Transient amplification enhances the persistence of tropicalising coral assemblages in marginal high latitude environments

Predicting the viability of species exposed to increasing climatic stress requires an appreciation for the mechanisms underpinning the success or failure of marginal populations. Rather than traditional metrics of long-term population performance, here we illustrate that short-term (i.e., transient) demographic characteristics, including measures of resistance, recovery, and compensation, are fundamental in the poleward range expansion of hard corals, facilitating the establishment of coral populations at higher latitudes. Through the annual census of tropical and subtropical Acropora spp. colonies in Japan between 2017-2019, we show how enhanced transient amplification (i.e., short-term increases in population growth following disturbance) supports the persistence of coral assemblages within more variable high-latitude environments. The transient dynamics of both the tropical and subtropical assemblages were strongly influenced by their corresponding recruitment patterns. However, we demonstrate that variation in colony survival and fragmentation patterns between the two assemblages determines their relative capacities for transient amplification. This latitudinal variation in the transient dynamics of Acropora spp. assemblages emphasises that coral populations can possess the demographic plasticity necessary for exploiting more variable, marginal conditions.

Methods
This dataset was collected through the repeated annual survey of tagged Acropora colonies within tropical (Okinawa) and subtropical regions (Kochi) of southern Japan, between 2017 and 2019. Across these surveys we documented colony survival, growth, fragmentation, and the size of newly appearing recruits.

The dataset is comprised of tagged colony metadata, specifically location (Country, Ecoregion, Site), Colony ID, timing of initial tagging, Species identity (Genus, species, etc.), and life-history classification. Next the datafile contains successive size estimates obtained for tagged colonies, however the data is not longitudinal, and so yearly entries for the same individual are entered on seperate rows. Therefore, each row contains each colonies size in the previous year (time.t), its bleaching state, and whether it was a product of fragmentation, the colonies size in the following year (time.t+1), its new bleaching state, and whether it had undergone fragmentation is then recorded. The row also details whether each entry corresponds with a new fragement or recruit colony (in which case colony size for the previous year is entered as NA). If a colony entry has a size entry for time.t but no entry for time.t+1 then the colony is considered dead.

预测面临日益加剧气候胁迫的物种生存适存性，需要明晰支撑边缘种群存续与消亡的内在机制。相较于传统的长期种群表现指标，本研究阐明，短期（即瞬态）种群统计特征——包括抗性、恢复力与补偿能力的量化指标——在硬珊瑚（hard corals）的向极范围扩张过程中至关重要，助力珊瑚种群在更高纬度区域成功定植。通过2017至2019年间对日本境内热带与亚热带鹿角珊瑚属（Acropora spp.）群落的年度普查，我们揭示了增强型瞬态扩增（即扰动后种群增长的短期提升）如何支撑珊瑚群落在波动更强的高纬度环境中存续。热带与亚热带珊瑚群落的瞬态动态均显著受其补充模式影响，但本研究证实，两类群落间的珊瑚株存活与断枝繁殖模式差异决定了它们各自的瞬态扩增相对能力。鹿角珊瑚属群落瞬态动态的纬度差异表明，珊瑚种群可具备利用更具波动的边缘生境所需的种群统计可塑性。

数据集采集方法
本数据集通过2017至2019年间对日本南部热带（冲绳）与亚热带（高知县）区域内标记鹿角珊瑚群落的重复年度调查采集所得。调查期间，我们记录了珊瑚株的存活情况、生长状况、断枝繁殖事件以及新出现的定植幼体尺寸。
数据集包含标记珊瑚株的元数据，具体包括地理位置（国家、生态区、调查位点）、珊瑚株编号（Colony ID）、首次标记时间、物种鉴定信息（属、种等）以及生活史分类。后续数据文件包含针对标记珊瑚株的连续尺寸估算数据，但该数据集并非纵向格式，因此同一珊瑚个体的年度记录会被分别录入不同行。每行数据包含该珊瑚株上一年度（时间t）的尺寸、白化状态、是否为断枝繁殖产生的个体，以及下一年度（时间t+1）的尺寸、新的白化状态与是否发生断枝繁殖。此外，每行还会标注该记录是否对应新的断枝或定植幼体个体（此类情况下上一年度尺寸记为NA）。若某珊瑚株记录仅包含时间t的尺寸数据，却无时间t+1的对应记录，则判定该珊瑚株已死亡。