Volatility in coral cover erodes niche structure, but not diversity, in reef fish assemblages

Cheng-Han Tsai; Hugh P A Sweatman; Loïc M Thibaut; Sean R Connolly

doi:10.1126/sciadv.abm6858

Volatility in coral cover erodes niche structure, but not diversity, in reef fish assemblages

Sci Adv. 2022 Jun 17;8(24):eabm6858. doi: 10.1126/sciadv.abm6858. Epub 2022 Jun 15.

Authors

Cheng-Han Tsai^{1

2

3}, Hugh P A Sweatman², Loïc M Thibaut^{4

5

6}, Sean R Connolly^{1

3

7}

Affiliations

¹ College of Science and Engineering, James Cook University, Townsville, QLD 4811, Australia.
² Australian Institute of Marine Science, Townsville MC, QLD 4810, Australia.
³ Australian Research Council Centre of Excellence for Coral Reef Studies, Townsville, QLD 4811, Australia.
⁴ School of Mathematics and Statistics, University of New South Wales, Sydney, NSW 2052, Australia.
⁵ Centre for Population Genomics, Garvan Institute of Medical Research and UNSW Sydney, Sydney, NSW, Australia.
⁶ Centre for Population Genomics, Murdoch Children's Research Institute, Melbourne, VIC, Australia.
⁷ Smithsonian Tropical Research Institute, Panama, Republic of Panama.

Abstract

The world's coral reefs are experiencing increasing volatility in coral cover, largely because of anthropogenic environmental change, highlighting the need to understand how such volatility will influence the structure and dynamics of reef assemblages. These changes may influence not only richness or evenness but also the temporal stability of species' relative abundances (temporal beta-diversity). Here, we analyzed reef fish assemblage time series from the Great Barrier Reef to show that, overall, 75% of the variance in abundance among species was attributable to persistent differences in species' long-term mean abundances. However, the relative importance of stochastic fluctuations in abundance was higher on reefs that experienced greater volatility in coral cover, whereas it did not vary with drivers of alpha-diversity. These findings imply that increased coral cover volatility decreases temporal stability in relative abundances of fishes, a transformation that is not detectable from static measures of biodiversity.