Host specialization is traditionally viewed as the pathway to speciation in parasitic plants. However, geographical and environmental changes can also influence parasite speciation through population isolation and secondary contact.
Climate change
Leaf size and climatic instability in a cloud forest avocado
Pleistocene glacial periods have had a major influence on the genetic variation and differentiation of plant populations in tropical mountains. However, the effect of these cycles on morphological differentiation remains virtually unexplored.