Rainforest canopies, home to one of the most complex and diverse terrestrial arthropod communities, are threatened by conversion of rainforest into agricultural production systems. However, little is known about how predatory arthropod communities respond to such conversion. To address this, we compared canopy spider (Araneae) communities from lowland rainforest with those from three agricultural systems in Jambi Province, Sumatra, Indonesia, i.e., jungle rubber (rubber agroforest) and monoculture plantations of rubber and oil palm. Using canopy fogging, we collected 10,676 spider specimens belonging to 36 families and 445 morphospecies. The four most abundant families (Salticidae N = 2,043, Oonopidae N = 1,878, Theridiidae N = 1,533 and Clubionidae N = 1,188) together comprised 62.2% of total individuals, while the four most speciose families, Salticidae (S = 87), Theridiidae (S = 83), Araneidae (S = 48) and Thomisidae (S = 39), contained 57.8% of all morphospecies identified. In lowland rainforest, average abundance, biomass and species richness of canopy spiders was at least twice as high as in rubber or oil palm plantations, with jungle rubber showing similar abundances as rainforest, and intermediate biomass and richness. Community composition of spiders was similar in rainforest and jungle rubber, but differed from rubber and oil palm, which also differed from each other. Canonical Correspondence Analysis showed that canopy openness, aboveground tree biomass and tree density together explained 18.2% of the variation in spider communities at family level. On a morphospecies level, vascular plant species richness and tree density significantly affected the community composition but explained only 6.8% of the variance. While abundance, biomass and diversity of spiders declined strongly with the conversion of rainforest into monoculture plantations of rubber and oil palm, we also found that a large proportion of the rainforest spider community can thrive in extensive agroforestry systems such as jungle rubber. Despite being very different from rainforest, the canopy spider communities in rubber and oil palm plantations may still play a vital role in the biological control of canopy herbivore species, thus contributing important ecosystem services. The components of tree and palm canopy structure identified as major determinants of canopy spider communities may aid in decision-making processes toward establishing cash-crop plantation management systems which foster herbivore control by spiders.

Abstract. Lia M, Rauf A, Hindayana D. 2021. Comparisons of the composition of spider assemblages in three vegetation habitats in Bogor, West Java, Indonesia. Biodiversitas 23: 244-255. Vegetation structures are known to influence the microclimate and consequently the invertebrate assemblages. This study, therefore, aims to compare the species composition of assemblages of ground- and foliage-dwelling spiders in three vegetation habitats: undisturbed urban forest, oil palm plantation, and cornfield, in Bogor, West Java. To ensure a thorough representation of all spider guilds, spiders were collected using pitfall traps, sweep net, and through a direct search on ground and vegetation from January to July 2016. A total of 2299 individual spiders, representing 28 families and 207 species/morphospecies were collected. The spider species richness, abundance, and diversity were higher in the forest and oil palm plantation, compared to the cornfield. Furthermore, the dominant guild in the forest habitat was orb weavers, while the oil palm and corn habitats were dominated by ground runners. The non-metric multidimensional scaling exhibited that the composition of spider assemblages varied among the three vegetation habitats, with spider assemblages in forest habitat associated with higher RH, while the corn habitat was correlated with high light intensity and air temperature. The indicator species analysis revealed that Tetragnathidae has high potential as indicators of the dense, complex vegetation structure of the forest, while Lycosidae is indicators of the more open vegetation of oil palm plantation and cornfield habitats.