I think that tropical rainforests and other similar bio-diverse ecological regions are more "seasonal" than they might seem on the surface.

First, such regions often experience "seasonal" changes such as rainy seasons, differing trade winds, and periodic massive storms (such as hurricanes). On this point, I think one of the keys is that the seeming “mild” and “unchanging” micro-ecosystems are periodically upset by the massive storms. This causes localized extinction events which opens up the door (or void) for new organism’s to fill.

Secondly, and perhaps even more importantly, they also benefit (and sometimes suffer from) the biotic effects of the seasonality of other regions of the globe--That is animals from other regions of the globe tend to migrate to and from the tropics with the changing seasons.

Those migrations then "stir-up" the genetic pot perhaps even more so in the tropics than in the areas that see a more pronounced seasonal weather pattern.

The pot gets stirred by many factors, but two of the most obvious would be competition between the migrating species and the local species (which would itself be a seasonal competition), and the fact that migrations provide a great way for genetic material carrying viruses to intermingle between seemingly unrelated species.

Man what a great thread this has the potential to evolve into!!!