Department of Biology, Old Dominion University, Norfolk, VA 23529, USA
Department of Biology, University of Hawai'i at Manoa, Honolulu, HI 96822, USA.
J Exp Biol. 2018 Dec 10;221(Pt 24):jeb188581. doi: 10.1242/jeb.188581.
Spatial heterogeneity in environmental characteristics can drive adaptive differentiation when contrasting environments exert divergent selection pressures. This environmental and genetic heterogeneity can substantially influence population and community resilience to disturbance events. Here, we investigated corals from the highly variable back-reef habitats of Ofu Island in American Samoa that thrive in thermal conditions known to elicit widespread bleaching and mortality elsewhere. To investigate the relative importance of acclimation versus site of origin in shaping previously observed differences in coral tolerance limits at Ofu Island, specimens of the common Indo-Pacific coral from locations with differing levels of thermal variability were acclimated to low and high thermal variation in controlled common garden aquaria. Overall, there were minimal effects of the acclimation exposure. Corals native to the site with the highest level of daily variability grew fastest, regardless of acclimation treatment. When exposed to lethal thermal stress, corals native to both variable sites contained elevated levels of heat shock proteins and maintained photosynthetic performance for 1-2 days longer than corals from the stable environment. Despite being separated by <5 km, there was significant genetic differentiation among coral colonies (=0.206, <0.0001; nuclear ribosomal DNA), whereas Symbiodiniaceae were all sp. (ITS type C15). Our study demonstrates consistent signatures of adaptation in growth and stress resistance in corals from naturally thermally variable habitats, suggesting that differences in the amount of thermal variability may be an important contributor to adaptive differentiation in reef-building corals.
当对比环境施加不同的选择压力时，环境特征的空间异质性可以驱动适应性分化。这种环境和遗传异质性可以极大地影响种群和群落对干扰事件的恢复能力。在这里，我们研究了来自美属萨摩亚奥富岛多变后礁生境的珊瑚，这些珊瑚在已知会引发其他地方广泛白化和死亡的热条件下茁壮成长。为了研究在塑造奥富岛先前观察到的珊瑚耐受极限差异方面，适应与起源地的相对重要性，我们从具有不同热变异性水平的地点采集了常见的印度-太平洋珊瑚的标本，并在受控的普通花园水族馆中适应低温和高温变化。总体而言，适应暴露的影响很小。无论适应处理如何，来自具有最高日变异性的地点的珊瑚生长最快。当暴露于致命的热应激时，来自两个可变地点的珊瑚都含有较高水平的热休克蛋白，并比来自稳定环境的珊瑚保持光合作用更长的 1-2 天。尽管相隔不到 5 公里，但珊瑚殖民地之间存在显著的遗传分化（=0.206，<0.0001；核核糖体 DNA），而共生藻均为 sp.（ITS 型 C15）。我们的研究表明，来自自然热变异性栖息地的珊瑚在生长和抗应激方面具有一致的适应特征，这表明热变异性的差异可能是造礁珊瑚适应性分化的一个重要因素。
