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| Author(s): |
Eduardo Miguel Zanette
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Rio Claro. 2023-04-27. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Biociências. Rio Claro |
| Defense date: | 2023-01-31 |
| Advisor: | Laurence Marianne Vincianne Culot; Ronald Bialozyt; Eckhard W Heymann |
| Abstract | |
Endozoochorous seed dispersal maintains forest community structure and dynamics, thus being an underpinning process for tropical forest biodiversity. In this scenario, Neotropical primates play a major role by dispersing seeds throughout their home ranges. However, high levels of forest degradation and fragmentation have modified their habitat into fragments of distinct sizes, shapes, and resource distributions, leading to a possible alteration of their functional role as seed dispersers. Despite the huge increase of primate seed dispersal studies during the last decades, it is still unknown how the seed dispersal service will be affected by local forest fragment characteristics. More recently, the development of agent-based models (ABMs) able to predict primate movement and the associated seed shadows opened new perspectives. The black lion tamarin (Leontopithecus chrysopygus or simply “tamarin”) is a seed disperser, endemic to the Atlantic Forest whose habitat is among the most fragmented among Neotropical primate species. Here, I developed an ABM to predict black lion tamarin seed dispersal patterns. In the first chapter, I explored the movement patterns of four tamarin groups inhabiting four forest fragments. I concluded that tamarins differ extensively in movement patterns, and this might be modulated by the fragment properties (size and shape), thus likely affecting seed dispersal distances. From this chapter, I derived “rules” for the ABM implementation in Chapter 2, where I adapted a previously developed model to the black lion tamarin. Most of the patterns (i.e., variables that emerge from the model), namely seed dispersal distance (SDD), home range size, and daily path length (DPL) were very similar to the observed. I further showed the model was able to reproduce other patterns not initially aimed, like the movement rate (MR) and path twisting (PT), therefore highlighting its potential to predict seed shadows in distinct forest fragments. The only drawback of the model was that it did not predict well home range sizes in continuous forest, where tamarins reach the largest observed home range sizes for the species. I then discussed the model implementation and processes that might be lacking, such as territoriality and conspecific interactions, in face of the recent ABM movement literature. In Chapter 3, I generated theoretical forest fragments with varying sizes, shapes, and resources distributions. I did this by creating a forest fragment generator, by predicting home range sizes for each of these fragments based on tamarin density and fragment size with statistical modeling, and I finally generate resource distributions based on a Thomas (point)-process. Preliminary results show a great effect of tamarin density on the SDD, followed by DPL and MR, but a small effect of the distance between fruiting trees (resource aggregation). The simple parameterization of the model with empirical velocities plus the estimates of feeding bouts and gut transit times, altogether linked with an energetic sub model, are enough do predict most of the variation in seed shadow. Although most patterns of interest were successfully predicted, further implementations of non-included processes in the model (such as territoriality) should continue through the modeling cycle, possibly enhancing the model predictability of movement and seed dispersal patterns in distinct environments. This might be attained by implementing more mechanistic rules – i.e., rules that rely less on parameterization and ad-hoc knowledge – further making the parameterization of the model with empirical velocities unnecessary. I highlight that the model structure captures the essence of movement and seed dispersal by tamarins. I hope this thesis has contributed to a greater understanding of black lion tamarin movement patterns and seed dispersal services and stimulates further modeling and sampling endeavors. (AU) | |
| FAPESP's process: | 20/11129-8 - Predicting seed shadows in different environmental contexts: a modeling approach applied to an arboreal frugivore |
| Grantee: | Eduardo Miguel Zanette Correia |
| Support Opportunities: | Scholarships in Brazil - Master |