Habitat Requirements of Dragonflies (Anisoptera) in the Urban matrix of Hong Kong, China

Abstract

The urban human population is projected to reach 70% of the worldʼs population by 2050 (UN-Habitat 2009). Although most of the urbanization is expected to take place in the Asian tropics, very limited studies on urban ecology have been done there (UNDESA 2012; Sachs 2000). This study evaluated the relative importance of different environmental variables on the dragonfly richness, abundance and species composition of the urban habitat fragments of Asian subtropical city Hong Kong. Among the 15 environmental variables tested using generalized linear mixed models (GLMM), distance to the nearest major road was found to be the most important predictor for dragonfly richness and abundance. Site area, on the other hand, was not a good predictor. Furthermore, predictors associated with human development surrounding a site were in general found to be a lot more important than those concerning the habitat characteristics within a site. Regarding species composition, urban parks, open drains and semi-wild sites each had a community that was distinct from the others according to canonical correspondence analysis. However, the average richness and abundance of semi-wild sites were both significantly higher than that of the other two habitat types (Kruskal-Wallis, Richness: χ2 = 6.38, df = 2, p=0.041; Abundance: χ2 = 9.30, df = 2, p=0.0096). Alongside with other minor suggestions, it was recommended that a network of small urban dragonfly sites distant to major roads be maintained with good connectivity. What constitutes a good connectivity pathway, however, requires further research.