Data and supplementary materials from: Balancing restoration and conservation: Source material selection for restoration of an endangered Australian seagrass, Posidonia australis

Abstract: Restoration of endangered species is an essential but challenging feature of the global response to biodiversity loss. Sourcing material from endangered species for restoration must not compromise conservation of existing populations, which can limit large-scale restoration opportunities. On Australia's east coast, Posidonia australis is a slow-growing endangered seagrass with limited seed production. Effective restoration relies on adult fragments sourced through direct transplanting from existing meadows, or from naturally detached “beach-cast” fragments. We assessed the relative success of these two donor sources and the effect of fragment size by monitoring shoot density, necrosis cover, and epiphyte cover over 18 months post-planting. Plots containing directly transplanted fragments maintained a shoot density of 97 %, while plots containing beach-cast fragments initially declined before stabilising at 60 % of the original density. Notably, mixed-source plots (50 % from each donor source) retained 91 % density. Fragment size (1–2 vs. >2 shoots) did not significantly impact seagrass density, indicating that smaller fragments—common in beach-cast material—remain viable for restoration. Beach-cast seagrass exhibited high necrosis in the first three months, likely due to physiological stress from beaching, but their long-term performance was comparable to directly transplanted fragments. These findings highlight a key trade-off in P. australis restoration: while direct transplantation yields higher density retention, it is constrained by legal protection and ecological concerns surrounding donor meadow harvesting. Beach-cast fragments, though more readily available, exhibit higher initial losses after planting. A mixed-source approach may provide an optimal balance, leveraging the resilience of directly transplanted fragments while minimising the ecological impact of donor harvesting. This listing contains two files: Tables 1, 2, and 3 containing raw data collected during experiment Supplementary images referred to in Methods section摘要： 濒危物种修复是全球应对生物多样性丧失进程中一项至关重要却极具挑战的工作。从濒危物种中获取修复所需材料，不得损害现有种群的保护工作，这一限制极大制约了大规模修复项目的开展。在澳大利亚东海岸，澳洲海神草（Posidonia australis）是一种生长缓慢的濒危海草，其种子产量极为有限。有效的修复工作依赖于两种来源的成体片段：一是从现存海草甸直接移栽获取的片段，二是自然脱落的“冲滩”海草片段。本研究通过监测种植后18个月内的枝条密度、坏死覆盖度及附生生物覆盖度，评估了这两种供体来源的相对修复效果，同时分析了片段大小对修复效果的影响。 仅包含直接移栽片段的样地，枝条密度维持在初始密度的97%；而仅包含冲滩片段的样地，初始密度出现下降，随后稳定在初始密度的60%。值得注意的是，混合供体样地（两种供体来源各占50%）的密度保留率达到了91%。片段大小（1~2株 vs 多于2株）对海草密度未产生显著影响，这表明常见于冲滩材料中的小型片段仍具备修复可行性。冲滩海草在种植后的前三个月坏死率较高，这大概率源于冲滩过程带来的生理胁迫，但其长期表现与直接移栽片段并无显著差异。 上述研究结果揭示了澳洲海神草修复工作中的关键权衡问题：直接移栽虽能实现更高的密度保留率，却受限于供体海草甸采收的法律保护与生态顾虑；冲滩片段虽更易获取，但种植后初期的损失率更高。采用混合供体的修复方案，或可实现最优平衡——既借助直接移栽片段的恢复韧性，又最大限度降低了供体采收带来的生态影响。 本数据集包含两个文件： 1. 实验采集的原始数据表1、表2与表3 2. 方法部分提及的补充图像