Appendix A. Fossil records documenting late Pleistocene Joshua tree distribution and Holocene migration rates.
Joshua tree fossils have been found frequently in packrat middens from across the Sonoran Desert of southern Arizona, the Colorado Desert of southern California, and the Mojave Desert of California, Nevada, and northwestern Arizona (Fig. 2; TABLE A1).
The southern portions of broad regional late Pleistocene distribution rapidly disappeared after the start of the Holocene, leaving only the northernmost localities intact. However a few Holocene records near what had been these northerly late Pleistocene stands allow some inferences of possible Holocene, post-ground sloth, movements.
One of Joshua tree's most northerly Pleistocene locations is in the Alabama Hills of California's Owens Valley (Koehler and Anderson 1995), about 10 km to the north of its current northern limit within the Owens Valley. These fossils could infer that its distribution has retreated southward sometime during the Holocene at a rate that averaged 0.9 m/yr over the entire period (10 km over 11,700 years). But, the rarity of midden records make it impossible to determine whether this was a slow, steady contraction, an instantaneous change, or the end product of many expansions and contractions through time. Whichever it was, the northern population limit did not change much during this period.
Alternately, a series of fossils from Eureka Valley, CA, near Joshua tree's current northern extent just east of the Owens Valley, could infer a northward Holocene expansion. Joshua tree is contained in one of four recent assemblages from the area, dated at < 200 years (Spaulding, 1980), but not in several older middens. The site is about 35 km northwest of its nearest recorded Pleistocene fossil locality in Death Valley (Wells and Woodcock, 1986). But Joshua tree is not contained in 3 other nearby Eureka Valley assemblages also dating to < 200 years, suggesting that its inclusion into these middens from on rocky slopes is infrequent despite its occurrence on the alluvial slopes well below the site (Spaulding 1980). Even if Joshua tree did migrate northward to this site over the Holocene, it is less than 20 km northwest of portions of Death Valley where it could reasonably be expected to have occurred considering the high elevation (~1500 m) of its Pleistocene occurrences nearby in Owens Valley (FIG. 2). Using this 20 km distance between the northernmost late Holocene midden record in Eureka Valley and the nearest likely Pleistocene occurrence in Death Valley, a maximum migration rate of 1.7 m/yr (20 km over 11,700 years) could be calculated. Thus a range of possible northward Holocene migration rates could be -1 to 2 m/yr, much slower than any other species yet studied (McLachlan et al. 2005; Yansa 2006; Cole et al. 2008a).
TABLE A1. Fossil records of Joshua tree associated with radiocarbon ages > 10,000 yr B.P.
Location | Radiocarbon Age(s) | Lat. | Long. | Source |
Alabama Hills, Owens Valley, CA |
13,350 19,070 20,310 21,130 25,660 31,450 |
36.63 | -118.13 | Koehler and Anderson 1995 |
Death Valley, CA | 19,550 | 36.58 | -117.33 | Wells and Woodcock 1985 |
Scodie Mts., CA |
12,870 12,960 |
35.58 | -117.95 | McCarten and Van Devender 1988 |
Joshua Tree National Park, CA | 12,015 | 33.99 | -116.07 | Holmgren et al., 2010 |
Granite Mts., CA | 24,400 | 35.45 | -116.54 | Koehler et al. 2005 |
Marble Mts., CA | 10,555 | 34.67 | -115.58 | Spaulding 1980 |
Whipple Mts., CA | 10,840 | 34.27 | -114.42 | Rowlands 1978 |
Whipple Mts., CA |
10,490 11,650 12,670 13,810 |
34.21 | -114.37 | Van Devender 1990 |
Picacho Peak, CA | 12,500 | 32.87 | -114.83 | Cole 1986 |
Amargosa Desert, NV |
10,010 11,370 11,610 12,730 14,810 16,980 17,530 |
36.57 | -116.09 | Spaulding 1985, and Personal Communication |
Amargosa Desert, NV |
10,240 15,470 16,065 17,940 |
36.63 | -116.27 | Spaulding, Personal Communication |
Specter Range, NV | 28,460 | 36.66 | -116.20 | Spaulding 1985 |
Frenchman Flat, NV | > 40,000 | 36.63 | -115.93 | Wells 1983 |
Sheep Range, NV | 19,200 | 36.70 | -115.27 | Spaulding 1981 |
Sheep Range, NV |
16,490 18,890 23,380 30,470 |
36.64 | -115.28 | Spaulding 1981 |
Sheep Range, NV |
11,550 19,400 |
36.47 | -115.25 | Spaulding 1981 |
Arrow Canyon Range, NV |
10,400 13,740 |
36.77 | -114.89 | Spaulding 1994 |
Gypsum Cave, NV |
11,360 11,690 |
36.22 | -114.90 | Laudermilk and Munz 1935, Steadman et al. 2005 |
Rampart Cave, AZ |
16,330 12,330 |
36.10 | -113.93 | Phillips 1977 |
Artillery Mts., AZ | 18,320 | 34.37 | -113.62 | King and Van Devender, 1977 |
Artillery Mts., AZ |
21,000 > 30,000 |
34.33 | -113.58 | Van Devender and King 1971. |
Kofa Mts., AZ | 11,450 | 33.43 | -114.10 | Van Devender 1973 |
Kofa Mts., AZ | 13,400 | 33.40 | -114.02 | King and Van Devender 1977. |
Tinajas Altas Mts., AZ | > 43,200 | 32.35 | -114.09 | Van Devender 1990 |
Puerto Blanco Mts., AZ | 14,120 | 31.95 | -112.78 | Van Devender 1987 |
Ajo Mts., AZ |
13,500 17,830 20,490 21,840 |
32.12 | -112.70 | Van Devender 1977 |
Waterman Mts, AZ |
12,530 19,270 21,233 22,380 |
32.35 | -111.46 | Van Devender 1990, Anderson and Van Devender 1991. |
LITERATURE CITED
Anderson, R. S., and T. R.Van Devender. 1991. Comparison of pollen and macrofossils in packrat (Neotoma) middens: A chronological sequence from the Waterman Mountains of southern Arizona, U.S.A. Review of Palaeobotany and Palynology 68:1–28.
Cole, K. L. 1986. The lower Colorado valley - A Pleistocene Desert. Quaternary Research 25:392–400.
Holmgren, C., J. Betancourt, and K. Rylander. 2010. A long-term vegetation history of the Mojave-Colorado Desert ecotone at Joshua Tree National Park. Journal of Quaternary Science 25:222–236.
King, J. E., and T. R. Van Devender. 1977. Pollen analysis of fossil packrat middens from the Sonoran Desert. Quaternary Research 8:191–204.
Koehler, P. A., and R. S. Anderson. 1995. Thirty thousand years of vegetation changes in the Alabama Hills, Owens Valley, California. Quaternary Research 43:238–248.
Koehler, P. A., R. S. Anderson, and W. G. Spaulding. 2005. Development of vegetation in the Central Mojave Desert of California during the late Quaternary. Palaeogeography, Palaeoclimatology, Palaeoecology 215:297–311.
Laudermilk, J. D., and P. A. Munz. 1935. Plants in the dung of Nothrotherium from Gypsum Cave, Nevada. Carnegie Inst. Washington, Pub 453, pp. 29–37.
McCarten, N., and T. R. Van Devender. 1988. Late Wisconsin vegetation of Robber's Roost in the western Mojave desert, California. Madroño 35:226–237.
MacLaughlan, J. S., J. S. Clark, and P. S. Manos. 2005. Molecular indicators of tree migration capacity under rapid climate change. Ecology 86:2088–2098.
Phillips, A.M., III., 1977. Packrats, plants, and the Pleistocene in the lower Grand Canyon. Ph.D. Dissertation, University of Arizona, Tucson, Arizona, USA.
Rowlands, P. G. 1978. The Vegetation Dynamics of the Joshua Tree (Yucca brevifolia Engelm.) in the Southwestern United States of America. Unpublished Ph.D. Dissertation, University of California, Riverside, California, USA.
Spaulding, W.G. 1980. The presettlement vegetation of the California Desert: Desert Planning Staff, California Bureau of Land Management, 97 pp.
Spaulding, W. G. 1981. The late Quaternary vegetation of a southern Nevada Mountain Range. Ph.D. Dissertation, University of Arizona, Tucson, 271 pp.
Spaulding, W. G. 1985. Vegetation and climates of the last 45,000 years at the Nevada Test Site and vicinity. Professional Paper 1329 U. S. Geological Survey, Denver (available as Open-File Report No. 83–535).
Spaulding, W. G. 1994. Paleohydrologic investigations in the vicinity of Yucca Mountain: Late Quaternary paleobotanical and palynological records. Job No. 8209-001, Dames and Moore, report submitted to Mifflin and Associates, Las Vegas, Nevada, USA.
Steadman, D., P. S. Martin, R. D. E. MacPhee, A. J. T. Jull, H. G. McDonald, C. A. Woods, M. Iturralde-Vinent, and G.W. L. Hodgins. 2005. Asynchronous extinction of late Quaternary sloths on continents and islands. Proceedings of the National Academy of Science, 102:11763–11768.
Van Devender, T. R. 1990. Late Quaternary vegetation and climate of the Sonoran Desert, United States and Mexico. Pages 134–165 in J. Betancourt, T. R. Van Devender, and P. S. Martin, editors. Packrat middens: the last 40,000 years of biotic change, The University of Arizona Press, Tucson, Arizona, USA.
Van Devender, T. R., 1973. Late Pleistocene plants and animals of the Sonoran Desert: A survey of ancient packrat middens in Southwestern Arizona. Ph.D. Dissertation, University of Arizona, Tucson, Arizona, USA.
Van Devender, T. R. 1977. Holocene woodlands in the Southwestern deserts. Science 198:189–192.
Van Devender, T. R. 1987. Holocene vegetation and climate in Puerto Blanco Mountains, southwestern Arizona. Quaternary Research 27:51–72.
Van Devender, T. R., and J. E. King. 1971. Late Pleistocene vegetational records in western Arizona. Journal of the Arizona Academy of Science 6:240–244.
Wells, P. V., 1983. Paleobiogeography of montane islands in the Great Basin since the last glaciopluvial. Ecological Monographs 53:341–382.
Wells, P. V., and D. Woodcock. 1985. Full-Glacial vegetation of Death Valley, California: Juniper Woodland opening to Yucca semidesert. Madrono 32:11–23.