Channel Island barberry (Berberis pinnata ssp. insularis), also known as island barberry or Catalina barberry, is a rare and endangered plant species native to the Channel Islands off the coast of Southern California. It is a member of the barberry family, Berberidaceae, and is known for its attractive evergreen foliage and vibrant yellow flowers.

Description: Channel Island barberry is a small, multi-stemmed shrub that typically grows up to 3 meters in height. It has shiny, leathery, and deep green leaves that are oblong or elliptical in shape and are about 3 to 5 centimeters in length. The leaves have sharp, spiny edges and are arranged in a spiral pattern along the stems.

In spring and summer, Channel Island barberry produces showy clusters of bright yellow flowers that are about 1.5 centimeters in diameter. The flowers have six petals and are followed by small, red, and edible berries that mature in the fall.

Habitat and Distribution: Channel Island barberry is endemic to the Channel Islands off the coast of Southern California, where it is found on rocky slopes, cliffs, and canyons. The species is found on four of the eight Channel Islands, including Santa Catalina Island, Santa Cruz Island, San Clemente Island, and Santa Rosa Island.

Ecological and Economic Importance: Channel Island barberry is an important plant species for the ecosystem of the Channel Islands. It provides food and shelter for a variety of animals, including birds, insects, and small mammals. The plant's berries are an important food source for island foxes and other wildlife.

The plant has also been used by humans for medicinal and ornamental purposes. Native Americans used the plant for medicinal purposes, including treating eye infections and digestive issues. The plant's attractive foliage and vibrant flowers make it a popular choice for landscaping in the region.

Conservation Status: Channel Island barberry is listed as an endangered species by the United States Fish and Wildlife Service. The plant is threatened by habitat loss and degradation due to human activities, including development, grazing, and invasive species. Efforts are underway to protect and conserve the remaining populations of Channel Island barberry, including habitat restoration and reintroduction programs.