Widespread variation in heat tolerance and symbiont load are associated with growth tradeoffs in the coral Acropora hyacinthus in Palau.

Brendan Cornwell,Marilla Lippert,Katrina Armstrong,Victor Nestor,Stephen R Palumbi,Nia S Walker,Yimnang Golbuu

doi:10.7554/elife.64790

Brendan Cornwell, Marilla Lippert + Show 5 more

Open Access

https://doi.org/10.7554/elife.64790

Copy DOI

Journal: eLife	Publication Date: Aug 13, 2021
Citations: 43	License type: CC BY 4.0

Affiliation: Stanford University, Palau International Coral Reef Center

Abstract

Climate change is dramatically changing ecosystem composition and productivity, leading scientists to consider the best approaches to map natural resistance and foster ecosystem resilience in the face of these changes. Here, we present results from a large-scale experimental assessment of coral bleaching resistance, a critical trait for coral population persistence as oceans warm, in 221 colonies of the coral Acropora hyacinthus across 37 reefs in Palau. We find that bleaching-resistant individuals inhabit most reefs but are found more often in warmer microhabitats. Our survey also found wide variation in symbiont concentration among colonies, and that colonies with lower symbiont load tended to be more bleaching-resistant. By contrast, our data show that low symbiont load comes at the cost of lower growth rate, a tradeoff that may operate widely among corals across environments. Corals with high bleaching resistance have been suggested as a source for habitat restoration or selective breeding in order to increase coral reef resilience to climate change. Our maps show where these resistant corals can be found, but the existence of tradeoffs with heat resistance may suggest caution in unilateral use of this one trait in restoration.

Highlights

Climate change is increasingly shifting species ranges, altering ecosystem dynamics, and generating strong selection differentials in wild populations (Chen et al 2011; Logan et al 2014; MacLean and Beisinger 2017; Wiens 2016; Parmesan &Yohe 2003; Chen et al 2011; Lenoir & Svenning 2015)
Characterizing the distribution of stress tolerant individuals could be the basis for investigating the mechanisms leading to heat stress resistance and, predicting how these populations will respond to climate change
We find lower symbiont load in most heat resistant corals, and that low symbiont levels are correlated with lower growth rates

Summary

Introduction

Yohe 2003; Chen et al 2011; Lenoir & Svenning 2015) Against this backdrop, there is an accelerated focus on characterizing the adaptive mechanisms that increase resilience to climate stressors in natural communities (King et al 2018; Walsworth et al 2019, NASEM 2019a). The practical importance of identifying populations that are locally adapted to climate stress is rooted in the possibility that populations already harboring stress tolerant individuals might be used in restoration projects or in assisted evolution efforts to enhance the resilience of vulnerable populations (Aitken and Whitlock 2013; Mascia & Mills 2017; Seddon et al 2014). Characterizing the distribution of stress tolerant individuals could be the basis for investigating the mechanisms leading to heat stress resistance and, predicting how these populations will respond to climate change Identifying source populations with such phenotypic variance could become especially critical for foundation species such as corals, forest trees, grasslands, and seagrasses (Franks et al 2014; Hodgins and Moore 2016, Morikawa and Palumbi 2019).

Objectives

Methods

Results

Conclusion