The Most Common Plants of Southern California
As of 8 November 2002, we have 52 trails and floras (lists for short in the following) in our Master List. We thought it would be fun to see which are the most common taxa. (See How Common Are The Plants Of Southern California? for histograms of the number of occurrences for all the taxa in our Master List.)
Note that there are many ways to define the "most common taxa":
- The taxa with the largest absolutely number of plants, regardless of how widely-distributed those taxa may be;
- The taxa with the widest distribution in Southern California, and hence are most likely to be found on a random trail; or
- The taxa with the highest combination of the above two characteristics, after weighting the two characteristics in some way.
Some taxa satisfy all of the above, such as chamise, Adenostoma fasciculatum, which is both widely distributed and abundant in most of its occurrences. Some taxa satisfy only one criterion. Goldfields, Lasthenia californica, often has a very large number of individual plants, but is not found on most trails. In contrast, laurel sumac, Malosma laurina, is widely distributed, and is found on most trails, but never with the large number of plants of chamise or goldfields.
In the future, we'll be able to quantify occurrences much better from our estimates of the abundance of each species along each trail. For now, we simply select the taxa which appear most frequently on the lists in our Master List. This selects species like laurel sumac in preference to species like goldfields.
Caveat: This is only a preliminary, just-for-fun list. This list will change as the trail guides become more complete. In particular, this list is incomplete for annuals due to the severe drought in 2002.
We arbitrarily selected all species that were found on at least half, 26, of the 52 lists. In addition, we manually added species that had 26 observations when a subspecies was combined with the species, since in many of the lists, a subspecies was not identified. We kept these taxa separate, since it is not possible to combine the observations without going back to the individual lists. We did not perform an exhaustive check for all such species, so that part of the list may also be incomplete. We have color-coded the separate taxa in the table that are a single species. Finally, even though neither species of wild oats were found on at least 26 lists, we included them to the table below, since many of the lists only have Avena sp. on them. Most of these should receive a species identification next spring. There is little doubt that both of the wild oats species will make this table when they are identified on those lists.
The table is presented in family order. Although the numbers are given for how many times each taxa was observed, the differences between those numbers are mostly not statistically significant. That is, if we produced a table sorted in order of commonness as of now, with 52 lists, and produced another table later with 60 lists, the species will not be found in the same order. We need well over 100 lists to begin to produce an ordered table that would be truly representative of the actual frequency in Nature.
There are at least two statistical effects which affect the observed number of occurrences:
- the randomness as to whether a given species actually occurs on a trail, even if the species is present in a given area. For example, laurel sumac, Malosma laurina, is spottily distributed in many areas. Some trails will not contain a laurel sumac simply because none of the plants in that area occurred on the location of the trail itself.
- the randomness of the location of the next trails we add to our Master List. If we add trails in areas where laurel sumacs are not found, for example at higher altitude, laurel sumac will fall behind other species found on those trails.
Thus although the differences between the observed occurrence numbers are not statistically significant now, there is no doubt that all of the species in this table are very common plants. Any list of common species would include all of these species. For comparison, the most frequent number of occurrences for all species in our Master List is ONE, which is way below the threshold here of 26! Most species in our Master List occur on only a single trail or on only a few trails. No matter how many lists we add to our Master List, none of the species with an occurrence number of one or two will ever come close to being found on half of our lists.
The numbers presented in the table below are:
Title Meaning #all number of all trails and floras in the database that contain this taxon (52 maximum) #muns number of floras by Bob Muns in the database that contain this taxon (13 maximum) #floras number of all floras in the database that contain this taxon (19 maximum) #trails number of our trails that contain this taxon (33 maximum)
There are 39 total species in the following table, of which 10 are non-natives, 26% of the total. This is higher than the percentage of non-natives in the total California flora, 17% (1023 non-natives out of a California flora of 5867 species, using the Jepson Manual numbers). This is simply due to the advantage that non-native taxa have in competing with native taxa.
Remember, this table is just-for-fun now. We'll make a proper list in the future when our trail guides are more complete.
For those of you who just cannot resist sorting these species in order of occurrences, here it is.
Latin Name Common Name Family #all #muns #floras #trails Malosma laurina laurel sumac Anacardiaceae 27 9 13 14 Toxicodendron diversilobum poison oak Anacardiaceae 28 11 14 14 Ambrosia psilostachya western ragweed Asteraceae 26 10 13 13 Artemisia californica California sagebrush Asteraceae 33 11 15 18 Artemisia douglasiana mugwort Asteraceae 26 11 14 12 Baccharis salicifolia mule fat Asteraceae 29 11 14 15 Brickellia californica California brickellbush Asteraceae 26 9 13 13 Centaurea melitensis *tocalote Asteraceae 32 12 16 16 Erigeron foliosus leafy daisy Asteraceae 12 9 10 2 Erigeron foliosus var. foliosus leafy daisy Asteraceae 15 0 3 12 Eriophyllum confertiflorum golden yarrow Asteraceae 15 10 11 4 Eriophyllum confertiflorum var. confertiflorum golden yarrow Asteraceae 21 0 5 16 Gnaphalium californicum California everlasting Asteraceae 27 11 15 12 Gnaphalium canescens ssp. microcephalum white everlasting Asteraceae 28 10 13 15 Hazardia squarrosa saw-toothed goldenbush Asteraceae 9 9 8 1 Hazardia squarrosa var. grindelioides saw-toothed goldenbush Asteraceae 18 0 4 14 Heterotheca grandiflora telegraph weed Asteraceae 29 11 15 14 Lessingia filaginifolia California-aster Asteraceae 10 9 8 2 Lessingia filaginifolia var. filaginifolia California-aster Asteraceae 26 2 7 19 Hirschfeldia incana *shortpod mustard Brassicaceae 31 12 15 16 Lonicera subspicata southern honeysuckle Caprifoliaceae 6 8 6 0 Lonicera subspicata var. denudata southern honeysuckle Caprifoliaceae 20 0 5 15 Sambucus mexicana blue elderberry Caprifoliaceae 34 12 17 17 Salsola tragus *Russian thistle Chenopodiaceae 28 11 14 14 Marah macrocarpus wild-cucumber Cucurbitaceae 12 11 12 0 Marah macrocarpus var. macrocarpus wild-cucumber Cucurbitaceae 14 0 3 11 Lotus scoparius deerweed Fabaceae 17 11 11 6 Lotus scoparius var. scoparius deerweed Fabaceae 13 0 4 9 Quercus agrifolia coast live oak Fagaceae 10 9 10 0 Quercus agrifolia var. agrifolia coast live oak Fagaceae 18 0 3 15 Erodium cicutarium *redstem filaree Geraniaceae 27 12 16 11 Marrubium vulgare *horehound Lamiaceae 26 12 15 11 Salvia apiana white sage Lamiaceae 27 8 12 15 Salvia mellifera black sage Lamiaceae 30 10 14 16 Epilobium canum California fuchsia Onagraceae 10 8 7 3 Epilobium canum ssp. canum California fuchsia Onagraceae 16 6 10 6 Epilobium canum ssp. latifolium mountain California-fuchsia Onagraceae 10 2 5 5 Eriogonum fasciculatum California buckwheat Polygonaceae 10 11 10 0 Eriogonum fasciculatum var. foliolosum California buckwheat Polygonaceae 23 0 4 19 Eriogonum fasciculatum var. polifolium California buckwheat Polygonaceae 13 0 2 11 Rhamnus ilicifolia hollyleaf redberry Rhamnaceae 30 9 14 16 Adenostoma fasciculatum chamise Rosaceae 28 9 13 15 Heteromeles arbutifolia toyon Rosaceae 33 10 14 19 Salix lasiolepis arroyo willow Salicaceae 29 9 14 15 Mimulus aurantiacus bush monkeyflower Scrophulariaceae 29 10 12 17 Avena barbata *slender wild oats Poaceae 24 11 15 9 Avena fatua *wild oats Poaceae 18 11 14 4 Bromus diandrus *ripgut brome Poaceae 33 12 16 17 Bromus hordeaceus *soft chess Poaceae 26 11 15 11 Bromus madritensis ssp. rubens *red brome Poaceae 29 11 13 16 Melica imperfecta small-flowered melica Poaceae 26 10 14 12
Copyright © 2002 by Tom Chester and Jane Strong
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Last update: 24 November 2002