Are tortoises important seed dispersers in Amazonian forests?

Area of Science:

• Ecology
• Zoology
• Botany

Background:

• Mammals and birds are traditionally recognized as primary seed dispersers in tropical forests.
• The role of other animal groups, such as reptiles, in seed dispersal remains under-investigated.

Purpose of the Study:

• To investigate the qualitative and quantitative aspects of seed dispersal by the tortoise Chelonoidis denticulata in the southeastern Amazon.
• To assess the influence of seasonal variations in tortoise movement patterns on seed shadow formation.

Main Methods:

• Estimating seed shadows by combining data on seed passage time (3-17 days) through the tortoise's digestive tract.
• Utilizing movement data from 18 C. denticulata individuals tracked via radio transmitters and spoon-and-line devices.
• Analyzing 4,206 seeds from 94 fecal samples, representing 50 seed morphotypes and at least 25 plant genera.

Main Results:

• Minimal external seed damage and no negative impact on seed germination after passage through the tortoise's digestive system.
• Seeds were dispersed an average of 174.1 m during the dry season and 276.7 m during the rainy season.
• The tortoise C. denticulata contributes significantly to seed dispersal, moving seeds away from parent plants.

Conclusions:

• Chelonoidis denticulata plays a crucial role in seed dispersal within Amazonian ecosystems.
• Seasonal variations in tortoise movements significantly impact the spatial distribution of dispersed seeds (seed shadows).
• Further research into reptilian seed dispersal is warranted to understand forest dynamics fully.