Data from: Heritable differences in fitness-related traits among populations of the mustard hill coral, Porites astreoides

A population’s potential for rapid evolutionary adaptation can be estimated from the amount of genetic variation in fitness-related traits. Inshore populations of the mustard hill coral (Porites astreoides) have been shown to be more tolerant to thermal stress than offshore populations, but it is unclear whether this difference is due to long-term physiological acclimatization or genetic adaptation. Here, we evaluated variation in growth rate and survival among 38 families of juvenile recruits of P. astreoides spawned by colonies originating from inshore and offshore locations. Recruits were reared in a common garden for 5 weeks and then subjected to two thermal treatments (28  and 31 °C) for 2.5 weeks. The most significant effects were detected during the first 5 weeks, before thermal stress was applied: 27–30% of variance in growth and 94% of variance in recruit survival was attributable to parental effects. Genotyping of eight microsatellite loci indicated that the high early mortality of some of the recruit families was not due to higher inbreeding. Post treatment, parental effects diminished such that only 10–15% of variance in growth rate was explained, which most likely reflects the dissipation of maternal effects. However, offshore-origin recruits still grew significantly less under elevated temperature compared with inshore-origin recruits. These differences observed in naive juvenile corals suggest that population-level variation in fitness in response to different thermal environments has a genetic basis and could represent raw material for natural selection in times of climate change.

种群的快速进化适应潜力，可通过其适合度相关性状（fitness-related traits）的遗传变异水平进行估算。此前已有研究表明，芥丘珊瑚（Porites astreoides）的近海种群相较于离岸种群对热胁迫（thermal stress）的耐受性更强，但目前尚不清楚该差异是源于长期生理驯化（physiological acclimatization），还是遗传适应（genetic adaptation）。本研究选取由近海与离岸生境的珊瑚成体群体所产卵繁育的38个芥丘珊瑚幼体家系，对其生长速率与存活率的变异情况开展了评估。研究将这些幼体置于同质园（common garden）环境中培育5周，随后施加2.5周的两种热胁迫处理（28℃与31℃）。在热胁迫施加前的5周培育阶段，我们检测到了最为显著的效应：生长速率变异的27%~30%、幼体存活率变异的94%，均可归因于亲本效应（parental effects）。针对8个微卫星位点（microsatellite loci）的基因分型结果显示，部分幼体家系的早期高死亡率并非由较高的近交（inbreeding）水平所致。热胁迫处理后，亲本效应的影响显著减弱，仅能解释生长速率变异的10%~15%，这大概率反映了母体效应（maternal effects）的消散。然而，相较于近海起源的幼体，离岸起源的幼体在高温处理下的生长速率仍显著更低。在未经过环境驯化的幼体珊瑚中观测到的这些差异表明，种群在不同热环境下的适合度变异具有遗传基础，且可在气候变化背景下成为自然选择（natural selection）的原材料。