Why are tropical rain forests so species rich? Classifying, reviewing and evaluating theories

Two classifications are presented that organize the major processes and the ories addressing the high species diversity of tropical rain forests. The f irst typology organizes environmental and biological processes within a spa tio-temporal hierarchy, whilst the second classifies 12 theories according to over-arching driving forces: genetic differentiation, environmental chan ge, niche/habitat diversification and biotic interaction. The theories are reviewed and evaluated by delineating the development and current state of academic knowledge pertaining to each. General issues that arise from exami ning species diversity within the tropical realm are discussed and this ind icates where the academic debate stands today. Some thoughts concerning fut ure research avenues are included.