Opisthobranch gastropods observed on the outer coast of San Diego County, California by James R. Lance, 1953-2001

Data were collected at varying frequency from eight intertidal sites spread over 23 km on the outer coast of San Diego. From 1953 to 2001, James Lance and colleagues recorded nearly 29,000 individuals in 97 species, or about half the number of opisthobranch species known from the entire Californian and Oregonian biogeographic provinces combined. At one site, South Casa Reef in La Jolla, they recorded 83 species, at least 50% more species than known from any other site in California or Oregon. In addition to highlighting this hotspot of biodiversity, the Lance data provide a solid baseline with which to evaluate long-term changes in the fauna, such as those related to climate variability, climate change, or the explosive growth in the last half of the 20th century of the San Diego/Tijuana metropolitan area.