臺灣鹿角珊瑚科光生理生態棲位之界定

Abstract

造礁珊瑚的生態分化 (ecological diversification) 通常受到資源利用方式與環境耐受性的差異所驅動，然而其背後的生理機制仍未被充分理解。對於共生珊瑚而言，其代謝表現主要仰賴共生藻 (Symbiodiniaceae) 的光合作用效率，因此，探討珊瑚光生理及相關光合作用特徵的變異，對於理解並預測不同物種在環境變遷下的適應能力與韌性，具有重要意義。 本研究以臺灣珊瑚礁海域之鹿角珊瑚科 (Pocilloporidae) 珊瑚為研究對象，比較不同物種之光生理特徵，以界定其光生理生態棲位 (photo-physiological niche)。採樣過程中，記錄各珊瑚群體之影像及環境因子，包括水溫、深度與光合有效輻射 (PAR)。針對每一目標群體，利用 Diving-PAM-II 螢光儀於現地建立快速光反應曲線 (rapid light curve, RLC)，測量珊瑚於不同光照強度下之光合作用效率，並以 Amirian–tanh 模型擬合曲線，推估四項光反應參數，包括初始光利用效率 (α)、光抑制係數 (β)、最大相對電子傳遞速率 (rETRmax) 及飽和光強 (Ek)。此外，亦量測共生藻密度 (ZD) 以及葉綠素 a 與葉綠素 c 濃度，並透過基因條碼進行珊瑚物種鑑定。最後，利用 PCA 視覺化各個體之光生理特徵，並以 PERMANOVA 比較不同分類群與地區間之差異。 研究結果顯示，Stylophora、Seriatopora 與 Pocillopora 三個屬在 PCA 排序空間中呈現明顯的光生理棲位分化，而大多數 Pocillopora 單倍型 (haplotypes) 之間具有高度重疊。PERMANOVA 分析進一步顯示，採樣地區與屬別皆對光生理變異具有顯著影響，顯示環境條件可能因物種而異地影響珊瑚對光資源的利用。不同物種的光生理分化可能反映其採取不同的光馴化策略 (photo-acclimatization strategies)，進而有助於降低資源競爭並促進物種共存。本研究增進了對近緣珊瑚物種間生理功能多樣性的理解，並提供預測未來環境變遷下珊瑚群聚組成與分布變化的重要基礎。

Ecological diversification among reef-building corals is often shaped by differences in resource use and environmental tolerance, yet the physiological mechanisms underlying this variation remain poorly understood. In symbiotic corals, metabolic performance largely depends on the photosynthetic efficiency of their algal partners, Symbiodiniaceae. Therefore, understanding variation in coral photo-physiology and associated photosynthetic traits is fundamental to interpreting and anticipating species resilience under changing environmental conditions. In this study, we examined the photo-physiological traits of members of the family Pocilloporidae across major coral regions in Taiwan to delineate and compare species-specific photo-physiological traits. Colonies were photographed in situ, and environmental parameters including temperature, depth, and photosynthetically active radiation (PAR) were recorded. For each targeted colony, a rapid light curve (RLC) was built in situ using Diving-PAM-II fluorometer measurements of coral photosynthetic efficiency under increasing irradiance. Using the Amirian–tanh model, four key light-response parameters (a, b, rETRmax, and Ek) were derived from each RLC. In addition, algal endosymbiont density (ZD) and chlorophyll a and c concentrations were quantified. Each colony was subsequently genetically barcoded for species identification. All individuals were visualized using principal component analysis (PCA) and statistically compared using PERMANOVA. We observed distinct photo-physiological niches among the three genera Stylophora, Seriatopora, and Pocillopora in the PCA ordination, whereas most Pocillopora haplotypes showed substantial overlap. Regions and genera had significant effects on photo-physiological variation, demonstrating that environmental variation appears to shape light utilization in species-specific patterns. Photo-physiological partitioning likely underpins mechanisms that facilitate species coexistence while reflecting divergent photo-acclimatization strategies. Collectively, this work advances understanding of physiological diversity among closely related coral species and provides insights into the potential responses and future redistribution of coral communities under ongoing environmental change.