As the raven flies: using genetic data to infer the history of invasive common raven (Corvus corax) populations in the Mojave Desert

Authors

  • ROBERT C. FLEISCHER,

    1. Center for Conservation and Evolutionary Genetics, National Zoological Park & National Museum of Natural History, Smithsonian Institution, Washington, DC 20008, USA;
    Search for more papers by this author
  • WILLIAM I. BOARMAN,

    1. Conservation Science Research & Consulting, 2522 Ledgeview Place, Spring Valley, CA 91977, and also Biology Department, San Diego State University, San Diego, CA 92182, USA;
    Search for more papers by this author
  • ELENA G. GONZALEZ,

    1. Center for Conservation and Evolutionary Genetics, National Zoological Park & National Museum of Natural History, Smithsonian Institution, Washington, DC 20008, USA;
    Search for more papers by this author
    • §

      Present address: Departamento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006 Madrid, Spain.

  • ALVARO GODINEZ,

    1. Center for Conservation and Evolutionary Genetics, National Zoological Park & National Museum of Natural History, Smithsonian Institution, Washington, DC 20008, USA;
    Search for more papers by this author
    • Present address: University of Maryland Biotechnology Institute (UMBI), 9600 Gudelsky Drive, Rockville, MD 20850, USA.

  • KEVIN E. OMLAND,

    1. Department of Biological Sciences, University of Maryland, Baltimore, MD 21250, USA
    Search for more papers by this author
  • SARAH YOUNG,

    1. Center for Conservation and Evolutionary Genetics, National Zoological Park & National Museum of Natural History, Smithsonian Institution, Washington, DC 20008, USA;
    Search for more papers by this author
    • ††

      Present address: Pennsylvania Association for Sustainable Agriculture, 650 Smithfield Street, Suite 210, Pittsburgh, PA 15222, USA.

  • LAUREN HELGEN,

    1. Center for Conservation and Evolutionary Genetics, National Zoological Park & National Museum of Natural History, Smithsonian Institution, Washington, DC 20008, USA;
    Search for more papers by this author
  • GRACIA SYED,

    1. Center for Conservation and Evolutionary Genetics, National Zoological Park & National Museum of Natural History, Smithsonian Institution, Washington, DC 20008, USA;
    Search for more papers by this author
  • CARL E. MCINTOSH

    1. Center for Conservation and Evolutionary Genetics, National Zoological Park & National Museum of Natural History, Smithsonian Institution, Washington, DC 20008, USA;
    Search for more papers by this author
    • ‡‡

      Present address: Laboratory of Genomic Diversity, National Cancer Institute, Building 560, Room 21-23, Frederick, MD 21702-1201, USA.


Robert C. Fleischer, CCEG, Science Building, NZP, PO BOX 37012, MRC 5503, Washington, DC 20008, USA. Fax: 1-202-673-0040; E-mail: fleischerr@si.edu

Abstract

Common raven (Corvus corax) populations in Mojave Desert regions of southern California and Nevada have increased dramatically over the past five decades. This growth has been attributed to increased human development in the region, as ravens have a commensal relationship with humans and feed extensively at landfills and on road-killed wildlife. Ravens, as a partially subsidized predator, also represent a problem for native desert wildlife, in particular threatened desert tortoises (Gopherus agassizii). However, it is unclear whether the more than 15-fold population increase is due to in situ population growth or to immigration from adjacent regions where ravens have been historically common. Ravens were sampled for genetic analysis at several local sites within five major areas: the West Mojave Desert (California), East Mojave Desert (southern Nevada), southern coastal California, northern coastal California (Bay Area), and northern Nevada (Great Basin). Analyses of mtDNA control region sequences reveal an increased frequency of raven ‘Holarctic clade’ haplotypes from south to north inland, with ‘California clade’ haplotypes nearly fixed in the California populations. There was significant structuring among regions for mtDNA, with high FST values among sampling regions, especially between the Nevada and California samples. Analyses of eight microsatellite loci reveal a mostly similar pattern of regional population structure, with considerably smaller, but mostly significant, values. The greater mtDNA divergences may be due to lower female dispersal relative to males, lower Ne, or effects of high mutation rates on maximal values of FST. Analyses indicate recent population growth in the West Mojave Desert and a bottleneck in the northern California populations. While we cannot rule out in situ population growth as a factor, patterns of movement inferred from our data suggest that the increase in raven populations in the West Mojave Desert resulted from movements from southern California and the Central Valley. Ravens in the East Mojave Desert are more similar to ones from northern Nevada, indicating movement between those regions. If this interpretation of high gene flow into the Mojave Desert is correct, then efforts to manage raven numbers by local control may not be optimally effective.

Ancillary