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The epithet, testudinaria, provided by Nylander, suggests that this
species was recognized for the reticulate pattern (of cortical ridges) on the cortical surface,
reminiscent of that seen on turtle shells, as also perhaps associated with
dilated branch segments, compared to the narrower, almost linear branches of Niebla homalea.
Spjut (1996)
emphasized the reticulate ridging for distinguishing N. testudinaria from
N. homalea. This appears associated with the prismatic shape of branches
of N. testudinaria in contrast to sub-tubular (elliptically shape in
x-sect) of blade-like branches
in N.
homalea.
Specimens with relatively narrow or linear prismatic branches, such as
Bratt 6431 from Santa Cruz Island, are similar to Niebla
flagelliforma. This species differs primarily by possessing a
relatively thinner cortex, especially on the branchlets, which, as a result, the branchlets appear coiled. The cortex on branchlets of N.
flagelliforma is generally less than 35 µm thick, compared to 75–150
µm thick in N. testudinaria. However, most California
species of Niebla have a thicker cortex in contrast to species in
Baja California with exceptions to N. infundibula, which
occurs on moist, relatively cooler, wind exposed ridges or peaks in Baja
California, and N. caespitosa in the Channel Islands. The
questions, therefore, are whether N. flagelliforma in California
developed a thicker cortex as a result of adaptation to the cooler
California climate, or whether N. testudinaria independently
evolved a morph like N. flagelliforma, or whether there is a past
history of hybridization between N. flagelliforma and N.
testudinaria?
Similarly,
the three specimens shown for Moran 1055, Bratt 3212, and Weber & Santesson,
could be interpreted as belonging to N.
caespitosa. Because typical
N. caespitosa from California is distinguished by its thinner cortex (<75 µm thick),
and the finding that it also occurs in Baja California, the decision has been to
recognize these morphs under N.
testudinaria. Divaricatic-acid species are generally
differentiated by their cortical features; therefore, the thickness
of the cortex was given more weight as opposed to shape of branches. |
