Field Season Recap: An observational study of Clarkia communities in California

Kate and Ed measuring plants at "Democrat," a site in the Kern River Valley where four species of Clarkia co-occur.

Kate and Ed measuring plants at “Democrat,” a site in the Kern River Valley where four species of Clarkia co-occur. Photo credit: Ian Hunter

It’s been almost two months since we left our field sites in southern California, but in some ways it’s like we never left: we’re still working away to process and analyze our data, and we’re thinking about the next times we’ll be back at our sites this fall and next spring. Before we get too much farther from the days we spent hanging out with plants and bees, I wanted to do a quick field season wrap up to share what my project was about this summer.

I’m working in Clarkia communities because I’m curious about how plants interact via their shared pollinators. Specifically, I want to know if pollinator sharing impacts natural selection on floral traits. There are a number of ways to address this question, but I started out with an observational study. My project involved measuring the floral traits and reproductive success of focal plants in different plant communities to determine if plant community composition impacts traits, fitness, and selection.

A patch of Clarkia speciosa plants in bloom

A patch of Clarkia speciosa plants in bloom

With the help of fearless field assistant Ed Higgins, we worked in 18 natural Clarkia communities that ranged from having one to four of the Clarkia species found in Kern County. At each site, we flagged and measured the traits of 50 plants per Clarkia species. These haphazardly selected plants became our focal plants—the plants that we tracked throughout the season that represent the selective environment of each community. We measured some traits directly on plants and flowers, like plant height and flower size. We also sampled one petal from each measured flower that we preserved in the form of a high resolution digital scan. Elizabeth Magno, a Cornell undergraduate student, will be extracting data on petal size, petal spots, and petal color from these images as part of an independent research project this fall.

Clarkia cylindrica growing in Kern County. It is very dry there!

A Clarkia xantiana plant with one open flower and several fruits (to the right of the flower). Some fruits have been chewed, likely by grasshoppers or caterpillars. Photo credit: Ian Hunter

A Clarkia xantiana plant with one open flower and several fruits (to the right of the flower). Some fruits have been chewed, likely by grasshoppers or caterpillars. Photo credit: Ian Hunter

Trait data comprises the majority of the dataset, but we also returned to our sites after the flowering period to estimate the fitness of our focal plants. Here I’m referring to fitness in the evolutionary sense, as a measure of the reproductive success of an individual in a specific environment. Measuring fitness is critical to evolutionary biology because while we tend to get excited thinking about flashy traits like flower color and petal spots, we need to know about how successful individuals are at passing on their genes to the next generation in order to study patterns of natural selection on traits. There are a number of ways that scientists measure fitness, depending on the organisms involved. I estimated fitness by measuring the size of and number of seeds in fruits from each focal plant. Once we finishing processing the trait and fitness data, I will explore how patterns of selection may differ across different plant communities.

My 'field office.' Not a bad place to make plans and dream about biology!

My ‘field office.’ Not a bad place to make plans and dream about biology!

Be sure to check back later for another update as we make more progress with data analysis!

The view from a Clarkia community in Kern County, California.

The view from a Clarkia community in Kern County, California.

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