The recent study, published in the journal Evolution, provided evidence that the low rates of extinction preceded the onset of the wet-winter, dry-summer climate of present-day California and similar regions. Instead, the topology and geography of the regions may have spared their resident species from extinction.
The wide range of habitats from beach to mountain peaks that can be found near each other in California, and similar areas, may have been one of the keys to make the region a refuge. As climates and weather patterns changed, plant species were able to find suitable areas nearby to sink new roots. For example, when the climate warmed, plant species moved to higher elevations.
Similar distances from the equator kept the regions warm during the ice ages, but not too hot during warmer times. Locations on the western coasts of continents allowed moist easterly winds from the ocean to keep the regions from becoming deserts during warm periods, according to the study.
IMAGE: California plant community, Santa Ynez Mountains, Santa Barbara County, Southern California. (Antandrus, Wikimedia Commons)