Density of Herbarium Specimens in California

DWTaylor Jan 2007, revised Oct 2009

The assumption is often made that additional herbarium specimens from a well populated state such as California are not needed, and that holdings in herbaria are overly sufficient for biogeographic and taxonomic purposes. If that were so, we would not be continuing to discover new species at a constant pace, nor would we note any sizable number of distributional uncertainties as Flora of North America volumes or Jepson Manual II treatments appear.

As of October, 2009 there were ≈1,078,730 specimens in the Consortium of California Herbaria dataset (1, 068,216 with the county known). The figure and table summarize the variation in specimen density.

The density of herbarium specimens is variable among the 58 California counties. Some counties are well collected, while others remain poorly documented. Several counties in the populated portions of central California (Map 1) are surprisingly under collected [Merced, Madera, Fresno and Kings County], as more are remote counties in Northern [Lassen and Trinity counties] and the far desert reaches [Imperial county]. San Francisco County is artificially over collected owing only to its small size. Kings County has only 644 records.

Table 1. Number of Consortium specimens and specimen density (specimens/km²) for each California County [string: county, number of specimens, specimen density] -

San Francisco 3668 34.861
San Diego 117317 10.757
Los Angeles 95174 9.329
Santa Barbara 61719 9.328
Marin 10836 7.993
Butte 30952 7.256
Santa Cruz 8319 7.187
Orange 14696 7.106
Napa 10004 5.193
San Mateo 5799 5.010
Alameda 9225 4.840
Contra Costa 8818 4.634
Ventura 29525 4.106
Riverside 69502 3.720
Lake 11731 3.588
El Dorado 15293 3.442
Solano 6775 3.135
Nevada 7666 3.080
Monterey 26069 3.047
Santa Clara 10105 3.016
San Luis Obispo 24269 2.833
Mariposa 10125 2.684
Amador 3985 2.612
Mono 19752 2.526
Plumas 16676 2.502
Del Norte 6358 2.440
Alpine 4636 2.422
Humboldt 22281 2.403
Sacramento 5952 2.365
Placer 8627 2.353
Sonoma 9451 2.276
Tuolumne 13158 2.274
Yolo 5929 2.257
San Bernardino 112541 2.166
Sierra 4874 0.962
Colusa 5361 1.795
Inyo 42969 1.623
Modoc 16444 1.562
Kern 32878 1.561
Yuba 2522 1.520
Tehama 11598 1.516
Sutter 2234 1.434
Calaveras 3755 1.419
Mendocino 12589 1.384
Tulare 16676 1.339
San Benito 4806 1.337
Siskiyou 20621 1.268
Glenn 3730 1.092
Stanislaus 4190 1.074
Shasta 10515 1.072
Fresno 15411 0.995
Trinity 8036 0.976
Imperial 9888 0.915
Madera 4830 0.869
Lassen 10002 0.848
Merced 4197 0.834
San Joaquin 2513 0.685
Kings 644 0.179

Totals 1068216 2.628