Climate and Competition as Controls on the Persistence and Richness of an Edaphicendemic Flora

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Scientists currently know little about how global climate change will affect edaphic endemics, or plants that are confined to certain unusual rocks or soils. In California there are over 200 plant species confined to serpentine soils, which are harsh, nutrient-poor soils derived from rocks of the ocean crust. Edaphic endemics may be unusually vulnerable to climate change for two reasons: because they are trapped on soil "islands" and are thus less able to shift their distributions, and because the effects of a harsh soil may exacerbate the stress of an adverse climate. We will examine this question in two ways: (1) by asking whether Californian serpentine endemics are non-randomly found in more favorable climates, as compared with their closest relatives; (2) by resampling 55-year-old transects in the Klamath Mountains (northern CA - southwestern OR) to ask whether there have been more species disappearances on serpentine at low elevation than on other soils or at higher elevations. Because edaphic endemics contribute substantially to global biodiversity, and because their geographic distributions are unlikely to fit the assumptions of standard climate-based models, this study will fill an important gap in our understanding of the biotic effects of global climate change.