Bird's nest ferns as model systems and conservation tools

Phillips, J.W.

Abstract

We are in a race against time to understand the response of natural systems to climate change and anthropogenic disturbances, such as large scale land conversion for oil palm expansion. However, it is incredibly difficult to quantify multi-trophic biodiversity-ecosystem function (BEF) relationships because natural ecosystems are complex. Nowhere is this challenge more apparent than in the primary tropical rainforests of Borneo where biodiversity reaches its highest concentration. The bird’s nest fern (Asplenium spp.) is an elegant solution to the problem of studying complex tropical rainforest because the ferns are natural microcosms. The ferns themselves, are keystone species in rainforest canopies, and studies have shown that they are hotspots for invertebrate biodiversity and functional processes such as decomposition in the rainforest canopy. Bird’s nest ferns are therefore the ideal natural model system, for testing ecological theory, investigating BEF relationships, and performing manipulation experiments to predict the effects of future disturbance. This thesis begins by defining the soil properties that allow bird’s nest ferns to regulate their internal microclimate in both rainforest and oil palm plantations. Quantifying the extent to which the ferns buffered extreme climate variation in these habitats, revealed why they are such important thermal refuges in both rainforest and oil palm. By defining the ferns’ soil properties, I was also able to determine the significant functional role of bird’s nest ferns in above ground water storage and natural flood mitigation. Because the ferns are model systems, so too are the animals they support. I used cockroaches collected from bird’s nest ferns in Borneo and the Eden Project to demonstrate the relationship between the oxygen isotopic composition (δ18O) of insect chitin and climate. By revealing that δ18O in chitin is independent of phylogeny, but entirely a reflection of climate and the way in which the physiological or behavioural traits of a species lead it to interact with its’ habitat, I paved the way for studies of δ18O in chitin to quantify species vulnerability or resilience to habitat disturbance and climate change. While cockroaches provided the ideal model animal for quantifying δ18O, centipedes were the ideal group for studying the role of predators in the bird’s nest ferns. This thesis presents the first study of centipedes in the forest canopy, and the first study of predators in bird’s nest ferns. It demonstrated that predation may be more important than competition, in structuring communities in forest canopies and that predators themselves behave in unexpected ways when it comes to using the ferns as a resource. My final chapter showed that the ferns can be used as conservation tools, to improve connectivity and facilitate the dispersal of animals through oil palm plantations. By transplanting ferns, and their faunal inhabitants, from rainforest to oil palm, I was able to increase biodiversity in plantations. Essentially priming the oil palm landscape with a boost of native biodiversity. This demonstrated that conservation practices in oil palm plantations can work to improve biodiversity, and indeed this is a critical component of the industry’s sustainability agenda. In revealing the importance of bird’s nest ferns as umbrella species for biodiversity and ecosystem function, I have paved the way for using these ubiquitous epiphytes as a novel tool for conserving biodiversity and improving sustainability within the oil palm landscape.

Citation

Phillips, J. Bird's nest ferns as model systems and conservation tools. (Thesis). University of the West of England. Retrieved from https://uwe-repository.worktribe.com/output/846445

• Thesis Type: Thesis
• Publicly Available Date: Jun 6, 2019
• Public URL: https://uwe-repository.worktribe.com/output/846445
• Award Date: May 31, 2019