ORIGIN AND DIVERSIFICATION OF THE CALIFORNIA FLORA: RE‐EXAMINING CLASSIC HYPOTHESES WITH MOLECULAR PHYLOGENIES |
| |
Authors: | Lesley T. Lancaster Kathleen M. Kay |
| |
Affiliation: | 1. National Center for Ecological Analysis and Synthesis, 735 State St., Suite 300, Santa Barbara, California 93101;2. Current address: Department of Biology, Ecology Building, Lund University, S‐223 62 Lund, Sweden;3. E‐mail: Lesley.Lancaster@biol.lu.se;4. Department of Ecology and Evolutionary Biology, 1156 High St., University of California, Santa Cruz, California 95060 |
| |
Abstract: | The California Floristic Province exhibits one of the richest floras on the planet, with more than 5500 native plant species, approximately 40% of which are endemic. Despite its impressive diversity and the attention it has garnered from ecologists and evolutionary biologists, historical causes of species richness and endemism in California remain poorly understood. Using a phylogenetic analysis of 16 angiosperm clades, each containing California natives in addition to species found only outside California, we show that CA's current biodiversity primarily results from low extinction rates, as opposed to elevated speciation or immigration rates. Speciation rates in California were lowest among Arcto‐Tertiary lineages (i.e., those colonizing California from the north, during the Tertiary), but extinction rates were universally low across California native plants of all historical, geographic origins. In contrast to long‐accepted ideas, we find that California diversification rates were generally unaffected by the onset of the Mediterranean climate. However, the Mediterranean climate coincided with immigration of many desert species, validating one previous hypothesis regarding origins of CA's plant diversity. This study implicates topographic complexity and climatic buffering as key, long‐standing features of CA's landscape favoring plant species persistence and diversification, and highlights California as an important refuge under changing climates. |
| |
Keywords: | Biogeography extinction fossils macroevolution phylogenetics speciation |
|
|