Excluding mammalian predators increases bird densities and seed dispersal in fenced ecosanctuaries

Rodent management in Aotearoa New Zealand: approaches and challenges to landscape-scale control

Aotearoa-New Zealand has only four rodent species, all introduced. In order of arrival, they are Pacific rat Rattus exulans, brown rat R. norvegicus, house mouse Mus musculus, and black rat R. rattus. Rodent management in New Zealand aims mainly to conserve indigenous biodiversity rather than to protect crops or manage diseases, as is usual elsewhere. We describe four major "regimes" and one major vision for rodent control in New Zealand to meet ecological restoration objectives. Current challenges for island eradications are for large islands that are remote or populated by people. Aerial 1080 is the only large-scale (tens of thousands of hectares) option for black rat control, but its application requires adjustment to counter subsequent rapid black rat repopulation. Unfenced "ecosanctuaries" (mean 720 ha) use ground-based traps and poisons to target mainly black rats and face constant reinvasion. Ecosanctuaries with mammal-resistant fences (up to 3500 ha) limit reinvasion and target more pest species and have enabled the return of previously extirpated taxa to the main islands. Predator Free 2050 aims to eradicate the rat species (but not mice) plus some other introduced mammals from New Zealand by 2050. This vision is not attainable with current tools, but research and experimental management is exploring techniques and technologies. The large scale (to 100 000 ha) at which black rats are now targeted for control to extremely low abundance seems to be unique to New Zealand.

Evaluating the success of functional restoration after reintroduction of a lost avian pollinator

Conservation translocation is a common method for species recovery, for which one increasingly frequent objective is restoring lost ecological functions to promote ecosystem recovery. However, few conservation translocation programs explicitly state or monitor function as an objective, limiting the ability to test assumptions, learn from past efforts, and improve management. We evaluated whether translocations of hihi (Notiomystis cincta), a threatened New Zealand passerine, achieved their implicit objective of restoring lost pollination function. Through a pollinator-exclusion experiment, we quantified, with log response ratios (lnR), the effects of birds on fruit set and seed quality in hangehange (Geniostoma ligustrifolium), a native flowering shrub. We isolated the contributions of hihi by making comparisons across sites with and without hihi. Birds improved fruit set more at sites without hihi (lnR = 1.27) than sites with hihi (lnR = 0.50), suggesting other avian pollinators compensated for and even exceeded hihi contributions to fruit set. Although birds improved seed germination only at hihi sites (lnR = 0.22-0.41), plants at sites without hihi had germination rates similar to hihi sites because they produced 26% more filled seeds, regardless of pollination condition. Therefore, although our results showed hihi improved seed quality, they also highlighted the complexity of ecological functions. When an important species is lost, ecosystems may be able to achieve similar function through different means. Our results underscore the importance of stating and monitoring the ecological benefits of conservation translocations when functional restoration is a motivation to ensure these programs are achieving their objectives.

Drivers of Ecological and Evolutionary Disruptions in the Seed Dispersal Process: Research Trends and Biases

As the sole opportunity for most plants to move, seed dispersal influences the biodiversity and functioning of plant communities. Global change drivers have the potential to disrupt seed dispersal processes, affecting plant communities and ecosystem functions. Even though much information is available on the effects of seed dispersal disruption (SDD), we still lack a comprehensive understanding of its main causes at a global scale, as well as the potential knowledge gaps derived from research biases. Here we present a systematic review of biotic and abiotic SDDs to ascertain the global change drivers addressed, dispersal modes impacted, plant processes affected, and spatial focus of existing research on this topic up-to-date. Although there are many modes of dispersal and global change drivers in temperate and tropical ecosystems worldwide, research efforts have predominantly addressed the effect of alien species for biotic seed dispersal in temperate systems and oceanic islands as well as how defaunation of bird or mammal dispersers has affected seed removal in the Neotropics. SDD studies were also biased toward forest ecosystems, with few in shrublands or grasslands. Finally, the effects of climate change, ecological consequences at the whole community level, and evolutionary changes were largely unrepresented in SDD studies. These trends are likely due to a combination of true geographic and ecological patterns in seed dispersal and global change and bias in research focus. We conclude that increased research investment in the less-studied systems and a better understanding of potential synergies and feedback between multiple global change drivers will be important to forecast the threats to plant biodiversity and those ecosystem functions derived from seed dispersal in the Anthropocene.