Analysis of tropical and temperate elevational gradients in arthropod abundance

K Supriya,Trevor D Price,Katerina Sam,Corrie S Moreau

doi:10.21425/f5fbg43104

Abstract

Arthropods are a major component of ecosystems, in terms of both their biomass and the variety of functional roles they play. Yet we lack a clear understanding of how arthropod abundance changes along environmental gradients. We compiled published literature on overall arthropod abundances (number of individuals) along elevational gradients and performed a formal meta-analysis on the role of latitude, climatic variables, and interactions with ants in shaping the pattern. Specifically, we asked if patterns of arthropod abundance along different elevational gradients are associated with gradients of seasonality and precipitation and whether ant abundance affects other arthropods. Arthropod abundance peaks at higher elevations at mid-latitudes than low latitudes; hence, the correlation between arthropod abundance and elevation shifts from negative to positive with an increase in latitude. We suggest these patterns reflect a steep elevational gradient in the length of growing season at mid-latitudes, with the short growing season at high elevations in mid-latitudes leading to synchronous emergence and reproduction of arthropods generating a sharp increase in abundance. Precipitation and ant abundance do not have a consistent effect on arthropod abundance along most elevational gradients. However, on gradients with a very dry base and sharp increase in precipitation with elevation, arthropod abundance peaks at higher elevations. Overall, our results suggest that future changes in the length of growing season will impact the elevation at which summer arthropod abundance peaks and the sharpness of the peak, likely affecting diversity and distribution of other taxa that interact with arthropods.

Highlights

Arthropods are the most diverse phylum of animals, not just in terms of the number of species and in their form and function, containing groups as different as butterflies, ants, spiders, springtails, millipedes, crabs, and scorpions
Reduction in arthropod abundance has been linked to declines in vertebrate populations that depend on arthropods for food (Lister and Garcia 2018) and lower, less stable crop yields for plants pollinated by insects (Aizen et al 2009)
Across 20 studies of arthropod abundance along elevational gradients spanning 0-40° latitude, we found that correlation of elevation and arthropod abundance increases with latitude (Fig. 3)

Summary

Introduction

Arthropods are the most diverse phylum of animals, not just in terms of the number of species and in their form and function, containing groups as different as butterflies, ants, spiders, springtails, millipedes, crabs, and scorpions. Despite their small size relative to vertebrates, arthropods constitute a much larger proportion of animal biomass in many terrestrial ecosystems (Fittkau and Klinge 1973). Arthropods play myriad roles in ecosystems as prey, predators, pollinators, parasites, and disease vectors (Miller 1993) Their numbers should have major effects on the diversity and distribution of the taxa they interact with (Bagchi et al 2014). These declines might be over‐estimates, it is generally accepted that arthropod

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Conclusion