Members of the Southern Coastal Scrub plant community are well adapted to the xeric and infertile conditions of the rocky California coastline. Much of this is attributed to Southern Coastal Species species losing their leaves in response to drought, or the presence of succulence where leaves store water and employ a special method of photosynthesis. These unique characters are the product of selection pressures imposed on these plant communities through millions of years. The high degree of specialization seen in this community is unparalleled to any other environment.Unfortunately having a high level of speciation makes the community especially vulnerable to human activity and being outcompeted by invasive species.
Fig A: Lavatera assurgenitflora, commonly know as Island Mallow, is seen throughout numerous southern coastal counties
An adaptation is a trait of an individual species that evolved in response to its environment. Adaptions increase the fitness and survival of the individual. Adaptions are the direct response of natural selection, as those with the advantageous trait are able to survive and reproduce. Over millions of years extraordinary and ecologically important traits are able to surface and often become persist in a gene pool.
The southern coastal scrub plant community plays host to species that possess some extraordinary and unique traits, which have allowed the species to thrive even with the absence of regular rainfall. This is in contrasting to northern coastal scrub environment, which enjoys comparatively more rainfall and a regular fog pattern. The following highlights a number of species from the southern coastal scrub plant community, and the traits that make them unique.
Coreopsis gigantea; Giant Coreopsis
-The Giant Coreopsis is drought deciduous. Losing its leaves during the summer months limits the amount of water passing through the plant. Water is absorbed through the roots, transpires up the plant, and then released into the atmosphere. Without leaves, the plant is able to decrease its water demand, survive through the dry summer and then regrow during the wet season. This trait is an advantage to the plant, therefore has been selected for and persisted in the population.
Dudleya farinosa; Sea Lettuce
D. farinosa is a low growing succulent that employs a unique variation on method of photosynthesis. Succulents retain water, preventing desiccation during extreme periods of drought. Many succulents have evolved a special means of photosynthesis in response to an environment with limited available resources. A majority of plants perform the light reactions (conversion of light energy to chemical energy from the splitting of water molecules) simultaneously with the carbon-fixation reactions. These plants continually permit the entry of CO2 in through the stomata. CAM (Crassulacean Acid Metabolism) photosynthesis, on the other hand, inhibits the entry of CO2 during the day by keeping the stomata closed when exposed to light. This prevents rapid transpiration of the limited available water, as both water exit and CO2 enter through stomata. In response to harsh conditions with limited resources, these plant have been selected for their unique method of photosynthesis.
-Diversity: total amount and abundance of species in a collection of individuals.
-Drought deciduous: losing leaves in response to drought.
-Evergreen: retaining leaves year round.
-Fitness: the ability of an organism to survive and reproduce; the degree to which it contributes to the gene pool.
-Gene Pool: the set of all genes in a population of an individual species.
-Mediterranean climate: one of five regions in the world with dry summers.
- Sclerophyllous: tough, sometimes waxy, leaves with a high carbon to nitrogen ratio.
-Stomata: minute openings on the surface of stems and leaves where gases enter and exit the plant body.
-Transpire: the movement of water and solutes through the plant body.
-Xeric: harsh and dry conditions with limited resources.
Species on Display
-Peter Raven, Ray Evert, and Susan Eichhorn. Biology of Plants. Sixth. New York: W.H. Freeman and Company, 1999. Print.
-Campbell, Neil, Jane Reece, et al. Biology. 8th. San Francisco: Pearson Education, 2008. Print
-Photo of Coreopsis gigantea: ©2010 Gary A. Monroe
-Photo of Larrea tridenta: Wikimedia Commons
-Calflora: Information on California plants for education, research and conservation.
[web application]. 2008. Berkeley, California: The Calflora Database [a non-profit organization].
Available: http://www.calflora.org/ (Accessed: Oct 20, 2008).