Biodiversity encompasses ecosystems, the species within those ecosystems, and the genetic variations within those species. Genetic diversity, in particular, is an essential yet often overlooked component of biodiversity. The images above depict four local variations of the California Poppy (Eschscholzia californica). Remarkably, there may exist hundreds of distinct local forms of this species!
Though the concept of local forms (also called local genotypes) of plants is not well understood, the fact that they exist is clear. This means that among plants of the same genus and species, there may be consistent and substantial genetic differences among them from place to place, across their ranges. Many of these unique differences between plants are adaptive (meaning they offer advantages) and can include differences in growth form, flower color, leaf shape or thickness, disease susceptibility or resistance, variation in secondary metabolites, and more.
Local coastal form California Poppy with distinct bi-colored flowers.
Our state flower, California Poppy (Eschscholzia californica), is one of the best examples of local genotypes. The presence of locally adapted forms among California's native plants suggests that merely identifying them by their correct names may not fully capture their essence. In reality, we are observing thousands of 'wild heirlooms', each uniquely evolved to suit its specific environment. The California Poppy (Eschscholzia californica) is native to a vast region in the Western US, spanning much of California and extending into parts of Oregon, Washington, New Mexico, Arizona, and Baja California. This expansive territory encompasses a wide range of macro and microclimates - think Baja vs the middle of Oregon, or the Bay Area vs western Arizona.
Since plants are sessile organisms, meaning they are fixed in place, they must endure the climatic nuances that these places have to offer. Whether situated in foggy or arid climates, experiencing summer monsoonal rainfall or none at all, enduring constant winds or calm conditions, receiving annual rainfall ranging from 7 inches to 50 inches, or coexisting with or without gophers, each habitat fosters distinct characteristics in the California Poppy (Eschscholzia californica).
California Poppy (Eschscholzia californica) at the Antelope Valley Poppy Reserve.
The familiar and possibly “best-known” form of California poppy seems to be that which is found at the Antelope Valley Poppy Reserve. Likely this genotype or similar has become the seed-stock for much of the nursery-sold seeds and plants over the last several decades, hence its familiar appearance. This form is typically identified as a notably orange-flowered, erect, and annual plant. Being from the arid interior, it is not adapted to coastal fog, which makes them rapidly succumb to powdery mildew. Since these plants are widely available for sale, when they become adjacent to any local populations, introgressions of their maladapted genes get into the remaining local plants. Note the differences in mildew prevalence and absence between these genotypes!
Interior form that can be found at Antelope Valley Poppy Reserve (left) showing lack of mildew resistance compared to local coastal form (right).
By contrast, our beautiful local form on campus is distinctly bi-colored, with more yellow in the flowers (yellower flowers may be an adaptation to being more visible to native bees in overcast conditions). Adapted to the fog belt, it experiences cool, humid summers- a far cry from the arid, hot summers the poppies in the Antelope Valley experience. Therefore, our local form of poppy is highly resistant to powdery mildew. On any given day in early June, native poppies in our area may experience “June gloom”- 60-degree days and 100% humidity- while on the very same day, the same taxon in the Antelope Valley will be experiencing searing temperatures over 90 degrees, with very low humidity.
Local coastal form California Poppy with distinct bi-colored flowers.
Our local poppies can also be perennials, living for several years. They can survive the dry Mediterranean summers since that are moderated by coastal conditions. By contrast, 100% of the poppies in the interior die from summer drought and are all annuals that spend the summers as seed. This is one way a subtle but beautiful example of biodiversity- local adaptations- can be degraded or lost, paradoxically by the seemingly benevolent action of sowing wildflower seeds. In trying to conserve our local poppy, we often remove “guerrilla gardened” plants prevalent in “seed bombs”. This preserves the genetic uniqueness of our fine-tuned form of poppy that truly represent our area’s wild, biodiverse, botanical heritage.
California Poppy at Point Conception.
So far, we have seen the marked differences between the well-known, interior Antelope Valley genotype and the form that is native to the UCSB campus area. Moving up the coast westward, we come to the place where the state again begins to turn north- Point Conception. There the prevailing winds in the channel are more pronounced and more regular than here in the lower part of the county. This means these delicate herbs predictably endure more coastal fog, strong prevailing winds, and blowing sand than campus plants. These notable differences have created a microclimate at Point Conception that bears both significant similarities and differences to that which we experience on campus. Yes, both are coastal, both are in the same county. The same weather systems and meteorological phenomenon that sweep through the region affect both locations, but in different enough ways that they have created a distinct ‘wild heirloom’ in each.
California Poppy at Point Conception.
Like our wonderful local form, the poppies at this dune-swept site are strongly mildew-resistant, have yellow in their flowers, and are perennial, but they take these attributes to another level. Unlike our flowers which are often half yellow and orange, these are almost entirely yellow. And while they are beautifully at place in the fog, bearing no powdery mildew, and perennial, they appear to be significantly long-lived. Some of these plants bear visibly large bases of tap roots that indicate a plant of considerable age. How old might they be (research project anyone)? Recall that 100% of the orange-flowered plants in the interior desiccate in summer heat and are short-lived annuals. Strikingly, these poppies are much lower growing than our plants close to home, which reach around 24” in height. Instead, these are profoundly prostrate, or low-lying. Forming a mat and sprawling across the surface of the sand, these plants keep their delicate leaves, stems, and flowers out of the incessant wind.
A genotype encompasses the complete genetic composition of an organism, including traits that are invisible to the naked eye. While we can readily observe adaptations such as flower color, form, and disease resistance, there are also subtle distinctions that elude visual detection. These nuances represent yet another layer of biodiversity, highlighting the remarkable diversity present in nature. Just twenty or thirty miles across the channel, there occurs an island form of Eschscholzia californica that looks nearly identical to the form we have on campus. Both forms are erect, bi-colored, mildew-resistant, and may be perennials.
California Poppy (Eschscholzia californica) on Santa Cruz Island.
However, there is something very interesting going on with these island plants that their myriad of mainland relatives do not share. Secondary metabolites are molecules made by plants to make themselves more competitive in their environments, and they are sometimes intricately involved in regulating plant-animal relationships, such as herbivory. Familiar metabolites that affect mammals are alkaloids such as nicotine, caffeine, and morphine- all derived from the plant world. The latter comes from the Papaveraceae, the same family that E. californica belongs to, meaning they also make secondary metabolites.
While these two genotypes may appear almost identical, all mainland forms have one significant environmental factor that island forms do not: a long evolutionary coexistence with gophers. Botta’s pocket gophers are ubiquitous in almost all mainland locations and have eaten California poppies for countless millennia. By contrast, island forms, such as those on Santa Cruz, have had no adjacency to these burrowing rodents for up to 500,000 years. Consequently, island poppies make 2.5 times less gopher-deterring alkaloids than their mainland relatives, making them much more desirable to captive gophers when given the option (Watts, 2011). In the same study, island plants were significantly less tolerant of simulated root herbivory compared to mainland plants. When you look at a wildflower or native plant in its wild place, you are quite likely looking at a locally adapted form of that plant. And when you see sown wildflowers, or native plants planted by humans, it is very likely that you are seeing a form of plant far from where it was originally from and maybe far from where it is ideally suited to growing. By doing this, maladapted genes can be introduced into wild populations, setting back the evolutionary uniqueness that took place over very long timescales to produce a finely tuned local form. We can avoid this misalignment by better understanding and using local genotypes.
Watts SM, Dodson CD, Reichman OJ (2011) The Roots of Defense: Plant Resistance and Tolerance to Belowground Herbivory. PLoS ONE 6(4): e18463. https://doi.org/10.1371/journal.pone.0018463