Diversity and Distribution of Dragonflies in Bukit Timah Nature Reserve, Singapore

Abstract

Biodiversity baselines were established for dragonflies (Insecta: Odonata) of Bukit Timah Nature Reserve, Singapore, based on quantitative and qualitative samplings. Surveys were conducted from December 2014 to February 2016. Hydrological, physicochemical parameters and habitats were analysed to understand the main drivers structuring the dragonfly community. A total of 829 odonate specimens were recorded during the quantitative sampling, comprising 36 species of 28 genera in 11 families. The species diversity in each of the six sampling sites was compared using the Shannon-Wiener Index (H'). Hierarchical clustering and Detrended Correspondence Analysis (DCA) indicated that three main groupings of sites existed, each with a distinct community of associated species. Further analysis by Non-metric multidimensional scaling (NMDS) on the relevant distance based on species composition at the six sampling sites, together with 21 environmental variables showed that these groups were significantly associated with respective environmental variables. An updated species list of Bukit Timah dragonflies is provided for future reference, with 55 species of 43 genera in 12 families. Disturbance and threats to the odonate fauna of the Bukit Timah Nature Reserve are identified and conservation management measures are discussed.

Physicochemical characteristics of streams in Bukit Timah Nature Reserve, Singapore

“…These factors play out through the expected interactions between soil, groundwater and rainfall. In turn, the physicochemical characteristics of the individual streams may be linked in part to the freshwater decapod crustaceans (Khoo et al, 2019), dragonflies and damselflies (Cai et al, 2019), and fishes (Li et al, 2019) that occur within each of them.…”

Synthesis of results from the Comprehensive Biodiversity Survey of Bukit Timah Nature Reserve, Singapore, with recommendations for management

“…The current survey found 43 species of dragonflies and damselflies (36 during quantitative surveys and another seven during ad hoc observations), new locality records bringing the total ever recorded to 55 species for BTNR including the adjacent nature parks (Cai et al, 2019). There were striking differences between locations, with between one and 16 species per site, meaning that sustainability of the total community depends on maintaining the full range of site conditions.…”

“…Stream acidification is one of the conservation concerns, as are total water flow, the amount of residual water remaining during very dry weather, and bank erosion. Concerns over freshwater crustaceans (Khoo et al, 2019) are very similar to those applying to dragonflies (Cai et al, 2019) and fishes (Li et al, 2019).…”

“…As also found for bees (Ascher et al, 2019), the diversity of butterflies in the buffering nature parks can be attributed to the availability of forest edge vegetation, open sunny conditions, and freely flowering shrubs and weeds as nectar sources. Just as nectar sources in secondary vegetation may provide a 'bridge' for bees in between occasional mass flowering years in the forest (Ascher et al, 2019), and as streams provide larval habitat for dragonflies whose adults disperse more widely (Cai et al, 2019), so for butterflies the plant species diversity within the forest may provide larval food sources and ecological niches for pupation that help to support the wider butterfly populations.…”

“…Stream enhancement initiatives should mirror those for the terrestrial habitat, for the survival of freshwater fish, decapods, dragonflies and other aquatic plant and animal species (Cai, 2019;Cai et al, 2019;Khoo et al, 2019;Li et al, 2019;Nguyen & Cai, 2019).…”