Tree canopy arthropods have idiosyncratic responses to plant ecophysiological traits in a warm temperate forest complex

Rudi C Swart,Michael J Samways,Francois Roets

doi:10.1038/s41598-020-76868-8

Rudi C Swart, Michael J Samways + Show 1 more

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https://doi.org/10.1038/s41598-020-76868-8

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Journal: Scientific Reports	Publication Date: Nov 16, 2020
Citations: 12	License type: open-access

Affiliation: Stellenbosch University

Abstract

Biodiversity studies on forest canopies often have narrow arthropod taxonomic focus, or refer to a single species of tree. In response, and to better understand the wide range of drivers of arthropod diversity in tree canopies, we conducted a large-scale, multi-taxon study which (a) included effect of immediate surroundings of an individual tree on plant physiological features, and (b), how these features affect compositional and functional arthropod diversity, in a warm, southern Afro-temperate forest. We found that tree species differed significantly in plant physiological features and arthropod diversity patterns. Surprisingly, we found negative correlation between surrounding canopy cover, and both foliar carbon and arthropod diversity in host trees, regardless of tree species. Subtle, tree intraspecific variation in physiological features correlated significantly with arthropod diversity measures, but direction and strength of correlations differed among tree species. These findings illustrate great complexity in how canopy arthropods respond to specific tree species, to immediate surroundings of host trees, and to tree physiological features. We conclude that in natural forests, loss of even one tree species, as well as homogenization of the crown layer and/or human-induced environmental change, could lead to profound and unpredictable canopy arthropod biodiversity responses, threatening forest integrity.

Highlights

Biodiversity studies on forest canopies often have narrow arthropod taxonomic focus, or refer to a single species of tree
Due to the large numbers of arthropod species supported at canopy level, many studies often focus on one arthropod taxonomic group[2,5] or on a single tree s pecies[6,7]
Host tree species identity is an important driver of arthropod diversity in forest canopies, determined largely by differences in plant physiological features such as leaf size and shape, chemical defences, turgor, and nitrogen c ontent[10]

Summary

Introduction

Biodiversity studies on forest canopies often have narrow arthropod taxonomic focus, or refer to a single species of tree. To better understand the wide range of drivers of arthropod diversity in tree canopies, we conducted a large-scale, multi-taxon study which (a) included effect of immediate surroundings of an individual tree on plant physiological features, and (b), how these features affect compositional and functional arthropod diversity, in a warm, southern Afro-temperate forest. We conclude that in natural forests, loss of even one tree species, as well as homogenization of the crown layer and/or human-induced environmental change, could lead to profound and unpredictable canopy arthropod biodiversity responses, threatening forest integrity. Trees and their associated arthropods contribute greatly to terrestrial biodiversity, though ecologists only recently have begun to decipher the complexities of their interactions[1]. A changing climate can increase water stress, reduce growth, and so disrupt plant-arthropod dynamics, but can increase forest vigour and growth, and lead to higher water use efficiency and extended growing seasons[16,17]

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