54792
This may exemplify a rare example of insular dwarfing in a mainland context , with the " islands " being formed by biogeographic barriers during arid climatic periods when forest distribution became patchy , and / or by the extensive river networks in the Amazon Basin .
 Amazon Basin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Amazon Basin