Ecology of palm populations and communities in a fragmented tropical landscape

Thesis

Dramatic declines in the global forested area in recent decades have been particularly severe in tropical areas. Tropical forests have been heavily impacted by a range of human activities including conversion to agriculture, hunting, and timber extraction. Deforestation has led to extensive habitat fragmentation, and most tropical forests are now embedded in human-modified landscapes comprising a mosaic of land-cover types. The consequences of these changes for biodiversity and species interactions are an area of active research interest.

In this thesis, I assess whether remnants of rainforest conserve species and interactions within a fragmented tropical landscape in tropical Mexico, and compare data from fragments with data from nearby protected and continuous rainforests. I focus on palms (Arecaceae), an ecologically and economically important plant family of tropical and subtropical regions, and investigate responses to fragmentation at the population and community level, as well as interactions with mutualists (pollinators) and antagonists (pathogens and herbivores).

I found evidence that management practices within fragments affects palm populations: palm abundances were lower in unprotected forest fragments than in those protected from human activities such as wood and timber extraction, extraction of plants and hunting and poaching. Community composition did not differ significantly between these protected and unprotected fragments. Edge effects were also apparent in forest fragments: changes in palm abundances and palm diversity were most pronounced within 100 m of the forest edge, and these edge effects were similar in both protected and unprotected fragments.

For one focal palm species, Geonoma interrupta, pollination and fruit production, and the likely consequences for demography, were investigated in detail. Reproductive success was significantly lower in fragments than in continuous forest. Native bees were the most frequent visitors and likely pollen vectors. Experimental exclusion of natural enemies in a field significantly increased seedling survival of two palm species. However, the effect of excluding enemies did not differ significantly between the forest edge and interior of a fragmented forest.

The results presented in this thesis should be valuable in informing conservation and management strategies to conserve viable populations of rainforest palms. They show that the full effects of habitat fragmentation on palm distributions, diversity and abundance are best understood by taking into account biotic interactions and human management practices.

Authors: Ceron-Martinez, G

• DOI: 10.5287/ora-aga4dkgg2
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: fragmentation; tropics; palms; plant-animal interactions
• Subjects: Ecology; Rain forest ecology