PLANT et al.: 121–149 Studia dipterologica 18 (2011) Heft 1/2 • ISSN 0945-3954

Higher taxon diversity, abundance and community structure of , and Brachystomatidae (Diptera: ) in tropical forests – results of mass-sampling in [Diversität, Abundanz und Gemeinschaftsstruktur höherer Taxa der Empididae, Hybotidae und Brachystomatidae (Diptera: Empidoidea) in tropischen Wäldern – Ergebnisse einer Massenbeprobung in Thailand]

by Adrian R. PLANT, Chayanit SURIN, Raewat SAOKHOD and Wichai SRISUKA

Cardiff (United Kindom) Chiang Mai (Thailand) Chiang Mai (Thailand) Chiang Mai (Thailand)

Abstract An overview of Empididae, Hybotidae and Brachystomatidae (Diptera: Empidoidea) in Thailand is presented using data from mass trapping of more than 35,000 specimens collected throughout the country supplemented with reference to the literature. Quantitative analyses were restricted to 18,675 specimens with associated numerical data and a subset of 16,805 collected using standardised trapping protocols. The diversity, abundance, distribution, habitat and biogeography of 21 genera of Hybotidae, 12 Empididae and 2 Brachystomatidae occurring in Thailand was assessed. Hybotidae were generally more abundant than Empididae, especially in the east and coastal peninsula and both families were more frequent at higher elevations. Brachystomatidae were rare and confined to northern mountains. Hybotidae were dominated by and Empididae by and although regional and altitudinal variations occurred. The Empididae and Hemerodromiinae were rare or absent in the east and coastal peninsula and did not occur below an altitude threshold at ca. 400 m. Seasonal phenology of subfamilies varied with region and altitude but maximal abundance coincided generally with the start and end of the wet seasons and was lowest during dry seasons. Diversity and abundance at generic level was investigated at a northern site and found to be positively correlated with the wet season. Cluster analysis of altitude and abundance tentatively identified 12 communities with distinct habitat, regional, altitudinal and phenological characteristics. Northern montane wet evergreen forests were particularly rich in Empidoidea and many genera occurring there have Palaearctic affinities consistent with a model (PLANT et al. 2012) in which historical climate changes drove immigration from the north. Unlike many of the Palaearctic elements, taxa with Oriental affinities have often successfully colonised the lowlands where they dominate -level assemblages in highly seasonal habitats. Key words Empididae, Hybotidae, Brachystomatidae, Oriental Region, Thailand, diversity, abundance, altitude, seasonality Zusammenfassung Auf der Grundlage von Daten aus dem Massenfang von mehr als 35.000 Exemplaren wird ein Überblick über die in Thailand vorkommenden Empididae, Hybotidae und Brachystomatidae (Diptera: Empidoidea) gegeben, ergänzt durch Angaben aus der Literatur. Quantitative Analysen wurden für 18.675 Exemplare durchgeführt, von denen numerische Daten vorlagen. Gleiches gilt für 16.805 Exemplare, die mit standardisierten Fangmethoden gesammelt wurden. Diversität, Abundanz, Verbreitung, Habitat und Biogeografie von 21 Gattungen der Hybotidae, 12 Gattungen der Empididae und 2 Gattungen der Brachystomatidae in Thailand wurden ermittelt. Hybotidae waren allgemein häufiger als Empididae, besonders im Osten und an den Küsten der Halbinsel, und beide Familien waren häufiger in größeren Höhen. Brachystomatidae waren selten und auf die nördlichen Bergregionen beschränkt. Unter den Hybotidae dominierten die Tachydromiinae und unter den Empididae die Empidinae und Hemerodromiinae, obwohl regionale und höhenab- hängige Variationen auftraten. Clinocerinae (Empididae) und Hemerodromiinae waren im Osten und an den Küsten der Halbinsel selten oder fehlten. Sie traten unter ca. 400 m Meereshöhe gar nicht auf. Das saisonale Auftreten der Unterfamilien variierte in Abhängigkeit von Region und

121 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand

Höhe, aber die maximale Abundanz fiel im allgemeinen mit dem Beginn und dem Ende der Regenzeiten zusammen und war in den Trockenzeiten am niedrigsten. Die Diversität und Abun- danz auf Gattungsniveau, die an einem nördlichen Fundort untersucht wurden, waren positiv korreliert mit der Regenzeit. Eine Clusteranalyse der Unterfamilien-Abundanz in Abhängigkeit von der Meereshöhe identifizierte 12 vorläufige Gemeinschaften mit jeweils verschiedenen Eigenschaften bezüglich Habitat, Region, Höhe und Phänologie. Die nördlichen immergrünen Bergregenwälder erwiesen sich als besonders reich an Empidoidea, wobei viele der dort vorkom- menden Gattungen Beziehungen zur Paläarktis zeigen – ein Ergebnis, das mit dem Modell von PLANT et al. (2012) übereinstimmt, wonach historische Klimaveränderungen die Einwanderung von Norden vorantrieben. Im Gegensatz zu vielen paläarktischen Elementen haben orientalische Taxa häufig erfolgreich die Tiefländer besiedelt, wo sie innerhalb der Gattungsgemeinschaften in saisonbeeinflussten Habitaten dominieren. Stichwörter Empididae, Hybotidae, Brachystomatidae, orientalische Region, Thailand, Diversität, Abundanz, Höhe, Saisonalität

Introduction Thailand is situated within both the Indo-Burma and Sundaland mega-hotspots identified by MYERS et al. (2000) as globally significant. In common with most, if not all tropical countries, Thailand’s biodiversity is poorly known with estimates of taxon richness and abundance based largely on relatively well studied vertebrates and higher plants. There are for example ~ 10,000 named of higher plants out of an estimated 12,000–18,000 and inventories of ~ 320 reptiles, ~ 550 fish and ~ 1,000 birds are likely to be reasonable approximations of the correct figures. Quantification of invertebrate diversity in Thailand, even to order of magnitude, is however unrealistic at present, as with the exception of a few groups such as butterflies () with 1,130 species (EK-AMNUAY 2006), they remain largely unknown. HUTACHARERN et al. (2007) catalogued 10,191 species of and mites from the country, but this is undoubtedly far short of the actual total. Knowledge of Thailand’s Diptera is very incomplete; the Oriental Catalogue (DELFINADO & HARDY 1973, 1975, 1977) listed 974 described species in 56 families while HUTACHARERN et al. (2007) reported 996 named species in 40 families. PAPP et al. (2006) reviewed the literature and recent collections in Thailand, concluding that 99 families were present, albeit with many represented only by undescribed species. Although the Empidoidea families Empididae and Hybotidae are numerous in collections from Thailand (e. g. PAPP et al. 2006) only 23 species of Empididae and 32 Hybotidae were listed by YANG et al. (2007) and a likely rich fauna of (not discussed further in the present work) is similarly under-recorded (YANG et al. 2006). Recent publications on the and systematics of Empidoidea in Thailand include: – Empididae: BARTÁK & KUBÍK (2008); DAUGERON & GROOTAERT (2003, 2005b); DAUGERON et al. (2011); GROOTAERT & KIATSOONTHORN (2001); HORVAT (2002); PLANT (2009a, 2009b, 2010). – Hybotidae: GROOTAERT & SHAMSHEV (2003, 2006, 2009, 2012); SHAMSHEV & GROOTAERT (2004, 2005, 2007, 2008); SHAMSHEV et al. (2006). Brachystomatidae: PLANT (2009c, 2010a). Currently 44 named species of Hybotidae, 43 Empididae and 3 species of Brachystomatidae have been reported from Thailand. Twelve genera of Empididae, 21 Hybotidae and 2 Brachystomatidae are now known from the country, although many of these have been recorded merely as present in wider faunistic or phylogeographic studies (GROOTAERT & SHAMSHEV 2009, GROOTAERT & SHAMSHEV 2012, PAPP et al. 2006, PLANT et al. 2012, SHAMSHEV & GROOTAERT 2007) and in the absence of detailed revisionary work, some generic assignments should be regarded as provisional.

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The genera of EMPIDIDAE known from Thailand are: Empidinae (3 genera): LINNAEUS, 1758; MEIGEN, 1822; MEIGEN, 1822. Hemerodromiinae (6 genera): Achelipoda YANG, ZHANG & ZHANG, 2007; Anactastoctedon PLANT, 2010; MACQUART, 1823; MACQUART, 1823; MEIGEN, 1822; ZETTERSTEDT, 1837. Clinocerinae (2 genera): Clinocera MEIGEN, 1803; MACQUART, 1823. Incertae sedis (1 genus): Hormopeza ZETTERSTEDT, 1838 which is regarded as incertae sedis in Empididae (SINCLAIR & CUMMING 2006) is also present. The genera of HYBOTIDAE known from Thailand are: (2 genera): MEIGEN, 1820; MACQUART, 1827. Oedaleinae (2 genera): ZETTERSTEDT, 1838; MEIGEN, 1820. Tachydromiinae (11 genera): HALIDAY in WALKER, 1851; Crossopalpus BIGOT, 1857; MEIGEN, 1822; Elaphropeza MACQUART, 1827; Megagrapha MELANDER, 1928; Nanodromia GROOTAERT, 1994; MACQUART, 1827; Pontodromia GROOTAERT, 1994; MEIGEN, 1803; MEIGEN, 1830; Stilpon LOEW, 1859. (6 genera): MACQUART, 1823; Chillcottomyia SAIGUSA, 1986; Euhybos COQUILLETT, 1895; MEIGEN, 1803; LOEW, 1857; WALKER, 1852. Harpamerus BIGOT, 1859 and Parahybos KERTÉSZ, 1899 which are now considered congeneric with Syneches (SINCLAIR 2011) also occur in Thailand. BRACHYSTOMATIDAE are represented by MEIGEN, 1822 (Brachystomatinae) and RONDANI, 1856 (). Bicellaria, Euhybos, Oedalea, Ocydromia and Tachypeza are here recorded for the first time from Thailand. With increased knowledge of the fauna, preliminary ecological, biogeographic and phylogeographic analyses have started to appear (GROOTAERT & KIATSOONTHORN 2003, PLANT 2009b, PLANT et al. 2012). Since 2006 mass trapping programmes throughout Thailand have yielded in excess of 35,000 examples of Empididae, Hybotidae and Brachystomatidae which have been made available to taxonomic specialists and have provided material for some of the taxonomic revisions mentioned above. The empidoid fauna is clearly diverse and numerous but a full taxonomic evaluation of it is a painstaking process that will take many years to accomplish. The present work sum- marises preliminary analyses of higher taxon diversity and abundance and attempts to relate the results to local, regional and altitudinal climate and ecology; perhaps the first time such a synthesis has been attempted for such diverse dipteran taxa in a tropical country as large and complex as Thailand. In order to provide a context for assessing the results, we here provide a summary of Thailand’s geography, surface geology, climate, biogeography and principle forest biomes. With an area of 514,000 km2 Thailand (Fig. 1) is situated entirely within the tropics, its North–South axis spanning 1,800 km and 15 degrees of latitude between 6–20°N. About 80 % of the country forms a compact northern land area bordered by Burma (Myanmar), Laos and ; the southern part is mostly formed by the Thai Peninsula, bordered to the south by Malaysia, to the east by the and to the west by the Andaman Sea and southernmost Burma. Mountains rise to 2,565 m in the north from which arise tributaries of the Chao Phraya river which flows southwards across a broad Central Plain, discharging to the sea at Bangkok. The Tenasserim Mountains form much of the western border with Burma and continue into Peninsula Thailand. Lower elevation mountains, more or less contiguous with the Cardamom Mountains of Cambodia, are present in the extreme southeast in Trat, Chanthaburi and Sa Kaew provinces. East of the Central Plain

123 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand

Fig. 1: Digital elevation map of Thailand. Remarks: Low elevations are coded by ‘cool’ and high elevations by ‘warm’ colours (blue represents land at about sea level, red indicates higher mountains etc.). Sampling sites are numbered 1–33 (see Tab. 1 for explanatory key). Geographical regions used in analyses are delimited by black lines and indicated by upper case letter. Abbreviations: C = Central Plain; E = East; N = North; NE = Northeast; W = West; S = South; SE = Southeast.

124 Studia dipterologica 18 (2011) Heft 1/2: 121–149 lies the Isaan Plateau, bounded to the south by the Dong Rek Mountains forming the border with Cambodia, to the east by the Mekong River, and with moderate elevation mountains along much of its western margins, especially in Chayaphum, Phetchabun and Loei provinces. The underlying geology is complex but most of the rocks are Palaeozoic or Cenozoic with belts of and rocks in places and Quaternary alluvial terraces and plains in the valleys. Igneous rocks (granites, rhyolites and basalts etc.) form the backbone of many of the ranges. Bands of metamorphic rocks occur in some of the ranges and there are extensive areas of sandstone and siltstone, especially on the Isaan Plateau. Limestones of different ages are found in pockets or strips throughout the country, sometimes forming impressive karst landscapes. Thailand lies wholly within the Oriental Realm and its biota is similar to that of surrounding countries with Indochinese and Indoburmese affinities predominating in the north and strong Sundaic influences in the Peninsula. The tectonic assembly of from mostly Gondwan continental fragments was largely complete by the late and it is likely that post-Triassic dispersal events have had greater influence on the history of Diptera in the region than has vicariance mediated by plate tectonics. Historical changes in climate have had profound influence on Southeast Asian biodiversity. For example, during the , tropical rain- forests probably covered all of Thailand but retreated southwards in response to development of a seasonal monsoon climate, perhaps as early as 15–20 MYA. Cenozoic orogenesis of the main mountain ranges continues to this day, providing moist montane refugia in an increasingly dry climate and perhaps providing montane ‘corridors’ along which incursion from the Palaearctic has taken place (see Discussion section). Progressive general cooling during the Pleistocene may also have mediated southward migration of Palaearctic elements into Thailand and the decreased sea levels associated with glacial maxima facilitated colonization by Sundaic ele- ments from the south. Thailand’s climate is entirely tropical, most of the country experiencing a rainy season lasting from June to October, coincident with the Southwest Monsoon, followed by a cool dry period from November to February and a hot dry period between March and May. The south however experiences less strongly pronounced dry periods and greater overall rainfall as it is exposed to the Northeast Monsoon between November and February. Seasonal aridity is greatest on the Isaan Plateau and lowland areas of central and northern Thailand but in the mountains of the north and west, annual rainfall is more evenly distributed and diurnal temperatures more variable (night-time temperatures below 12 °C are commonplace and ground frosts sometimes occur on the northern mountains). About 28 % of the land area is under forest including 12 % primary forest, 10 % modified natural forest with the remainder consisting of production plantations. Most lowland areas are deforested and used for agriculture. The interplay of latitude, climatic, ecological and geological history has resulted in an extremely complex mosaic of habitats but some broad generalisations as to forest biomes are possible. Tropical Evergreen Forest (tropical rain forest) occurs from sea level to 1,000 m only in the far south of Thailand, south of ~ 9°N (Yala, Songkhla, Narathiwat, Tarutao Island) with perhaps a few small areas in Trat (~ 12.2°N 102.6°E) and Chantaburi (~ 12.5°N 102.3°E) in the southeast. It requires minimal seasonal variation in rainfall and temperature and is only found where precipitation is at least 2,000 mm/year without a prolonged dry season. It is the most floristi- cally diverse forest type in Thailand.

125 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand

Figs A, B: Collecting sites in Thailand. – A: Hill Evergreen Forest, Doi Phu Kha National Park (NE Region). A – B: Epiphyte-rich Moist Hill Evergreen Forest, Doi Inthanon National Park (North Region). B

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Figs C, D: Collecting sites in Thailand. – C: Pinus merkusii forest and ‘thung’ grassland at Thung Salaeng C Luang National Park (North-East Region). – D: Bamboo groves on disturbed ground merging into Dry D Evergreen Forest alongside the River Kwai Noi, Kanchanaburi (West Region).

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Figs E, F: Collecting sites in Thailand. – E: Mangroves, Pran Buri River (Coastal Peninsula Region). – F: E Deciduous/Dry Evergreen Forest, Si Nan National Park (North-East Region). F

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Semi-evergreen Forest is a somewhat transitional form of tropical evergreen forest, slightly more tolerant of periodic dry conditions and is found in central Peninsula Thailand below about 1,000 m, north to about the level of Chumphon (~ 10.5°N), but extending slightly further in the hills along the Burmese border and with small areas in southeast Thailand. Dry Evergreen Forest (confusingly also sometimes known as semi-evergreen forest) is unique to mainland Southeast Asia and is the dominant form of evergreen forest in Thailand. It is found along the wetter parts of the Tenasserim range from Chumphon north to Chiang Rai (~ 20.1°N 99.7°E); along the Dongrek range on the Cambodian border (~ 14.3°N 103.5°E); in the Petchabun range (~ 16.7°N 101.5°E) north to the Laos border; in the northeast; in the Phu Phan Range in Sakhon Nakhon (~ 17.4°N 107.7°E); and in northern Nong Khai (~ 18.3°N 103.4°E) along the Mekong river. It thrives where rainfall is rather high (typically 1,200–2,000 mm/year) but can tolerate a dry season of up to five months. Compared with wetter evergreen forest types, the canopy is more open and mutilayered with a less diverse flora and fauna. Hill Evergreen Forest occurs above 1,000 m in areas where annual rainfall exceeds 2,000 mm and is fairly evenly distributed throughout the year. It is found on the upper slopes of many of the northern mountains, in Chantaburi, Khao Yai (~ 14.4°N 102.3°E) and in the Petchabun range. It also occurs on the upper slopes of the Khao Luang range in Nakhon Si Thammarat and Surat Thani in the south (~ 8.7°N 99.5°E). Hill evergreen forests are dominated by Fagaceae such as Castanopsis, Lithocarpus and Quercus and these characteristically temperate genera become more frequent toward the north where members of the families Aceraceae, Lauraceae, Magnoliaceae and Rosaceae are abundant. Hill evergreen forests are rich in epiphytes and show high endemism. The term moist hill evergreen forest is usually employed to describe the upper continuum of this biome above 2,000 m. Pine Forest prefers sandy, well-drained soils at elevations of 400–1,400 m. Pure stands of pines are indicators of controlling effects of fire and climax pine forest is found in Loei (~ 17.4°N 101.6°E) and Petchabun provinces at the northwest margin of the Isaan Plateau but also occurs in patches throughout the north. Patches of ‘thung’ (savannah) grassland may be interspersed with pine forest. Mixed Deciduous Forest is also known as deciduous monsoon forest, is found in areas receiving 1,250–2,000 mm of annual rainfall, with pronounced wet and dry seasons at eleva- tions up to 1,000 m. Although formerly dominant at lower elevations in the west and north, it is rich in commercially important trees such as Teak (Tectona grandis), Dipterocarpus alatus, Shorea obtusa and and has been extensively exploited. Remnants remain, especially in the Phetchabun and Phu Phan ranges. Dry Dipterocarp Forest replaces mixed deciduous forest where annual rainfall is below 1,250 mm and the dry season lengthens to six months. It inhabits dry, lateritic and shallow soils lacking humus. Structurally more open than mixed deciduous forests, many of the trees are highly resistant to fire and most dry dipterocarp forests are burned regularly with natural regeneration occurring readily. It is dominant in the east with extensive areas also found in the northern part of the central plain from Nakhon Sawan to Uttaradit (~ 15.7°N 99.4°E – 17.9°N 100.7°E), in the southeast, and in the west around Kanchanaburi (~ 14.4°N 99.1°E). Beach and Mangrove Forests still occur around the Gulf of Thailand and Andaman sea coasts but have been much degraded by settlement, shrimp farming and tourism developments. As little as 1,720 km2 mangrove forest now remains.

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Materials and methods Trapping localities. Empididae, Hybotidae and Brachystomatidae from three mass trapping projects in Thailand were used in the analyses. Sampling localities are shown in Fig. 1 and Tab. 1. Most material was identified to subfamily level but that from Doi Chiangdao was identified to genus. (I) TIGER Project. The TIGER (Thailand Group for Entomological Research) Project operated 5,999 traps comprising 3,605 Malaise traps, 1,928 pan traps and 466 litter samples in national parks throughout Thailand between 2006 and 2009. Malaise traps were serviced at 7 day intervals and pan traps every 3 days. In excess of 35,000 individual Empididae, Hybotidae and Brachystomatidae were collected. Although we extracted target taxa from all these samples for wider taxonomic studies and used taxonomic information so gathered in assessing overall diversity, quantitative analyses were restricted to a subset of samples of indeterminate number in which only samples containing target families were studied, and comprised. 725 Malaise traps yielding 13,635 specimens (dataset TIGER-M); 129 pan traps yielding 371 specimens; 7 litter samples yielding 43 specimens. A small number (29) of trapping events at light or with flight interceptions traps yielded 66 specimens. (II) HLP samples. The HLP Project (High Land Project) employed two Malaise traps set 400 m apart in evergreen forest, between 26.vii.2008 and 27.xi.2009 at HRD Pakea Station (1,560 m; 19°18'N 98°49'E), Doi Chiangdao, Chiang Mai Province. Traps were serviced every 7 days yielding 102 samples containing 2,288 specimens (dataset HLP-MA). In 2008 Malaise traps were run for 7 day periods on various dates in coffee, apricot, peach and persimmon plantations adjacent to the evergreen forest sites, resulting in 13 samples containing 123 specimens (dataset HLP-MB). (III) QSBG samples. During 2006–2009, 93 Malaise trap samples were obtained from the grounds of Queen Sirikit Botanic Garden (QSBG), Chiang Mai Province (620–868 m; 18°53'N 98°51'E); five samples from Doi Suthep, Chiang Mai (1,356 m; 18°49'N 98°53'E); 10 samples from Romklau Plant Collection Station, Phitsanulok (999–1,023 m; 17°36'N 100°54'E); one from Phu Soi Dao, Uttaradit (697 m; 17°41'N 100°56'E). Additionally, 24 flight interception trap samples from QSBG and 7 samples collected by hand or at light at Mae Surin, Channabot, Doonlampan Sanctuary and QSBG are also represented. Malaise traps were serviced at varying intervals but 64 from QSBG (dataset QSBG-M) and 10 from Romklau (dataset P-M) were from seven-day trapping periods. Analyses. Analyses of overall composition and abundance used the combined data from all TIGER, HLP and QSBG samples (18,675 individual Empididae, Hybotidae and Brachystomati- dae from 1,141 collection events) and discussion of general faunistics incorporated information from all sources (more than 35,000 specimens). All other analyses utilized only the combined data from standardized seven-day Malaise trapping; specifically datasets. TIGER-M, HLP-MA, HLP-MB, QSBG-M and P-M, comprising 16,805 individuals from 914 seven-day trapping events (however, analyses of elevational relationships used only 843 of the 914 seven-day Malaise trap data for which altitude data was available). Determination of diversity parameters, Fisher’s alpha and Dominance (1-Simpson index) and cluster analysis of the mean number of individuals of the major subfamilies at differing elevations employed PAST (HAMMER et al. 2001). Linear regression, standard deviation and means were calculated in Microsoft Excel. Where specific habitat data was not available from sample labels, broad habitat categories were inferred from personal knowledge of specific sites and local or regional forest types. Regional climatic data was downloaded from the Thailand Meteorological department (www.tmd.go.th) and from www.climatetemp.info/thailand. Climatic data for Doi Chiangdao in 2009 from reporting

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Tab. 1: Sampling sites in Thailand; name, approximate geographical coordinates and number of samples from each site. Remarks: Locality numbers and regions correspond with sample locations and geographical area from which data were grouped for analyses as indicated in Fig. 1 (note that locality no. 13 is the only sample from the Central Plain and is here referred to as from the Coastal Peninsula). Abbreviations: no. = number; NP = National Park.

Coordinates No. of Locality no. Name Region (approx.) samples 01 Chae Son NP North 18°50'N 099°28'E 25 02 Doi Phahompok NP North 20°03'N 099°08'E 82 03 Doi Chiangdao NP North 19°18'N 098°49'E 172 04 Huai Nam Dang NP North 19°18'N 098°36'E 58 05 Namtok Mae Surin NP North 19°21'N 097°60'E 22 06 Queen Sirikit Botanic Garden North 18°53'N 098°51'E 101 07 Doi Inthanon NP North 18°35'N 098°29'E 24 08 Doi Suthep NP North 18°49'N 098°53'E 5 09 Mae Wong NP West 16°05'N 099°07'E 41 10 Khuean Srinagarindra NP West 14°30'N 098°53'E 40 11 Pu Toei NP West 14°58'N 099°26'E 53 12 Kaeng Krachan NP West 12°32'N 099°28'E 58 13 Khao Sam Roi Yot NP Coastal Peninsula 12°06'N 099°57'E 28 14 Khao Sok NP South 08°54'N 098°39'E 48 15 Namtok Yong NP South 08°16'N 099°39'E 73 16 Khao Khitchakut NP Southeast 12°49'N 102°09'E 34 17 Khao Yai NP East 14°25'N 101°23'E 40 18 Pa Hin Ngam NP East 15°39'N 101°26'E 12 19 Tat Tone NP East 15°56'N 102°06'E 13 20 Nam Pong NP East 16°37'N 102°34'E 3 21 Phu Kao-Phu Phan Kham NP East 16°49'N 102°37'E 6 23 Phu Phan NP East 17°06'N 104°01'E 12 23 Channabot District East 18°05'N 102°36'E 1 24 Doonlampan Sanctuary East 16°46'N 103°02'E 1 25 Pha Taem NP East 15°37'N 105°37'E 24 26 Phu Kradueng NP East 16°53'N 101°47'E 3 27 Phu Ruea NP East 17°31'N 101°21'E 25 28 Nam Nao NP East 16°44'N 101°35'E 27 29 Khao Kho NP Northeast 16°33'N 101°02'E 16 30 Thung Salaeng Luang NP Northeast 16°34'N 100°52'E 32 31 Ramklau Northeast 17°36'N 100°54'E 14 32 Phu Soi Dao NP Northeast 17°42'N 100°57'E 1 33 Doi Phu Kha NP Northeast 19°12'N 101°05'E 48

131 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand 90 1–5 381 888 958 Total Total 1,192 4,639 10,518 87–966 12–927 120–924 293–2,500 481–1,375 168–1,396 in m Altitude range e 0 4 R n 13 0.03 0.50 5.38 4.56 1.47 0.53 6.80 204 143 1,369 1,025 h R 2.11 4.81 6.18 6.45 13.57 16.13 17.36 0 % 1.4 4.4 13.0 17.2 14.9 22.1 1 8 5 2 1 4 12 nSite Hemerodromiinae + Clinocerinae Hemerodromiinae 0 0 9 0 28 34 3 n 111 13 167 489 121 192 230 nTrap = trapping rate for Empididae. e Clinocerinae 90 381 888 958 1192 4,639 nSpec 10,518 0 0 0 % 2.2 0.8 0.3 0.3 1 n 84 18 506 178 2,630 1,306 0 4 n 13 195 140 % 0.3 9.5 excluded. Abbreviations: nSpec = total number of individuals; nTrap = number of trapping events; nSite = number = nSite events; trapping of number = nTrap individuals; of number total = nSpec Abbreviations: excluded.

1,139 1,012 25.0 42.4 18.6 20.0 28.2 Empididae are

n 72 380 804 686 780 7,888 3,333 0 Hemerodromiinae % 1.4 4.4 10.8 16.4 14.6 21.8 % Hybotidae 99.7 90.5 75.0 57.6 81.4 80.0 71.8 = trapping rate as number of individuals / trap event for Hybotidae; R h West West Region Coastal Peninsula East North Northeast South Southeast Region Coastal Peninsula East North Northeast South Southeast Tab. 2 : Geographical Tab. variation in abundance of Empididae and Hybotidae in Thailand (combined TIGER + + HLP QSBG samples). Remarks: The percentage (with number of individuals in parenthesis) of Empididae and Hybotidae trapped in regions different is given. Regions correspond with geographical areas delimited in Fig. The 1. altitude range Brachystomatidae for Data given. also is events trapping of of trapping locations; R 3 : Geographical Tab. variation in abundance of Hemerodromiinae and Clinocerinae in Thailand (combined TIGER + HLP + QSBG samples). The percentage (with number of individuals in parenthesis) of each subfamily and combined totals for individuals of all taxa trapped in different regions is given. The total number of Empididae + Hybotidae trapped in each region is given. delimited in Fig. 1. Regions correspond with geographical areas

132 Studia dipterologica 18 (2011) Heft 1/2: 121–149 stations approximately 500 m from Malaise trap sites was supplied by the Maeta Man Watershed Management Unit, Maena, Chiangdao District. Altitude is quoted as elevation above mean sea level. Nomenclature of higher taxa follows SINCLAIR & CUMMING (2006).

Results Higher taxon faunistics Hybotidae constituted 74.6 % of 18,675 individuals in the combined TIGER + HLP + QSBG samples and comprised 61.6 % Tachydromiinae, 12.8 % Hybotinae, with Ocydromiinae and Oedaleinae together accounting for only 0.2 %. Empididae constituted 25.3 % of which 13.4 % were Hemerodromiinae, 10.5 % Empidinae and 1.4 % Clinocerinae. Hormopeza and Brachystomatidae were < 0.1 % of the fauna. Hybotidae were consistently more abundant than Empididae across all regions of Thailand (Tab. 2). Both families were more abundant in the North and West in terms of total numbers of individuals collected and numbers recovered per trap event. Using only stand- ardised seven-day trap catch data, Tachydromiinae were the most abundant subfamily of Hybotidae comprising 79.8 % of Hybotidae Fig. 2: Weekly changes in abundance of Empididae (open squares) and Hybotidae (closed squares) using standardised seven-day Malaise trap in the North (West), 95.4 % (East), data from all geographical regions combined. 93.0 % (South), 72.4 % (Southeast) and 99.7 % (Coastal Peninsula). In most regions, Empininae were the most abundant subfamily of Empididae comprising 47.9 % of empidids in the North region, 59.7 % (Northeast), 77.8 % (Southeast). Empidinae were especially prevalent in the East (84.5 %) but were proportionally less abundant in the West (21.5 %), South (19.7 %) and virtually absent in the Coastal Peninsula (0.3 %). Amongst Empididae, aquatic or semi-aquatic Hemerodromiinae and Clinocerinae were absent or rare in the East and Coastal Peninsula but constituted 13.0–22.1 % of total Empididae + Hybotidae in the North, Northeast and West regions (Tab. 3).

Seasonal faunistics and phenology Based on standardised seven-day Malaise trap data, abundance of Empididae and Hybotidae in Thailand (Fig. 2) peaked between early May and mid July, followed by a decline in late July and August, a broad but erratic peak between September and January and a further decline from Feb- ruary to April. However, there were pronounced differences in seasonal patterns of abundance in different geographical regions (Fig. 3). In northern Thailand abundance of hybotids was bimodal with maxima between September and November and in May and June (Fig. 3, North) whereas in the West, a major peak of abundance occurred from November to January with a lesser peak in

133 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand

Fig. 3: Radial plots of regional monthly variation in rainfall and abundance of Hybotidae and Empididae in Thailand (standardized seven-day Malaise trap data). Remarks: Boundaries of geographical regions are as indicated in Fig. 1. Monthly abundance of Hybotidae (light shading) and Empididae (dark shading) as mean number of individuals per seven-day trap event is plotted along the January axis. Total number of seven-day Malaise trap events was 419 (North), 155 (West), 108 (South) and 76 (East). Rainfall as monthly average (mm) is plotted (open squares) on the April axis using data from Chiang Mai (North), Kanchanaburi (West), Nakhon Si Thammarat (South) and Ubon Ratchatani (East).

May (Fig. 3, West). In the Northeast (data not shown) emergence patterns were similar to those in the North. In southern Thailand (Fig. 3, South) maximum abundance of hybotids occurred in February with a smaller broader peak between June and September. Emergence patterns of hybotids in the East (Fig. 3, East) were less easy to discern, possibly on account of relatively low samples number (n = 76 seven-day trap samples) but peaks were apparent in November and

134 Studia dipterologica 18 (2011) Heft 1/2: 121–149 between July and September. Empididae were less numerous than Hybotidae in the samples but their seasonal phenology was broadly similar regionally. Insufficient data were available from the Southeast (n = 34) and the Coastal Peninsula (n = 28) to warrant detailed analysis.

Altitudinal influences Pooled standardised seven-day Malaise trap data for all Thailand indicated that abundance of Hybotidae and Empididae increased with altitude (Fig. 4). The hybotid subfamilies Tachy- dromiinae and Hybotinae were present from 0–2,500 m (Fig. 4B) but the empidid subfamilies Clinocerinae and Hemerodromiinae were absent and Empidinae rare below 400 m (Fig. 4A). Hybotidae were more numerous than Empididae at all altitudes between 0–2,500 m in all geo- graphical regions (Tab. 4) (except between 501–1,000 m in the Southeast where the apparent rarity of Hybotidae is probably an error arising from small sample size). In northern Thailand, where there is a greater elevational range than elsewhere in the country, the bimodal seasonality of Hybotidae with peaks of abundance in April–June and October–November was largely inde- pendent of altitude (Fig. 5). Bimodal seasonality was also observed in Empididae at elevations greater than 1,000 m (Fig. 5, > 1,000 m) but occurred about one month later than in Hybotidae. Below 1,000 m, seasonal abundance patterns of Empididae were not clear but a peak in February (Fig. 5, < 1,000 m) was due to a high number of specimens of a single morphospecies collected in a single trap event; the trap had probably been sited fortuitously to intercept populous swarming activity of the species.

Community structure Community-level elevational relationships of the subfamilies of Empididae and Hybotidae were investigated by cluster analysis. Oedaleinae, Ocydromiinae and Brachystomatidae were very minor components of the empidoid fauna and were not included in the analysis. Twelve major clusters were recovered, albeit with low bootstrap support (Fig. 6) and were considered to approximate to more or less distinct communities occurring at different altitude ranges and with different proportional representation of the subfamilies. The characteristics of these communities will be discussed later.

Fig. 4: Influence of altitude on abundance of Empididae and Hybotidae subfamilies. – A: Empididae; – B: Hybotidae. Remarks: The mean number of individuals caught during seven-day trap events at specific altitudes throughout Thailand is plotted against altitude. Regression lines are fitted for Hemerodromiinae (r2 = 0.415), Empidinae (r2 = 0.283), Clinocerinae (r2 = 0.214), Tachydromiinae (r2 = 0.240) and Hybotinae (r2 = 0.256).

135 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand 51 n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. 2001–2500 6.46 [20.77] (0–112) 21.98 [56.62] (1–299) 119 n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. 1501–2000 6.35 [13.45] (0–108) 14.85 [14.99] (0–109) 29 42 19 20 n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. n. s. 1001–1500 8.5 [8.53] (0–28) 9.45 [8.68] (0–33) 2.15 [4.18] (0–14) 10.38 [16.54] (0–87) 24.57 [35.14] (0–116) 50.04 [55.29] (1–208) 55.42 [55.23] (1–155) Altitude range in m 100.16 [59.71] (11–209) 3 23 53 60 23 104 n. s. n. s. n. s. 501–1000 1.00 [0] (1–1) 0.74 [1.74] (0–6) 0.08 [0.27] (0–1) 2.02 [5.98] (0–42) 4.52 [4.45] (1–14) 2.56 [3.45] (0–16) 5.91 [9.99] (0–47) 4.66 [7.23] (1–13) 6.10 [10.44] (0–62) 11.94 [15.21] (0–70) 11.94 9.03 [14.22] (0–108) 14.04 [15.79] (1–65) 54 10 52 47 85 22 27 0–500 0.10 [0.32] (0–1) 0.56 [0.94] (0–5) 0.30 [0.91] (0–5) 0.48 [0.95] (0–6) 2.45 [1.74] (0–7) 0.18 [0.39] (0–1) 0.03 [0.19] (0–1) 2.22 [4.08] (0–18) 4.60 [5.13] (1–18) 4.78 [3.21] (1–13) 3.76 [4.47] (0–18) 5.06 [5.02] (1–26) 13.19 [17.53] (1–114) 14.07 [21.22] (1–109) Hybotidae Empididae n Hybotidae Empididae n Hybotidae Empididae n Hybotidae Empididae n Hybotidae Empididae n Hybotidae Empididae n Hybotidae Empididae n Peninsula

: Variation in abundance of Hybotidae and Empididae at different altitudes in different regions of Thailand. Remarks: Individual Hybotidae and Empididae were counted in counted were and Empididae Hybotidae Individual Remarks: Thailand. of regions in different altitudes at different and Empididae of Hybotidae in abundance Variation : Region North Northeast East South Southeast Costal West 843 seven-day Malaise trap samples for which altitude data was available. The mean [standard deviation] and (range) are indicated for each 500 m altitude range in each geographical geographical each in range altitude m 500 each for indicated are (range) and deviation] [standard mean The available. was data altitude which for samples trap Malaise seven-day 843 samples. trap of number = n available; samples no = s. n. Abbreviations: area. Tab. 4 Tab.

136 Studia dipterologica 18 (2011) Heft 1/2: 121–149

Material collected from the HLP at Doi Chiangdao was assigned entirely to the I-type community resolved by cluster analysis (Fig. 6) and was studied in further detail. Using only the 102 Malaise trap samples from forest sites (dataset HLP-MA) and excluding the 13 samples from adjacent plantations, we found that Hybotidae (69.7 % of individuals) predominated over Empididae (30.3 %). Amongst Hybotidae, the subfamily Tachydromiinae was most abundant with Elaphropeza (49.6 % of Hybotidae), followed by Platypalpus (19.1 %), Stilpon (and putative new genera closely allied to it) (9.3 %), Tachydromia (8.3 %), Drapetis (1.9 %), Nanodromia (0.6 %) and Tachypeza (0.4 %). Hybotinae were represented by Hybos and Syndyas representing 9.5 % and 0.9 % of total Hybotidae respectively and Ocydromiinae only by Ocydromia (0.4 %). Amongst Empididae the subfamily Empidinae was represented by Empis (53.6 % of Empididae), Hilara (13.4 %) and Rhamphomyia (6.3 %). Hemerodromiinae comprised Anaclastoctedon (15.7 % of Empididae), Chelipoda (7.3 %) and Achelipoda (3.6 %). Seasonal changes in the abundance of the 10 most numerous genera are compared with local climatic conditions in Fig. 7.

Fig. 5: Radial plots of monthly variation in abundance of Hybotidae and Empididae below and above 1,000 m in standardised seven-day trap events from the North + Northeast regions combined. Remarks: Monthly abundance of Hybotidae (light shading) and Empididae (dark shading) as mean number of individuals per seven-day trap event is plotted along the January axis. Total number of trap events was 192 (< 1,000 m), 241 (> 1,000 m).

General Discussion Diversity and abundance Empididae and especially Hybotidae are amongst the more conspicuous and abundant families of Diptera in Thailand. Measuring abundance as number of individuals / trap event, they were clearly most numerous in the North and West region (Tab. 2) but were common in all regions and present in all the major forest biomes as well as in savannah, scrub and croplands adjoining forests. Agricultural lands are extensive in Thailand but have not been surveyed. These include horticultural plots, numerous fruit, sugar cane and root crop fields and especially rice paddies where the predatory habits of Hybotidae in particular may have potential significance in pest

137 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand control (PATNAIK & SATPEY 1984, STARK & WETZEL 1987, KÜHNE & SCHRAMEYER 1994). Limestone karsts, with their often high endemicity (CLEMENTS et al. 2006) have been sampled only at their periphery and mangroves, which have a rich fauna of Tachydromiinae elsewhere in Southeast Asia (SHAMSHEV & GROOTAERT 2007), remain largely unstudied in Thailand. Similarly, specialised habitats such as riverine marginal sediments, marine intertidal and supralittoral and freshwater marshlands have not been specifically sampled. The results discussed here consequently apply mostly to the major forest biomes occurring in Thailand. Sample sorting protocols enabled formal analysis of diversity and abundance at the level of subfamily for a total of 18,675 specimens and genus level analysis only for 2,288 specimens from Doi Chiangdao. In the following discussion of diversity and abundance, the formal analyses are supplemented by informal data gained from having sorted and examined the entire dataset of more than 35,000 specimens and from our ongoing taxonomic studies of particular taxa. Hybotidae predominated over Empididae throughout Thailand, especially in the East on the Isaan Plateau and on the Coastal Peninsula of the Central region (Tab. 2). The hybotid subfamily Hybotinae is most diverse and abundant in tropical and subtropical regions of the Oriental and Neotropical realms (CHVÁLA 1983) and constituted 12.8 % of Empidoidea (exclusive of Dolichopodidae which are not discussed here) in Thailand. The genus Hybos was the most abundant and widespread hybotine, with perhaps 50 species present, mostly undescribed, but with approximately 20 % also known from southern China (pers. obs.). It is present in profoundly seasonal lowland forest types as well as less seasonal montane evergreen forests (where it is perhaps more speciose and abundant), Pinus- and thung grasslands. Approximately 70 % of the 164 known species of Hybos (YANG et al. 2007) are from the Oriental Realm with about 90 species in China alone, and the eastern Oriental Realm is apparently its centre of diversity. The largely tropical genus Syneches is less abundant and obviously less diverse than Hybos although it too occurs in a wide variety of habitats. Syndyas, Parahybos, Euhybos and Chillcottomyia are much less frequent, probably less speciose and perhaps commoner in the less seasonally arid forests on mountains in the north and west than in seasonally arid biotopes at lower elevation or further south. Bicellaria is uncommon and confined to a few hill evergreen forest sites on northern mountains. Tachydromiinae was the dominant subfamily of Hybotidae accounting for 72.4–99.7 % of individual hybotids trapped in the different regions and Elaphropeza predomi- nated over other hybotid genera in all habitats and regions (excepting community cluster ‘A’, see discussion below). Elaphropeza was conspicuously abundant in the highly Tachydromiinae- rich and characteristically lowland community clusters ‘C’ and ‘D’ (Fig. 6), and especially in cluster ‘J’ in which it was the only tachydromiine. The genus is also abundant and undoubtedly species-rich at mid and high elevations but in such situations other Drapetini and genera such as Platypalpus feature more prominently amongst Tachydromiinae. Elaphropeza is particularly speciose in the tropics and subtropics where a great diversity of similar species may indicate recent active radiation (CHVÁLA 1975). SHAMSHEV & GROOTAERT (2007) recognised two species groups of Elaphropeza, a monophyletic E. biuncinata group confined to the tropics, and a rather less well defined E. ephippiata group more widely distributed. Species conforming to both groups are present in Thailand. Currently only a single widespread Southeast Asian species (E. hirsutitibia DE MEIJERE, 1914) has been reported from Thailand, but our observations suggest that the genus is mega-diverse there. In Singapore, SHAMSHEV & GROOTAERT (2007) found 52 species of Elaphropeza of which only four had been described elsewhere previously. While some species are cosmopolitan, others have specific habitat preferences and lack of regional faunistic ovelap might indicate local endemism as well as reflecting huge under-sampling. There can be little doubt that Elaphropeza will prove to be extremely speciose in much larger, ecologically

138 Studia dipterologica 18 (2011) Heft 1/2: 121–149 complex and biogeographically varied Thailand. We concur with SHAMSHEV & GROOTAERT (2007) that there is a tendency for black-bodied Elaphropeza and other Drapetini to inhabit open areas while yellow-bodied forms are more frequent in dense forest. The large genus Platypalpus is best known from the Palaearctic but most of the species-groups found there also occur in the Oriental where they show some preference for higher altitudes, although there are a few species groups with stronger tropical affinities (GROOTAERT & SHAMSHEV 2006). In Thailand we mostly collected Platypalpus in the mountains of the North and West at localities such as Doi Chiangdao or Doi Inthanon where it is conspicuously abundant and obviously speciose. Overall, Platypalpus shows a high level of regional endemism and GROOTAERT & SHAMSHEV (2006) found 10 new species at a single site at 500 m in Loei Province (East Region) so it seems likely that the northern mountains will prove to have a rich Platypalpus fauna. Tachydromia and Tachypeza also seem to be most frequent in the North and West and are possibly more strongly associated with hill evergreen forest types than is Platypalpus, which also occurs in montane dry evergreen forest and to a lesser extent in mixed deciduous / dry dipterocarp and bamboo forest. Tachydromia has radiated in the Palaearctic with fewer species in the Oriental Realm and, with a few exceptions, does not seem to have penetrated into Oriental tropical lowlands, being more frequent in the moun- tainous northern transition zone between the two realms (SHAMSHEV & GROOTAERT 2009). Other tachydromiine genera Stilpon, Nanodromia, Megagrapha, Drapetis, and Crossopalpus were less frequent in the samples and we are unable to conclude much about their occurrence except that there are multiple undescribed species of Stilpon and Drapetis, especially in the North and that Megagrapha is only known from moist hill evergreen forest between 2,200–2,500 at a single site (GROOTAERT & SHAMSHEV 2009). Recent revisionary work (SHAMSHEV & GROOTAERT 2004) has revealed a rich Stilpon fauna in the Oriental Realm, supporting the hypothesis of CUMMING & COOPER (1992) that the genus originated there. The genus Chersodromia is usually associated with specific marine intertidal or supralittoral habitats (CHVÁLA 1975) but two species have been reported from Thailand from unusual habitats (GROOTAERT et al. 2007). Chersodromia flavicaput GROOTAERT, CUMMING & SHAMSHEV, 2007 inhabits forests while C. obscura GROOTAERT, CUMMING & SHAMSHEV, 2007 is associated with river banks in bamboo forest. The taxonomy of some of the smaller Drapetini found in Thailand requires a more thorough appraisal than we are able to provide here and it is possible that further genera will be found. For example we are unsure if the Chinese genus Sinodrapetis YANG, GAIMARI & GROOTAERT, 2004 occurs in Thailand. Ocydromiinae and Oedaleinae were the least abundant subfamilies of Hybotidae. Amongst Ocydromiinae, Ocydromia occurred primarily in hill evergreen forests between 1,300–1,700 m in the North, Northeast and West regions, but also slightly lower in Pinus dominated forest in the East region. Leptopeza was not found during this study but was recorded by PAPP et al. (2006). The oedaleine Oedalea is rather rare in hill evergreen and moist hill evergreen forests on a few mountains in the North region. Two species of Anthalia have been described from Thailand (GROOTAERT & SHAMSHEV 2009) in material collected by the TIGER Project in the upper moist hill evergreen forest of Doi Inthanon. We can add no further records. Empididae were less abundant than Hybotidae, accounting for 25.3 % of the abundance of the two families. The subfamilies Empidinae, Hemerodromiinae and Clinocerinae comprised 41.5 %, 52.9 % and 5.5 % of empidid abundance respectively. Empidinae are predominantly of temperate forests and mountains and have radiated in both northern and southern hemispheres but are rather poorly represented in the tropics. Three genera of Empidinae occur in Thailand, all apparently most frequent in the mountains of the North, Northeast and West, although the subfamily is rare at low elevations (Fig. 4A). Rham-

139 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand phomyia is known from a single Thai species (BARTÁK & KUBÍK 2008) belonging to the subgenus Pararhamphomyia FREY, 1922 and is the southernmost representative of the ciliatopoda group. Other, presumably undescribed species of Rhamphomyia occur in Thailand but the genus does not appear to be species rich there. Empis is represented by a perhaps surprisingly rich fauna which has hardly penetrated into the lowlands. Most species belong to the predominantly Oriental Empis (Coptophlebia) hyalea group sensu DAUGERON & GROOTAERT (2003, 2005a, 2005b). The Empis (Coptophlebia) hyalipennis group which is conjectured to have originated in the Oriental tropics (DAUGERON et al. 2011) is also present but clearly less speciose. Members of the Hemerodromiinae Hemerodromiini sensu PLANT (2011) are entirely depend- ant on lotic or lentic aquatic habitats and Hemerodromia is widespread and often abundant in such situations throughout Thailand. Although sometimes encountered at considerable distance from known water bodies in high elevation wet forests, in seasonally arid lowland forests we have never seen it more than a few tens of metres away from water courses. PLANT et al. (2012) considered Hemerodromia to be of relatively recent western Palaearctic origin spreading into the Oriental from northern dispersal loci. Chelifera is uncommon and probably not speciose in Thailand. It is confined to higher mountains of the North region and was considered by PLANT et al. (2012) likely to have dispersed into the Oriental from the Palaearctic along montane corridors uplifted by the ongoing Himalayan orogenesis. The hemerodromiine tribe Chelipodini is represented by three genera in Thailand, all of which have immature stages probably associated with damp soils rather than aquatic habitats (PLANT 2011). Species richness and abundance of Chelipoda increases with altitude in Thailand with 14 species known (PLANT 2009b) although others await description, especially from the mountains of the west and north of the country. In a study of Hemerodromiinae on Thailand’s highest mountain, Doi Inthanon, PLANT et al. (2012) described a Chelipoda-rich community of Hemerodromiinae characterized by cosmopolitan associations with various hill evergreen forest types between 1,700–2,500 m and a Hemerodromia-rich community in moist hill evergreen forest between 2,200–2,500 m. An impoverished com- munity occurred at lower elevations (~ 1,200 m) corresponding with vegetational transitions between lower and dry mixed deciduous or pine forest into rather less seasonally water-stressed evergreen forest. On Doi Inthanon, a high level of local endemism in Chelipoda was found on the upper moist hill evergreen forests above ~ 2,000 m (PLANT 2009b) and although some of the species found at this locality have subsequently been found in similar habitat near the summit of Doi Phahompok (2,285 m, also in the North region), the upper forest zone remains of great importance to Hemerodromiinae. Currently two species of Anaclastoctedon are known from Thailand (PLANT 2010b) but more await description. Phylogenetic studies suggest affinities with many southern hemisphere Chelipodini (PLANT 2011) and it may have had a southern temperate origin with later dispersal into Asia, exploiting increasing connectivity between the mountains of eastern Australia and Asia as Australia drifted northwards during the Tertiary (PLANT 2010b, PLANT et al. 2012). Achelipoda is an east Asian genus with a single species in Thailand (PLANT 2009a). It is mostly found between 600–1,200 m in dryer forest types including Pinus-savannah habitats. PLANT et al. (2012) considered that its dispersal history may have been facilitated by episodes of climatic drying associated with Pleistocene glacial maxima. Clinocerinae have aquatic immature stages and adult Dolichocephala are strongly associ- ated with headwater streams and seepages (or at least extremely wet areas) in hill evergreen forest types, occurring only rarely in lower forests. Although it can be abundant in such situations, it is apparently not very speciose (B. J. SINCLAIR pers. com). Dolichocephala was the predominant genus in the Clinocerinae-dominated community ‘J’ discussed below and although we do not have small scale habitat data for this community, a linkage with

140 Studia dipterologica 18 (2011) Heft 1/2: 121–149 precipitation-fed Sphagnum bog is possible. Clinocera is less abundant than Dolichocephala and is apparently mostly found near streams in montane forests of the North and West in Thailand. Clinocerinae and Hemerodromiinae did not occur below an altitude threshold at ~ 400 m (Fig. 4A). Brachystomatidae are poorly represented in Thailand with two species of Trichopeza (PLANT 2009c) and one of Brachystoma (PLANT 2010a), both of which are confined to high elevations on northern mountains and considered to be Palaearctic elements.

Community structure Although bootstrap support for cluster analysis was not strong (Fig. 6), by comparing the frequency of trap samples at different altitude ranges and numbers of individual specimens in each taxon in a cluster with forest biome, geographic region, phenology and climate information, we tentatively propose the following community relationships of Empididae and Hybotidae in Thailand. Cluster A comprised individuals occupying elevations up to 1,500 m, with a peak in trapping frequency at 500–1,000 m (Fig. 6, Cluster A). It was rich in Empidinae (80 % of total individuals) and Hybotinae (20 %) but other subfamilies were absent. Adult emergence was more or less restricted to August–October coincident with the latter part of the rainy season in the North and especially East regions where it mostly occurs in mixed deciduous, dry evergreen, bamboo and other seasonally dry habitats. Cluster A1 will not be discussed further as it included only a single trap sample exceptionally rich in Hybotinae (96 %) from 485 m at Chae Son (North region). Cluster B was recovered at altitudes between 500–1,500 m with a peak in trapping frequency at 1,000–1,500 m. Empidinae (54.6 % of individuals) predominated with abundant Hemerodromiinae (17.5 %) and proportionally reduced Tachydromiinae. The community is apparently associated with dry evergreen and lower hill evergreen forests, and with highest frequency (88 %) in the North and Northeast regions. Adult emergence was predominantly between December and March associated with the cool season. Cluster B1 included two trap samples containing equal numbers of Hybotidae and Hemero- dromiinae from 758 m at Khao Yai (East region). It will not be discussed further. Cluster C and Cluster D comprised individuals most frequent below 500 m but extending up to 1,000 m (Cluster D) or 1,500, (Cluster C). Tachydromiinae predominated in both clusters with other families each contributing less than 6 % of abundance but with slightly more abundant Hemerodromiinae and Hybotinae in Cluster D. Both C and D communities were widespread and abundant throughout Thailand in seasonally dry forest biomes including mixed deciduous, dry dipterocarp, dry evergreen, Pinus merkusii and lower hill evergreen forests. Cluster E included individuals from all elevations but with highest frequency at 1,000–1,500 m and a smaller peak above 2,000 m. Although Tachydromiinae predominated (56.2 %), this com- munity contained the highest proportion of Hemerodromiinae (20.4 %) in this study and relatively abundant Hybotinae (15.6 %). The predominant habitat associations were with hill evergreen forest types in the North (75 % of individuals) and West regions (24 %). Adults were trapped throughout the year but in somewhat reduced numbers from June–August. Cluster F was restricted to elevations greater than 2,000 m and was characterised by exceptionally abundant Clinocerinae (43.0 %) with Tachydromiinae comprising only 38.2 % or relative abun-

141 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand

142 Studia dipterologica 18 (2011) Heft 1/2: 121–149 dance. This community is unique to moist hill evergreen forest on the upper slopes of the mountain Doi Inthanon (North region). Interestingly PLANT et al. (2012) identified a distinctive and rich community of Hemerodromiinae in the upper moist hill evergreen forest of the mountain. Similar habitat also occurs near the summits of a few of the highest mountains in northern Thailand and although these were not represented in the trap samples analysed here, hand collecting at these sites suggests that they have exceptional interest for Empididae and Hybotidae (pers. obs.). Cluster G was recovered at altitudes between 500–1,500 m with a peak in frequency at 1,000–1,500 m. It had relatively abundant Hybotinae (23.9 %) and Hemerodromiinae (17.9 %) and moderately abundant Tachydromiinae (52.7 %). The main forest biome inhabited by this community is probably lower hill evergreen but it clearly extends down into dryer deciduous and dipterocarp forest types and perhaps also semi evergreen types in the South. Cluster H occurred at similar altitudes as Cluster G, with maximal frequency at 1,000–1,500 m but extending at lower frequency up to 2,000 m. Hemerodromiinae occurred with similar relative abundance (19.5 %) but Hybotidae were reduced (6.4 %) and Tachydromiinae more abundant (70.1 %). This community is predominantly linked with hill evergreen forest but perhaps less strongly associated with dryer lowland forest types than Cluster G. Cluster I comprised individuals from all altitudes up to 2,000 m with highest frequency at 500–1,000 m. Although Tachydromiinae predominated, this community was relatively enriched in Empidinae (18.4 %) and Hybotinae (14.8 %). Mostly confined to the North (79 % trap frequency) and West (16 %), it occurs mostly in dry evergreen and hill evergreen forests. Cluster J occurred at similar elevation range as Cluster D, with peak frequency below 500 m but differed in being composed almost entirely of Tachydromiinae (95.9 %). It is clearly associated with dryer lowland forest types including mixed deciduous, dry dipterocarp and beach forests. Approximately 50 % of data from specimen labels implies proximity of open ground (e. g. camp- grounds, flower fields, thung grassland etc.) or specifies open deciduous forests. The community is likely to be associated with relatively open or marginal areas of seasonal lowland forests and grasslands.

Seasonal phenology With the exception of small areas of lowland tropical evergreen forest (‘’) in the South, all Thailand’s forests experience cyclic alternation of monsoon rains with intervening drought and are best classified as ‘monsoon forests’. The phenology of many in tropical monsoon forests is profoundly influenced by seasonal rainfall patterns (e. g. SPITZER 1983, FRITH & FRITH 1990, WIWATWITAYA & TAKEDA 2005, WOLDA 1980). Although in relatively aseasonal lowland tropical ‘rainforest’ insect emergence is sometimes less strongly seasonal (e. g. GRIMBACHER & STORK 2009), complex temporal patterns of abundance and diversity may be present and tropi- cal insects can show a wide array of seasonal patterns, even at the same site (WOLDA 1988). In Thailand, Hybotidae and Empididae showed complex seasonal phenology, varying between

Fig. 6: Cluster analysis of elevational relationships of the most numerous subfamilies of Empididae and Hybotidae using unweighted pair-group average and Bray-Curtis similarity indices. Remarks: Bootstrapping was performed with 1,000 resamples; the percentage of replicates where each of the major clusters is still supported is shown at nodes. The altitude of each terminus is given and major clusters are designated A, A1, B, B1, C, D, E, F, G, H, I and J. The histograms indicate the frequency of seven-day trap samples in each 500 m altitude range and correspond to each of the major clusters (except A1 and B1 represented by only one altitude range). Altitude ranges are (1), 0–500 m; (2), 501–1,000 m; (3), 1,001–1,500 m; (4), 1,501–2,000 m; (5), 2,001–2,500 m. The percentage of individuals in each subfamily occurring in each cluster is indicated to the right (n = number of individual specimens).

143 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand

Fig. 7: Monthly climate and phenology of Empididae and Hybotidae at Doi Chiangdao. – A: Total monthly rainfall (open squares) and monthly average daily temperature maxima (open circles) and minima (closed circles); – B–D: Monthly variation in mean abundance calculated from the mean of all seven-day trapping events in each month (B = Hybotidae; C = Empidinae; D = Hemerodromiinae).

Fig. 8: Monthly changes in genus level diversity parameters, Fisher’s alpha and Dominance, for Hybotidae and Empididae at Doi Chiangdao. Remarks: Parameters were determined from counts of the number of individuals of each genus in each seven-day Malaise trap and monthly averages plotted. regions and with elevation. For example, in the North, peak abundance coincided with the start and end of the rainy season (Fig. 3, North) whereas in the West it was greatest in the cool dry season following the Monsoon (Fig. 3, West). In the North, West and East abundance was lowest during the hot dry season between February and April. Annual rainfall is much greater in the South due to influence of the Northeast Monsoon between November and February and maximum abundance of Hybotidae in particular was recorded at the end of this monsoon phase (Fig. 3, South) with a smaller peak coincident with the onset of the Southwest Monsoon from June to September. Although the temporal dynamics of hybotid and empidid abundance were

144 Studia dipterologica 18 (2011) Heft 1/2: 121–149 complex, the general pattern was of maximal activity coinciding with the start and end of the rains and lowest during hot dry periods. Tropical streams are strongly influenced by the monsoon cycle which causes high discharge during the wet season and decreased flow during dry season (PRAMUAL & KUVANGKADILOK 2009) and the life cycles of aquatic invertebrates are often timed to avoid arid periods or washout during spates (DUDGEON 2000, PRAMUAL & WONGPRAM 2010). The abundance of aquatic Hemero- dromiinae and Clinocerinae is likely to be strongly related to water availability although this was not investigated here. At Doi Chiangdao, the abundance of different genera correlated in different ways to seasonal rainfall patterns although overall, they were more abundant during the wet season (Fig. 7). Generic level diversity of Hybotidae increased with the onset of the wet season to a maximum at its end (Fig. 8). Diversity of Empididae genera was high during the rainy season but was maximal towards the end of the cool dry season. The Doi Chiangdao study area experienced a bimodal peak in monsoon rainfall between May and October coincident with elevated daytime and night time temperatures (Fig. 7A). Different genera were correlated in subtly different ways to the climate pattern. Abundance of Empis for example was strongly associated with the onset of the monsoon (Fig. 7C) whereas Elaphropeza, Platypalpus, Hybos (Fig. 7B), Chelipoda, and Achelipoda (Fig. 7D) were more persistent throughout the rainy season. Emergence of Hybos and Achelipoda was apparently correlated with precipitation in the same month (r2 = 0.361 and 0.442 respectively, data not shown) whereas Elaphropeza and Platypalpus, appeared to be better correlated with rainfall occurring three months previously (r2 = 0.490 and 0.230 respectively) than they were with current rainfall (r2 = 0.065 and 0.033 respectively). Stilpon and Anaclastoctedon were not obviously associated with cycles of precipitation and indeed Stilpon appeared to be weakly negatively correlated with rainfall two months previously (r2 = – 0.302) and Anaclastoctedon was still more weakly correlated with precipitation (r2 = varying between – 0.147 for the current month and – 0.166 for two months previous rainfall). The peak emergence of Anaclastoctedon during the cool dry to hot dry season has been noted previously (PLANT 2010b) and is perhaps surprising as Hemerodromiinae require essentially moist edaphic conditions or aquatic environments for development (PLANT 2011). In Thai- land Anaclastoctedon is largely restricted to rather damp hill evergreen forest types between 1,700 and 2,200 m although it does occur in dryer habitats such as Pinus / savannah down to 1,200 m (PLANT et al. 2012). Although species diversity was not analysed in the present study, the seasonal abundance profile of Chelipoda was broadly similar to that found by PLANT (2009b) in a study of species richness and abundance on the mountain Doi Inthanon (approximately 180 km southwest of Doi Chiangdao). On Doi Inthanon, species richness was greatest from August–November and March–May but patterns of abundance were seasonally different for different species and seasonal influences on abundance were greatest at lower altitudes.

Concluding remarks Although this study has revealed that Empidoidea are undoubtedly very diverse and abundant in Thailand’s tropical forests, our findings are essentially preliminary and sometimes tentative. Several research groups, including our own, are working to describe the taxa collected by the surveys described here and a full and more authoritative assessment of the fauna must await the results of these studies.

145 PLANT et al.: Empididae, Hybotidae and Brachystomatidae (Empidoidea) in Thailand

We would like to call particular attention to two striking results. Firstly, although all Thailand’s forest biomes are rich in Empidoidea and may have distinctive communities associated with them, the threatened (PATTANAVIBOOL & DEARDEN 2002) montane evergreen forests in the transition zone between the Palaearctic and Oriental Realms in northern and western Thailand are particularly rich and important. Many taxa are more or less confined to hill evergreen forest at high elevation. Secondly many of the genera occurring in montane evergreen forest are probably of Palaearctic or Holarctic origin (e. g. Rhamphomyia, Hilara, Chelifera, Platypalpus, Tachypeza, Trichopeza, Brachystoma, Anthalia, Ocydromia, Oedalea and Megagrapha) and in general, are probably not very speciose. There are relatively few groups with clear Oriental affinities (e. g. Hybotinae, many Drapetini and certain Empis species groups) although some of these (e. g. Elaphropeza and Hybos) may be exceptionally diverse. Unlike many of the Palaearctic elements, Oriental elements have often successfully colonised the lowlands where they dominate genus-level assemblages in highly seasonal lowland habitats. On a global scale, taxon richness follows a latitudinal gradient with higher richness at lower latitudes (CHOWN & GASTON 2000). This situation appears to be reversed locally in Thailand with more empidoid diversity, at least at generic level, in the more temperate regions of the north. ‘Reversed’ gradients of taxon richness have also been found for Limoniidae (Diptera) (PETERSEN & COURTNEY 2010) and Sphingidae (Lepidoptera) (BECK et al. 2007) and were postulated to be consequences of increased landscape heterogeneity in the north or a ‘peninsula effect’ in the south. North-south clines of decreasing intra-specific genetic diversity have been reported, for the diptera families Culicidae (MORGAN et al. 2011) and Simuliidae (PRAMUAL et al. 2005) and interpreted as evidence of post-glacial recolonization of the south from Pleistocene glacial refugia in the north. We have recently proposed a Climate History Model to explain the biodiversity ‘hotspot’ in northern Thailand and indeed the wider Indo-Burma hotspot (PLANT et al. 2012). The Model proposes that the richness of the regions’ wet montane forests has arisen from historical altitu- dinal displacement of lowland rainforest biota in a drying climate augmented by immigration from outside the region along montane corridors of moist forest and lowland corridors of dryer habitat. The model postulates. – (i) Historically concurrent Cenozoic orogenesis of mountain ranges, a southward retreat of in response to a developing seasonally arid monsoon climate resulting from the elevation of the Tibetan Plateau, and dry periods associated with Pleistocene glacial maxima, may have forced altitudinal migration into and subsequent radiation in aseasonal moist forests that developed on nascent mountains. – (ii) Cenozoic orogenesis of the northern mountains provided montane refugia and corridors of moist forests which functioned as sources of diversity and dispersal routes for immigration. – (iii) Isolation and altitudinally zoned habitat heterogeneity on nascent mountains provided foci of radiation. – (iv) Lowland dispersal of cool- and dry-adapted biota was promoted by the extension of more open and seasonal habitats (e. g. Pinus-savannah) during Pleistocene glacial maxima. The preponderance of essentially Palaearctic genera of Empidoidea in the mountains of the northern transition zone between the Oriental and Palaearctic Realms is entirely consistent with this model. The timing of Palaearctic incursions is however, far from clear. Were they associated with the Pleistocene drying and cooling when extensive migrations of plants, mammals, birds and insects occurred in Southeast Asia [see discussion in MORGAN et al. (2011), PLANT (2009b), PLANT et al. (2012)] or were they initiated earlier, driven by development of an increasingly seasonal monsoonal climate initiated in the Miocene?

146 Studia dipterologica 18 (2011) Heft 1/2: 121–149

Acknowledgements

The support of Brian BROWN (Los Angeles, USA), Chaweewan HUTACHARERN (Bangkok, Thailand), Michael SHARKEY (Kentucky, USA) and especially the collecting efforts of national parks staff in Thailand are gratefully acknowledged. Christophe DAUGERON (Paris, France), Patrick GROOTAERT (Brussels, Belgium), Pairot PRAMUAL (Maha Sarakham,Thailand), Igor SHAMSHEV (St. Petersburg, Russia) and Bradley SINCLAIR (Ottawa, Canada) provided useful discussion during the preparation of this paper. Prachawan SUKUMOLANAN (Chiang Mai, Thailand) is thanked for maintaining Malaise traps and a climate data-logger on Doi Chiangdao. TIGER Project was supported by USA NSF (grant no. DEB-0542846).

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Author’s addresses

Adrian R. PLANT Department of Biodiversity and Systematic Biology National Museum of Wales Cathays Park Cardiff, CF10 3NP United Kingdom E-mail: [email protected]

Chayanit SURIN, Raewat SAOKHOD, Wichai SRISUKA Entomology Section, Queen Sirikit Botanic Garden PO Box, Mae Rim Chiang Mai 50180 Thailand E-mails: [email protected]; [email protected]; [email protected]

The paper was accepted on 22 October 2012. Editum: 20 December 2012.

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