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The status of these vernal pools and lovely wildflowers is rather dismal. They are surrounded by buildings in a rapidly growing area zoned for industry. Many of the vernal pools have been intentionally damaged by deep tire ruts and the dumping of debris. Raised topography (mounds) near the vernal pools once supported burrowing owls, but they haven't been seen in this field for years.

The San Diego fairy shrimp (Branchinecta sandiegoensis) is endemic to vernal pools of coastal San Diego County. They have also been recorded from a few localities in Orange County and Baja California. Since most of the vernal pool habitats have been destroyed in southern California due to urbanization and pollution, these tiny crustaceans have been added to the U.S. Fish & Wildlife Service Endangered List in accordance with the Endangered Species Act. Their plight in the San Marcos area is uncertain due to the dumping of debris in the few remaining pools within a rapidly developing industrial zone.

This minute crustacean belongs to the order Anostraca, along with brine shrimp (Artemia). Other related orders of microscopic crustaceans include Cladocera (water fleas), Copepoda (copepods), Ostracoda (seed shrimp), Notostraca (tadpole shrimp), and Conchostraca (clam shrimp). All of these crustaceans are visible to the naked eye, although magnification is required to see details of their body structure. San Diego fairy shrimp are small and transparent, about 5 to 8 mm long.

During winter and early spring, when the ponds collect water, fairy shrimp mature quickly, live as adults, and reproduce. During their mating cycle the male attaches to the female with his clasping antennae. Each female lays hundreds of eggs, which settle into the soft bottom mud and silt as the pool dries out. At this time the adult fairy shrimp die, and plants bordering the pools bloom and set seed for the next winter wet season. During the dormant stage, fairy shrimp survive as embryos within resistant eggs called cysts which are embedded in the desiccated mud sediment. They can remain here for years until sufficient winter rains once again fill the shallow depressions with water. As the vernal pools refill, the mud imbibes water and the cysts hatch, thus releasing a new generation of fairy shrimp into the shallow ponds. Clay hardpan depressions that fill with water during the winter and early spring provide the essential requirements for the survival and perpetuation of fairy shrimp. If vernal pool habitats are destroyed by land developers, the fairy shrimp will not emerge from their dormant cysts and will disappear forever. Unlike many other aquatic crustaceans, they cannot survive in permanent ponds or lakes. They must have the specific requirements of a vernal pool.

The San Marcos variant brodiaea has intermediate characteristics between two other species. One of the most obvious characteristics that indicate possible hybridization is a structure called a staminodium which represents a sterile, nonfunctional stamen. All three species (A, B & C) have three staminodia in the center of the flower, just outside the three yellow stamens. The three staminodia of the variant are intermediate between the conspicuous, petaloid staminodia of Coastal BTK (A) and the slender (filiform), inconspicuous staminodia of B. filifolia (C). The three staminodia of the variant appear strap-shaped and are visible in the center of the flower, just outside the three yellowish stamens. The variant occurs throughout several acres of the property and may have reproduced asexually through cormlets. In May 2005 I visited this same site but did not observe any variants. Instead I found numerous B. filifolia and Coastal BTK. The previous winter and spring was an exceptional year for rainfall in San Diego County and brodiaea populations were plentiful. Unfortunately, the fate of this 40 acre field of brodiaeas is dismal because of the rapid (uncontrolled) urbanization of northern San Diego County. The field is within an industrial zone and is surrounded by buildings.

On the Santa Rosa Plateau of Riverside County populations of BTK exhibit a wide range of variation, including strap-shaped staminodes similar to the San Marcos "variant." Could it be that the San Marcos variant brodiaea is simply a variation within the BTK population?

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