Size-Energy Relationships in Ecological Communities

Abstract

Hypotheses that relate body size to energy use are of particular interest in community ecology and macroecology because of their potential to facilitate quantitative predictions about species interactions and to clarify complex ecological patterns. One prominent size-energy hypothesis, the energetic equivalence hypothesis, proposes that energy use from shared, limiting resources by populations or size classes of foragers will be independent of body size. Alternative hypotheses propose that energy use will increase with body size, decrease with body size, or peak at an intermediate body size. Despite extensive study, however, size-energy hypotheses remain controversial, due to a lack of directly-measured data on energy use, a tendency to confound distinct scaling relationships, and insufficient attention to the ecological contexts in which predicted relationships are likely to occur. Our goal, therefore, was to directly evaluate size-energy hypotheses while clarifying how results would differ with alternate methods and assumptions. We comprehensively tested size-energy hypotheses in a vertebrate frugivore guild in a tropical forest in Madagascar. Our test of size-energy hypotheses, which is the first to examine energy intake directly, was consistent with the energetic equivalence hypothesis. This finding corresponds with predictions of metabolic theory and models of energy distribution in ecological communities, which imply that body size does not confer an advantage in competition for energy among populations or size classes of foragers. This result was robust to different assumptions about energy regulation. Our results from direct energy measurement, however, contrasted with those obtained with conventional methods of indirect inference from size-density relationships, suggesting that size-density relationships do not provide an appropriate proxy for size-energy relationships as has commonly been assumed. Our research also provides insights into mechanisms underlying local size-energy relationships and has important implications for predicting species interactions and for understanding the structure and dynamics of ecological communities.

Using Stable Isotopes to Infer the Impacts of Habitat Change on the Diets and Vertical Stratification of Frugivorous Bats in Madagascar

“…For objective one, we hypothesized that, although all three species are largely frugivorous [ 12 , 31 , 38 , 39 ] their diets would differ. Specifically, in accordance with previous evidence of differences in the composition and abundance of food items in the diet of the three species [ 13 , 33 ], we expected among-species differences in diet would be stronger than within-species differences. Similarly, we hypothesized that diet breadth would differ between species; we expected that, in accordance with previous studies on dietary diversity, P .…”

“…Bat foraging studies typically use a standard set of methods: cafeteria trials on captive bats [ 10 ], pollen/seed sampling from captured bats [ 11 ], field examination of feeding refuse [ 7 ], guano analyses [ 12 ], direct observations of free-ranging bats [ 13 ], radio telemetry [ 5 ], and stable isotope analyses [ 14 ]. Of these methods, stable isotope analyses provides several advantages for long-term and large-scale examination of fruit bat diets and the factors that affect them.…”

Metabolic Scaling in Complex Living Systems

“…Very little attention has been given to the whole-system scaling of metabolic rate or other energy related processes at the population, community or ecosystem levels. Although several studies have scaled energy use or production at these levels to organismal body size (e.g., [233][234][235][236][237][238][239]), hardly anything is known about how the "metabolism" of ecological systems scales to their higher-order size (but see [240][241][242][243]). Here I suggest that all of the theoretical approaches emphasized in this review could be applied at the level of ecological systems.…”

Frugivore assemblage of Ficus superba in a warm‐temperate forest in Yakushima, Japan

“…There have been numerous studies on frugivore Electronic supplementary material The online version of this article (doi:10.1007/s11284-016-1398-z) contains supplementary material, which is available to authorized users. assemblages at fruiting figs showing that many species of birds and mammals visit figs and that their relative contributions to syconia consumption vary among fig species or regions (Jordano 1983;Coates-Estrada and Estrada 1986;Goodman et al 1997;Tello 2003;Sreekar et al 2010;Kattan and Valenzuela 2013;Sewall et al 2013).…”