BUECHLER, WALTER K. Boise, Idaho. - A revision of Salix hesperia (Knowlton) Condit and allied species.
Salix hesperia (Knowlton) Condit and Salix inquirenda
Knowlton are Miocene species with an interwoven taxonomic history.
Salix hesperia was first described as Juglans hesperia
by Knowlton (1898). Brown (1937) included it in S. inquirenda,
together with S. remotidens, hereby disregarding the priority
of the epithet hesperia. Condit (1944) corrected this error and
united all three species under the name S. hesperia. Axelrod
(1992) reestablished S. inquirenda as a separate species, but
did not give a formal description. Based on revisions of 105
specimens, the present study introduces new distinguishing
characteristics, including overall leaf shape, base and apex form,
length to width ratio, venation pattern and marginal tooth form.
Leaves of S. hesperia had a length-to-width ratio between 2 and
4.4. Those of S. inquirenda were between 3.6 and 7.5. About 20%
of specimens were in the overlapping region between 3.6 and 4.4. The
study discusses morphological similarities with modern S.
floridana Chapman and S. bonplandiana Kunth, and with a
fossil species from the Late Miocene of Austria. Salix hesperia
appeared in Late Oligocene or Early Miocene in the Northwest, and
S. inquirenda during Middle Miocene. Over time, both species
moved southward to California, leaving the West in Late Miocene or
Early Pliocene, at about the same time as Taxodium.
Key words: Salix bonplandiana, Salix floridana, Salix hesperia, Salix inquirenda