Data from: Dispersal constraints for the conservation of the grassland herb Thymus pulegioides L. in a highly fragmented agricultural landscape

Species-rich grassland communities are one of the most important habitats for biodiversity and of high conservation priority in Europe. Restoration actions are mainly focused on the improvement of abiotic conditions, such as nutrient depletion techniques, and are generally based on the assumption that the target community will re-establish at the restored site when the target species exist in the neighborhood. Information on the contemporary seed-dispersal range is therefore crucial to develop effective conservation measures. Here, we investigated the contemporary long-distance seed dispersal and genetic structure of the grassland herb Thymus pulegioides in an intensively managed agricultural landscape in Flanders (Northern Belgium). Assignment tests based on amplified fragment length polymorphisms revealed very low levels of effective seed dispersal between populations although seed availability and seed viability was not a limiting factor. The process of fragmentation has resulted in a high population differentiation and without further incoming gene flow the remnant populations are prone to further genetic erosion and perhaps extinction. Our findings illustrate that restoring suitable abiotic habitat conditions in the neighborhood of existing populations does likely not guarantee colonization for this grassland specialist. For the survival of the species, existing populations should be functionally connected and seed addition may be necessary for successful conservation to overcome dispersal-limitation.

物种丰富的草原群落是欧洲生物多样性最重要的栖息地之一，同时也是欧洲生物多样性保护的高优先级对象。当前的修复行动主要聚焦于改善非生物环境条件，例如养分耗竭技术，且通常基于这样的假设：若目标物种存在于修复位点周边，则目标群落可在该修复位点重新建立。因此，掌握当代种子扩散范围的相关信息，对于制定高效的保护措施至关重要。本研究针对比利时北部佛兰德斯地区一处集约化管理的农业景观中的草地草本植物毛脉百里香（Thymus pulegioides），探究了其当代长距离种子扩散模式与种群遗传结构。基于扩增片段长度多态性（amplified fragment length polymorphisms, AFLP）的个体分配分析结果显示，尽管种子可获得性与种子活力并非限制因素，但种群间的有效种子扩散水平极低。生境破碎化过程已导致种群间出现极高的遗传分化，若缺乏后续的外来基因流，残存种群将面临进一步的遗传侵蚀，甚至可能走向灭绝。本研究结果表明，在现存种群周边修复适宜的非生物生境条件，大概率无法保证这一草原特化物种成功定植。为保障该物种的存续，现存种群之间需要实现功能连通性；而为克服扩散限制以达成成功保护目标，可能需要进行种子补给。