Philadelphus hitchcockianus Hu
Family: Hydrangeaceae
Discussion:
In 1995, Chris Frazier compiled "A Taxonomic Study of Philadelphus
As It Occurs in New Mexico" for Tim Lowrey's Advanced Taxonomy
Class at UNM. The following is a synopsis of Frazier's report
and must serve as the review document for all the Philadelphus
species on our review list. Frazier made a complete review of
the literature concerning southwestern Philadelphus species. He
also examined 98 UNM specimens and scored them for a 31 character
data set which was used for a principal component and discriminant
analysis.
Frazier found that many of the characteristics considered
important by previous authors were unreliable. His analysis found
three characters: axillary bud type (exserted vs. enclosed); leaf
face (isofacial or bifacial); and sepal tomentosity (glabrous
or ciliate vs. tomentose) all perfectly correlated and with factor
loadings above 0.9 on the first axis. Two clusters are obvious
which he calls the "microphyllus group" (buds enclosed,
leaves bifacial, sepals persistent) and "mearnsii group"
(buds exposed, leaves isofacial, sepals deciduous in fruit).
When other characters are applied, the PCA of these groups show that
P. hitchcockianus of the Guadalupe Mts. and P. mearnsii of southwest
and south-central NM are fairly tightly clustered and not much
different. The "microphyllus group" is much more spread
out and separable into three slightly overlapping taxa. Fraiser
proposes only the four following taxa be recognized in NM:
Philadelphus mearnsii W.H. Evans ex Rydb. (syn = P. hitchcockianus Hu).
This is a low growing xeric shrub with a distinct maple syrup odor. The
only difference Frazier could detect between the Guadalupe Mts.
population and the other P. mearnsii collections was glabrous
hypanthia in the Guadalupes vs. slightly strigose for the rest.
Frazier believes this is too little to distinguish two taxa. Occasional
in canyons and cliffs of Chihuahuan desert mountains. In New Mexico
it ranges from Hidalgo County, as far north as the Fra Cistobal Mts.
and east to the Guadalupe Mountains. Also occurs in northern Mexico
and west Texas. Spellenberg (1981) cites 12 NM collections of
P. mearnsii prior to Frazier's proposal to include P. hitchcockianus
in that species. Spellenberg's report was sufficient to drop this
species to a 3C rank in federal status.
Philadelphus microphyllus A. Gray subsp. microphyllus (syn = P.
m. var. ovatus Hu).
Large bush with bifacial leaves and glabrous or nearly glabrous hypanthium and sepals.
This is our most common Philadelphus. In NM it ranges from San Juan Co. south to
Grant Co. then northeast to Colfax Co. North to Wyoming.
Philadelphus microphyllus subsp. argenteus(Rydb.) C.L. Hitchcock
(syn = P. argenteus Rydb., P. madrensis Hemsl., P. occidentalis A.
Nels. as applied by Martin & Hutchins)
Hypanthium strigose with straight hairs. This is the common Philadelphus of southern
NM and adjacent southwest AZ and north-central Mexico.
Philadelphus microphyllus subsp. argyrocalyx
(Woot.) C.L. Hitchcock (syn = P. argyrocalyx Woot., P. ellipticus Rydb.,
P. wootonii Hu
Hypanthium tomentose. This subspecies is endemic to Sacramento
Range and Capitan Mountains of south-central NM - Lincoln and
Otero Counties. (ed. note: It is fairly common within its limited
range.) For P. wootonii Frazier says "Hu described P. wootonii
as a sympatric congener of P. argyrocalyx distinguished from it
by having disciform flowers, pubescent center on the disk and
base of style, and short-tailed seeds. The corolla character is
unreliable and the pubescence of the disk likely to be an inconsistent
correlate with the overall greater density of pubescence of subsp.
argyrocalyx. Seed tail length is a developmentally and environmentally
variable character. I see no reason to distinguish P. wootonii
from argyrocalyx." (ed. note: This critique is likely correct,
but I must caution: P. wootonii is apparently only known from
its type collection and Frazier has not seen the type specimen.)
Additional note: Frazier believes there is no documented proof
that Philadelphus serpyllifolius occurs in NM. Hitchcock (1943)
did cite one New Mexico locality for P. serpyllifolius in his
'Materials Seen' section, but this is for the type which was collected
"between western Texas and El Paso, New Mexico" -- El
Paso is in western Texas. Frazier also thinks the Hu map (1956)
that places serpyllifolius in southwest NM and southeast AZ is
somehow mixed up with the distribution of P. mearnsii. (ed. note:
Even if P. serpyllifolius is in NM, it ranges from west Texas
to Coahila, and would be a peripheral here.)
Important Literature:
Frazier, C. 1995. A taxonomic study of Philadelphus
as it occurs in New Mexico. Unpubl. class report, available from
Tim Lowrey, UNM Herbarium.
Hitchcock, C.L. 1943. The xerophyllous species of Philadelphus in
southwestern North America. Madrono 7:35-56.
Hu, S. 1956. A monograph of the genus Philadelphus. Jour. Arn. Arb. 37:15-90.
Spellenberg, R.W. 1981. Status Report on Philadelphus mearnsii. Submitted to USFWS,
Albuquerque, NM.
Information Compiled By: Bob Sivinski, 1998
