Phylogeography

RESEARCH APROACH

California Black Rails are patchily distributed in marsh habitats near the West coast including in the San Francisco Bay area, Sierra Nevada Foothills, Lower Colorado River, Imperial Valley and Baja California.  Through the combined analysis of genetics and stable isotopes we hope to determine the origins of Black Rails in California and understand the connectivity between regions.  We are currently collecting blood and feather samples from Black Rails throughout the state to be used for genetic and stable isotope analyses. The genetic data from these samples can be used to understand how the rails moved into their current distribution in California.  In addition, this genetic data can be combined with stable isotope data to understand movements of individual birds among regions. 

We also collect skin samples for genetic analysis from specimens of Black Rails held in local museums including the Museum of Vertebrate Zoology (University of California, Berkeley, CA) and the California Academy of Sciences (San Francisco, CA).  By comparing genetic data from older museum specimens to the genetic data from modern captured birds we can look at changes in the genetic structure of Black Rails over time.

Historically, it is hypothesized that Black Rails followed the California coast north, colonizing coastal marshes first and then colonizing the inland parts of the state by following natural waterways and, in the last few centuries, colonizing artificial irrigation-dependent wetlands.

WHAT WE HAVE LEARNED

We have identified three genetically distinct groups of Black Rails in California originating from the San Francisco Bay area, the Sierra Nevada Foothills and the Imperial Valley (Figure 1). Genetic analyses suggest that the San Francisco Bay Area and the Sierra Nevada foothills populations are more closely related to each other than to the Imperial Valley population. A preliminary analysis suggests that individual birds may be dispersing between the Bay Area and the foothills.  Genetic analyses of additional samples (e.g., from the Lower Colorado River and Baja California) and the analysis of stable isotope data are needed to better understand movements between these regions.

Fig. 1. Mitochondrial DNA haplotype frequencies (shaded pie charts) for California Black Rails from the San Francisco Bay Area, the Sierra Nevada foothills, and the Imperial Valley, and the current known Black Rail distribution, shaded in gray. This genetic data tells us that the Bay Area and foothills populations are more similar to eachother than either is to the southern California population.