Modeling Extinction Risk of Endemic Birds of Mainland China

Table 2

Detailed description of alternative evolutionary models used for modeling the extinction risk of endemic birds of China.

Model name	Model description
Delta	Delta < 1 describes that the evolution rate of extinction risk of species occurs rapidly early in the history of a clade and then slows through time. Delta > 1 describe an increasing evolution rate of extinction risk of species through time. Delta = 0 is identical to a Brownian motion model.
LinearChange	This model assumes that that evolution rate of extinction risk of species should change linearly overtime. If the rate is increased linearly up to the present time, then the fitting slope of the linear relationship is positive. In contrast, if the evolutionary rate is decreased linearly over the time, then the fitting slope should be negative. No change on the evolutionary rate implies that the fitting slope is zero.
TwoRate	This model allows that the evolution rate of extinction risk of species shifts to a new value at some time point over the phylogeny (if the new evolution rate is larger than 1, evolution is believed to increase, otherwise decrease). Before and after the shifting point, the evolutionary rates are kept constant.
Null	This model assumes a global constant evolutionary rate for extinction risk. Thus, only a single constant value is returned when fitting the null model.