Data from: Rewilded mammal assemblages reveal the missing ecological functions of granivores

1. Rewilding is a strategy for ecological restoration that uses reintroductions of animals to re-establish the ecological functions of keystone species. Globally, rewilding efforts have focused primarily on reinstating the ecological functions of charismatic megafauna. In Australia, rewilding efforts have focused on restoring the ecological functions of herbivorous and omnivorous rodents and marsupials weighing between 30-5000g inside of predator-proof exclosures. 2. In many arid ecosystems, mammals are considered the dominant seed predators. In Australian deserts, ants are considered to be the primary removers and predators of seeds and mammals unimportant removers and predators of seeds. However, most research on granivory in Australian deserts has occurred in areas where native mammals were functionally extinct. 3. Here, we compare rates of seed removal by mammals and ants on shrub seeds and abundance of shrub seedlings in two rewilded desert ecosystems (Arid Recovery Reserve and Scotia Wildlife Sanctuary) with adjacent areas possessing depauperate mammal faunas. We used foraging trays containing seeds of common native shrubs (Acacia ligulata and Dodonaea viscosa) to examine rates of seed removal by ants and mammals. We quantified the abundance of A. ligulata and D. viscosa seedlings inside and outside of rewilded areas along belt transects. 4. By excluding ants and mammals from foraging trays, we show that ants removed more seeds than mammals where mammal assemblages were depauperate, but mammals removed far more seeds than ants in rewilded areas. Shrub seedlings were more abundant in areas with depauperate mammal faunas than in rewilded areas. 5. Our study provides evidence that rewilding of desert mammal assemblages has restored the hitherto unappreciated ecological function of omnivorous rodents and bettongs as seed predators. We hypothesize that the loss of omnivorous mammals may be a factor that has facilitated shrub encroachment in arid Australia. 6. We contend that rewilding programs aimed at restoring ecological processes should not ignore consumers with relatively lower per capita consumptive effects. This is because consumers with low per capita consumptive effects often occur at high population densities or perform critical ecological functions and thus may have significant population level impacts that can be harnessed for ecological restoration.

1. 再野化（Rewilding）是一种生态修复策略，通过重新引入动物以重建关键物种（keystone species）的生态功能。全球范围内的再野化工作主要聚焦于恢复具有公众吸引力的巨型动物群（megafauna）的生态功能。在澳大利亚，再野化工作则集中于在防捕食者围栏（predator-proof exclosures）内，恢复体重介于30至5000克之间的植食性与杂食性啮齿类及有袋类动物的生态功能。
2. 在多数干旱生态系统中，哺乳动物被视为主要的种子捕食者。而在澳大利亚沙漠中，传统认知认为蚂蚁是种子的主要移除者与捕食者，哺乳动物的种子移除与捕食作用则微不足道。然而，绝大多数针对澳大利亚沙漠种子取食（granivory）的研究，均开展于本土哺乳动物已功能性灭绝的区域。
3. 本研究对比了两种再野化沙漠生态系统——干旱恢复保护区（Arid Recovery Reserve）与斯科蒂亚野生动物保护区（Scotia Wildlife Sanctuary）——及其周边哺乳动物区系贫乏区域内，哺乳动物与蚂蚁对灌木种子的移除速率，以及灌木幼苗的丰度。我们使用装载有常见本土灌木（无脉金合欢*Acacia ligulata*与粘叶假叶树*Dodonaea viscosa*）种子的觅食托盘（foraging trays），探究蚂蚁与哺乳动物的种子移除速率；同时沿样带（belt transects）计数再野化区域内外的无脉金合欢与粘叶假叶树幼苗丰度。
4. 通过在觅食托盘上设置蚂蚁与哺乳动物的排除装置，我们发现：在哺乳动物区系贫乏的区域，蚂蚁的种子移除量高于哺乳动物；而在再野化区域，哺乳动物的种子移除量则远高于蚂蚁。相较于再野化区域，哺乳动物区系贫乏区域的灌木幼苗丰度更高。
5. 本研究提供的证据表明，沙漠哺乳动物群落的再野化已恢复了杂食性啮齿类与袋狸鼠（bettongs）作为种子捕食者的此前未被认知的生态功能。我们提出假说：杂食性哺乳动物的丧失，或许是推动澳大利亚干旱地区灌丛扩张的关键因素之一。
6. 我们认为，旨在恢复生态过程的再野化项目，不应忽视人均消耗效应相对较低的消费者类群。这是因为这类人均消耗效应较低的消费者，往往种群密度较高，或承担着关键生态功能，因此可能在种群层面产生显著影响，可被用于生态修复工作。