California

===Ecology===
{{Main|Ecology of California|Environment of California}}
[[File:Mount Whitney 2003-03-25.jpg|thumb|right|[[Mount Whitney]], in the Sierra Nevada, is the highest mountain in the [[contiguous United States]].]]

California is one of the ecologically richest and most diverse parts of the world, and includes some of the most endangered ecological communities. California is part of the [[Nearctic realm]] and spans a number of terrestrial [[ecoregion]]s.<ref name="Checklist of the Scarabaeoidea of the Nearctic Realm">{{Cite web |date=2003 |title=Checklist of the Scarabaeoidea of the Nearctic Realm |url=http://www.iscc.ca.gov/docs/CaliforniaInvasiveSpeciesList.pdf |access-date=October 5, 2010 |publisher=digitalcommons.unl.edu (University of Nebraska State: Papers in Entomology)}}</ref>

California's large number of [[endemic (ecology)|endemic]] species includes [[Relict (biology)|relict]] species, which have died out elsewhere, such as the Catalina ironwood (''[[Lyonothamnus floribundus]]''). Many other endemics originated through differentiation or [[adaptive radiation]], whereby multiple species develop from a common ancestor to take advantage of diverse ecological conditions such as the California lilac (''[[Ceanothus]]''). Many California endemics have become endangered, as urbanization, logging, [[overgrazing]], and the introduction of [[exotic species]] have encroached on their habitat.