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Seeds of Success Program

8

Tecate Cypress: Risky Reproduction

Lauren and Sandra Mardonovich sow Tecate cypress seeds in long pots that provide spacious room for roots.

The Tecate cypress Hesperocyparis forbsiiis a tree found only in Southern California and northern Baja California, Mexico. It has a limited range and is fire dependent, which means the cypress needs fire to reproduce. The cones of this species are serotinous, which means the seeds are released by an ecological trigger (in this case, fire) instead of being released once they reach maturity. When the cones are exposed to heat, the resin that keeps them sealed is melted, the cone opens, and the seed is released. Without fire, the Tecate cypress keeps its seed bank within persistent cones in the tree canopy. When a fire burns a mature stand of Tecate cypress, new seedlings pop up in its place. If this second generation is burned before it reaches maturity, it could wipe out the entire population. There are only four stable populations remaining in California, three of which are in San Diego County. It is because of its limited range and risky reproduction technique that this tree is such a sensitive species.

Tecate cypress cones collected from Otay Mountain await processing.

The Applied Plant Ecology Division at the San Diego Zoo Institute for Conservation Research has partnered with the Nature Conservancy, the Bureau of Land Management, and the California Department of Fish and Game to preserve this unique species. The goal of the project is to provide a safe guard against high-frequency fires wiping out the population.

To do this, we collected enough seed from a mature population to have a portion for safe keeping in the Native Plant Seed Bank at the Safari Park and a portion that could be germinated and planted as a nursery stand. Cones were collected from Otay Mountain and processed at the State of California’s Lewis A. Morgan Reforestation Center. The processed cones resulted in thousands of seeds, and of those, a fraction was planted. From the planted seeds, we are hoping to get 400 to 500 seedlings.

Here's a close-up view of the seeds before being covered with soil.

Once the seedlings have grown to a suitable size, they will be planted at the Rancho Jamul Ecological Reserve. The planted cypress trees will be monitored over the next six months. These trees will be used as a sort of “plantation” where more seeds can be collected as needed in case the other stands burn before reaching sexual maturity.

Lauren Anderson is an intern at the San Diego Zoo Institute for Conservation Research through the Bureau of Land Management’s Seeds of Success Program. Read her previous post, The Desert: Blooms and Hail.

4

Wake Up, Seeds! Germination Testing

Germinating seeds

Germination testing is used to determine the correct method for bringing seeds out of dormancy. A seed typically consists of the embryonic plant with its food reserve wrapped in a seed coat, which acts as a protective layer between the embryo and outside elements. Some scientists define germination as the emergence of the radical (the first root), but at the Native Seed Bank here at the San Diego Zoo Safari Park, we define it as the emergence of the radical and the emergence of at least one cotyledon (first leaf). This is because some seeds may have enough energy to produce the tip of a root but then lack the ability to develop further.

Most seeds enter a dormant stage in nature, and we can extend this state for decades by lowering their moisture content and storing them at cold temperatures for our Native Seed Bank. However, when seeds enter this phase in their life cycle, it can be very difficult to get them to “wake up” again. In nature, seed germination is triggered by factors such as fire, water, and temperature changes. To test the germination ability of seeds placed in storage, we try different dormancy-breaking mechanisms to determine which protocol is effective. Scientists look at things like the species’ natural habitat and what triggers have worked with closely related species. The process is further complicated by the fact that species require different combinations depending on how long they have been in storage. For example, a trigger that works for seeds stored for 10 years may not work for seeds stored for 50 years. Another complicating variable is that even within the same species, different populations may have been reproductively isolated enough so that their seeds have different requirements.

Some of the Native Seed Banks many seeds awaiting study

At the Safari Park, all seed lots placed into the Seed Bank are testable once they have been stored for at least one month. Twenty or so seed lots that have been placed in storage around the same time period are then removed and soaked in water overnight before different triggers are tested on them. For some seed lots, this initial soaking is the only stimulus they need, but others have additional requirements.

Some of the other tests we perform include:

Cold Stratification:
Here we expose seeds to changes in temperature by placing them in moist, cold conditions that alter them in physiological ways so that they are able to germinate when warmer conditions follow. This simulates winter followed by spring. The same is true for warm stratification, which allows seeds to germinate in response to cooling temperatures similar to what they would naturally encounter in the fall.

Smoke Water:
In nature, one environmental condition that triggers germination is fire. Either heat, the chemicals released by burned plant matter, or a combination of the two causes seeds to come out of dormancy. To mimic the chemicals released by burned plants, we collect samples of different chaparral species and turn them into charcoal, which is then mixed in water along with the actual smoke, to give us “smoke water.” In some cases, when this water is absorbed through the seed coat, it triggers the seed to grow.

Hot Water Soak and Boiling Water Dip:

There are some species that need to have their seed coat damaged before they can absorb enough water to germinate. One way this occurs in nature is by the high acidity found in animal stomachs (to which seeds are exposed when they are ingested). Instead of soaking seeds in acid, (which can damage the seeds in the wrong concentrations), we use a hot water bath or a boiling water dip. This allows the seed coat to become permeable without damaging the embryo within.

Discovering the correct combinations is like working a time-consuming, yet fascinating, puzzle. Despite all the details that have to be taken into account, germination testing is an extremely important area of study. After all, what’s the point of seed banks if we are unable to germinate the seeds?

Lauren Anderson is an intern at the San Diego Zoo Institute for Conservation Research through the Bureau of Land Management’s Seeds of Success Program. Read her previous post, Native Seed Bank.

3

Native Seed Bank

Lauren processes native yucca seeds.

When I tell people I collect seeds for seed banking, the first question I’m asked is if the collections are stored in the Svalbard Global Seed Vault, which is located on the Norwegian island of Spitsbergen. While it’s awesome that so many people know about that bank, please know that it is used primarily for agricultural species. Native plant species, especially those that are not threatened or endangered, receive much less attention. There are very few native seed banks around the world, and San Diego County happens to have one of them.

Seedlots await processing. Note the cut out in the wall, showing the building is made of straw bales.

The seed bank here at the San Diego Zoo Safari Park houses more than 500 different plant populations. It is a straw-bale, solar-powered structure that has all sorts of interesting contraptions used for seed processing. The seed bank is located at the back of the Safari Park and is the first permitted straw-bale building in San Diego County. Cleaning and storing seeds is time consuming and often tricky, but it can also be very rewarding. Our goal is to collect multiple populations of the same species, as each population may have adaptations unique to its location. San Diego County is home to over 1,500 different native plant species, so that adds up to a lot of seed collections!

When we first find a population that we want to collect, we take clippings of the plant and press them to preserve the specimens as herbarium vouchers. It is best to take a sample that has both flowers and leaves so that a specialist can verify the species. Our herbarium vouchers are sent to the San Diego Natural History Museum for verification. Data on the location, soil color, slope, habitat, and associated species are also collected. After theses initial steps are taken, we monitor the population until enough of the seeds ripen for a collection. We often have to compete with herbivores and rough weather to collect the seeds before they are lost.

Lauren at work conserving seeds native to San Diego County.

Once the collection is made, it is taken back to the seed bank and processed. The steps involved in processing the collections generally depend on each particular species. The seed and plant material is often rubbed over screens of various sizes until the seed is separated from its various shells, pods, leaves, pappi, and stems. Once separated, it is run through air separators so that lighter material is blown off and/or the seeds are lifted away from the heavier debris. Even after all of these techniques are used, we are often left with seed that is still mixed with extra plant material. When this happens, our only option left is to clean the seed by hand. With larger seeds this can be fairly easy, but with the small seeds it often involves a microscope, tweezers, and a lot of patience!

Clean seed lots are placed in the drying room to lower their moisture level. Once the seeds reach a moisture content of five to nine percent, they can be placed in long-term storage in a hefty freezer. Five hundred of the seeds are counted out into groups of 100 and then weighed. We then weigh the entire collection of seed in order to estimate the total number of seeds. At least 10,000 seeds are placed in storage at a time. If there are extra, they are set aside for future restoration and research. The seed is sealed in double-layered foil bags and frozen. It has been proven through germination testing that frozen seeds remain viable for decades.

Lauren Anderson is an intern at the San Diego Zoo Institute for Conservation Research through the Bureau of Land Management’s Seeds of Success Program. Read her previous post, Exploring Anza-Borrego Desert.

1

Exploring Anza-Borrego Desert

Lauren takes in the view at Anza-Borrego.

Lauren Anderson and Miguel Kaminsky are interns at the San Diego Zoo Institute for Conservation Research through the Bureau of Land Management’s Seeds of Success Program. As part of the internship, they make collections of seeds from plant species vital to Southern California habitats. The seeds will be preserved and studied, and eventually help restore habitats damaged by fire or during development projects.

From day one at the Institute I’ve heard people talk about how beautiful the Anza-Borrego Desert is. This year’s Seeds of Success collections focused more on the areas surrounding Ramona. While the properties we scouted in the Ramona area were very diverse and interesting, they were all composed of the same types of plant communities. This was the first week we’ve been able to make it out to the desert transition areas leading into Anza-Borrego, and it offered the chance to explore something new.

Roadrunner

When planning to explore a new property, the first step is to find one that has access. For our internship, we are only allowed to make seed collections on Bureau of Land Management (BLM) lands, and they don’t always have roads. We look at layers of BLM land on GIS and then choose one that looks reasonable to access. To do this, we largely depend on images from Google Earth. The only problem with this is that it can be difficult to determine if something is a dry creek or a little-used road. But for this desert adventure we were fairly sure that we could get within walking distance of the site.

Another part of scouting that is always fun is navigating back roads. The first dirt road we turned off on was well kept, the second one was less so, and on the third road I felt the tires sink a few inches into soft ground. We managed not to get the truck stuck, which was a very good thing since we didn’t have cell phone reception and faced having to hike several miles to a main road if we did.

The site itself was a combination of hills and dry-wash ravines with an amazing number of different plant species. Anza-Borrego definitely lived up to the hype. After exploring for a couple of hours, we determined that we could make three collections starting next week when the seeds would likely be mature enough to collect. Really exciting, and a reason to come back to enjoy Anza’s beauty!

0

What’s the Difference between a Species and a Variety?

Wild buckwheat Eriogonum fasciculatum

Miguel Kaminsky and Lauren Anderson are interns at the San Diego Zoo Institute for Conservation Research through the Bureau of Land Management’s Seeds of Success Program. As part of the internship, they make collections of seeds from plant species vital to southern California habitats. The seeds will be preserved and studied and eventually help restore habitats damaged by fire or during development projects.

This internship has provided a lot of new experiences and opportunities for learning. Specifically, events during the collection of wild buckwheat Eriogonum fasciculatum seeds at El Capitan Open Space Preserve compelled me to review some basic biological concepts regarding speciation. The whole exercise began when Lauren and I went on a seemingly routine mission to collect Eriogonum seeds. By the time we each filled a quarter of a bucket with seeds and associated material, Lauren pointed out extensive variation in the leaf morphology of the plants we were collecting. Some plants had linear, light green leaves while others had much wider, blue-green leaves with an almost woolly layer of flattened hairs. To make matters more confusing, some plants had shoots exhibiting both leaf types. This made us think there was hybridization of some sort going on, so we decided to do some further research before packaging this collection to ensure we had seeds from just one species.

Upon consulting a plant atlas, we learned that there are three varieties of Eriogonum fasciculatum in the area we were sampling.  These are var. fasciculatum, var. foliolosum, and var. polifolium.  Var. polifolium has the wider, oblong, woolly leaves while var. foliolosum has the linear leaves that aren’t nearly as woolly on their upper surface. In turn, we inferred that the individuals we encountered were  vars. foliolosum, polifolium, and mixes of the two.

Although we determined the collection was not useful to us because we needed seeds with a varietal lineage free of comingling, this left me with some fundamental questions. Why aren’t these morphologically distinct populations classified as different species? What is the difference between a species and a variety?

Lauren Riesberg, in her extensive writings addressing speciation and hybridization, cited Mayr’s definition of a species as “groups of interbreeding natural populations reproductively isolated from other such groups.” However, species that are not geographically isolated have been known to interbreed and produce hybrid offspring. Wikipedia defines a variety as a genetically, and in turn, morphologically distinct subset of a species that is geographically isolated from other populations within that species. However, when the geographic barrier is removed, this subset interbreeds with the rest of the species, resulting in an influx of genes that erodes the variety’s distinct features, thus reintegrating it into the greater species group. With this in mind, I distinguish species and varieties based on the fact that a hybrid of two species produces offspring with reduced fertility, such as malformed pollen grains, while a hybrid of two subspecific varieties produces offspring that show no such deformities and reflects the traits of the original species.

El Capitan Open Space Preserve

In light of these considerations, I came to the conclusion that the El Capitan Open Space Preserve is a very special place in the origins and family history of Eriogonum fasciculatum. According to “Flora of North America,” Eriogonum fasciculatum var. folilosum came about from an ancient hybridization event between vars. fasciculatum and polifolium. This event likely happened at places much like the El Capitan Open Space Preserve, where these populations intermingle. Eventually, isolated populations of these varieties might inbreed to the point that they become reproductively isolated from the parent varieties, giving rise to new species through divergent evolution.

El Capitan offers a living snapshot into the evolutionary history that drives speciation. In conclusion, this experience reminds me that speciation is a dynamic process taking place in our backyards, in present times, while we go about our daily lives.