Philadelphus mearnsii W.H. Evans ex Rydb.
Discussion: In 1999, Chris Frazier published "A Taxonomic Study of Philadelphus As It Occurs in New Mexico" in the New Mexico Botanist. The following is a synopsis of Frazier's paper 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. Frazier proposes only the four following taxa be recognized in NM:
Philadelphus mearnsii W.H. Evans ex Rydb. (syn = P. hitchcockianus Hu).
Philadelphus microphyllus A. Gray subsp. microphyllus (syn = P.
m. var. ovatus Hu).
Philadelphus microphyllus subsp. argenteus(Rydb.) C.L. Hitchcock
(syn = P. argenteus Rydb., P. madrensis Hemsl., P. occidentalis A.
Nels. as applied by Martin & Hutchins)
Philadelphus microphyllus subsp. argyrocalyx
(Woot.) C.L. Hitchcock (syn = P. argyrocalyx Woot., P. ellipticus Rydb.,
P. wootonii Hu
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.)
Frazier, C.K. 1999. A taxonomic study of Philadelphus (Hydrangeaceae) as it occurs in New Mexico. The New Mexico Botanist 13:1-6.
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