Temperature directly and indirectly influences food web structure

Jean P Gibert

doi:10.1038/s41598-019-41783-0

Abstract

Understanding whether and how environmental conditions may impact food web structure at a global scale is central to our ability to predict how food webs will respond to climate change. However, such an understanding is nascent. Using the best resolved available food webs to date, I address whether latitude, temperature, or both, explain the number of species and feeding interactions, the proportion of basal and top species, as well as the degree of omnivory, connectance and the number of trophic levels across food webs. I found that temperature is a more parsimonious predictor of food web structure than latitude. Temperature directly reduces the number of species, the proportion of basal species and the number of interactions while it indirectly increases omnivory levels, connectance and trophic level through its direct effects on the fraction and number of basal species. While direct impacts of temperature are routinely taken into account to predict how ecosystems may respond to global climate change, indirect effects have been largely overlooked. These results thus suggest that food webs may be affected by a combination of biotic and abiotic conditions, both directly and indirectly, in a changing world.

Highlights

Food web structure can affect the dynamics and stability of large species assemblages (e.g.1–3) as well as the flow of energy and matter across ecosystems (e.g.4,5)
Some theoretical studies suggest that temperature impacts on food web structure can be difficult to predict due to the potential for idiosyncratic temperature responses of the species embedded within food webs[27]
While all models fitted the data very well (Table 1), the model that only included temperature as an abiotic correlate was the most parsimonious (Table 1). The one including both latitude and temperature in all cases explained the most variance (Table 1, Appendices 4 and 5). These results were largely consistent for both aggregate and non-aggregate food webs (Appendix 4) and taking or not into account the 7 food webs for which temperature was not available from GIS layers did not alter the results presented here (Appendix 5)

Summary

Introduction

Food web structure can affect the dynamics and stability of large species assemblages (e.g.1–3) as well as the flow of energy and matter across ecosystems (e.g.4,5). Systematic sampling of pitcher plant food webs across a continental-scale latitudinal gradient showed that both the number of species and the number of interactions per species increased with latitude Despite these results, low amounts of total explained variation led the authors to conclude that food web structure was broadly independent of abiotic climatic factors[40]. Low amounts of total explained variation led the authors to conclude that food web structure was broadly independent of abiotic climatic factors[40] Together, these results suggest that do we still lack a general understanding of how latitude and temperature influence food web structure, but we have so far not been able to tease apart their potentially independent effects from their joint effects

Methods

Results

Discussion

Conclusion