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.

长期以来，保护工作一直以保护或修复原生生态系统为核心。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。尽管外来物种（non-native species）在原生生态系统中通常呈现中性或有害作用，但即便那些臭名昭著的入侵物种，也有可能在新型生态系统中发挥有益或兼具双重性的生态功能。我们在密克罗尼西亚的关岛开展研究，考察了两种长期定殖的外来物种——菲律宾鹿（*Rusa marianna*）与野猪（*Sus scrofa*）的影响。该区域内本土脊椎动物食果动物在功能上已缺失，导致森林丧失了种子传播者。我们对比了鹿与野猪在石灰岩喀斯特森林中对幼苗存活、种子传播以及植物群落结构的调控作用。即便种群密度较低，鹿也通过降低幼苗与藤本植物的丰度，对森林群落造成了显著的负面影响。与之形成鲜明对比的是，野猪并未表现出此类关联，且野猪粪样中检出的种子数量显著多于鹿粪，这表明野猪承担了关岛森林已丧失的一项关键生态系统功能——种子传播。本研究揭示了两种传统上被统一管理的外来物种间的作用差异，这一发现颇具颠覆性；同时表明，在管理新型生态系统时，或许更应考量其生态功能，而非单纯以物种的外来身份作为管理依据。