DSpace at VNU: Aquatic insect faunas and communities of a mountain stream in Sapa Highland, northern Vietnam

Limnology (2008) 9:219–229 DOI 10.1007/s10201-008-0250-8 ASIA/OCEANIA REPORT Aquatic insect faunas and communities of a mountain stream in Sapa Highland, northern Vietnam Sang Woo Jung Ỉ Van Vinh Nguyen Ỉ Quang Huy Nguyen Ỉ Yeon Jae Bae Received: 22 November 2006 / Accepted: 13 August 2007 / Published online: July 2008 Ó The Japanese Society of Limnology 2008 Abstract Aquatic insect communities were investigated from the Muonghoa Stream in the Sapa Highland (highest peak 3,143 m), a subtropical mountain stream in northern Vietnam Field investigations for quantitative (Surber net 50 cm 50 cm, mesh size 0.2 mm, riffle and pool/run) and qualitative (hand net, mesh size mm) sampling were conducted at nine sites along the watercourse between 27 November and December 2005 As a result, a total of 216 species (the majority of them undescribed) belonging to 139 genera, 61 families, and nine orders were recognized: 53 Ephemeroptera species (24.5%), nine Odonata species (4.2%), 15 Plecoptera species (6.9%), seven Hemiptera species (3.2%), 35 Coleoptera species (16.2%), one Megaloptera species (0.5%), 29 Diptera species (13.4%), 66 Trichoptera species (30.6%), and one Lepidoptera species (0.5%) Trichoptera, Ephemeroptera, and Coleoptera represented the major aquatic insect groups with regard to taxonomic and individual richness, whereas Hemiptera and Odonata were relatively less diverse and abundant than in studies of other tropical Southeast Asian streams The dominance, richness, and diversity indices (H0 ) fell within the following ranges [mean ± standard deviation (SD)]: 0.18–0.76 (0.42 ± 0.19), 4.13–9.19 (7.06 ± 1.45), and 1.61–3.22 (2.67 ± 0.55), respectively Riffle habitats generally yielded numbers of aquatic insect species and individuals approximately twice that sampled in pool/run habitats Shredders were relatively larger in proportion within the headwater reach, whereas scrapers and collectorgatherers were more abundant in the middle and lower stream reaches This functional feeding group composition is characteristic of temperate streams in East Asia The results of detrended correspondence analysis and Bray– Curtis cluster analysis indicated that aquatic insect compositions at the sampling sites were very reflective of the reach characteristics, which evidence gradual changes with altitude and stream order along the stream watercourse This is the first comprehensive investigation of aquatic insects in highland Southeast Asian regions Keywords Aquatic insect fauna Á Biodiversity Á Community composition Á Tropical stream Á Southeast Asia Introduction S W Jung Á Y J Bae Department of Biology, Seoul Women’s University, Seoul, South Korea V V Nguyen Á Q H Nguyen Department of Invertebrate Zoology, Hanoi University of Science, Hanoi, Vietnam Present Address: Y J Bae (&) Lab of Animal Systematics and Ecology, Division of Life Sciences and Biotechnology, Korea University, Anam-dong, Seongbuk-gu, Seoul 136-701, South Korea e-mail: yjbae@korea.ac.kr The Sapa Highland is located in northern Vietnam (Fig 1) and has been identified as the center of biodiversity in mainland Southeast Asia (Nguyen and Harder 1996) This area embraces Mt Fansipan (3,143 m), the highest mountain within peninsular Southeast Asia, and the associated mountain range extends to the adjacent Yunnan Province of China and further to the Himalayas Although tropical Asian streams are known to constitute rich habitats for diverse groups of freshwater organisms, including aquatic insects, the actual makeup of the fauna inhabiting these regions remain poorly understood In 123 220 Limnology (2008) 9:219–229 Fig Study sites (St 1–St 9) in the Muonghoa Stream of Sapa Highland, northern Vietnam previous studies, Nguyen et al (2001) studied the altitudinal distribution of aquatic insects in a stream in Tam Dao National Park in northern Vietnam, and Cao et al (2008) conducted a faunistic study of aquatic insects in Bach Ma National Park in central Vietnam Hoang and Bae (2006) demonstrated that a tropical stream in southern Vietnam evidenced a higher degree of aquatic insect diversity than that observed in temperate streams in Korea The aquatic insect fauna and the community compositions of the Sapa Highland have not yet been investigated, with the exception of a few fragmented taxonomic studies of some aquatic insect groups (Nguyen and Bae 2004; Hoang and Bae 2005; Cao et al 2007) In this paper, we provide faunistic and community data of aquatic insects in the Sapa Highland, based on a comprehensive field investigation, in order to explain biodiversity in tropical mountain streams Materials and methods Study stream and sites The Sapa Highland is located in northern Vietnam, approximately 38 km west of Lao Cai Province and 375 km northwest of Hanoi (22°070 –22°280 N, 103°430 – 104°040 E) (Fig 1) The region covers an area of 67,864 and has an average elevation of 1,500 m above sea level The climate is generally humid (humidity 76–96%) all year, with an average yearly rainfall of 2,770 mm The heaviest rains occur in July and August The average 123 temperature is approximately 15°C, in a range between 3°C and 20°C, and December and January are the coldest months Snow falls on 1–3 days per year The Muonghoa Stream runs across the Sapa Highland and is approximately 42 km in total length As the stream flows from the high mountain peaks to the lowland areas along the watercourse, the stream and riparian areas represent diverse temperate and tropical forest elements (Nguyen and Harder 1996) Nine sampling sites belonging to stream orders I–V (stream orders were determined with a map of scale 1:60,000) were selected as follows along the watercourse; all but one site (site 3) were located on the mainstream watercourse (Fig 1) Site was located at a tributary headwater within the upper stream reach The environmental factors at each sampling site are shown in Table St St St St St St St St St (22°210 88700 (22°210 33400 (22°210 83300 (22°200 48900 (22°190 25000 (22°180 29400 (22°170 25000 (22°150 95600 (22°220 00500 N, N, N, N, N, N, N, N, N, 103°460 66600 103°460 25000 103°470 98200 103°480 59700 103°500 33400 103°530 30100 103°550 18400 103°580 04800 104°040 26300 E): Thac-Bac (upper) E): Thac-Bac (lower) E): Quy-Ho E): Shin-Chai E): Cat-Cat E): Ta-Van E): Cau-May E): Ban-Ho E): Ben-Den Field investigations and analyses Field investigations were conducted from 27 November to December in 2005 Aquatic insects were sampled with a Depth and current speed were measured at the sampling points Substrate: S sand, G gravel, P pebble, C cobble, B boulder, L leaf litter, M moss, A algae; dominant substrates are indicated in bold c a, b 1139.4 ± 667.5 46.7 ± 39.8 24.2 ± 24.5 18.7 ± 8.1 26.6 ± 11.1 3.0 ± 0.8 0.4 ± 0.6 15.3 ± 3.4 7.3 ± 0.9 7.5 ± 0.5 79 V Mean ± SD Village agriculture Village C, S, G, P 7.65 8.70 20.6 4.64 30 16 60–65 Village St 100–110 0 C, B, P, A B, P, A, C 8.39 6.94 7.18 7.85 17.5 18.4 1.00 3.96 3.13 40 31 30 23 35–38 50–57 95–100 404 IV St 643 III St 982 III 50–60 Forest agriculture Pasture agriculture C, P, B G, 7.06 8.20 18.7 2.80 30 15 40–45 Forest St 1,250 III 80–90 30 C, P, G, B 7.59 7.78 13.1 1.00 2.97 41 30 10–12 Forest St 1,358 III 25–30 90 C, P, B, G 8.10 6.85 12.1 2.80 23 23 5–6 Forest St 1,669 I 20–22 100 L, P, C, B 7.31 6.62 13.1 2.42 11 1–4 Forest St 1,830 II 2,040 I St 8–10 80 90 C, M, L, P B, M, P, C 7.25 7.60 5.71 6.90 12.8 11.7 1.40 2.42 1.98 20 18 10 10 1–3 Pool/run Pool/run Riffle Riffle St 5–10 1–2 Substratec DO (mg/l) pH Water temp (°C) Current speed (m/s)b Depth (cm)a Water width (m) Stream Altitude (m) order Stream width (m) 221 Site Table Environmental data of the Muonghoa Stream of Sapa Highland, northern Vietnam (DO dissolved oxygen, SD standard deviation) 10–15 Canopy Landscape (%) Limnology (2008) 9:219–229 Surber net (50 cm 50 cm, mesh size 0.2 mm) for quantitative purposes; two Surber samples were obtained in riffle and pool/run habitats (total sampling area 5,000 cm2 per site) Additional samples were obtained with a hand net (mesh size mm) in a variety of microhabitats for qualitative purposes General environmental factors, including geographic location and altitude [portable global positioning system (GPS): SP24XC, MLR, USA], stream width and depth, surface current velocity (Craig 1987), water temperature, pH and dissolved oxygen (portable water checker: WQC-22A, TOA, Japan), and substrate composition (subjectively estimated percentage cover of bedrock/boulder [ 256 mm, cobble 64–256 mm, pebble 16–64 mm, gravel 2–16 mm, coarse sand 0.5–2 mm, and fine sand/silt \ 0.5 mm) were determined at all sampling sites All sampled materials were maintained in 250 ml plastic vials with Kahle’s solution and brought to the laboratory for sorting of aquatic insects The sorted aquatic insects were preserved in 80% ethyl alcohol (EtOH) The aquatic insects were identified to the species or lowest taxonomic categories, from available references (Wiederholm 1983; Morse et al 1994; Yoon 1995; Merritt and Cummins 1996; Wiggins 1996; Dudgeon 1999; Kawai and Tanida 2005) We also employed additional taxonomic articles (e.g., Sangpradub and Boonsoong 2004) for the identification of specific aquatic insect groups Taxa without taxonomic references to species level, which describes the majority of the cases in this study, were separated into morphospecies, based primarily on external ultrastructures All materials are housed in the Aquatic Insect Collection of Seoul Women’s University and Hanoi University of Science McNaughton’s dominance index (DI), Margalef’s richness index (RI), and Shannon species diversity index (H0 ) were calculated according to Smith and Smith (2001) Detrended correspondence analysis (DCA) (Hill and Gauch 1980) and Bray–Curtis (Bray and Curtis 1957) similarity measure were employed in the analyses of aquatic insect communities between the study sites Functional feeding groups (FFGs) were classified mainly according to Morse et al (1994) and Merritt and Cummins (1996) All these community analyses were on the basis of the quantitative samples, but we excluded all Diptera taxa in the community analyses because their species level treatments, particularly the larvae of Chironomidae and Simuliidae, may have created biased results due to sampling and identification difficulties in poorly known aquatic insect communities We have, however, included the list of Diptera taxa in Appendix to provide an understanding of the general faunistic features of the area 123 222 Results Stream environments The habitat topology and general environmental factors of the sampling sites, including stream width and water temperature, changed gradually as the stream flowed to the lower reaches (Table 1) A number of waterfalls and small cascades existed in the upper reaches of the stream Cobble and boulder-sized stones predominated throughout the sampling sites, although other diverse substrates, including pebbles, gravel, sand, leaves, mosses, and attached algae, were found mixed with larger stones The riparian forest consisted of a variety of evergreen trees and grasses, including bamboo, palm, vine, and Carex (Cyperaceae) Aquatic macrophytes were relatively rare, partially due to the fact that the sampling season was in late autumn, and because of other anthropogenic influences In the middle and lower stream reaches, drainage areas were affected to a moderate degree by human influence, including terraced rice paddies, pastures, roads, and villages Aquatic insect fauna On the basis of quantitative and qualitative sampling, a total number of 216 species (the majority of which were undescribed) belonging to 139 genera, 61 families, and nine orders were recognized in the Muonghoa Stream (Appendix 1) Trichoptera (66 species, 30.6%), Ephemeroptera (53 species, 24.5%), and Coleoptera (35 species, 16.2%) constituted the three major aquatic insect groups, and Diptera (29 species, 13.4%), Plecoptera (15 species, 6.9%), Odonata (nine species, 4.2%), Hemiptera (seven species, 3.2%), Megaloptera (one species, 0.5%), and Lepidoptera (one species, 0.5%) were the taxa (in descending order) in terms of species richness (Appendix 1) Ephemeroptera: Ephemeroptera was one of the most species-rich and abundant aquatic insect groups in the Muonghoa Stream, and this phenomenon was apparent in the middle and lower stream reaches The Leptophlebiidae were relatively more abundant in the upper stream reach, whereas Baetidae and Heptageniidae were more abundant in the middle and lower stream reaches Epeorus aculatus and Ecdyonurus cervina (Heptageniidae) were commonly found throughout the stream reaches Nigrobaetis sp (Baetidae) predominated in the lower stream reach Potamanthus sp (Potamanthidae), Vietnamella sp (Ephemerellidae), and Caenis sp (Caeniidae) were rarely found, and were limited to the lower stream reach Isonychia formosana (Isonychiidae) was found only at the lowermost site (site 9) Odonata: Odonata species and individual numbers were relatively poorly represented, and no members of this order 123 Limnology (2008) 9:219–229 were found in the upper stream reach (sites and 2) Gomphidae species were only rarely found in the lower stream reach Bayadera sp (Euphaeidae), Anotogaster sp (Cordulegastridae), and Ophiogomphus sp (Gomphidae) inhabited the pool areas, whereas Brachythemis sp (Libellulidae) was found in the riffle areas Plecoptera: the majority of Plecoptera species were found in the upper stream reach (sites 1–4), while Perlidae was found throughout the sampling sites (sites 1–9) Togoperla (Perlidae) showed a relatively wider altitudinal distribution, and Tetropina and Neoperla (Perlidae) were found in the middle and lower stream reaches, respectively Hemiptera: Hemiptera species and individual numbers were relatively low, and only seven species were found in the sampling sites Heleocoris sp (Naucoridae) and Aphelocheirus sp (Aphelocheiridae) were found throughout the sampling sites, whereas a number of immature Micronecta sp (Corixidae) individuals were collected in a pool in the middle stream reach (site 7) Coleoptera: 35 species of Coleoptera occurred throughout the entire sampling sites Elmidae was the most species-rich taxon of Coleoptera in the Muonghoa Stream, and members of the family inhabited the riffle areas and were found on the surfaces of moss-covered cobble and boulder-sized stones Scirtidae were found in the upper stream reach, whereas Psephenidae more richly occurred in the lower stream reach Haliplidae, Ptilodactylidae, Dytiscidae, Noteridae, and Lampyridae were rarely found in restricted habitats Megaloptera: only one species of Corydalidae, Protohermes sp., occurred more abundantly in the middle stream reach Diptera: 29 species of Diptera occurred throughout the sampling sites Simuliidae dominated in riffle areas in the uppermost stream site (site 1), and the family also abundantly inhabited the upper stream reach Chironomidae were abundantly found throughout the sampling sites, and Tipulidae and Blephariceridae also occurred abundantly in the lower stream reach Few red chironomids were found in the sampling sites Trichoptera: 66 species of Trichoptera in 15 families occurred throughout the sampling sites This represented the highest degree of species richness of aquatic insects in the stream They inhabited a wide range of habitats according to the taxa Net-spinning caddisflies, including Cheumatopsyche, Ceratopsyche, and Hydropsyche (Hydropsychidae), were found more abundantly in the riffle areas of the middle stream reach Glossosoma sp (Glossosomatidae) was also found abundantly in the middle stream reach Diplectrona (Hydropsychidae), Dolophilodes (Philopotamidae), and Psilotreta (Odontoceridae) were found only in the headwater stream sites (sites and 3) Limnology (2008) 9:219–229 223 Lepidoptera: only one species of Pyralidae, Parapoynx sp., occurred in the lower stream reach (sites 6–8) Community On the basis of quantitative sampling, three major tropical aquatic insect groups (Ephemeroptera, 2,541 individuals, 62.7%; Trichoptera, 686 individuals, 16.9%; Coleoptera, 382 individuals, 9.4%) represented 89% of the total individual number of aquatic insects collected from the sampling sites, whereas the other remaining taxa (Hemiptera, 204 individuals, 5.0%; Plecoptera, 200 individuals, 5.0%; Megaloptera, 19 individuals, 0.5%; Odonata, 18 individuals, 0.5%) contributed to the aquatic insect community to a lesser degree Quantitative data at each sampling site (Figs 2, 3) also indicated that the Ephemeroptera, Trichoptera, and Coleoptera represented almost the entire aquatic insect communities In general, the aquatic insect communities inhabiting the Muonghoa Stream were dominated by philopotamid larvae (Dolophilodes sp 1) or nemourid larvae (Nemoura sp 2) in the upper stream reach, as well as baetid mayfly larvae (Nigrobaetis sp 2) in the middle and lower stream reaches (Table 2) The riffle habitats generally yielded larger species and individual numbers, and higher diversity indices (number of species 33.6 ± 7.2 per 2,500 cm2; individual number 293.9 ± 186.1 per 2,500 cm2; H0 2.58 ± 0.56) than in pool per run habitats (number of species 21.0 ± 9.8 per 2,500 cm2; individual number 156.1 ± 128.7 per 2,500 cm2; H0 1.98 ± 0.68) at most sampling sites (Table 3) The numbers of species and individuals at each sampling site were significantly different (P \ 0.01 and P \ 0.05, respectively) between the habitat types (Table 3) The dominance indices (DI), richness indices (RI), and diversity indices (H’) fell within the following ranges [mean ± standard deviation (SD) 0.18–0.76 (0.42 ± 0.19), 4.13–9.19 (7.06 ± 1.45), and 1.61–3.22 (2.67 ± 0.55)], respectively (Table 2) Shredders represented a relatively larger proportion at the headwater sites (sites and 3) than at the other lower stream sites, but the proportions themselves remained rather small (Fig 4) Scrapers and collector-gatherers were increasingly abundant in the lower stream reach (sites 4–8) The first two axes of the DCA ordination accounted for the majority of the variation in the species data, with eigenvalues of 0.69 and 0.41 for axes and 2, respectively, with a total inertia (total variation in the species data) of 3.08 The first axis corresponds to the most important gradient in the data (Fig 5) On the basis of the aquatic insect community data, the sampling sites of Muonghoa Stream can be separated into two groups (sites 1–3; sites 4– 9) on axis I The former and latter groups represented high and mid–low altitude sites, respectively, although site is Fig Average number of species of aquatic insects, excluding Diptera, per Surber sample (2,500 cm2) in the Muonghoa Stream of Sapa Highland, northern Vietnam Fig Average individual number of aquatic insects, excluding Diptera, per Surber sample (2,500 cm2) in the Muonghoa Stream of Sapa Highland, northern Vietnam situated somewhat apart from the other stream sites Sites and 3, which belonged to stream order I, are apart from the other sites (sites and 4–9) on axis II This can be best explained by general habitat difference between the headwater sites (sites and 3) and other mainstream watercourse sites (sites and 4–9) (Table 1) In addition, site is a tributary stream below site 2, and it represented the most different species composition from that of all other stream sites The Bray–Curtis similarity matrix indicates that the middle stream sites, including sites and (63.8%) and sites and (47.1%) can be grouped relatively closely, but that the tributary headwater site (site 3) and lowermost site (site 9) are the most distant (20–24%) from the other sites (Fig 6) Discussion The biodiversity of aquatic insects in a stream can be determined by a variety of ecological and environmental factors on local, basin, and regional scales, including habitat complexity and biogeographical history (Vinson and Hawkins 1998; Hoang and Bae 2006) Although the 123 224 Limnology (2008) 9:219–229 Table Average number of species and individual numbers, first and second dominant species, dominance index (DI), richness index (RI), and diversity index (H0 ) of aquatic insects, excluding Diptera, per Site (altitude) Surber sample (2,500 cm2) in the Muonghoa Stream of Sapa Highland, northern Vietnam No of species No of individuals First dominant species (%) Second dominant species (%) DI RI H0 2.94 St (2,040 m) 45 346 Dolophilodes sp (26.9) Zaitzevia sp (6.9) 0.34 7.53 St (1,830 m) 42 274 Ecdyonurus cervina (13.5) Labiobaetis sp (9.5) 0.23 7.30 3.15 St (1,669 m) 21 127 Nemoura sp (32.3) Epeorus aculatus (15.7) 0.48 4.13 2.29 St (1,358 m) 46 St (1,250 m) 57 236 444 Nigrobaetis sp (16.9) Nigrobaetis sp (26.1) Epeorus aculatus (14.4) Epeorus aculatus (12.8) 0.31 0.39 8.24 9.19 3.08 3.04 St (928 m) 51 788 Nigrobaetis sp (50.8) Ecdyonurus cervina (7.7) 0.59 7.50 2.27 St (643 m) 48 772 Nigrobaetis sp (31.5) Micronecta sp (22.4) 0.54 7.07 2.44 St (404 m) 40 864 Nigrobaetis sp (62.2) Platybaetis sp (14.0) 0.76 5.77 1.61 St (79 m) 37 199 Platybaetis sp (9.5) Ceratopsyche sp (8.0) 0.18 6.80 3.22 Mean ± SD 38.0 ± 10.2 450.0 ± 283.8 Table Comparison of species and individual numbers of aquatic insects, excluding Diptera, per Surber sample (2,500 cm2) between the riffle and pool/run habitats in the Muonghoa Stream of Sapa Highland, northern Vietnam The difference in the quantitative data between the riffle and pool/run habitats was examined by paired t test Site (altitude) 0.4 ± 0.2 7.1 ± 1.5 2.7 ± 0.6 No of species Riffle Pool/run Riffle St (2,040 m) 37 24 252 94 St (1,830 m) 37 20 199 75 St (1,669 m) 20 106 21 St (1,358 m) 27 29 137 99 St (1,250 m) 39 38 208 236 St (928 m) 41 20 378 410 St (643 m) 39 19 551 221 St (404 m) 27 25 631 233 St (79 m) 35 183 16 Mean ± SD 33.6 ± 7.2 P (n = 9) \ 0.01 Muonghoa Stream in the Sapa Highland is located within mainland Southeast Asia, its general environment and aquatic insect fauna differ from those of typical tropical streams in Southeast Asia due to its geographical location This area is subtropical in terms of latitude, but the majority of the stream reaches are located within a highland mountain area, with the exception of the lowermost site (site 9) Because of this, the aquatic insect faunas and community compositions of the stream evidenced a mixture of temperate and tropical features The number of aquatic insect taxa found in the Sapa Highland (216 species, 139 genera, and 61 families) was larger than that of Tam Dao National Park in northern Vietnam (145 species, 127 genera, and 63 families) (Nguyen et al 2001) or Bach Ma National Park in central Vietnam (143 species, 119 genera, and 65 families) (Cao et al 2008), but was smaller than that of Dak Pri stream in southern Vietnam (268 species, 230 genera, and 91 families) (Hoang and Bae 2006) Although these comparisons were not predicated on the same sampling methods (i.e., 123 No of individuals 21.0 ± 9.9 293.9 ± 186.1 Pool/run 156.1 ± 128.7 \ 0.05 spatial and temporal scales and duplicates), the taxa richness of the Sapa Highland was determined to be relatively larger than has generally been observed in northern Vietnamese streams (e.g., Tam Dao National Park) or Northeast Asian temperate streams (e.g., Gapyeong stream in Korea) (Hoang and Bae 2006) One of the unique features of the aquatic insect fauna of the Sapa Highland is the high degree of species richness of Trichoptera (66 species, 30.6%) The numbers of Trichoptera species tend to be generally smaller than those of Ephemeroptera in other Vietnamese tropical streams (Nguyen et al 2001; Cao et al 2008), but they are relatively larger in the majority of temperate streams (Hoang and Bae 2006) Mey (2005) demonstrated that Mt Fansipan and its surrounding highland areas constitute the center of caddisfly diversity in tropical Southeast Asia The Odonata and Hemiptera were found to be less species-rich than is normally found in southern Vietnamese tropical streams In general, the diversity of Odonata is substantially influenced by temperature and tends to be Limnology (2008) 9:219–229 Fig Individual number composition of functional feeding groups of aquatic insects, excluding Diptera, per Surber sample (2,500 cm2) in the Muonghoa Stream of Sapa Highland, northern Vietnam Fig DCA ordination based on species composition of aquatic insects, excluding Diptera, sampled from nine study sites in the Muonghoa Stream of Sapa Highland, northern Vietnam correlated with vegetation cover in streams (Corbet 1999) Aquatic macrophytes were poorly developed in the Muonghoa Stream, which may also explain the generally low species richness of Odonata Simuliids were relatively abundant, particularly in the upper reaches of the stream, another feature of temperate streams (McCreadie et al 2005) However, the species richness of Coleoptera, in particular the Elmidae, was relatively larger than that normally observed in temperate streams, and this is characteristic of tropical streams (Brown 1981; Hoang and Bae 2006) Species richness and community compositions were similar between the sampling sites, with the exception of the tributary headwater site (site 3) (Fig 2), whereas 225 Fig Bray–Curtis similarity diagram of study sites based on species composition of aquatic insects, excluding Diptera, sampled from nine study sites in the Muonghoa Stream of Sapa Highland, northern Vietnam individual abundance increased with decreasing altitude, with the exception of the lowermost site (site 9) (Fig 3) The relatively smaller number of individuals at the site is probably attributable to anthropogenic influences from a nearby town The riffle habitats yielded approximately double the species richness, diversity, and individual abundance than was observed in the pool/run habitats This is due primarily to the larger numbers of swimmers (e.g., baetid mayflies) and clingers (e.g., heptageniid mayflies and hydropsychid caddisflies) inhabiting the riffle habitats Functional feeding groups (FFGs) of the Muonghoa Stream differed to some degree from those of other tropical streams in Southeast Asia, which are influenced by riparian forests and in-stream environmental conditions, including substrate compositions and marginal macrophytes Typical tropical streams, e.g., the Dak Pri stream in southern Vietnam (Hoang and Bae 2006), are almost completely covered by riparian forest, and the substrates are more heterogeneous, harboring an abundance of leaf packs and root masses However, the Muonghoa Stream is generally open to sunlight and lacks abundant aquatic macrophytes in the middle and lower stream reaches Owing to this, scrapers such as the Heptageniidae, Glossosomatidae, and Psephenidae were relatively more abundant in the middle and lower reaches It remains unclear, however, as to the manner in which food resources influence aquatic insect communities, as well as the manner in which the feeding strategies of tropical aquatic insects differ from those of the temperate streams (Yule 1996; Motta and Uieda 2004; Tomanova et al 2006) According to Tomanova et al (2006), the FFG classifications of aquatic insects of neotropical streams are not always congruent with their congeners inhabiting temperate streams The results of DCA indicated that the aquatic insect communities of Muonghoa Stream are influenced primarily 123 226 by altitudinal differences, along with other environmental factors, including stream size, current velocity, water temperature, dissolved oxygen (DO), substrate, food resource, and canopy (see Fig and Table 1) The Bray– Curtis similarity diagram (Fig 6) is also quite reflective of the habitat characteristics of the middle stream (sites and 5) and lower stream (sites 6, and 8) sites The communities of the upper stream reaches (sites and 2) and the tributary and lowermost stream reaches (sites and 9) differ from those of the middle stream sites, which may also reflect differing environmental conditions in the sampling sites Acknowledgments This work was supported by a Korea Research Foundation Grant (KRF-2005-212-C00002) Appendix Aquatic insect taxa in the Muonghoa Stream of Sapa Highland, northern Vietnam Order Ephemeroptera Family Leptophlebiidae Choroterpes sp Choroterpes sp Choroterpes vittata Habrophlebiodes prominens Isca fascia Isca sp Thraulus bishopi Thraulus sp Family Potamanthidae Potamanthus sp Family Ephemeridae 10 Ephemera sp Family Ephemerellidae 11 Cincticostella gosei 12 Cincticostella sp 13 Epharacella sp 14 Serratella sp 15 Torleya arenosa 16 Torleya sp 17 Torleya sp Family Austremerellidae 18 Vietnamella sp Family Caenidae 19 Caenis sp Family Isonychiidae 20 Isonychia formosana Family Heptageniidae 21 Afronurus meo 22 Afronurus mnong 23 Epeorus hieroglyphicus 24 Epeorus aculatus 123 Limnology (2008) 9:219–229 25 Epeorus bifurcates 26 Epeorus sp 27 Ecdyonurus cervina 28 Ecdyonurus landai 29 Ecdyonurus sp 30 Ecdyonurus sp 31 Iron martinus 32 Iron sp 33 Rhithrogena sp 34 Rhithrogeniella tonkinensis 35 Rhithrogeniella sp Family Baetidae 36 Acentrella sp 37 Baetiella sp 38 Baetiella sp 39 Baetiella sp 40 Baetiella sp 41 Baetis sp 42 Baetis sp 43 Baetis sp 44 Centroptella sp 45 Centroptella sp 46 Heterocloeon sp 47 Heterocloeon sp 48 Labiobaetis sp 49 Nigrobaetis sp 50 Nigrobaetis sp 51 Platybaetis sp 52 Platybaetis sp 53 Procloeon sp Order Odonata Family Calopterygidae 54 Mnais sp 55 Neurobasis sp Family Euphaeidae 56 Bayadera sp 57 Euphaea sp Family Aeshnidae 58 Aeschnophlebia sp Family Cordulegastridae 59 Anotogaster sp Family Gomphidae 60 Ophiogomphus sp Family Libellulidae 61 Brachythemis sp 62 Brachythemis sp Order Plecoptera Family Nemouridae 63 Ampinemura sp 64 Nemoura sp 65 Nemoura sp 66 Protonemura sp 67 Sphaeronemoura sp Limnology (2008) 9:219–229 Family Leuctridae 68 Perlomyia sp 69 Rhopalopsole sp Family Perlidae 70 Acroneuria sp 71 Kamimuria sp 72 Kiotina sp 73 Neoperla sp 74 Tetropina sp 75 Togoperla sp 76 Togoperla sp 77 Togoperla sp Order Hemiptera Family Naucoridae 78 Heleocoris sp Family Aphelocheiridae 79 Aphelocheirus sp Family Corixidae 80 Micronecta sp Family Helotrephidae 81 Helotrephes sp Family Hebridae 82 Hyrcanus sp 83 Nieserius sp Family Gerridae 84 Rhyacobates sp Order Coleoptera Family Gyrinidae 85 Gyretes sp 86 Gyrinus sp Family Haliplidae 87 Haliplus sp Family Dytiscidae 88 Hydrovatus sp 89 Rhantus sp Family Hydrophilidae 90 Berosus sp 91 Enochrus sp 92 Hydrobius sp 93 Hydrochara sp 94 Paracymus sp Family Hydraenidae 95 Limnebius sp 96 Ochthebius sp Family Lampyridae 97 Luciola sp Family Noteridae 98 Hydrocoptus sp Family Sciritidae 99 Cyphon sp Family Ptilodactylidae 100 Stenocolus sp Family Dryopidae 227 101 Helichus sp Family Psephenidae 102 Eubrianax sp 103 Eubrianax sp 104 Psephenoides sp 105 Psephenus sp Family Elmidae 106 Atractelmis sp 107 Heterlimnius sp 108 Macronychus sp 109 Macronychus sp 110 Ordobrevia sp 111 Promoresia sp 112 Stenelmis sp 113 Stenelmis sp 114 Stenelmis sp 115 Stenelmis sp 116 Zaitzevia sp 117 Zaitzevia sp 118 Zaitzevia sp 119 Zaitzevia sp Order Megaloptera Family Corydalidae 120 Protohermes sp Order Diptera Family Tipulidae 121 Antocha sp 122 Dicranota sp 123 Hexatoma sp 124 Hexatoma sp 125 Holorusia sp 126 Limnophila sp 127 Tipula sp 128 Tipula sp 129 Tipula sp Family Blephariceridae 130 Blepharicera sp 131 Philorus sp Family Psychodidae 132 Pericoma sp Family Simuliidae 133 Prosimulium sp 134 Simulium sp Family Ceratopogonidae 135 Bezzia sp Family Chironomidae 136 Chironominae sp 137 Chironominae sp 138 Chironominae sp 139 Chironominae sp 140 Chironominae sp 141 Chironominae sp 142 Chironominae sp 123 228 143 Chironominae sp 144 Orthocladiinae sp 145 Tanypodinae sp 146 Tanypodinae sp Family Empididae 147 Hemerodromia sp Family Tabanidae 148 Tabanus sp 149 Tabanus sp Order Trichoptera Family Ecnomidae 150 Ecnomus sp Family Hydropsychidae 151 Amphipsyche sp 152 Arctopsyche sp 153 Arctopsyche sp 154 Arctopsyche sp 155 Ceratopsyche sp 156 Ceratopsyche sp 157 Ceratopsyche sp 158 Ceratopsyche sp 159 Ceratopsyche sp 160 Ceratopsyche sp 161 Ceratopsyche sp 162 Ceratopsyche sp 163 Ceratopsyche sp 164 Cheumatopsyche sp 165 Cheumatopsyche sp 166 Cheumatopsyche sp 167 Cheumatopsyche sp 168 Diplectrona sp 169 Hydropsyche sp 170 Hydropsyche sp 171 Hydropsyche sp 172 Hydropsyche sp 173 Hydropsyche sp 174 Hydropsyche sp 175 Hydatomaicus sp 176 Hydromanicus sp 177 Hydromanicus sp 178 Macrostemum sp 179 Parapsyche sp 180 Parapsyche sp 181 Potamyia sp 182 Potamyia sp 183 Trichomacronema sp Family Polycentropodidae 184 Neureclipsis sp 185 Plectrocnemia sp 186 Plectrocnemia sp 187 Polycentropus sp Family Psychomyiidae 188 Lype sp 123 Limnology (2008) 9:219–229 189 Psychomyia sp 190 Psychomyia sp 191 Tinodes sp Family Philopotamidae 192 Chimarra sp 193 Chimarra sp 194 Dolophilodes sp 195 Dolophilodes sp 196 Wormaldia sp Family Stenopsychidae 197 Stenopsyche ulmeri 198 Stenopsyche sp Family Glossosomatidae 199 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(e.g., Tam Dao National Park) or Northeast Asian temperate streams (e.g., Gapyeong stream in Korea) (Hoang and Bae 2006) One of the unique features of the aquatic insect fauna of the Sapa Highland... Muonghoa Stream of Sapa Highland, northern Vietnam Fig Average individual number of aquatic insects, excluding Diptera, per Surber sample (2,500 cm2) in the Muonghoa Stream of Sapa Highland, northern