21. The fern is a keystone species in Hawaiian ecosystems, and primary productivity in some areas. 22. The Salmon is a keystone species culturally and ecologically to the Tsi Aki Maidu tribe. 23. The whitebark pine is a keystone species in upper subalpine forests of the northern Rocky Mountains. 24. They are considered keystone species within their habitat. 25. The prairie was formerly maintained by grazing pressure of American bison, which is the keystone species . 26. Oaks are keystone species in a wide range of habitats from Mediterranean semi-desert to subtropical rainforest. 27. Is the human a kind of keystone species ? 28. They may also serve as keystone species , regulating the populations of the species they prey on. 29. Gopher tortoises are found in many areas, the burrows they dig making them a keystone species . 30. Figs are sometimes considered to be potential keystone species in communities of black howler monkeys in Belize.
