The function is described as follows:
De’ath, Glenn. 2007. “Boosted Trees for Ecological Modeling and Prediction.” Ecology 88 (1): 243–51. https://doi.org/10.1890/0012-9658(2007)88[243:BTFEMA]2.0.CO;2.
The package authors don't update the package now, and whether the "dismo" package deal with the question.
Thanks in advance.