Meeting Abstract

12.4  Saturday, Jan. 4 11:00  All set for adaptation: high heritability of heat tolerance and associated gene expression in a reef-building coral BAY, L. K.; DAVIES, S. W.; MATZ, M .V.*; Australian Institute of Marine Science; University of Texas at Austin; University of Texas at Austin matz@utexas.edu

Reefs along the length of the Great Barrier Reef (GBR) differ widely in mean temperature and temperature variability, yet maintain high genetic connectivity of broadcast-spawning corals. This creates the potential for rapid evolutionary rescue of coral populations from ocean warming, but only if there is pronounced heritable variation in heat tolerance among locations. To investigate this issue, we crossed two parental colonies of Acropora millepora from Orpheus Island (middle GBR, cool location) with two colonies from Princess Charlotte Bay (northern GBR, warm location) in a diallel crossing design and quantified mortality of the larval families under heat stress. Parental effects were responsible for >80% of the variation in mortality, with narrow sense heritability on the order of 0.5 (0.95 credible interval: 0.26-0.95). To identify genes associated with larval heat tolerance, we correlated larval mortality rates with gene expression measured prior to stress exposure. We also measured gene expression in the parental colonies under both benign and heat-stress conditions. Comparing gene co-expression networks between larvae and their parents and with previous data on larval gene expression under heat stress, we find that (i) gene expression variation is strongly heritable and is predominantly additive, and (ii) higher larval heat tolerance and associated gene expression are strongly correlated with the parental origin from the warmer GBR location. Notably, the majority of genes associated with heat tolerance are not involved in the heat stress response itself. We conclude that heat tolerance in the A. millepora larvae has strong genetic basis and is highly variable among coral populations along the GBR, which should favor evolutionary rescue as climate change progresses.