Doctor of Philosophy
Tarszisz, Esther, The ecophysiology of seed dispersal by Orangutans in Bornean peat swamp forest, Doctor of Philosophy thesis, , University of Wollongong, 2016. https://ro.uow.edu.au/theses/4828
The study of an ecosystem process like seed dispersal is at the forefront of the dynamic field of ecophysiology, the study of how animals and environments interact. Understanding spatial movements is essential to unravelling how animals interact with their ecosystem and tie animal ecology to ecosystem processes, particularly to animal mediated seed dispersal (zoochory). The movement of seeds through an animal gut (endozoochory), from one place to another is an essential driver of forest structure and is a complex process that depends on a variety of environmental and physiological factors. Seed dispersal is a crucial component of plant population dynamics, influencing plant populations and communities through both short and long distance dispersal. The spatial arrangement of seed deposition also contributes to at least half the gene-flow of plants, and their population genetic structure can be highly dependent on fauna-mediated seed dispersal, particularly in tropical regions.
A review on the role of physiology in conservation translocation was evaluated for over a decade worth of peer-reviewed studies (2000-2010) to highlight both the relative rarity of including physiological analyses in such a significant conservation undertaking, and the absolute essentiality of addressing this lack, especially in the face of todays changing world.
The data here link a number of stages in endozoochorous provision by the orangutan. In an ex-situ setting, the first ever measurement of the transit time of indigestible seed mimics was made, with study subjects that were fed a diet consisting largely of plant matter. Elimination pattern of seed mimics was measured, demonstrating a pulse dose excretion, often in one or two single defecation events, with smaller amounts both before and after this peak. The average transit time of seed mimics across all bead sizes was 76 hours, a figure that was later used to create a predictive model of faecal deposition patterns of seeds in an in-situ situation. Orangutans were shown to have the potential to provide very long distance dispersal from the parent plant due to their long transit times and large home ranges. Large bodied frugivores, such as the orangutan, are likely to be critically important seed dispersers as there are typically few animals that can effectively disperse large-seeded species. This has often lead to coevolution of the plant-animal interaction particularly with regards to large seeds which many other frugivores cannot swallow intact.
The application of Time Local Convex Hull (T-LoCoH) is the first objective tool of its kind in orangutan ecological research in tropical peat swamp forest (TPSF), and the first application of T-LoCoH to ecological service provision anywhere. T-LoCoH is a new technique that models animal movement over both time and space. This modeling accurately predicted where orangutans would deposit faeces when compared to real-time data gathered in the Sabangau Forest, Central Kalimantan, Indonesia (Indonesian Borneo). This environment exhibits a relative lack of secondary seed removal and orangutans can be expected to play a disproportionate role in seed dispersal here, particularly of large sized seeds and over wide ranging areas. This method provides a basis to establish a training method to make a priori projections of seed dispersal dynamics in novel ecosystems.
Evaluation of post-defecation germination potential of seeds provided further insight into the orangutan;s role in dispersal of 13 different seed species. Surprisingly endozoochorous travel through the orangutan gut was not the most significant factor in germination as manually extracted seeds showed the highest rates of germination over both orangutan “gut-treated” seeds and whole fruits. However seeds passed intact via orangutan faeces still germinated and contributed to the primary dispersal of many plant species. Orangutans might also play a more important role in germination when seeds are moved, by spitting whole seeds out.