Anderson, J.B. and L.P. Brower. 1996. Freeze-protection of overwintering monarch butterflies in Mexico: critical role of the forest as a blanket and an umbrella. Ecological Entomology 21:107-116.
Borders, B. 2012. A Guide to Common Milkweeds of Nevada. The Xerces Society for Invertebrate Conservation, Portland, OR, in collaboration with USDA-NRCS. Available online: http://www.xerces.org/wp-content/uploads/2011/10/NV-milkweed-guide_XercesSoc2-1.pdf. Accessed 2 November 2016.
Borders, B. 2012. A Guide to Native Milkweeds of Oregon. The Xerces Society for Invertebrate Conservation, Portland, OR, in collaboration with USDA-NRCS. Available online: http://www.xerces.org/wp-content/uploads/2011/10/OR-milkweed-guide_XercesSoc2.pdf. Accessed 2 November 2016.
Borders, B. 2012. A Guide to Native Milkweeds of Washington. The Xerces Society for Invertebrate Conservation, Portland, OR, in collaboration with USDA-NRCS. Available online: http://www.xerces.org/wp-content/uploads/2011/10/WA-milkweed-guide_XercesSoc1.pdf. Accessed 2 November 2016.
Borders, B., E. Eldredge, E. Mader, and C. Burns. 2012. Great Basin Pollinator Plants: Native Milkweeds (Asclepias spp.). The Xerces Society for Invertebrate Conservation, Portland, OR, in collaboration with USDA-NRCS Great Basin Plant Materials Center, Fallon, NV. NVPMC Technical Note No. 56. Available online: www.xerces.org/wp-content/uploads/2011/03/NativeMilkweedsGreatBasin.pdf. Accessed 22 November 2016.
Borders, B. and E. Mader. 2011. California Pollinator Plants: Native Milkweeds (Asclepias spp.). The Xerces Society for Invertebrate Conservation, Portland, OR, in collaboration with USDA-NRCS. Available online: http://www.xerces.org/wp-content/uploads/2011/03/xerces-nrcs-california-milkweed-guide.pdf. Accessed 22 November 2016.
Brower, L.P. and R.M. Pyle. 2004. The interchange of migratory monarchs between Mexico and the Western United States, and the importance of floral corridors in the fall and spring migrations. In Conserving Migratory Pollinators and Nectar Corridors in Western North America, edited by G. Nabhan, 144-166. Tucson: University of Arizona Press.
Calflora: Information on California plants for education, research and conservation. [web application]. 2014. Berkeley, California: The Calflora Database [a non-profit organization]. Available online: http://www.calflora.org/. Accessed May 2016.
Calvert, W.H. and J.A. Cohen. 1983. The adaptive significance of crawling up onto foliage for the survival of grounded overwintering monarch butterflies (Danaus plexippus) in Mexico. Ecological Entomology 8:471-474.
Chaplin, S.B. and P.H. Wells. 1982. Energy reserves and metabolic expenditures of monarch butterflies overwintering in southern California. Ecological Entomology 7:249-256.
Cronquist, A., A.H. Holmgren, N.H. Holmgren, J.L. Reveal, and P.K. Holmgren. 1984. Intermountain flora, Vol. 4. Bronx: New York Botanical Garden. 573 pp.
Decker, K. 2006. Asclepias uncialis Greene (wheel milkweed): a technical conservation assessment. [Online.] USDA Forest Service, Rocky Mountain Region. Available online: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5206820.pdf. Accessed 2 November 2016.
Dingle, H., M.P. Zalucki, W.A. Rochester, and T. Armijo-Prewitt. 2005. Distribution of the monarch butterfly, Danaus plexippus (L.) (Lepidoptera: Nymphalidae), in western North America. Biological Journal of the Linnaean Society 85:491-500.
Flockhart, D.T.T., L.I. Wassenaar, T.G. Martin, K.A. Hobson, M.B. Wunder, and D.R. Norris. 2013. Tracking multi-generational colonization of the breeding grounds of monarch butterflies in eastern North America. Proceedings of the Royal Society B 280:20131087 (Supplementary Material in addition).
Handley, J. and W. Fertig. 2001. Asclepias hallii, Hall’s milkweed. State Species Abstract. Wyoming Natural Diversity Database. Available online: https://www.uwyo.edu/wyndd/_files/docs/reports/speciesabstracts/asclepias_hallii.pdf. Accessed 2 November 2016.
Herman, W.S. 1981. Studies on the adult reproductive diapause of the monarch butterfly, Danaus plexippus. Biological Bulletin 160:89-106.
Hill, H.F. Jr., A.M. Wenner, and P.H. Wells. 1976. Reproductive behavior in an overwintering aggregation of monarch butterflies. American Midland Naturalist 95(1): 10-19.
Hitchcock, C.L. and A. Cronquist. 1973. Flora of the Pacific Northwest. Seattle: University of Washington Press. 730 pp.
James, D. 2016. Personal communication with Candace Fallon, the Xerces Society for Invertebrate Conservation.
Jepsen, S. and S.H. Black. 2015. Understanding and conserving the Western North American monarch population. In Monarchs in a Changing World: Biology and Conservation of an Iconic Butterfly, edited by K. Oberhauser, S. Altizer, and K. Nail, 147-156. Ithaca: Cornell University Press.
Jepsen, S., D.F. Schweitzer, B. Young, N. Sears, M. Ormes, and S.H. Black. 2015. Conservation Status and Ecology of Monarchs in the United States. 36 pp. NatureServe, Arlington, Virginia, and the Xerces Society for Invertebrate Conservation, Portland, Oregon. Available online: http://www.xerces.org/wp-content/uploads/2015/03/NatureServe-Xerces_monarchs_USFS-final.pdf. Accessed June 2016.
Kartesz, J.T., The Biota of North America Program (BONAP). 2015. North American Plant Atlas. (http://bonap.net/napa). Chapel Hill, N.C. [maps generated from Kartesz, J.T. 2015. Floristic Synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)].
Kearney, T. H., R. H. Peebles, and collaborators. 1960. Arizona Flora. University of California Press: Berkeley and Los Angles, CA. 1085 pp.
Lane, J. 1993. Overwintering monarch butterflies in California: past and present. In Biology and Conservation of the Monarch Butterfly, edited by S.B. Malcolm and M.P. Zalucki, 335-344. Los Angeles: Natural History Museum of Los Angeles County.
Leong, K.L.H. 1990. Microenvironmental factors associated with the winter habitat of the monarch butterfly (Lepidoptera: Danaidae) in central California. Annals of the Entomological Society of America 83:907-910.
Leong, K.L.H. 1999. Restoration of an overwintering grove in Los Osos, San Luis Obispo County, California. In 1997 North American Conference on the Monarch Butterfly, edited by J. Hoth, L. Merino, K. Oberhauser, I. Pisanty, S. Price, and T. Wilkinson, 218-221.
Leong, K.L.H., W.H. Sakai, W. Bremer, D. Feurstein, and G. Yoshimura. 2004. Analysis of the pattern of distribution and abundance of monarch overwintering sites along the California coastline. In The Monarch Butterfly: Biology and Conservation, edited by K.S. Oberhauser and M.J. Solensky, 177-185. Ithaca: Cornell University Press.
Lyons, J.I., A.A. Pierce, S.M. Barribeau, E.D. Sternberg, A.J. Mongue, and J.C. de Roode. 2012. Lack of genetic differentiation between monarch butterflies with divergent migration destinations. Molecular Ecology 21:3433-3444.
Martin, W.C. and C. R. Hutchins. 1980. A flora of New Mexico: Volume 2. J. Kramer, Germany.
Masters, A.R., S.B. Malcolm, and L.P. Brower. 1988. Monarch butterfly (Danaus plexippus) thermoregulatory behavior and adaptations for overwintering in Mexico. Ecology 69(2):458-467.
Morris, G.M., C. Kline, and S.M. Morris. 2015. Status of Danaus plexippus population in Arizona. The Journal of the Lepidopterists’ Society 69(2): 91-107. doi: http://dx.doi.org/10.18473/lepi.69i2.a10.
Nabhan, G., S. Buckley, and H. Dial. 2015. Pollinator Plants of the Desert Southwest: Native Milkweeds (Asclepias spp.). USDA‐Natural Resources Conservation Service, Tucson Plant Materials Center, Tucson, AZ. AZPMC Technical Note No. 16‐1. Available online: www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/azpmctn12744.pdf. Accessed 22 November 2016.
Pellissier, L., G. Litsios, M. Fishbein, N. Salamin, A.A. Agrawal, and S. Rasmann. 2016. Different rates of defense evolution and niche preferences in clonal and nonclonal milkweeds (Asclepias spp.). New Phytologist 209(3): 1230-1239. doi:10.1111/nph.13649.
Pelton, E., S. Jepsen, C. Schultz, C. Fallon, and S.H. Black. 2016. State of the Monarch Overwintering Sites in California. 40+vi pp. Portland, OR: The Xerces Society for Invertebrate Conservation. Available online: http://www.xerces.org/wp-content/uploads/2016/07/StateOfMonarchOverwinteringSitesInCA_XercesSoc_web.pdf. Accessed October 2016.
Pleasants, J.M., and K.S. Oberhauser. 2012. Milkweed loss in agricultural fields because of herbicide use: effect on the monarch butterfly population. Insect Conservation and Diversity 6:135-144.
Pyle, R.M. 1999. Chasing Monarchs: Migrating with the Butterflies of Passage. 307 pp. Boston: Houghton Mifflin Harcourt.
Pyle, R.M. 2015. Monarchs in the mist: new perspectives on monarch distribution in the Pacific Northwest. In Monarchs in a Changing World: Biology and Conservation of an Iconic Butterfly, edited by K. Oberhauser, S. Altizer, and K. Nail, 237-247. Ithaca: Cornell University Press.
[SEINet] Southwest Environmental Information Network – Arizona Chapter. 2016. Available online: http://swbiodiversity.org/seinet/. Accessed May 2016.
Singhurst, J., B. Hutchins, and W.C. Holmes. 2015. Identification of Milkweeds in Texas. Texas Parks and Wildlife Department. Available online at: http://tpwd.texas.gov/publications/pwdpubs/media/pwd_rp_w7000_1803.pdf. Accessed 22 November 2016.
Stevens, S.R. and D.F. Frey. 2010. Host plant pattern and variation in climate change predict the location of natal grounds for migratory monarch butterflies in western North America. Journal of Insect Conservation 14:731-744.
Stevens, W.D. 2005. New and interesting milkweeds (Apocynaceae, Asclepiadoideae). Novon 15(4): 602-619.
Sundell, E. 1993. Asclepiadaceae milkweed family. Journal of the Arizona-Nevada Academy of Science 27(2): 169-187.
Tidestrom, I. 1941. A flora of Arizona and New Mexico. The Catholic University of America Press: Washington, D.C. 897 pp.
Tilley, D., L. St. John, and D. Ogle. 2010. Plant guide for Welsh’s milkweed (Asclepias welshii). USDA-Natural Resources Conservation Service, Idaho Plant Materials Center. Aberdeen, ID. Available online: https://plants.usda.gov/plantguide/pdf/pg_aswe3.pdf. Accessed 2 November 2016.
Tuskes, P.M. and L.P. Brower. 1978. Overwintering ecology of the monarch butterfly, Danaus plexippus L., in California. Ecological Entomology 3(2):141-153.
USDA Natural Resources Conservation Service. 2016. The PLANTS Database (http://plants.usda.gov, May 2016). National Plant Data Team, Greensboro, NC 27401-4901 USA.
Vandenbosch, R. 2007. What do monarch population time series data tell us about eastern and western population mixing? Journal of the Lepidopterists’ Society 61(1):28-31.
Wassenaar, L.I., and K.A. Hobson. 1998. Natal origins of migratory monarch butterflies at overwintering colonies in Mexico: New isotopic evidence. Proceedings of the National Academy of Sciences 95:15436-15439.
Waterbury, B. and T.K. Ruth. 2015. Survey for milkweed (Asclepias spp.) and monarch butterflies (Danaus plexippus) in Lemhi County, Idaho. Idaho Department of Fish and Game, Boise, USA. 26 pp.
Xerces Society Western Monarch Overwintering Sites Database. The Xerces Society for Invertebrate Conservation. 2016.
Yang, L.H., D.M. Ostrovsky, M.C. Rogers, and J.M. Welker. 2015. Intra-population variation in the natal origins and wing morphology of overwintering western monarch butterflies (Danaus plexippus). Ecography DOI: 10.1111/ecog.01994.
Zahn, S., W. Zhang, K. Niitepold, J. Hsu, J.F. Haeger, M.P. Zalucki, S. Altizer, J.C. de Roode, S.M. Reppert, M.R. Kronforst. 2014. The genetics of monarch butterfly migration and warning colouration. Nature 514:317-321.