Rainforest conversion to monocultures favors generalist ants with large colonies

Abstract

The conversion of natural ecosystems to agricultural land is one of the most important drivers of biodiversity decline worldwide, particularly in the tropics. Species loss is typically trait‐associated, leading to filtering of disturbance‐resistant species during community assembly, which affects ecosystem functioning and evolutionary potential of communities. To understand the ecological and phylogenetic impact of rainforest conversion to agricultural systems, we combine analysis of nesting habit, feeding habit, colony size, and body size of canopy ants (Formicidae) with a phylogenetic analysis of species collected in four land‐use systems in Sumatra, Indonesia: (1) lowland tropical rainforest, (2) jungle rubber (extensive rubber agroforest), and smallholder plantations of (3) rubber and (4) oil palm. Canopy ant communities in these land‐use systems differed in trait composition, with a larger proportion of generalist nesting and generalist‐omnivore feeding species in oil palm compared to rainforest and a larger proportion of generalist nesters and species with large colonies (>1000 individuals) in rubber than in rainforest. Traits of canopy ant communities in jungle rubber were more similar to those in rainforest than to those in rubber and oil palm plantations. In rainforest, mean pairwise phylogenetic distance was lower than expected for random community assembly, but did not differ from random in the other land‐use systems. Of the traits nesting habit, feeding habit, and colony size, only feeding habit exhibited phylogenetic signal. Our results show that rainforest conversion to agricultural systems is accompanied by shifts in trait composition of canopy ant communities. Further, our results argue against environmental filtering of closely related canopy ant species as the major community assembly mechanism in plantation systems, but suggest that the Sumatran lowland rainforests harbor recently diverged endemic ant species that are particularly vulnerable to rainforest conversion to agricultural systems. Given the importance of ants for tropical ecosystems, the ecological differences among ant communities along the land‐use gradient might have important consequences for ecosystem functioning and services in plantation systems.

Rainforest conversion to cash crops reduces abundance, biomass and species richness of parasitoid wasps in Sumatra, Indonesia

“…Supporting our first and second hypotheses, abundance and morphospecies richness of total parasitoid wasps as well as braconid wasps were highest in rainforest, intermediate in jungle rubber and lowest in rubber and oil palm plantations. This pattern resembles that of previous studies at the same study sites focusing on other animal taxa, such as ants (Kreider et al, 2021; Nazarreta et al, 2020; Rizqulloh et al, 2021), butterflies (Panjaitan et al, 2019, 2020), frogs (Paoletti et al, 2018), pseudoscorpions (Liebke et al, 2021) and spiders (Junggebauer et al, 2021; Potapov et al, 2020). The pattern is quite likely driven by declining population densities of potential host taxa, which in turn are likely the consequence of reduced vegetation diversity and structural complexity from rainforest to rubber and oil palm plantations (Böhnert et al, 2016; Kusuma et al, 2018).…”

Tree Diversity Enhance Species Richness of Beneficial Insect in Experimental Biodiversity Enrichment in Oil Palm Plantation

“…Although prey diversity was not measured, we assumed that the missing prey contributed on the lack of ant richness in the plantation without tree biodiversity enrichment. The dominance of generalist nesting and predator ants in this research reminisce the result that shows establishing large scale monoculture oil palm plantation would shift the specialist ants (Luke et al 2014;Kreider et al 2021). Collecting high abundance of Oligomyrmex sp., Crematogaster sp.1, and Pheidole sp1 by using pitfall trap did not surprise us, since all species built their nest in soil.…”

Rainforest conversion to plantations fundamentally alters energy fluxes and functions in canopy arthropod food webs

“…Δ 15 N values not only of omnivores, such as Hemiptera and Formicidae, but also of higher trophic level taxa, such as Diptera, Staphylinidae and Araneae, were remarkably constant across land-use systems. This suggests that, despite high diversity within taxonomic groups (Azhar et al, 2022;Basset, 2001;Nazarreta et al, 2020;Ramos et al, 2022), overall trophic niches and therefore ecological functions of these supra-specific taxa are relatively constant (Kreider et al, 2021;. In contrast to the relatively low Δ 13 C values in plantation systems, in rainforest and jungle rubber canopy arthropods were on average 5‰-6‰ enriched in 13 C compared to canopy leaves as potential basal resource; Δ 13 C maxima in rainforest were even close to 9‰ above those of leaves.…”