UCDavis - Western USA - Monarch Butterflies - 1892-2005

Study Extent

Collection records for monarch butterflies in western North America were collated from museum and private databases and specimen labels.

Sampling

The data sources included collections from the Nevada State Museum (George Austin), Brigham Young University, the California Academy of Sciences, the Los Angeles County Museum of Natural History, the Bohart Museum (University of California, Davis), the University of Utah and Utah State University. Additional data sources were collections and observations from John Hinchliff’s Oregon Butterfly Atlas (via Oregon State University), Andrew Brower, Robert Pyle, Arthur Shapiro and Larry Speers.

Method steps

1. In the source datasets, collection sites or observations were variously recorded as latitude–longitude coordinates, descriptions of collecting sites, and coordinates in US township, range and section format. Latitude–longitude coordinates were estimated from site descriptions with the Street Atlas USA software (version 7.0, DeLorme, Yarmouth, Maine, USA). Township, range and section values were converted to latitude–longitude coordinates with the TRS2LL program (Martin Wefald, San Francisco, CA 94121, USA). Altitude data were obtained from the GTOPO30 global digital elevation model (United States Geological Survey, 1996: http://edc.usgs.gov/products/elevation/ gtopo30.html). Long-term average temperature data for USA weather stations were obtained from the CLIM81 dataset (National Climatic Data Center, 1999: http://lwf.ncdc.noaa.gov/oa/climate/normals/usnormalsprods.html). River locations were obtained from the Hydrography Features of the United States GIS layer (United States Geological Survey, 1999: http://www.nationalatlas.gov/mld/hydrogm.html). To create temperature surfaces for mapping, the CLIM81 weather station data were converted to grids by inverse distance weighted interpolation. Because temperature decreases with altitude, temperatures were adjusted to sea level before interpolation and adjusted back afterwards. This was done by addition of a degrees-per-metre value calculated by regression of temperature and altitude differences between nearest neighbour stations.

1. Danaus plexippus
   common name: Monarch butterfly rank: species
2. Asclepias
   common name: milkweed rank: genus
3. Asclepias speciosa
   common name: showy milkweed rank: species
4. Asclepias tuberosa
   common name: butterfly milkweed, butterflyweed rank: species
5. Buddleja
   common name: butterfly bush, butterflybush rank: genus
6. Cleone leitens
   rank: species
7. Cosmos
   common name: cosmos rank: genus
8. Cosmos sulphureus
   common name: sulphur cosmos rank: species
9. Physostegia
   common name: lionsheart rank: genus
10. Solidago
    common name: goldenrod, verges d'or rank: genus
11. Tithonia
    common name: tithonia rank: genus
12. Verbena bonariensis
    common name: pretty verbena, purpletop vervain rank: species

Western north America including locations in Hawaii and southern Canada. The collection locations are recorded to the nearest one-hundredth of a degree, but accuracy will generally be to the nearest few kilometres. The descriptions of the collection sites were often too vague for precise latitudes and longitudes to be determined. Latitude–longitude coordinates were estimated from site descriptions with the Street Atlas USA software (version 7.0, DeLorme, Yarmouth, Maine, USA). Township, range and section values were converted to latitude–longitude coordinates with the TRS2LL program (Martin Wefald, San Francisco, CA 94121, USA).