FSD 2010 - Jansen

5th International Symposium-Workshop on Frugivores and Seed Dispersal (1985-2010)

Patrick A. Jansen

Wageningen University, The Netherlands

Smithsonian Tropical Research Institute, Panama

patrick.jansen(a)wur.nl

Activities

My main interest is in how animals affect plant recruitment and ultimately community composition and diversity of forests through their seed dispersal, seed predation and seedling herbivory behaviour. Most of my work has been with scatter-hoarding rodents, which display these behaviours while managing their food reserves. My study species include(d) acouchies in French Guiana, woodmice in the Netherlands, and agoutis in Panama. In Central Panama, my collaborators and I currently run a variety of projects which aim to understand how animal behaviour can enhance tree diversity. We study animal communities, animal behaviour and ultimately seed and seedling fate are affected by tree population density on the one hand and animal removal (hunting) on the other. During the past few years, I have been simultaneously affiliated with the Smithsonian Tropical Research Institute in Panama and the Universities of Groningen and Wageningen in the Netherlands.

Abstract

Hunting impacts on recruitment of large-seeded palm species: Are tropical forests getting palm-dominated?

with Joe Wright, Marco Visser and others

Poaching lowers the abundances of large-bodied animals, including many important seed dispersers and seed predators of particularly large-seeded plant species. The resulting simultaneous reduction of seed dispersal and seed predation by vertebrates likely affects the recruitment success of large-seeded species, but it is unclear and hard to predict how. We studied how poaching affected patterns of seed dispersal, seed predation and seedling recruitment in large-seeded palms in the tropical moist forest of Central Panama. These palms are primarily dispersed by agoutis, which scatter-hoard seeds as food supplies throughout the forest understory. We found that poaching negatively affected seed dispersal due to satiation of the few remaining dispersers, resulting in increased seed exposure to seed-predatory insects. However, poaching reduced predation of cached seeds by vertebrates so much that seedling recruitment nevertheless increased dramatically. Seedlings were more clumped under poaching yet density-dependent seedling mortality did not compensate for the recruitment advantage.

It appears that palms benefit from poaching as long as agoutis do not go extinct, because it affects predation more than dispersal. Studies on other palm species suggest that this phenomenon is common in Neotropical forests. Palms tend to attain dominance in disturbed forests, which usually have high levels of hunting, at the cost of other tree species and hence biodiversity.

Related References

Jansen, P.A., H.C. Muller-Landau & S.J. Wright (2010). Bushmeat hunting, tropical biodiversity and carbon. Science 327: 30.

Gálvez, D., B. Kranstauber, R.W. Kays & P.A. Jansen (2009). Scatter hoarding by the Central American agouti: a test of optimal cache spacing theory. Animal Behaviour 78: 1327-1333.

Jansen, P.A., F. Bongers & P.J. Van der Meer (2008). Is farther seed dispersal better? Spatial patterns of offspring mortality in three rainforest tree species with different dispersal abilities. Ecography 31: 43-52.

Forget, P.-M. & P.A. Jansen (2007). Hunting increases dispersal limitation in the tree Carapa procera, a non-timber forest product. Conservation Biology 21: 106-113

(Photos : Central American Agouti Dasyprocta punctata © Hellen esser; Palma negra Astrocaryum standleyanum adult tree, fruit and seeds from Barro Colorado Island, Panama © Pierre-Michel Forget)