Complex sentence: It marks the transition zone between moist deciduous forest the Mainland Southeast Asia biogeographical region in the north and wet seasonal dipterocarp forest in the Sundaland region in the south and has been shown to be the biogeographical transition between Indochinese and Sundaic faunas.
Split into simpler sentences: It marks the transition zone between the moist deciduous forest in the Mainland Southeast Asia biogeographical region in the north and the wet seasonal dipterocarp forest in the Sundaland region in the south. It has been shown to be the biogeographical transition between Indochinese and Sundaic faunas.