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plant conservation

8

Tecate Cypress: Risky Reproduction

By
Lauren Anderson
– April 26, 2012Posted in: Animals and Plants, Conservation, Conservation at the Zoo, Plants, Projects in the Field, Uncategorized

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.

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

By
Miguel Kaminsky
– November 29, 2011Posted in: Animals and Plants, Conservation, Conservation at the Zoo, Plants, Uncategorized

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.

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