Large herbivores facilitate the persistence of rare taxa under tundra warming

Eric Post,Christian Pedersen,David A Watts

doi:10.1038/s41598-022-05388-4

Abstract

Ecological rarity, characterized by low abundance or limited distribution, is typical of most species, yet our understanding of what factors contribute to the persistence of rare species remains limited. Consequently, little is also known about whether rare species might respond differently than common species to direct (e.g., abiotic) and indirect (e.g., biotic) effects of climate change. We investigated the effects of warming and exclusion of large herbivores on 14 tundra taxa, three of which were common and 11 of which were rare, at an inland, low-arctic study site near Kangerlussuaq, Greenland. Across all taxa, pooled commonness was reduced by experimental warming, and more strongly under herbivore exclusion than under herbivory. However, taxon-specific analyses revealed that although warming elicited variable effects on commonness, herbivore exclusion disproportionately reduced the commonness of rare taxa. Over the 15-year duration of the experiment, we also observed trends in commonness and rarity under all treatments through time. Sitewide commonness increased for two common taxa, the deciduous shrubs Betula nana and Salix glauca, and declined in six other taxa, all of which were rare. Rates of increase or decline in commonness (i.e., temporal trends over the duration of the experiment) were strongly related to baseline commonness of taxa early in the experiment under all treatments except warming with grazing. Hence, commonness itself may be a strong predictor of species’ responses to climate change in the arctic tundra biome, but large herbivores may mediate such responses in rare taxa, perhaps facilitating their persistence.

Highlights

Ecological rarity, characterized by low abundance or limited distribution, is typical of most species, yet our understanding of what factors contribute to the persistence of rare species remains limited
While rarity is a common state in nature, its converse, commonness, is unusual[1,2]. This dichotomy of states is evident across scales of organization, with most biomes, ecosystems, and local communities comprising a few common species and many rare ones[2,3]
While rare species tend to display a combination of predictable attributes, including habitat specialization, small local population size, and limited geographic r anges[4], understanding how rare species persist despite being rare has remained a challenge in ecology for d ecades[5,6]

Summary

Introduction

Ecological rarity, characterized by low abundance or limited distribution, is typical of most species, yet our understanding of what factors contribute to the persistence of rare species remains limited. Commonness itself may be a strong predictor of species’ responses to climate change in the arctic tundra biome, but large herbivores may mediate such responses in rare taxa, perhaps facilitating their persistence. Numerous recent syntheses and meta-analyses have emphasized that rare species, or species with some aspect of rarity such as low abundance or restricted distributions, are at greatest risk of extinction due to effects of climate change on local bioclimatic suitability or habitat availability[9,10,11,12]. For instance, removal of a keystone herbivore, especially in combination with warming, can rapidly erode local diversity as competitively dominant plant species increase in abundance or occurrence and rare species are lost from the local assemblage[14,15]. Warming-driven invasion of tundra by Scientific Reports | (2022) 12:1292

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Conclusion