarcation line between freshwater biologists and forest botanists. It is most probable that traditional boundaries of research and scholarship have tended to discourage the synthesis of information and ideas from different disciplines necessary to progress in this field. As dragonflies are non-phytophagous aquatic insects, the forest environment in which they occur may seem peripheral to their needs. However when one considers the role forests play in mediating macro- and microclimates, the concomitant effects they have on riparian vegetation, landscape, hydrology and water quality, and the many potential prey items which they support, and the added foraging space created by the third dimension of the tropical rainforest and its canopy, it is obvious that tropical rain forests are very important indeed to the survival of many, perhaps most, odonate species. No clearer evidence of this dependence is provided than by the paucity of stream odonates in equatorial south-east Asian lowlands once surrounding forest has been removed. In a state of nature virtually the entire land surface of Borneo, the third largest island in the world, was covered with forest. Only small alpine areas and inland lakes interrupted the continuous, closed canopy tree cover. These forests contained an extraordinary diversity of plant life, with 10,000-15000 species of seed plants alone (Merrill 1921, 1950). Owing to the perhumid, aseasonal, high rainfall climate all forest habitats were richly supplied with permanent streams, and where topography permitted, permanent or semipermanent standing water. With the encroachment of man, especially over the last 100 years, a good deal of forest has been felled and has given way to
Odonata in Bornean tropical rain forest formations 53 non-forest, variously agricultural or urban and wasteland, or is in varying stages of regeneration. Based on data now 15 years old, Collins et al (1991) estimated forest cover on Borneo at 72.2% of total land area, comprising 53% lowland forest (mixed dipterocarp and secondary formations), 6.2 % montane forests, 10.7 % inland swamp (mostly peatswamp) and 2.3 % mangrove. These figures surely must now be revised down considerably after a disastrous decade of continuing legal and illegal logging and cycles of drought followed by accidental or deliberately set fires. The assessment of Collins et al (1991) was rather inexact in its designation of forest types. Generally six major natural formations are recognised (Cranbrook and Edwards 1994, Ashton 1964, Anderson and Marsden 1984, Whitmore 1984) i.e.: Littoral Forests, Mangrove, Peatswamp Forests, Riparian (mainly freshwater swamp) Forests, Mixed Dipterocarp (including montane) Forests and Heath Forests, each of which has several subdivisions, so that the total number of recognisable formations is well over 30. A seventh major formation, secondary forests, is now a highly significant and diverse component of the island s vegetation. The various forest formations differ greatly, not only in the physiognomic and floristic differences by which they are defined, but also in edaphic, topographic and hydrological characteristics, all of which have profound consequences for their suitability as dragonfly habitats. The great predominance of perhumid forest habitats in Borneo is reflected in the habitat preferences of its odonate fauna (Table 1). These figures are approximate, with more than 11% classified as indeterminate due either to a gross deficiency of data or to the difficulty of classifying those species occurring in multiple habitats. Habitat definition here is restricted to presumed breeding habitat as many species, especially crepuscular feeders, regularly forage in open areas but return to forest pools to breed, while conversely, species which breed in open ponds and lakes may forage in the forest canopy. In total nearly 70% of all species are confined to forests or require forest habitats in which to breed. For the Zygoptera this figure is over 80%. The 19.3% predominantly found in non-forest are now mostly very abundant, eurytopic species. Presumably these were once localized on lakes, an uncom- Table 1. Proportions of Bornean Odonata confined or nearly confined to forest and non-forest breeding habitats (Based on 280 known species and compiled from Lieftinck 1954, Hämäläinen 1994, Orr 2001, Orr 2003, Dow 2005, Kalkman 2005 and Orr, unpublished data). Forest Non-Forest Indeterminate Zygoptera 82.7% 10.7% 6.6% Anisoptera 56.7% 27.3% 16.0% TOTAL 69.3% 19.3% 11.4%
54 A. G. Orr mon habitat in most of Borneo, and temporary pools in forest gaps, and in many cases would have been quite rare. However, despite changing conditions, very large areas of Borneo remain forested and provide habitat for the majority of the rich odonate fauna, especially its endemic elements. From a conservation viewpoint, it is important to know how this forest fauna is distributed within the diverse forest formations, and how well protected these formations are. FAUNISTIC STUDIES OF DRAGONFLIES IN BORNEO To date, regional or local faunistic surveys of dragonflies in Borneo have been very limited, especially those that relate occurrence to habitat (in a sense understood by modern forest ecologists). Exceptions to this are Brunei, (Thompson and van Tol 1993, Orr 2001, Kalkman 2005), Gunong Kinabalu (Laidlaw 1934, Hämäläinen 1994), in which old or uncorrelated records can easily be related to modern phytogeographical knowledge, and the Danum Valley Field Centre in eastern Sabah, where similar lists can be related to a well known landscape. Approximately 64 percent of the Bornean odonate fauna has been recorded from within the small sultanate of Brunei (area 5765 km 2 ), covering less than one percent of the land area of Borneo, hence this may serve as an exemplar for the whole island. LANDFORMS AND FOREST HABITATS OF BRUNEI Brunei provides a microcosm in which almost every major vegetational formation found on the island of Borneo is well represented. (Lacking are the mixed dipterocarp forests on ultramafic soils of eastern Sabah (Proctor et al. 1988), pure limestone formations and upper montane forest; the montane forest present is very difficult to access and too limited in extent to support extensive stream systems). Moreover, with over 1900 tree species and 3500 species of all seed plants (Wong, 1999), Bruneian forests are both exceptionally rich, and exceptionally well studied floristically (Ashton 1964, Anderson and Marsden 1984), hence it is possible to state with some precision the floristic differences between forests of very similar physiognomy. Because of sound conservation policy and practice (more than 20 % of the land area is protected), microhabitats can be revisited over many years without suffering significant anthropogenic disturbance. Despite some destruction by fire in 1997, total forest cover is probably still nearly 80% of land area (Table 2). Because Brunei is relatively low lying, the area of peatswamp forest is substantially greater than the average for the island of Borneo.
Odonata in Bornean tropical rain forest formations 55 Table 2. Extent and composition of Brunei forests (based on Anderson and Marsden, 1984). Forest formation Area km 2 % of land area Primary lowlandmixed dipterocarp 2158 36.5 Montane oak/laurel 72 1.2 Peatswamp 909 15.4 Mangrove 184 3.1 Kerangas (heath) 35 0.6 Alluvial and other freshwater swamp 127 2.1 Littoral Figures unavailable Small Secondary 1279 21.6 TOTAL 4764 80.5 Fig. 1. Distribution of major forest formations of Brunei (secondary forests not separated from primary mixed dipterocarp)
56 A. G. Orr Figure 1 shows the distribution of main forest formations in Brunei. Remaining littoral forest, kerangas, and most types of freshwater swamp forest, including alluvial forest, occupy areas too small to be indicated on this map, and either exist as small patches interdigitating with or else reticulating throughout other forest types, especially peat swamp and lowland mixed dipterocarp forest; nevertheless some minor formations provide very important odonate habitats. Throughout Borneo, forest formation is influenced primarily by topography and substratum. Mangroves, grow on tidally inundated silty deltas and are highly salt tolerant. Littoral forests grow in slightly more elevated situations near the sea, mostly growing on undeveloped sand or mixed clay and sand. Generally the forest is fairly open and water, running and standing, is scarce. On the low plains inland behind the beaches are broad expanses of peatswamp forest. Thickness of peat varies considerably, to a maximum of about 20 m. Deposits tend to be laid in patches several km in diameter with the peat, lens shaped in section, deep and raised in the middle and thin at the edges (Anderson 1964). In normal (non-drought) conditions the peat is completely waterlogged, although exposed standing water tends to be more available around the edges. The ph of water in pools deep in the forest may reach 4.0 or even lower. Peatswamp occurs in several sub-formations, which form concentric bands around the peat dome. Anderson (1961) recognised a catenary sequence of 6 formations, ranging from a mixed or Campanospermun dominated outer band, through several Shorea albida dominated formations, (the most impressive being virtual monocultures, recognised from the air by the grey-green canopy of nearly uniform height, up to 80 m), through to stunted pole forest in the centre. The complete sequence is present only in the oldest and deepest peat deposits, up to 11,000 years old. Often the central area is occupied by inner tall Shorea albida formations. Interspersed among the peat deposits are low islands of pure white sand, and sometimes higher outcrops of various shale/sandstone/clay formations. On the sand grows kerangas forest, often dominated by the conifer Agathis borneensis. On the shale/sandstone/clay formations grows lowland mixed dipterocarp forest. At the ecotones between kerangas and peatswamp, and between mixed dipterocarp forest and peatswamp, are often found tannin stained freshwater swamp associations, distinguished from true peatswamp by the lack of peat in the substratum and the higher ph of the water, usually above 5.5. Another form of freshwater swamp occurs in alluvial forest, growing in low lying, flat or gently undulating country, beside streams and rivers with a developed floodplain. The most extensive kerangas formations were formerly found just inland in a long belt between coastal littoral formations and inland peat; almost all are now destroyed, principally by repeated fire over the last three decades.
Odonata in Bornean tropical rain forest formations 57 As the terrain rises to more than a few metres a.s.l., the forest becomes almost entirely lowland mixed dipterocarp, a formation which may vary greatly floristically according to topography and soil type, while retaining an almost uniform physiognomy. Bornean mixed dipterocarp forests are among the tallest statured rainforests in the world (Ashton 1964, Whitmore 1984), with highly complex vertical zonation, and, with over 231 tree species per hectare (Paulsen et al 1996), also the most floristically diverse. The principle odonate habitats are streams, both small and large, although springs, seepages, and phytotelmata are also significant. The most diverse microhabitats are provided by highly dissected landscapes in steep terrain. Lowland mixed dipterocarp formations undergo a transition to the similar hill dipterocarp, from about 500-1000 m, above which they are succeeded by montane oak/laurel associations, then elsewhere in Borneo by ericacious upper montane forest. The latter is present above 2000 m and is not represented in Brunei. GENERAL HABITAT ASSOCIATIONS OF DRAGONFLIES IN BRUNEI Orr (2001), lists 174 species from 35 sites in Brunei, 25 of which were forest habitats of known formation. Later records (Kalkman 2005, Orr unpublished) bring this total to 179 species. A full list is provided in Appendix 1. Of these a total of 12 species (14.3%) of Zygoptera and 36 species (37.9%) of Anisoptera were generally found unassociated with forest (although a few occasionally entered forest near its margins or were routinely present on exposed hilltops and forest canopies). Information concerning almost all species in this category was supported by large samples from multiple sites, and for each species, at least 95% of records were made outside forest, including areas well removed from forest. Table 3 summarises the family composition of nonforest and forest odonate faunae, from which it may be seen that the former is highly unbalanced and unrepresentative of the fauna as a whole, being composed mainly of libellulids and coenagrionids. It is concluded that these, mostly wide ranging, common and eurytopic species did not require forest as essential habitat, and, at most, used it facultatively for foraging or occasionally for breeding. It is believed that if the forests of Brunei were felled, this assemblage, 26.8 % of the known fauna, would continue to flourish and many species would probably increase in numbers and distribution. These need concern us no further. Of the remaining 73.2 % of species, it is probable that most are completely dependent on forests (or at least forest margins) for their existence as none was ever found associated with water at any distance from forest. Several crepuscular aeshnids were observed foraging in open country or were at-
58 A. G. Orr Table 3. Numbers of species in major families and family groups associated with forest and non-forest habitats in Brunei (Data from Orr, 2001; Kalkman, 2005) Family Non-forest Forest Total Calopterygoidea 0 26 26 Coenagrionidae 11 13 24 Other Zygoptera 1 34 35 Libellulidae 31 26 57 Other Anisoptera 5 32 37 TOTAL 48 131 179 tracted to light, as were a few stray coenagrionids which entered my house, about 100 m from the nearest closed forest, during the six years I lived in Bandar Seri Begawan, but it is quite certain that the breeding habitats of these species were well inside closed canopy forest. HABITAT ASSOCIATIONS OF DRAGONFLIES WITHIN BRUNEI FORESTS Of the forest dependent species the questions remain: to what extent are species associated uniquely with particular forest formations? And, to what extent are the species assemblages supported by different forest formations characteristic to those formations? The analysis presented by Orr (2001), suggests answers to both these questions: similar habitat types clustered together in a similarity analysis, and the family profiles of mixed dipterocarp forest sites were rather similar, and quite different from those of swampy forested areas (Figure 2). The present analysis is more directly species oriented, with a definite aim of defining habitat preferences in relation to various forest formations. To the 25 forest sites listed by Orr (2001), it was possible to add another 7 forest sites (Orr, unpublished), giving a total of 32 sites. This approximates the total number of forest formations recognised for Brunei (Cranbrook and Edwards 1994), and although several of these (Mangrove and Littoral formations) are largely irrelevant to this exercise, since they support poor faunas and were poorly sampled, and montane forest was omitted for logistic reasons, it is obvious that duplication of similar formations was in many cases impossible. The five lowland mixed dipterocarp forest formations sampled represent three different soil types with up to 80 % difference in the tree species present between sites (Ashton 1964, and pers com). Added to this is the problem that it was impossible to duplicate the stream habitats within each sampling area, and it is difficult to say whether observed differences
Odonata in Bornean tropical rain forest formations 59 Fig. 2. Average family profiles of odonate species assemblages from sites in mixed dipterocarp forest, swamp forests & kerangas, and non forest (modified from Orr 2001). relate in some fundamental way to forest formation or its topographic or geological/edaphic correlates, or rather are just a consequence of local topography. Therefore, in the first instance, I consider the associations of dragonflies relative to a coarse-grained classification of forest formations, namely, lowland mixed dipterocarp, secondary (formerly mixed dipterocarp), peatswamp, freshwater swamp and alluvial forest, kerangas (tropical heath) and mangrove. In order to avoid the spurious inference of habitat association which may result from single records, I have adopted the following protocol in my analysis of associations species are included only if they are recorded from at least three sites or at least five individuals, these latter represented in at least two samples separated by not less than one month. As Table 4 shows, the greatest number of species occurs in mixed dipterocarp forest with nearly half of all forest species confined to mixed dipterocarp. Eleven species were found in both mixed dipterocarp and freshwater swamp,
60 A. G. Orr Table 4. Total species in six main forest formations and degree of overlap between formations (principal diagonal gives number of species confined to a particular formation, cross references give number of shared spp.). Based on 100 forest species for which minimum data requirements are met, data mainly from Orr (2001) and the parent data set. Figures represent numbers of species, but may also be read as percentages (because of fortuitous sample size). md, mixed dipterocarp; fw, freshwater swamp; ps, peatswamp; kg, kerangas; mg, mangrove; sd, secondary dipterocarp. md fw ps kg mg sd md 47 11 2 2 0 10 fw 8 21 6 1 13 ps 3 4 1 7 kg 0 0 2 mg 1 1 sd 0 Total spp. in habitat 62 44 23 7 3 18 generally in areas where the two habitats lay close together. Other overlaps between mixed dipterocarp and other forest types were few, except for secondary dipterocarp, with which 10 species were shared. The next richest habitat was freshwater swamp forest, with 44 species, 8 of which were found nowhere else. True peatswamp forest was about half as rich with 23 species, 21 of which were shared with freshwater swamp. Only three species were confined to peatswamp. Only seven forest species were present in kerangas (although some non-forest species were present as vagrants or foraged there sporadically), none of which was unique to the habitat. Similarly mangrove was inhabited by only three forest species, one specialist, with two others shared. Secondary dipterocarp forest was rather poor compared with its parent formation (but see below), with only 18 species, many shared with other formations. Non-forest species were more likely to encroach in secondary formations than in primary mixed dipterocarp forest. ENDEMICITY AND FOREST FORMATIONS Of forest species found in Brunei, 52.7% are Bornean endemics, a further 29.0 % are regional endemics, confined to Sundaland and Palawan and only 18.3% are wide ranging. Conversely, only one non-forest species, Pseudagrion lalakense, is endemic and only 10.4% of non-forest species are regional endemics; 87.5% are wide-ranging Table 5. Of species found in mixed dipterocarp forest, 56.5% are Bornean endemics and 29.0% are regional endemics. A relatively small proportion are wider
Odonata in Bornean tropical rain forest formations 61 Table 5. Levels of endemicity and regional endemicity amongst forest and non forest species as indicated by numbers and percentage of total forest and non-forest species respectively. Borneo endemic Confined to Wider ranging Total Sundaland + Palawan Forest 69 (52.7%) 38 (29.0%) 24 (18.3%) 131 Non-Forest 1 (2.1%) 5 (10.4%) 42 (87.5 %) 48 TOTAL 70 43 66 179 Table 6. Levels of endemicity and regional endemicity amongst mixed dipterocarp dwelling species versus swamp forest species, expressed as numbers of species and percentages of totals found in each forest type (data deficient spp excluded) Borneo endemic Confined to Wider ranging Total Sundaland + Palawan Mixed dipterocarp 35 (56.5%) 18 (29.0%) 9 (14.5%) 62 Swamp Forest 17 (35.4 %) 22 (45.8%) 9 (18.8%) 48 (all formations) TOTAL 52 40 18 100 ranging. Within swamp forest, a lower percentage (35.4 %) are Bornean endemics but 45.8% are regional endemics. Less than 20 % are wide ranging. Clearly, both mixed dipterocarp forests and swamp forests provide key habitat for endemic and regional endemic species. This is essential information for conservation planning. ACCOUNTS FOR EACH FOREST TYPE Lowland Mixed Dipterocarp Formation Of the forest assemblages sampled by Orr (2001), the greatest numbers of species (a diversity) and the greatest variability between sites (b diversity) was among the mixed dipterocarp formations, especially stream habitats. In some cases distinct assemblages occupied different microhabitats within the same forest formation and were separated by less than 50 m (notably in the steep, highly dissected terrain of the Kuala Belalong Field Studies Centre - KBFSC), as shown by Figures 3-6, where 54 species have been recorded from within an area about 100 m square. As an obvious corollary, such sites were also were home to the highest proportion of endemic species. Of the sites sampled extensively, several associations were recognised, based on a similar-
62 A. G. Orr ity analysis of species assemblages (Orr, 2001). The following summary demonstrates the considerable differences which occur between selected sites. Kuala Belalong formation (soil: Setap shale formation, grey clay and shale) Myrmeconauclea/ cobbled open canopy stream association (Figure 4) In Brunei this was represented only by the Sungei Belalong (KBFSC) and nearby Sungei Temburong, but similar broad streams in the Crocker ranges and Danum Valley, Sabah have similar faunas (Hamalainen in lit, Orr, unpublished data). At the point illustrated in figure 4 the stream runs north south, and receives direct sunlight for approximately half the day. Humidity remains high all day (>80% RH) owing to the closely bordering vegetation. The rheophyte Myrmeconauclea probably plays little role in the lives of odo- 20 sp forest 3 sp 20 sp tributary 1 sp 2 sp main stream 15 sp 100 m Fig. 3. Contour map of Kuala Belalong Field studies Centre (KBFSC), Brunei, showing proximity of sites with distinct species assemblages; numbers within areas enclosed by dashed lines indicate number of species at each site; circled numbers indicate number shared between sites. (contour intervals 5 m). Data from Orr, 2001. N
period when direct sunlight reaches stream Odonata in Bornean tropical rain forest formations 63 0900h 1200h 1500h 0600h 1800h 30 height (m) 20 10 0 10 20 30 m 0 Fig. 4. Profile of stream and riparian forest on the main stream, shown in figure 3, at KBFSC. (Compilation of forest mensuration data from several sources). nates, but serves to identify the association. This was the only habitat in Brunei which supported many calopterygoid species, such as Neurobasis longipes, Vestalis amoena, Heliocypha biseriata, Libellago stictica, Rhinocypha aurofulgens, and, Euphaea tricolor. Libellago semiopaca, Rhinocypha cucullata and Dysphaea dimidiata, shared with other mixed dipterocarp streams were also present. The chlorocyphids all oviposited in large, semi-submerged logs and developed in leaf trash in eddies behind such obstructions, whereas N. longipes, V. amoena and E. tricolor larvae lived in riffles, often in leaf packs. The only other zygopteran was Prodasineura verticalis, which oviposited in root masses where the stream banks were undercut. Several gomphids (Megalogomphus, Sieboldius, Microgomphus ) were present as were corduliids such as, Macromidia fulva, Macromia westwoodii and other Macromia species. In most cases gomphids and corduliids were more easily sampled in the larval stage. The libellulids Onychothemis coccinea and Orthetrum pruinosum, both present in other mixed dipterocarp were common, while Zygonyx iris was rare. Rocky closed canopy stream association (Figure 5) a small tributary ascending abruptly from the main stream at KBFSC, the Sungei Mata Ikan, with mainly rocky bed and steep banks on which few rheophytes grew. At the site shown in profile in Figure 5 a short reach runs nearly north south. Differ-
64 A. G. Orr 30 20 10 height (m) 0 0 10 20 30 m Fig. 5. Profile of stream and forest on the tributary, shown in figure 3, at KBFSC. (Compilation of forest mensuration data from several sources). ent sections of the stream are sequentially illuminated by broad patches of sun throughout the day, especially from 0900-1500h. Humidity remains close to that of the forest understorey (RH > 85%). Only two species were shared with the main stream. Typical species were Devadatta podolestoides, Vestalis amaryllis, V. atropha, Rhinocypha humeralis, R. stygia, Euphaea impar (rare), E. subcostalis, Rhinagrion borneense (rare), Coeliccia cyaneothorax and Drepanosticta rufostigma, among Zygoptera. Indaeschna grubaueri and Cratilla metallica, widespread forest understorey species, here occurred beside a permanent leafy rock pool. Heliogomphus blandulus is believed to prefer this habitat. Macromia westwoodi was more common here than on the main stream. Other gomphid and corduliid species may be present. Seepage/ forest understorey association (Figure 6) This formation is exemplified by the area around a marshy spring at the head of the Sungei Mata Ikan and in the surrounding forest. The forest stature is greater than beside the stream banks and only small sun flecks reach the forest floor.
Odonata in Bornean tropical rain forest formations 65 30 20 10 height (m) marshy area 0 10 20 30 m 0 Fig. 6. Profile of forest, including marshy area, within the forest site shown in figure 3, at KBFSC. (Compilation of forest mensuration data from several sources). Humidity at ground level is always high (RH > 90%). At this site the following species are found: Devadatta podolestoides, Vestalis beryllae, Bornargiolestes sp, Stenagrion dubium, Coeliccia borneensis, C. nigrohamata, Drepanosticta attala, D. forficula, D. versicolor, Drepanosticta sp. A, Drepanosticta sp. B, Protosticta sp. A, Protosticta sp. B, Leptogomphus pasia, L. pendleburyi. Some species are known to perch in sun flecks higher in the subcanopy 10-20 m above the ground. A similar, but less well sampled fauna, is known from seepages in the dipterocarp forest at Sungei Ingei. Pinanga/Dipteris/gravel and sand open stream formation (Soil: Lambir formation, sandstone and ahale with thin limestone and marl) A common association in several localities in Brunei, especially the Labi Hills is open or semi open streams with rheophytic vegetation dominated by the fern Dipteris lobata, in the rockier less exposed places, and the low palm Pinanga tenella. In general the terrain is more gentle than KBFSC, and it is difficult to separate small and large stream associations, hence slight overlap with both stream associations at KBFSC will be noted. Species present include Devadatta podolestoides, Vestalis amabilis, Libellago aurantiaca, Sundacypha petiolata, Dysphaea dimidiata, D. lugens, Euphaea ameeka, E. impar, Rhinagrion born-
66 A. G. Orr eense, Coeliccia sp. A aff macrostigma, Drepanosticta rufostigma, Elattoneura analis, Prodasineura sp. aff hosei, Leptogomphus mariae, Macrogomphus parallelogrammus, Megalogomphus sumatranus, Oligoaeschna platyura, Macromia cincta, M. corycia, Orthetrum pruinosum, Onchothemis coccinea (rare), O. culminicola, Zygonyx iris. Pandanus/ fine gravel-muddy open stream (merges into freshwater swamp) (soil: Belait formation, soft sandstone, clay and lignite). This association occurs in a number of locations in Brunei, notably Sg Ingei, where Thompson sampled in 1991 (Thompson and van Tol 1993). Species recorded were rather similar to the last formation and included Vestalis amabilis, Libellago aurantiaca, Rhinocypha cucullata, Sundacypha striata, Dysphaea lugens, Euphaea ameeka, E. impar, Rhinagrion borneense, Elattoneura analis, Prodasineura sp. aff hosei, Burmagomphus insularis, Macrogomphus parrallelogrammus, Megalogomphus sumatranus, Idionyx yolanda, Macromia corycia, Orthetrum pruinosum, Onychothemis coccinea and O culminicola. Phytotelmata association The mixed dipterocarp phytotelmata association appears to be fairly uniform across all lowland mixed dipterocarp formations. Even in forests where no phytotelmata could be located, placing artificial humus and water filled containers near the base of tree trunks invariably attracted members of the association (Artificial containers did not attract odonates in swamp or kerangas). It is probable however that large buttress pans, which host the richest communities (Orr, 1994, Kitching and Orr, 1996), tend to be most common where the topography is steep, as the buttresses on the upper side of the slope are complexly folded, creating watertight depressions. Moreover, most such trees sampled at KBFSC were Belian (Eusideroxylon Lauraceae) which appears particularly given to such basal growth forms. This tree species is rare or absent from many mixed dipterocarp formations. Most phytotelmata do not dessicate, even in drought conditions (Orr, 1994), unlike those of seasonal forests in Panama (Finke 1992, in litt). Pericnemis triangularis is present in most phytotelmata including small rot holes, but also large buttress pans. Lyriothemis cleis is almost always present in medium to large phytotelmata. The larvae may suffer extreme dessication without harm (Orr, 1994). Indaeschna grubaueri is present in most buttress pans, but also breeds in ground pools where the terrain permits their presence. Cratilla metallica prefers ground pools but will also develop in large log holes and disturbed buttress pans. The very rare Camacinia harterti has been reported ovipositing in buttress pans (Lieftinck, 1954) and may belong to this assemblage, (although listed below as a non-forest species). The phytotelmata assemblage, although small, is interesting in that it is clearly absolutely dependent on the presence of intact forest for survival. Each phytotelma represents an isolated community, with an allochthonous energy supply in the form of leaf litter. Bruneian communities are notable for their
Odonata in Bornean tropical rain forest formations 67 Predators Indaeschna Lyriothemis Pericnemis Detritovores Tipulidae Scirtidae Other 0 50 100 relative biomas (% total) Fig. 7. Pyramids of biomass and proportional contribution by major species for five large treeholes in Brunei. After Orr, 1997. relatively simple structures, with few species of detritovores and lower level carnivores, and a high biomass of top predators, invariably odonates, which often exceed in biomass, lower trophic levels Orr (1997), indicated by Figure 7. It is possible that small phytotelmata are found in the sub canopy, and might be utilized by certain Zygoptera which have been collected in canopy fogging operations. However the existence of such microhabitats remains hypothetical, and if present, they may not be sustainable as long term sources of standing water given low diurnal relative humidity in the canopy and resulting high evaporation. Freshwater Swamp Formation The freshwater formations best sampled were alluvial forest and stunted forest growing in depressed waterlogged areas in dipterocarp or at the kerangas/peatswamp boundary. These are believed to support the richest odonate assemblages, with at least 8 species not found in other formations. Tidal brackish swamp forest - Poorly sampled but known to support an odonate assemblage, believed to be species poor and comprised of mainly eurytopoc species. Tidal freshwater swamp forest - poorly sampled but known to support an odonate assemblage, grading into the next category. Alluvial forest with silty streams Low growing forest, many of the small trees with prop roots and pneumatophores, present beside many lowland streams and larger rivers. Limited variation between similar formations but any given site may be very rich. Thompson and van Tol (1993) record 35 forest species from this formation in an area adjoining three other forest types. Most species are found in pools and runnels above the stream level and include: Vestalis amabilis, Libellago aurantiaca, L. hyalina, Sun-
68 A. G. Orr dacypha striata, Orolestes wallacei, Podolestes orientalis, Amphicnemis remiger, A wallacei, Archibasis incisura, A. tenella, Teinobasis rajah, Copera vittata, Prodasineura sp. aff hosei, Gynacantha basiguttata, G. dohrni, Leptogomphus coomansi, Macrogomphus quadratus, Rhisiophlebia dohrni, Brachygonia oculata, Nannophyopsis chalcosoma, Tyriobapta torrida, Agrionoptera insignis, Cratilla lineata, Nesoxenia lineata, Orchithemis pulcherrima, Pornothemis serrata. Tannin stained, non-acidic freshwater swamps at borders of peatswamp and kerangas. Low formation of small trees, dense undergrowth, (possibly should be classified as marginal peatswamp forest). A rich assemblage of swamp forest species, including several possibly confined to this formation, or at least most common in it: Libellago hyalina, Amphicnemis erminea, Archibasis melanocyana, A. viola, Coeliccia macrostigma, Prodasineura collaris, Prodasineura dorsalis, Gynacantha basiguttata, Heliaeschna crassa, Oligoaeschna sp, Ictinogomphus acutus, Hemicordulia tenera, Metaphya micans (DD), Macromia cincta, Brachygonia oculata, Tyriobapta laidlawi, Cratilla lineata, Orchithemis pulcherrima, O. pruinans, O. xanthosoma, Pornothemis serrata, Pseudagrionoptera diotima (DD) Shallow depressions in MDF (tannin stained, non acidic water). Depending on the size of the basin, this is a distinct forest formation with low trees with prop roots and a dense undergrowth of rattans, or may be a small patch in Dipterocarp forest, with few small trees growing in swampy ground. Typical swamp forest assemblage with few unique: Vestalis amabilis, Podolestes orientalis, Onychargia atrocyana, Amphicnemis erminea, A. wallacei, Archibasis viola, Coeliccia sp. A aff macrostigma, Prodasineura collaris, P. haematosoma, P, hyperythra, Prodasineura sp. aff dorsalis, Prodasineura sp. aff hosei, Gynacantha basiguttata, Tyriobapta kuekenthali, T. laidlawi, T. torrida, Orchithemis pulcherrima. Peatswamp forest Of six recognised formations (Anderson 1964, Davies and Kamariah, 1999), four were sampled. In general formations of mixed species at the outer margins of the peat deposit where the peat layer is thinner were richer in species than Shorea albida monocultures on deeper peat deposits. In areas where the peat is raised ground water may be very limited and few odonates present. Most peatswamp species are shared with freshwater formations. Three species which appear confined to outer to middle formations in low wet forest are Podolestes chrysopus, P. harrissoni and Amphicnemis martini. Kerangas formations close to swamp forest often harbour swamp species which may establish feeding territories at high abundance (Orr 2004b), especially Libellago hyalina and several libellulids. Rare ground water attracts widespread swamp and dipterocarp forest species such as Cratilla metallica. Small, clear streams in elevated kerangas supported Prodasineura sp.
Odonata in Bornean tropical rain forest formations 69 aff hosei, and rarely, P. dorsalis. Kerangas growing on hilltops in dipterocarp forest was generally dry and devoid of odonates, except in hilltop clearings where non-forest species foraged. Mangroves - A total of six formations are recognised (Cranbrook and Edwards 1994) Typically 3-5 zones seaward to landward in the Rhizophora formation the specialist Raphismia bispina occurs, apparently breeding in oligohaline water. Other species occurring in mangrove do so facultatively, including several non-forest generalists, and seldom venture beyond the landward Xylocarpus or Bruguiera zones. Nipah occurs upstream in brackish water, and barely qualifies as forest. No specialized odonata are known from this formation. Secondary dipterocarp -A heterogeneous formation, often with swampy elements. Secondary formations sampled were not as diverse as the total primary dipterocarp forest, in terms of soils, topography and stream types. The numbers of species recorded are boosted by invasions from nearby swampy areas. Consequently, although it is clear that secondary dipterocarp is less rich than the parent primary forest, it is very difficult to quantify this effect with present data. Pericnemis stictica, a key element of the phytotelmata assemblage, appears to be absent. Ecotones: megadiverse sites in many situations on the plains of Brunei several different forest types may interdigitate forming a mosaic over an area of as little as one km 2. Thompson and van Tol (1993) report 43 forest species from Sungei Ingei, over a mosaic of mixed dipterocarp forest, alluvial forest, peatswamp forest and kerangas. Such sites are of undoubted conservation value, although as sites for ecological investigations they may be less useful, as the proximity of different habitats may obscure the species associations usual for each forest formation. DISCUSSION Orr (2001) concluded that the richest odonate assemblages in Brunei were present in primary mixed dipterocarp formations, especially in sites with a highly dissected landscape, allowing high species turnover between microhabitats, and although family profiles tend to remain similar between dipterocarp forests on different soils, species assemblages vary considerably. Thus both a and b diversity of the total fauna is maintained principally by assemblages occurring within this formation. Orr (2001) also concluded that the contribution to a diversity of freshwater swamp formations was very important. The information presented above, based on almost the same data set, affords similar conclusions.
70 A. G. Orr The data set of the Orr (2001) study included about 1250 specimens collected within forests, supplemented by well over 10,000 observational records, and yet in some respects it was limited as a survey of habitat associations. The uniqueness of many sites within Brunei, and impracticality of working beyond its boundaries meant sites were not adequately duplicated. Some sites were sampled for larvae and others were not. Locating equivalent stream habitats within different dipterocarp formations was at times impossible, partly because of the inaccessibility of many places in Brunei. Clearly a study over a more extensive area, including sites in western Sabah and northern Sarawak would yield a broader-based data set from which generalisations could be made with greater confidence. In tropical rainforest surveys it is desirable to sample both adults and larvae to achieve a proper balance in the data. There is also a constant need for more baseline data. A significant number of species known from north Borneo have not yet been named. More probably await discovery. Life histories are known in detail for only a handful of species, and in many cases early stages are completely unknown. We understand little about the way odonates utilize the physical structure of the forest. For example many gomphids and females of other families appear on stream beds only briefly during the day, and may be seen disappearing into the subcanopy, where presumably they spend most of their time. The canopy and subcanopy as dragonfly habitat remains virtually unknown, so that even a few days dedicated observation from one of the many canopy towers and walkways now available throughout the tropics might contribute significantly to our knowledge. The best understood system within the forest is the simplest; the phytotelmata association. The reasons various species are restricted to forest habitats are poorly understood. It was not possible in the Brunei study to document the effect of forest clearance, except in the case of one freshwater swamp association adjoining peat swamp and extensive areas of peat swamp, in which the forest fauna was replaced by a depauperate assemblage of non-forest species following removal or death of trees. Parallel surveys in forested areas and equivalent areas from which forests have been cleared, especially stream habitats, are desirable firstly to determine which species are genuinely dependent on the presence of intact forest, and secondly to document as many environmental parameters as possible which might be responsible for observed associations. (A little work on this theme has been done at Danum Valley centre in eastern Sabah, where a known history of logging and regrowth makes it ideally suited to such studies, but most have been carried out by undergraduates and are of very limited scope.) For deep forest species, forest clearance obviously radically alters the physical environment, raising the temperature of the air and water in seepages, lowering the relative humidity, possibly exceeding the innate tolerances of
Odonata in Bornean tropical rain forest formations 71 both adults and larvae. For larger streams, clearing forests may radically alter the hydrology of the system, causing erosion of banks and increasing turbidity of water. Lack of forest to retard run-off can result in more violent spates following every rain storm, leading to scouring of sand and silt deposits (Ross & Dykes, 1996). The amount of vegetable detritus in leaf packs in riffles and in deep macerated deposits may be greatly reduced, depriving larvae of living space and detritivorous prey items. Rheophytes essential for oviposition may not grow in exposed situations or may be out-competed by weedy grasses. The relative humidity of the air above the stream may drop significantly with forest clearance. Many rainforest insects are poorly adapted to withstand low humidity, and it is known that in cleared urban areas in Brunei RH drops to 60% or lower in the middle of the day, an effect that also occurs in the forest canopy. An observation I have often made, is that in the Australian wet tropics in open forest and in Thailand, especially at higher altitudes and in what was formerly monsoon forest, rivers and streams support quite rich faunas, including some species which occur also in deep closed canopy forest. In Brunei, at 5 latitude deforested streams support poor faunas. It is not clear if this difference is due to a lesser reduction in RH in cleared areas in tropical areas 10-15 latitude from the equator, or whether the forest odonates from more seasonal and drier regimes are better adapted to dry conditions (in some cases the same species are involved), or if other variables are involved. Simple measurements of environmental parameters would help resolve these questions. In brief, we understand to some extent the pattern of habitat associations in Borneo, and these results are expected to apply at least to most of Sundaland. Further data would refine and broaden the picture, but probably not radically alter our present view. On the other hand we have a very poor understanding of the underlying process(es) which have produced this pattern. It is difficult to say exactly what most needs investigation, as any study of ecology or behaviour is likely to further our understanding in some important way. An understanding of the ecological requirements of odonates is critical to their conservation. Our present understanding of patterns of distribution indicate that both primary mixed dipterocarp and swamp forest, especially freshwater swamp, are key habitats, necessary to the continuing existence of the greater part of the Bornean odonate fauna. As conservation is most effective when concentrated on unusual and endemic forms (Moore 1997), the same conclusions are reinforced by analysis of endemicity among forest species. Unfortunately these same forests are under intensive pressure from logging concerns, especially mixed dipterocarp forest and Shorea albida peatswamp forest, the latter designated as an endangered ecosystem (Davies and Kamariah 1999). Kerangas forest, which may include odonate rich swamps
72 A. G. Orr around its margins, exists now only in tiny pockets and is highly vulnerable to fire. Draining of peatswamps (Davies and Kamariah 1999) has catastrophic consequences for the forests, the hydrology and dragonflies. It does not seem likely that odonate conservation can compete with legalised logging, except in Brunei which is supported by its petroleum industry, and where, with 10% of the land area and all critical habitats protected, the odonate fauna can be regarded as secure, despite unfortunate habitat destruction due to fire in peatswamp and kerangas during el Niño droughts (Orr, 2001). For the rest of Borneo, including Sarawak, Sabah and Kalimantan, about 5% of the total land area lies in gazetted reserves and adequate areas of a majority of essential habitats, as presently understood, are included in this category (Orr 2003). There is however considerable doubt as to whether nominal protection is adequately enforced, and the disastrous cycle of forest fires seems likely to continue, despite the fact that the associated smoke pall makes human habitation in cities in the region extremely unhealthy and uncomfortable. Thus, in Borneo, and much of south-east Asia, odonate conservation equates with forest conservation. This has the advantage that the same conservation policies are good not just for endemic dragonflies, but more charismatic species, orang-utan, rhinoceros, gibbons, birds, butterflies and indigenous forest-dwelling humans. Nevertheless, this does not negate the importance of special efforts directed at Odonata, and it is an unfortunate fact that the island of Borneo is so poorly studied that not a single species can be with certainty given a definite conservation ranking (Orr 2004a), although certain genera are believed to be at least vulnerable. Conservation is as much a political as a scientific exercise. Having the information to flag an iconic species as endangered appeals directly to political sensibilities. Vague statements of data deficiency do not carry same weight. There is a pressing need to involve local people in the study of odonatology and dragonfly conservation. To this end, there is a very great need for local field guides. At present the expertise and the will to produce such guides exists, but funding does not. Field guides must compete in a commercial publishing environment, and seldom qualify for scientific grants. An exception of which I am aware is a proposal to fund guides in local languages. This is a gimmick, and serves only to encourage obscure and poorly produced booklets. In south-east Asia the educated minority who buy books and have disproportional political influence are also mostly highly competent in English and proud of it. Good field guides rely heavily on their illustrations, and subtleties of literary expression are not an issue. For them English has become the new Latin, a universal language of scholarship, and the greatest difficulty they experience in understanding English scientific books is the old Latin, represented abundantly in terminology and Linnean names.