Interspecific Hybridization May Provide Novel Opportunities for Coral Reef Restoration

Abstract

Climate change and other anthropogenic disturbances have created an era characterized by the inability of most ecosystems to maintain their original, pristine states, the Anthropocene. Investigating new and innovative strategies that may facilitate ecosystem restoration is thus becoming increasingly important, particularly for coral reefs around the globe which are deteriorating at an alarming rate. The Great Barrier Reef (GBR) lost half its coral cover between 1985 and 2012, and experienced back-to-back heat-induced mass bleaching events and high coral mortality in 2016 and 2017. Here we investigate the efficacy of interspecific hybridization as a tool to develop coral stock with enhanced climate resilience. We crossed two Acropora species pairs from the GBR and examined several phenotypic traits over 28 weeks of exposure to ambient and elevated temperature and pCO 2 . While elevated temperature and pCO 2 conditions negatively affected size and survival of both purebreds and hybrids, higher survival and larger recruit size were observed in some of the hybrid offspring groups under both ambient and elevated conditions. Further, interspecific hybrids had high fertilization rates, normal embryonic development, and similar Symbiodinium uptake and photochemical efficiency as purebred offspring. While the fitness of these hybrids in the field and their reproductive and backcrossing potential remain to be investigated, current findings provide proof-of-concept that interspecific hybridization may produce genotypes with enhanced climate resilience, and has the potential to increase the success of coral reef restoration initiatives.

The roles of age, parentage and environment on bacterial and algal endosymbiont communities in Acropora corals

“…Bacterial and Symbiodiniaceae communities were the same in hybrid and purebred Acropora offspring within each cross, indicating that parentage plays a minor role in shaping these communities at the early coral life stages. At 7 months of age, hybrids showed ~16%–34% higher survival than purebred A. tenuis in the A. tenuis × A. loripes cross, and ~14%–22% higher survival than both purebred offspring groups in the A. sarmentosa × A. florida cross (Chan et al, ). Our findings suggest these early life stage fitness differences are unlikely due to the microbial communities, unless the same communities expressed different genes in hybrid and purebred corals (which was not tested).…”

“…Light was provided at ~120 µE m −2 s −1 using Aquaillumination Hydra following the natural light/dark cycle. Fitness comparisons (e.g., survival, growth) between hybrids and purebreds are reported in Chan et al (). At the end of the 7‐month experiment (July 2016), three recruits from three randomly selected tanks of each treatment were sampled and stored in absolute ethanol (EtOH) ( n = 3 per offspring group per tank per treatment, 144 samples in total).…”

“…The aim of this study was to investigate the composition and succession of bacterial and Symbiodiniaceae communities in hybrid and purebred Acropora corals. Hybrid Acropora corals naturally occur in the Caribbean (Fogarty, ; Vollmer & Palumbi, ) and Indo‐Pacific (Willis, van Oppen, Miller, Vollmer, & Ayre, ), and they have been shown in some studies to have comparatively high fitness in the laboratory (Chan, Peplow, Menéndez, Hoffmann, & van Oppen, ; Isomura, Iwao, & Fukami, ; Willis et al, ) and in the wild (Fogarty, ). However, information about their bacterial and Symbiodiniaceae communities is lacking.…”

“…Access to purebred and interspecific hybrid offspring from four Acropora species bred in the laboratory and exposed to ambient and elevated conditions (temperature and p CO 2 ) for 7 months, followed by a 13‐month grow‐out period under ambient conditions, allowed us to examine the influence of coral age, parentage and treatment conditions on the composition of the microbiome. A second aim was to examine whether the coral‐associated microbial communities contributed to the differences in holobiont fitness previously reported in Chan et al ().…”

Hybridization as a conservation management tool

“…Increasingly, management options targeted at enhancing genetic variation and adaptive potential of a species or population are being discussed both within the context of revegetation and coral reef restoration (Breed, Stead, Ottewell, Gardner, & Lowe, 2013;Chan, Peplow, Menéndez, Hoffmann, & Van Oppen, 2018;Hamilton & Miller 2016;Hoffmann et al, 2015;Hoffmann & Sgrò 2011;Jones & Monaco 2009;van Oppen et al, 2017;Vitt, Havens, Kramer, Sollenberger, & Yates, 2010). This represents a shift from a traditional focus on restoring local genetic materials to consideration of using nonlocal genetic variation (Jones & Monaco 2009).…”