Latitudinal effects on treehopper species richness (Hornoptera: Membracidae)

Abstract. 1. Membracid species richness declines with increasing latitude in the Western hemisphere but begins to increase again in temperate regions. In northern latitudes this transition occurs in the highlands of Mexico and is the result of the emergence of a new tribe and greater host specialization.
2. The relationship between number of species per genus and latitude is parabolic.
3. We suggest the low number of species per genus in tropical regions may be due to the lack of host specialization and reduced coordination of life history with host phenology.