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Tropical Natural History 20(1): 16–27, April 2020 2020 by Chulalongkorn University Endemism, Similarity and Difference in Montane Evergreen Forest Biodiversity Hotspots: Comparing Communities of Empidoidea (Insecta: Diptera) in the Summit Zones of Doi Inthanon and Doi Phahompok, Thailand ADRIAN R. PLANT1*, DANIEL J. BICKEL2, PAUL CHATELAIN3, CHRISTOPHE DAUGERON3 AND WICHAI SRISUKA4 1Department of Biology, Faculty of Science, Mahasarakham University, Kantharawichai District, Mahasarakham 44150, THAILAND 2Australian Museum, Sydney, NSW 2010, AUSTRALIA 3Muséum national d’Histoire naturelle, 57 rue Cuvier, CP 50, F-75005 Paris, FRANCE 4Entomology Section, Queen Sirikit Botanic Garden, Mae Rim, Chiang Mai 50180, THAILAND * Corresponding author. Adrian R. Plant ([email protected]) Received: 7 August 2019; Accepted: 12 November 2019 ABSTRACT.– Composition and structure of communities of the Diptera superfamily Empidoidea (30,481 individuals of 511 species in 55 genera in the families Empididae, Dolichopodidae, Hybotidae and Brachystomatidae) were compared in Upper Montane Forests on Doi Inthanon and Doi Phahompok in northern Thailand. Based on taxon similarity (α-, β-diversity), structural diversity (the species abundance distribution and importance of dominant species), cluster analysis of community composition and the relative importance of inferred Oriental and Palaearctic influences, it was concluded that communities in Upper Montane Forest at 2,036 – 2,105 m near the summit of Doi Phahompok were most similar to those at 1,639 – 2,210 m on Doi Inthanon. Approximately 33% of species recorded at 2,036 – 2,105 m on Doi Phahompok were endemic to the mountain. Upper Montane Forest is a rare, dispersed and isolated habitat in southeastern Asia with scattered patches likely to experience comparable levels of β-diversity and endemism as found here. The conservation importance of Upper Montane Forest on Doi Phahompok and on other mountains in northern Thailand is stressed. The upper slopes of Doi Inthanon (>2,200 m) are reaffirmed as a unique haven of endemic species and distinctive Empidoidea communities in a habitat judged to be of utmost conservation interest. KEY WORDS: conservation, Brachystomatidae, Dolichopodidae, Empididae, Hybotidae INTRODUCTION diversity. A recent study of Empidoidea on the mountain Doi Inthanon in northern Diptera (true flies) are one of the Thailand (Plant et al., 2019) identified three megadiverse and abundant insect orders that major habitat and elevation delimited contribute greatly to the biodiversity of community-types (designated Moist Hill tropical forests and are major components of Evergreen, ‘MHE’ [>2,000 m]; Mid the exceptionally rich biodiversity of insects Elevation Evergreen ‘EM’ [1,000 – 2,000 in the montane evergreen forest of northern m] and Dry Lowland ‘DL’ [<1,000 m]; the Thailand (Plant et al., 2018). The Diptera names specifically refer to dipteran superfamily Empidoidea (represented in communities, even though they reference Thailand by the families Empididae, characteristics of the forests in which the Dolichopodidae, Hybotidae and Brachy- communities were found). The occurrence stomatidae) is a large and important taxon of MHE, EM and DL fly communities comprising approximately 10% of global fly corresponded well with the occurrence of PLANT ET AL. — COMPARING COMMUNITIES OF EMPIDOIDEA (INSECTA: DIPTERA) 17 formal forest types resolved by Santisuk Brachystomatidae in Thailand, is entirely (1988) and designated as Upper Montane confined to the upper slopes of the mountain Forest (at >1,800 m), Lower Montane Forest (Plant, 2009a; 2010a) and several genera of (at 1,000 – 1,800 m) and Lowland Deciduous Hybotidae are local endemics, restricted to Forest (at <1,000 m) respectively. Because the upper forests of the peak (Grootaert and the elevational succession of Upper Shamshev, 2009; Plant et al., 2019). Recent Montane Forest - Lower Montane Forest - taxonomic revisions (e.g. Plant, 2009b; Lowland Deciduous Forests with which 2010b; 2013; 2015) have identified MHE, ME and DL Diptera communities are numerous species of Empididae and associated is widespread in northern Hybotidae restricted to high elevation Thailand, it is likely that the description of habitats on Doi Inthanon which is clearly a diversity characteristics of fly communities ‘hot-spot’ of empidoid diversity and found on Doi Inthanon is scalable over a endemism (Plant, 2009c). Apart from much wider geographic area (Plant et al., remarkable endemism, another striking 2019), albeit with community turnover and feature of high elevation MHE communities local endemism influences superimposed. on Doi Inthanon is that many species are Montane evergreen forests occur widely extraordinarily abundant (Chatelain et al., in northern Thailand where they are 2018; Plant et al., 2011, 2019; Sinclair and important but threatened centres of Plant, 2017). The species abundance biodiversity (Pattanavibool and Dearden, distribution curves of EM and DL 2002) and this is especially true of Upper communities are similar but that of MHE is Montane Forest which is a rare habitat, of very different form and MHE mostly restricted to a few mountains in the communities are characteristically uneven Thanon Thongchai, Den Lao, Khun Tan and with high dominance and have fewer Luang Prabang ranges that rise above 1,800 numerically rare species compared to lower m. The most extensive tracts of Upper EM and DL communities (Plant et al., 2019). Montane Forest (only ~5 km2) are found on MHE communities are phylogenetically Doi Inthanon, Thailand’s highest mountain richer and also have a higher proportion of (2,565 m) in the Thanon Thongchai range, taxa considered to be of Palaearctic rather and a smaller patch near the summit of the than Oriental origin. Interestingly, the second highest mountain, Doi Phahompok temporal turnover of community (2,288m) in the Den Lao range. The summit composition is slower (seasonality is zone of Doi Inthanon is well known for its relaxed) compared with lower elevation rare and endemic biota, and there are, for communities. Biodiversity, or at least that of example, many insect species known, more Empidoidea, is structured very differently in or less, only from there, or which are at the MHE compared with EM and DL southern extremity of their ranges, communities. including, for example, Coleoptera (de While there can be no doubt that the Rougemont, 2003), Collembola (Bedos and Upper Montane Forests of Doi Inthanon Deharveng, 1994), Plecoptera (Sivec and with their associated MHE Empidoidea Stark, 2010) and Diptera (Hippa, 2011; communities are of exceptional interest and Takaoka et al., 2013). The Empidoidea conservation importance, the question fauna of Doi Inthanon is exceptionally rich remains, are other Upper Montane Forests in and important; for example, the family northern Thailand equally striking? Do they 18 TROPICAL NATURAL HISTORY 20(1), April 2020 warrant the particular attention deserved by a better understanding of local patterns of those on Doi Inthanon? Can we apply the endemism and richness providing rational description of diversity characteristics of support for delineating areas of conservation MHE Diptera communities across other priority in Thailand. Upper Montane Forests? To what extent does species composition turnover (β- MATERIALS AND METHODS diversity) across different representatives of this forest type? Given that Upper Montane Study site Forests occur as widely dispersed patches The study site on the mountain, Doi on mountain peaks that are separated from Phahompok (2,288m) is located in Chiang each other by extensive lowlands, should we Mai Province, northern Thailand. Three expect high levels of β-diversity with rich Malaise traps were positioned in Upper endemism amongst the communities of each Montane Forest, within 530 m horizontal isolated Upper Montane Forest patch? distance of each other, slightly offset from The Empidoidea inhabiting Upper the summit ridge at 2,036 m (Trap 1, Montane Forest of Doi Phahompok have 20.050417°N, 99.144056°E), 2,059 m (Trap been poorly surveyed compared with those 2, 20.052222°N, 99.142389°E) and 2,105 m on Doi Inthanon and although species of (Trap 3, 20.054917°N, 99.142389°E). Traps Hybotidae apparently endemic to the were run throughout 2014 and serviced mountain have been reported (Plant, 2013) monthly (note all samples were lost in and the previously mentioned taxonomic August, and two samples in September, revisions indicate a potentially species-rich probably due to interference by domestic empidoid fauna. Analysis of the distribution cattle). The study site and sampling of endemicity of the hybotid genus Hybos methodology at Doi Inthanon have been (Plant, 2013, 2014) suggested that both the described previously (Plant et al., 2018; Thanon Thongchai and Den Lao ranges are 2019). Briefly, it comprised 12 Malaise traps centres of endemism, so we might expect at run along a 21.7 km long elevational transect least some empidoid taxa to have ranges with three traps in Lowland Deciduous restricted to either Doi Inthanon or Doi Forest (one trap each at 412, 662 and 710 m), Phahompok. Nothing is known of how four in Lower Montane Forest (two each at diversity is structured in Upper Montane 1,376 and 1,639 m) and four in Upper Forest on Doi Phahompok. During 2014, we Montane Forest (two at 2,210 m two at 2,534 sampled Empidoidea in this habit on the m) and one at the summit bog (2,545 m). summit ridge of Doi Phahompok, Taxon sorting and taxonomy concomitant with