Biology subjects

Sivault, E.

Publications and source records attributed to Sivault, E..

3 recordsLinked to original sources

bioRxiv2023

Insectivorous birds and bats outperform ants in the top-down regulation of arthropods across strata of a Japanese temperate forest

O_LIBirds, bats, and ants are recognized as significant arthropod predators. However, empirical studies reveal inconsistent trends in their relative roles in top-down control across strata. Here, we describe the differences between forest strata in the separate effects of birds, bats, and ants on arthropod communities and their cascading effects on plant damage. C_LIO_LIWe implemented a factorial design to exclude vertebrates and ants in both the canopy and understory. Additionally, we separately excluded birds and bats from the understory using diurnal and nocturnal exclosures. At the end of the experiments, we collected all arthropods and assessed herbivory damage. C_LIO_LIArthropods responded similarly to predator exclusion across forest strata, with a density increase of 81% on trees without vertebrates and 53% without both vertebrates and ants. Additionally, bird exclusion alone led to an 89% increase in arthropod density, while bat exclusion resulted in a 63% increase. Herbivory increased by 42% when vertebrates were excluded and by 35% when both vertebrates and ants were excluded. Bird exclusion alone increased herbivory damage by 28%, while the exclusion of bats showed a detectable but non-significant increase (by 22%). In contrast, ant exclusion had no significant effect on arthropod density or herbivory damage across strata. C_LIO_LIOur results reveal that the effects of birds and bats on arthropod density and herbivory damage are similar between the forest canopy and understory in this temperate forest. In addition, ants were not found to be significant predators in our system. Furthermore, birds, bats, and ants appeared to exhibit antagonistic relationships in influencing arthropod density. These findings highlight, unprecedentedly, the equal importance of birds and bats in maintaining ecological balance across different strata of a temperate forest. C_LI

ecology↗

bioRxiv2022

Vertebrates but not ants protect rainforest trees from herbivorous insects along an elevational gradient in Papua New Guinea

AimThe theory on trophic interactions between plants, insect herbivores, and their predators predicts that predators increase plant biomass by feeding on herbivores. However, it remains unclear whether different types of predators regulate herbivores to the same degree, and how the trophic interactions affect lower trophic levels along elevational gradients where predator communities differ significantly. Therefore, we aimed to investigate the impact of vertebrate predators and ants (individually and in combination) on arthropod communities and leaf herbivory along a complete tropical forest gradient. LocationPapua New Guinea TaxonMulti-taxon MethodsWe excluded predators from 560 saplings in two six-month long predator exclusion experiments spanning wet and dry seasons. Saplings were spread across 8 study sites which were evenly spaced at 500 m elevational increments from 200 to 3700m a.s.l.. ResultsOn average the density of arthropods increased significantly by 37% and 33% respectively when vertebrate predators, and both ants and vertebrates predators, were removed. Both season and elevation mediated this effect significantly. At lower trophic levels, both the exclusion of both vertebrates alone, and exclusion of vertebrates plus ants, led to a significant increase in leaf damage by 50% and 36% respectively. In contrast, the exclusion of ants alone had no significant effect on arthropod density or leaf damage, which increased by 12% and 9% respectively. Main conclusionsOur results indicate that the relative contribution of birds and bats changes at different elevational sites, while the overall effect of vertebrate predators remains consistent along the whole elevational gradient. This contrasts with ant driven trophic cascades which brought about increased herbivory only at the most productive sites of the elevational gradient, where ant abundance is highest. We conclude that disappearance of insectivorous vertebrate predators can lead to substantial negative consequences for plants.

ecology↗

bioRxiv2022

Species richness and community structure of bats along a forest elevational transect in Papua New Guinea

Over the past decades, elevational gradients have become a powerful tool with which to understand the underlying cause(s) of biodiversity. The Mt. Wilhelm elevational transect is one such example, having been used to study the birds, insects, and plants of Papua New Guinea (PNG). However, a survey of mammals from this forest elevational transect was lacking. We thus aimed to investigate patterns in the community structure and species richness of bats (Chiroptera) along the transect, link the species to available regional data, and explain the observed patterns by including environmental characteristics. Bat communities were surveyed between 200 m and a timberline at 3,700 m a.s.l. at eight study sites separated by 500 m in elevation. We conducted mist-netting and acoustic surveys to detect and identify species at each site. Regional data were compiled to compare local with regional diversity. Finally, biotic (i.e., food availability, habitat features) and abiotic (i.e., mean daily temperature, available land area) factors were included in our analyses to disentangle the ecological drivers underlying bat diversity. Results revealed that species richness decreases with ascending elevation and was best explained by a corresponding decrease in both area and temperature. We also observed community turnover along the transect at local and regional scales, along with the increase of species elevational ranges. Consequently, despite that the study was restricted to one mountain in PNG, it demonstrates how basic inventory surveys can be used to address ecological questions in other similar and undisturbed tropical mountains.

ecology↗