December 2012 Number 1 - Utah Native Plant Society

Calochortiana December 2012 Number 1
Figure 4. Map of the Arizona distribution of Allium
bigelovii based on Ownbey (1947).
Figure 3. First collection of Allium bigelovii in Arizona,
Palmer 532 Walnut Grove, Yavapai County.
Allium bigelovii in New Mexico as “…a desert species
of southwestern New Mexico”, therefore, a Chihuahuan
Desert species. At the start of this study twenty six collections
at Arizona herbaria (ARIZ, ASU, ATC, Grand
Canyon National Park (GC), Museum of Northern Arizona
(MNA), and BLM Safford [BLMS]), had been
identified or annotated as A. bigelovii (Table 1). Based
upon these annotations, A. bigelovii was widely variable
in habitat from desert to chaparral, grassland, oak woodland,
pinyon-juniper woodland, and ponderosa pine and
wide ranging geographically from southeastern Arizona
westward beyond Wickenburg into the Sonoran Desert
and northwestward to the Hopi lands and the Grand
Canyon on the Colorado Plateau (Figure 5). This situation
made its identity as a species and its natural habitat
in Arizona puzzling.
By examining these collections, I determined that
over half had been misidentified and only twelve were
actually Allium bigelovii (Table 1). The misidentified
collections were annotated by me to several other species,
the majority (8) as A. bisceptrum var. palmeri,
three as A. macropetalum, two as A. acuminatum, and
one as A. atrorubens var. cristatum (Table 1). The large
number of misidentifications of Allium bigelovii as A.
bisceptrum var. palmeri was due to their pairing in the
key in Kearney and Peebles (1960) and the vague species
differentiation based on qualitative characters there.
To make species determinations I used the two species’
descriptions in Ownbey (1947) that included quantitative
morphological characters as well as information on
herbarium labels of habitat and geographic data. The
basis for species definition was thus an evolutionary
combination of morphology and ecology, a species’
physical characters, and the niche a taxonomic entity
occupies in nature. The refinement of the identity of A.
bigelovii in Arizona combined with a knowledge of its
habitat and range in New Mexico demonstrated that A.
bigelovii is a Chihuahuan Desert species (Figure 6) that
extends from southwestern New Mexico into southeastern
Arizona (Figure 7) (Gunder AZ930-8 ASU; Lunt 6
BLMS).
The localities of the remaining Arizona collections of
Allium bigelovii followed an interesting disjunct pattern
of distribution that extended the range of A. bigelovii
discontinuously on Mid-Late Tertiary lacustrine deposits
across central Arizona. This relictual “steppingstone”
pattern had been documented by me (Anderson
1996) for many species of various floristic affinities including
other Chihuahuan Desert species: Anulocaulis
leisolenus (Torrey) Standl., Polygala scoparioides Chodat.,
and Thamnosma texana (A. Gray) Torrey. The
lacustrine deposits (Nations et al. 1982) containing A.
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