Interspecific hybridisation increases genetic diversity and has played a significant role in the evolution of corals in the genus Acropora. In vitro fertilisation can be used to increase the frequency of hybridisation among corals, potentially enhancing their ability to adapt to climate change. Here, we assessed the field performance of hybrids derived from the highly cross-fertile coral species Acropora sarmentosa and Acropora florida from the Great Barrier Reef. Following outplanting to an inshore reef environment, the 10-month survivorship of the hybrid offspring groups was intermediate between that of the purebred groups, although not all pairwise comparisons were statistically significant. The A. florida purebreds, which had the lowest survivorship, were significantly larger at 10 months post-deployment compared to the other three groups. The four offspring groups harboured the same intracellular photosymbiont communities (Symbiodiniaceae), indicating that observed performance differences were due to the coral host and not photosymbiont communities. The limited differences in the performance of the groups and the lack of outbreeding depression of the F1 hybrids in the field suggest that interspecific hybridisation may be a useful method to boost the genetic diversity, and as such increase the adaptive capacity, of coral stock for restoration of degraded and potentially genetically eroded populations.

Parental coral colonies of A. tenuis and A. loripes were collected from Trunk Reef on the central Great Barrier Reef in November 2015. During spawning, four offspring groups (i.e., reciprocal F1 hybrids and two parental purebreds: TT (purebred A. tenuis), TL (hybrid), LT (hybrid) and LL (purebred A. loripes), were recruited and settled onto ceramic plugs. Detailed crossing protocol and experimental design is described in Chan et al. (2018). Coral recruits were reared under treatment conditions in filtered seawater for seven months at the National Sea Simulator of the Australian Institute of Marine Science. Treatment conditions included exposure to ambient or elevated temperature and pCO2 conditions: ambient conditions (27ºC and 415 ppm pCO2) elevated conditions (ambient +1 °C and 685 ppm pCO2) RNA-sequencing was conducted and the analysis showed that gene expression of the hybrid Acropora also showed clear maternal effects. Further details are presented in the paper Chan, WY, Chung, J, Peplow, LM, Hoffmann, AA, van Oppen, MJH. Maternal effects in gene expression of interspecific coral hybrids. Mol Ecol. 2021; 30: 517– 527. https://doi.org/10.1111/mec.15727

Parental coral colonies of A. tenuis and A. loripes were collected from Trunk Reef on the central Great Barrier Reef in November 2015. During spawning, four offspring groups (i.e., reciprocal F1 hybrids and two parental purebreds: TT (purebred A. tenuis), TL (hybrid), LT (hybrid) and LL (purebred A. loripes), were recruited and settled onto ceramic plugs. Detailed crossing protocol and experimental design is described in Chan et al. (2018). Coral recruits were reared under treatment conditions in filtered seawater for seven months at the National Sea Simulator of the Australian Institute of Marine Science. Treatment conditions included exposure to ambient or elevated temperature and pCO2 conditions: ambient conditions (27ºC and 415 ppm pCO2) elevated conditions (ambient +1 °C and 685 ppm pCO2) RNA-sequencing was conducted and the analysis showed that gene expression of the hybrid Acropora also showed clear maternal effects. Further details are presented in the paper Chan, WY, Chung, J, Peplow, LM, Hoffmann, AA, van Oppen, MJH. Maternal effects in gene expression of interspecific coral hybrids. Mol Ecol. 2021; 30: 517– 527. https://doi.org/10.1111/mec.15727

An 18-month reciprocal field transplant experiment was undertaken to examine the environmental and genetic drivers behind variation in survival, weight gain, heat tolerance and algal symbiont community between the reef flat and slope habitats. Pocillopora damicornis colonies from Heron Island were used in a two-part experiment of a replicated RTE across depth habitats and a common garden stress test. Three vital traits were measured between March 2012 – August 2013., and then the relative heat tolerance was measured by exposing the surviving colonies to 14 days of ex situ experimental heat stress. At each site and habitat, 23 – 26 colonies were collected (total n = 97) and fragmented into two halves. One half of each colony was places onto experimental rack in its habitat of origin and the other haps was transplanted to the reciprocal habitat within each site. 2 x 2 m wire mesh racks were installed approximately 0.5m above the substrate and fragmented coral colonies were attached across the rack with cable ties in a haphazard manner. This resulted in four treatment groups replicated at two sites: flat to flat (FF), flat to slope (FS), slope to flat (SF), and slope to slope (SS). Partial colony mortality and weight gain were measured in the field four times between March 2021 and August 2013. A number of colonies were sampled for Symbiodiniaceae community in coral tissue per site and treatment group at two time points in April 2012 and March 2013. At the end of the field transplant experiment on 17 August 2013, the remaining live colonies were transported to the Australian Institute of Marine Science in Townsville, and kept in outdoor 1000L tanks for 10 days. They were then further fragmented into single branches and acclimatized in indoor 30L flow-through tanks at 24°C. Treatment temperatures for the heat stress exposure included 24°C, 29°C, 30°C and 31°C. Between 3 and 20 replicate fragments per colony were exposed each temperature level, for a total of 14 days heat stress. Heat tolerance was quantified by proxy of the maximum quantum yield (Fv/Fm), measured with Pulse-Amplitude Modulation (PAM) fluorometry. Analyses were conducted of Symbiodiniaceae community composition by source and transplant habitats (flat and slope) and physiological traits, percent partial mortality and percent cumulative weight gain. Heat stress analysis was also conducted among different temperatures and contrasts of treatment groups. See published papers linked below for further details.

Wild coral colonies of Acropora tenuis were collected throughout the Great Barrier Reef and transferred to the Australian Sea Simulater (SeaSim). Corals were spawned, and produced purebred and hybris crosses, see Quigley & van Oppen (2022) and Dixon & Kenkel (2019) for full details of spawning and reproductive crossing. Larvae produced from these crosses were sampled for gene expression and assayed using RNAseq before being exposed to control and heat stress for 36 hours (27 and 35.5 °C) in replicates of n=6 (“post” exposure samples). Separate cohorts of each larval cross not used in the heat trials were then induced to settle and exposed to four symbiont treatments. These replicates were sampled for RNAseq for each of the crosses prior to the heat stress at time 0 and 56 hours at 27°C and 35.5°C treatments. For survival measurements, individual larvae were counted within net-wells in replicate plates within each temperature treatment. Each larval survival measurement represents a discrete sample measurement. The unit of measure is the number of individual replicate wells containing larvae. Juvenile replicates RNAseq samples were taken in each of the crosses after 58 days at 27 and 32°C. Survival measurements represent individual juvenile survival. Each represents a discrete sample measurement. The unit of measure is the number of individual replicate juveniles per replicate well, per replicate plate, per replicate tank for each temperature and symbiont treatment. Larval survival was counted from 0 to 56 hours at 27°C and 35.5°C. Juvenile survival was counted at 0 and after 58 days at 27 and 32°C treatments. Larvae were assayed for RNAseq at 0 and 56 hours, and juveniles only at 58 days. Experimental metadata of detailed replicates for larval treatments are found on the github repository in file J19188meta.csv. For“pre”, and “post-ambient” there were 33 larval replicates. For “post-hot” there were 30 replicates. Each replicate represented 10 pooled larvae. Each of the 11 crosses was replicated 3 times within each of those 3 treatment groups. There was a total of 96 larval samples. Experimental metadata for juvenile data is found on the github repository in file J19234meta.csv. Of the juvenile samples, 119 werein ambient conditions with 27 in the heat treatment. Each of the 10 crosses was represented in the juvenile dataset 12-18 times. Thesymbiont treatments had 29 samples in C1, 38 samples in D1, 43 samples in SED, and 36 in SS1. There was a total of 146 juvenile samples. Derived statistics presented are defined as independent observations of n= independent larval or juvenile survival based on the number

Marine heatwaves are becoming more frequent during summer and pose a significant threat to coral reef ecosystems. Restoration efforts have the potential to support native coral populations and guard them against some degree of environmental change, while global action against climate change takes place. Interspecific hybridization is one approach through which resilient coral stock could be generated for restoration. Here we compared the performance of Acropora kenti and A. loripes hybrid and purebred coral recruits under a simulated thermal stress event. A. kenti eggs were successfully fertilized by A. loripes sperm to produce ‘KL’ hybrids, but no ‘LK’ hybrids could be produced from A. loripes eggs and A. kenti sperm. Despite corals in the elevated treatment accruing thermal stress (>12 degree heating weeks over 2 months) known to result in mass bleaching, both purebred and hybrid recruits showed no signs of stress under the simulated temperature regime, based on the performance indicators survivorship, size, color (a proxy of bleaching), and photochemical efficiency of photosystem II. Comparisons between the hybrids and purebreds studied here must be interpreted with caution because hybrid sample sizes were small. The hybrids did not outperform both of their purebred counterparts for any metrics studied here, demonstrating that there are limitations to the extent to which interspecific hybridization may boost the performance of coral stock. In general, the purebred A. loripes recruits performed best under both ambient and elevated conditions. The performance of the KL hybrid corals was similar to the maternal parental species, A. kenti, or not significantly different to either parental purebred species. The Symbiodiniaceae communities of the KL hybrids were characteristic of their maternal counterparts and may have underpinned the performance differences between the A. kenti/KL hybrid and A. loripes recruits.

Seeding reefs with heat tolerant corals could enhance reef resilience under climate change. Selective breeding is an intervention that might be used to generate heat tolerant corals for reef restoration. We estimated thermal thresholds for gravid colonies of two Acropora species from Moore Reef and Davies Reef on the Great Barrier Reef using the Sea Simulator In A Box experimental system on AIMS research vessel, the Cape Ferguson. Rankings of photochemical efficiency thermal thresholds were used to select broodstock and selectively breed offspring in the National Sea Simulator. We then tested the heat tolerance of the offspring using the laboratory facilities at AIMS. The collected data was analysed to evaluate: 1) whether a rapid heat stress assay can be used to identify heritable heat tolerance in coral populations and 2) whether there is a trade-off between coral heat tolerance and fecundity that could impact the efficacy of selective breeding.

This dataset was generated during a coral hybridization experiment in 2016. The dataset include fertilization rates, survival and settlement success of hybrid and purebred Acropora corals. Detailed descriptions of the materials and methods can be found in the paper: “Interspecific gamete compatibility and hybrid larval fitness in reef-building corals: Implications for coral reef restoration” in Scientific Reports.

Acropora cervicornis, A. palmata and Orbicella faveolata are important reef-building coral species in the Florida Reef Tract (FRT). These species have experienced alarming declines throughout the FRT, resulting in an increased risk of inbreeding depression and susceptibility to decreased fitness in surviving colonies. Acropora cervicornis, A. palmata and O. faveolata are broadcast spawners, introducing genetic diversity through sexual recombination of gametes during annual spawning events. Successful reproduction during this time is critical for curbing the deleterious effects of inbreeding depression, and in successfully restoring wild colonies to self-sustaining levels of genetic diversity. A critical step in the reproductive cycle of these species is the success of gamete fertilization following mass spawning events. Several abiotic causes of gametic incompatibilities have been reliably observed in these species, and incompatibility between certain genotypes has been shown to occur. This dataset represents the collection of gametes from three coral species following nine spawning events in the Florida Keys during two spawning years (2019 and 2022), reciprocal fertilization trials with gametes from each parent and determined fertilization success for each cross. Additionally, tissue fragments were collected from each A. cervicornis parent, DNA was isolated from the tissue and single nucleotide polymorphism analyses were performed using the Axiom Coral-Algae Genotyping array (Axiom AcropSNP, ThermoFisher Scientific). This data package contains images of coral eggs post fertilization trial and the results in spreadsheet format. The raw A. cervicornis single nucleotide polymorphism (SNP) data are also provided.

This study combined phenotypic, pedigree, and genomic marker data from colonies sourced from a warm reef on the Great Barrier Reef reproductively crossed with conspecific colonies from a cooler reef to produce combinations of warm purebreds and warm-cool hybrid larvae and juveniles. Corals of the species Acropora spathulata were collected from one reef in the far north of the Great Barrier Reef (Tijou) and one reef in the central GBR (Backnumbers). During spawning, the eggs and sperm were separated and then mixed, resulting in larvae from 30 distinct familial crosses. These crosses include three produced from two parents sourced from the warm far northern reef (WW1, WW2, WW3), one cross with a warm dam and cool sire (WC) and one with a cool dam and warm sire (CW). This study focused on the five familial crosses sequenced at both the larval stage (27.5°C) and the juvenile stage (27.5°C and 31°C). Aposymbiotic juveniles were infected with Symbiodinium tridacnidorum, Cladocopium goreaui, and Durusdinium trenchii with cultured material obtained from the AIMS Symbiont Culture Facility. Full details of the collection, environmental parameters of each location, permits, spawning, larval and juvenile rearing, and symbiosis establishment can be found in Quigley et al. (2020) Individual larvae were genotyped (total n = 68) across five families representing three population crosses (n = WW: 34, WC: 15, CW: 19). Statistical analysis of SNP metrics were conducted in R, along with modelling SNP frequency distributions. Full details are in the linked paper, Quigley, Bay and van Oppen (2020).