How mammalian predation contributes to tropical tree community structure

Area of Science:

• Ecology
• Forestry
• Zoology

Background:

• Seedling recruitment is a critical demographic process for tropical rainforest trees.
• The impact of tropical forest mammals on tree community structure is not well understood.
• Mammals consume numerous seeds, but their precise role in shaping forest dynamics requires further investigation.

Purpose of the Study:

• To evaluate the effects of different mammal size classes on seed predation and subsequent tree community structure.
• To determine how seed consumption by mammals influences species diversity, composition, and coexistence.
• To understand the long-term consequences of altered mammalian seed predator communities on tropical forests.

Main Methods:

• Monitoring of 8,000 seeds from 24 tree species over 4.4 years.
• Utilizing exclosure cages with selective permeability for three mammal size classes (small, medium, large).
• Quantifying seed removal rates and analyzing impacts on seedling recruitment and community metrics.

Main Results:

• Small and medium-bodied mammals removed significantly more seeds than large mammals.
• Small and medium mammals were key drivers of beta diversity and negative density dependence.
• All mammal size classes reduced overall diversity and influenced local species composition, with smaller mammals having a stronger effect.

Conclusions:

• Small and medium-bodied mammals play a more critical role in structuring tropical tree communities and promoting species coexistence than large mammals.
• Altered composition of mammalian seed predator communities can have substantial long-term effects on tropical forest structure.
• Seed limitation in seedling recruitment underscores the importance of mammalian seed predation in forest regeneration and dynamics.