Landscape Ecology, Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, Sweden.
PLoS One. 2013 May 2;8(5):e62763. doi: 10.1371/journal.pone.0062763. Print 2013.
Humans are known for their capacity to disperse organisms long distances. Long-distance dispersal can be important for species threatened by habitat destruction, but research into human-mediated dispersal is often focused upon few and/or invasive species. Here we use citizen science to identify the capacity for humans to disperse seeds on their clothes and footwear from a known species pool in a valuable habitat, allowing for an assessment of the fraction and types of species dispersed by humans in an alternative context. We collected material from volunteers cutting 48 species-rich meadows throughout Sweden. We counted 24,354 seeds of 197 species, representing 34% of the available species pool, including several rare and protected species. However, 71 species (36%) are considered invasive elsewhere in the world. Trait analysis showed that seeds with hooks or other appendages were more likely to be dispersed by humans, as well as those with a persistent seed bank. More activity in a meadow resulted in more dispersal, both in terms of species and representation of the source communities. Average potential dispersal distances were measured at 13 km. We consider humans capable seed dispersers, transporting a significant proportion of the plant communities in which they are active, just like more traditional vectors such as livestock. When rural populations were larger, people might have been regular and effective seed dispersers, and the net rural-urban migration resulting in a reduction in humans in the landscape may have exacerbated the dispersal failure evident in declining plant populations today. With the fragmentation of habitat and changes in land use resulting from agricultural change, and the increased mobility of humans worldwide, the dispersal role of humans may have shifted from providers of regular local and landscape dispersal to providers of much rarer long-distance and regional dispersal, and international invasion.
人类以远距离传播生物的能力而闻名。长距离传播对于受到栖息地破坏威胁的物种可能很重要，但对人类介导的传播的研究往往集中在少数几种或入侵物种上。在这里，我们利用公民科学从一个已知的物种库中确定人类在一个有价值的栖息地中通过衣服和鞋子传播种子的能力，从而评估人类在另一种情况下传播的物种的比例和类型。我们从志愿者身上收集了在瑞典各地的 48 个物种丰富的草地上修剪的材料。我们统计了 24,354 颗 197 种种子，代表了 34%的可用物种库，包括几种稀有和受保护的物种。然而，有 71 种（36%）在世界其他地方被认为是入侵物种。特征分析表明，带有钩子或其他附属物的种子更容易被人类传播，而具有持久种子库的种子也更容易被传播。草地的活动越多，传播的物种和来源群落的代表性就越多。平均潜在传播距离为 13 公里。我们认为人类是有能力的种子传播者，他们在活动的植物群落中运输了很大一部分植物，就像牲畜等更传统的传播者一样。当农村人口较多时，人们可能是定期而有效的种子传播者，而农村人口向城市的净迁移导致景观中人类数量减少，这可能加剧了当今植物种群减少所导致的传播失败。随着栖息地的破碎化和农业变化导致土地利用的变化，以及全球人类流动性的增加，人类的传播作用可能已经从定期的本地和景观传播的提供者转变为更罕见的长距离和区域传播的提供者，以及国际入侵的提供者。
