California's diverse habitats sheltered plant species through 45 million years of environmental changes and made the state a biodiversity hotspot, although a recent study suggested the rate of new species evolution doesn't seem to have been particularly high in the state.
"Because California has so many unique and relatively young plant species, it was long assumed by biogeographers and naturalists that high speciation rates were the cause of California's biodiversity," first author Lesley Lancaster of Lund University in Sweden said in a press release. "It turns out that these species have not arisen at a particularly high rate in California compared to elsewhere. Instead, features of California's climate, topography, and latitude have preserved these species, allowing us to see them today, when they may have simply gone extinct if they had arisen elsewhere."
The secret to California's plant protection may be shared by other regions, but not just because of similar climates, contends the new study. Previous studies suggested that the similar climates of California, the cape of Africa, Southwestern Australia, the west coast of Chile, and around the Mediterranean sea may have led to the high level of biodiversity in those regions.
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)