Complex sentence: A proposed explanation is that the melanic forms have a thermal advantage directly linked to the pollution aspect of industrialization, since smoke and particulates in the air reduce the amount of sunlight that reaches the habitats of these species.
Split into simpler sentences: A proposed explanation is that the melanic forms have a thermal advantage. This is argued to be directly linked to the pollution aspect of industrialization, since smoke and particulates in the air reduce the amount of sunlight that reaches the habitats of these species.