Data from: Contrasting ecological roles of non-native ungulates in a novel ecosystem

Conservation has long focused on preserving or restoring pristine ecosystems. However, understanding and managing novel ecosystems has grown in importance as they outnumber pristine ecosystems worldwide. While non-native species may be neutral or detrimental in pristine ecosystems, it is possible that even notorious invaders could play beneficial or mixed roles in novel ecosystems. We examined the effects of two long-established non-native species – Philippine deer (Rusa marianna) and feral pigs (Sus scrofa) – in Guam, Micronesia, where native vertebrate frugivores are functionally absent leaving forests devoid of seed dispersers. We compared the roles of deer and pigs on seedling survival, seed dispersal, and plant community structure in limestone karst forests. Deer, even at low abundances, had pronounced negative impacts on forest communities by decreasing seedling and vine abundance. In contrast, pigs showed no such relationship, and more seeds were found in pig scats than deer scats, suggesting that pigs provide an ecosystem function – seed dispersal – that has been lost from Guam. Our study presents a surprising discrepancy between the roles of two non-native species that are traditionally managed as a single entity, suggesting that ecological function, rather than identity as a non-native, may be more important to consider in managing novel systems.

保护生物学长期以来始终以保护或恢复原生生态系统（pristine ecosystems）为核心目标。然而，随着全球范围内新型生态系统（novel ecosystems）的数量超过原生生态系统，对其开展研究与管理的重要性与日俱增。尽管非本土物种（non-native species）在原生生态系统中可能仅产生中性或有害影响，但即便声名狼藉的入侵物种（invaders），也有可能在新型生态系统中发挥有益或兼具利弊的作用。

我们针对密克罗尼西亚关岛的两种长期定殖的非本土物种展开了研究：菲律宾鹿（Rusa marianna）与野化家猪（Sus scrofa）。该区域的本土脊椎动物食果动物（native vertebrate frugivores）已在功能层面完全缺失，致使森林丧失了种子传播者（seed dispersers）。我们对比了鹿与野化家猪对石灰岩喀斯特森林（limestone karst forests）的幼苗存活率（seedling survival）、种子传播（seed dispersal）以及植物群落结构（plant community structure）的影响。

研究结果表明，即便种群密度较低，菲律宾鹿也会通过降低幼苗与藤本植物的丰度，对森林群落造成显著的负面影响。与之形成鲜明对比的是，野化家猪未表现出此类关联；且其粪便中检出的种子数量多于鹿粪，这表明野化家猪承担了关岛已丧失的一项关键生态系统功能——种子传播。

本研究揭示了两种长期被作为同一管理单元进行管控的非本土物种间的功能差异，这一发现颇具颠覆性。研究提示，在新型生态系统的管理中，更应关注的或许是物种的生态功能，而非其作为非本土物种的身份属性。