Complex indirect effects of epiphytic bromeliads on the invertebrate food webs of their support tree

Abstract

Ecosystem engineers are species that affect others through the provision of habitat rather than consumptive resources. The extent to which ecosystem engineers can indirectly affect entire food webs, however, is poorly understood. Epiphytic tank bromeliads (Bromeliaceae) are ecosystem engineers that are common throughout the Neotropics, and are associated with a variety of predatory arthropods. Here, we examine if bromeliads, by increasing predator densities, indirectly benefit their support tree through reduction in herbivorous insects and leaf damage. We observed and manipulated bromeliad densities in Costa Rican orange orchards, and measured impacts on leaf damage and arboreal and bromeliad invertebrate communities in two different seasons. Our results show that bromeliads are associated with predatory and herbivorous invertebrates but not leaf damage. Bromeliads were correlated with increased densities of their associated predators, especially ants and hunting spiders, but we could not confirm a causal link. Associations with bromeliads changed over time, with seasonal shifts interfering with responses to our manipulations. Bromeliads had a reduced association with predators in the dry season. Moreover, a null association between bromeliads and herbivorous invertebrates in the dry season unexpectedly became positive in the wet season. In summary, we have only limited evidence that bromeliads indirectly promote the top‐down control of arboreal herbivores; instead, our manipulations suggest that bromeliads increase herbivore densities in the wet season. This research suggests that although bromeliads may act as ecosystem engineers, indirectly influencing the invertebrate food web on support trees, their effects are trophically complex and seasonally dependent. Abstract in Spanish is available with online material.

Morphology and life cycle of a new species of Psilocladus Blanchard, 1846 (Coleoptera, Lampyridae, Psilocladinae), the first known bromeliad-inhabiting firefly

“…Our study is the first detailed report of fireflies living in bromeliad tanks, as far as we are aware. Other studies in South America have indeed found firefly larvae in bromeliad tanks, but rather focusing on the plant's ecology, that is, not on the insects themselves, and the identity of the species were never addressed (e.g., Givnish et al, 1984;Aguilera-Arango et al, 2011;Rogy et al, 2019).…”

Gallers as leaf rollers: ecosystem engineering in a tropical system and its effects on arthropod biodiversity

“…We suggest that leaf shelters can be an adequate place to ambush and capture prey, in addition to having an adaptive value, as predators resting and nesting inside them can save time and energy by occupying already existing structures (Fukui, 2001; Vieira & Romero, 2013; Slinn et al ., 2017). In addition, shelters can provide small predators with protection from larger predators, such as insectivorous birds that forage around the canopies sometimes looking for damaged and modified leaves (Romero & Vasconcellos‐Neto, 2005; Rogy et al ., 2019).…”

Do bromeliads affect the arboreal ant communities on orange trees in northwestern Costa Rica?

“…All fieldwork was led by P.R. as part of a larger, three-site study on how bromeliads affect arboreal insect food webs and leaf herbivory [ 30 ]. The third site, a commercial orange plantation, had such low ant abundances as to prevent analyses of ant composition, and is therefore excluded in this study.…”

“…The data on ant community composition and species richness from this experiment has not been previously published. The data on ant abundance has been only presented before in aggregate form for a larger set of sites [ 30 ]. We re-analyse this abundance data just for the two sites in our study to compare patterns in total abundance to those of the other community descriptors.…”