Introductory
SPECIES: Yucca whipplei | Our Lord's Candle 



ABBREVIATION : 
YUCWHI

SYNONYMS : 
   Hesperoyucca whipplei (Torr.) Baker
   Yucca newberryi McKelvey


SCS PLANT CODE : 
   YUWH


COMMON NAMES : 
   Our Lord's candle
   chaparral yucca
   quixote yucca


TAXONOMY : 
The currently accepted scientific name of Our Lord's candle is Yucca
whipplei Torr.  The Yucca genus is described as both variable and
unstable [46].  Natural hybridization is common, and numerous
intermediate forms occur [45].  The yuccas have received only limited
attention from past researchers, and many taxonomic questions remain
[11].  Our Lord's candle is a particularly difficult group.  Earlier
researchers suggested placing this taxonomic entity in a separate genus,
Hesperoyucca, to accomodate its unique range of characters [5].
However, modern taxonomists have retained this group within the Yucca
genus as Yucca whipplei.  In many areas, hybridization and gene flow
occur freely across populations, while in other areas, populations are
isolated by geographic barriers [18].  As a result, this species
exhibits much variation in growth habit, general ecology, reproductive
strategies, phenology, and gross morphology.

Modern taxonomists have identified five or more distinct subspecies
[5,17]; numerous ecotypes also occur [18].  Currently recognized
subspecies are as follows [17,31]:

        Yucca whipplei ssp. caespitosa Jones
        Yucca whipplei ssp. intermedia Haines
        Yucca whipplei ssp. percursa Haines
        Yucca whipplei ssp. parishii
        Yucca whipplei ssp. whipplei

A number of researchers also recognize the following subspecies [18,45]:

        Yucca whipplei ssp. peninsularis (McKelvey) Webber
        Yucca whipplei ssp. eremica Haines and Epling
        Yucca whipplei ssp. newberryi (McKelvey) Webber
        
However, several of these taxa occur in isolated parts of northern
Mexico and have not been well studied [18].  Very little is known about
morphological characteristics used to delineate these groups.

Controversy still surrounds the five most widely recognized subspecies.
The subspecies whipplei was formerly known as typica [13], and some
confusion still exists in older published accounts.  McKelvey [28]
considered typica and parishii to warrant recognition as varieties
rather than as subspecies, although many later researchers delineated
them as valid subspecies.  Researchers have noted much variation
throughout all subspecies and hint that many morphological
characteristics are not "taxonomically reliable" [13].  However, many
taxonomists recommend maintaining these five subspecies for the
following reasons [18]:

(1) each entity occupies a fairly definite geographic area
(2) individual morphological characteristics are variable, but
    overall, statistically different morphs do exist
(3) all are in common use in the literature 

Clearly, much more research is needed to fully document variation of
this species and to determine appropriate taxonomic relationships.


LIFE FORM : 
Shrub

FEDERAL LEGAL STATUS : 
No special status

OTHER STATUS : 
NO-ENTRY


COMPILED BY AND DATE : 
D. Tirmenstein, April 1989


LAST REVISED BY AND DATE : 
NO-ENTRY


AUTHORSHIP AND CITATION : 
Tirmenstein, D. A. 1989. Yucca whipplei. In: Remainder of Citation

Related categories for Species: Yucca whipplei | Our Lord's Candle