FOLIAR TRICHOME VARIATION IN QUERCUS SECTION PROTOBALANUS (FAGACEAE)

13 Pages·1993·8.1 MB·English

by  Paul S Manos

QUERCUS
TRICHOME VARIATION
IN
FOLIAR
PROTOBALANUS (FAGACEAE)
SECTION
MANOS^
PAUL
S.
LH.
Hortoriwn
Bailey
Mann
467 Lilnwy. Cornell Unwers/ty
NY
14S33. U.S.A.
Ithaca,
ABSTRACT
PwlnhnLnm^ smallest section of the oaks, were studied
Foliar trichomcs of section tlic
Q/zertv/.i
Distmct complements of iion-glandLilar trichome types
using scanning electron microscopy-
were observed for each of the five recognized species (Q. ceclrosemis C.I I. Mull., Q. chrysolepis
Engelm., and imxmtfolta Kell.).
Liebm., O.^^^/ZmT/ Engelm. [Q. Juufin Kell.], Q. tmuentdla Q.
Trichome characters Rilly support the current taxonomy of the section and provide additional
both
trichome variation was used to address
hitraspecific
characters for species identification,
Contrary
and hypotheses of hybridization between several species-pairs. to
geographic variation
m
documented
complement non-glandular trichomes section
of
previous reports, the total
and white oak groups.
observed both the larger red (black)
diverse that in
VrotohcdiiUiis is as as
RHSUMCN
mediante microscopio electron ico de barrido, los tricomas foliares de Q/zmv/^
Se estudiaron, el
que seccion mas pequena de los robies. Se observaron distintas
seccion ProtobciLnnis, es la
C.H.
cantidades de tipos de tricomas no glandulares en cada unade las cinco especies (Q. cechosemis
Engelm.,
chmnn tommtdlu
Q Liebm., palwen Engelm., Kell.], Q. y Q.
MLilh, chrysoltps Q. {Q.
apoyan taxonomfa aceptada de seccion
vcaxinifolid Kell.). Los caracteres de los tricomas la la y
adicionalespara identificacion de especies. La variacion intraespecificade los
ofrecen caracteres la
como para hacer hipotesis de
tricomas se uso tanto para explicar la variacion geografica
hibridacion entre varios pares de especies. Contrariamente a lo que se liabfa citado previamenre,
como
cantidad total de tricomas no glandulares en la seccion Protobahvins es tan diversa la
la
observada en grandes grupos de robies blancos y rojos (negros).
los
INTRODUCTION
trichomes provide a valuable set of analytical characters for species
Foliar
back
Qmrns. The use of trichome characters in Qi/erais dates to
delimitation
in
Camus (1936-54) and Dyal (1936), and their wide-
taxonomic of
the studies
taxonomy through the use of scanning
oak has increeised
spread application to
&
Nixon
microscopy (SEM; Hardin 1975, 1976, 1979a, 1979b;
electron e.g.
& Many
Thomson Mohlenbrock of the trichome differences
1979)-
1981;
Steele
SEM (EM)
microscopy
with standard light
under discernible
the also are
visible
such
morphological
even hand but certain cryptic differences, as
or a lens,
SEM.
with
nrr-ir^mr-nr nf rrirbnmp nre better observcd
T'Av^
NC A
Duke Durham, 27708-0338, U.S.
Department of Botany, University,
Present address:
391-403.
SiDA 1993
15(3):
392 Sum
1993
15(3):
9
section Protobalanus
tomentella
Q.
Qchrysolepis
KjMj l_"L -1/1 "1_
mJ^- r.-r
palmeri
cedrosensis
Q.
vaccinifolia
Q.
Fig. ApproximatL- disrribucion ofQ/zem/s The
1 section Prulohalaiii/s. range oiQ. cbysoUfii
. is
taken in part from Griffin and Critclifield (1972). The remaining mapped
species are according
to recent Held and herbarium (Manos
studies
1992).
Manos, Trichome Quercus 393
Variation
in
Q
With
fQ
some monophyletic groups. Other groups, however, such as the red oaks ofeastern
North America, show hmited trichome diversity, and the dehmitation of
Trichome
subgroups using trichomes alone (Hardin 1979a). type a
difficult is
is
diagnostic character for a few putatively monophyletic species groups within the
m
The type found species of the
white oaks (section Q//ercus). fused-stellate all
white oak group one example.
oaks" (subsection of the
''southern live V/rentes) is
Trichome have been used the most the species level in the white
characters at
complements
oak group, and numerous examples of species-specific trichome
Hardin
have been documented in taxa considered to be closely related (e.g 97 9a,
1
.
& &
The
Thomson Mohlenbrock Nixon
1979b; 1979; Steele 1981). identifica-
between white oak been addressed with patterns of
tion of hybrids species h-as
&
many Tucker Muller 1958; Tucker 1963;
trichome variation in studies (e,g.
Ma^e Cottam These authors documented that hybridization
1968; 1982).
et
al.
between species can result in additive combinations of the trichomes of each
expected other quantifiable characters.
species, in addition to modifications in
Hardin (1976, 1979b) classified the trichomes of a fairly large sample of red
on attachment,
and white oaks 10 different types based primarily glandularity,
as
morphology comprehensive treatment of
and ray Jones (1986), in his foliar
of Fagaceae, discussed the distribution of trichome types found within
features
'(Q
Q
subgenus
Quera/s Q
(Nixon western North America and consists offive species
in press), restricted to
is
medium
of shrubs and small to sized trees (Fig. In previous descriptions of the
1).
876-1
(Engelmann
morphology of the species ofsection Protohalanns 877, 880;
1 1
Mtill
taxonomic
J
According
only three non-glandular types in section Protobalanm, to his treat-
complement non-glandular
of
ment, section Protohalanm has the least diverse
trichome types of sections of the genus.
all
My
preliminary observations of herbarium, field coUec
LM
discriminate the trichomes of the recognized species of section Protobalanus.
purposes
Scanning microscopy, however, very useful for illustrative
electron
is
LM.
and determine some not apparent with These potential
to fine detail
have not been quantified or described in any previous systematic
characters
studies of the group. The purpose of this study is to establish the extent of foliar
oiQuenm
Table Range and mean quantitative features of trlcliomes types found in species section
for
1.
394
SiDA
1993
15(3);
ProtolhiLnui}
Ray (mm)
S[u'cics NLimbcT Rays
Iciiut^li of
Mean
Rani;c Mean
Raiit^e
Q. cedyoscHsis
apprc'ssctl- fasciculate O.H) 0.15 0.13 2-4
2.5
fascicularc O.IS- 0.25 0.20 5-
[2
8.3
scciuue 0.20-0.35 6-
0.29
8.7
1
^
0.37-0.60 3-10
niuliiracliiirc 0.52
7.2
fasciculate
niLiItiradiatc 0.07-0.2^^ 0.11 5-12
8.1
Q. Vih'dnifolid
stellarc 0.03-0. 12 0,06 4-15
.S; 7.5
m
in arc
rati
L]
1
trichome
diversity within section Protobahni/iS and to provide additional charac-
ters for species identification.
AND MEM
MATHRIALS
lODS
The
majority of specimens used stndy were obtained during
in this
several field
trips to areas throughout the geographic range of section FrotokiLniiis (Fig.
1).
These
collections represent population samples, most of wliich were used other
in
studies of morphological and molecular
variation in section ProtohcihniKS (Manos
1992). Additional herbarium material was examined the following
at herbaria:
ASC, DAV, SDM, UCSB, UCR, and SBBG. The Cornelius H. Oak
Mtiller
Herbarium l-CHM)
(BI was a rich source of material of section Protohuhnim. The
personal oak collection of Kevin C, Nixon, soon to be incorporated into BH,
provided
additional material
for study.
Studies of trichome variation were conducted on individuals throughout
the
A
rangeofeach
species. light microscope(4()x and 2()()x magnifications) was used
determine trichome and make
to type
observations for eventual calculations of
mean
range in ray length, ray length, range of ray number, and mean number of
These were from
rays. calculated 10 representative trichomes per individual
examined Ray
(Table wasmccisured from
lengtli point of divergence of
1). tlie the
and
ray base of the trichome. Because samples were not random, standard
and
deviations confidence Intervals were not cakulated from
these
obser\^ations.
Following
the initial sur\xy of trichomes outlined above, specimens
exhibit-
ing typical species-specific trichomes were prepared examination with SEM,
for
This material was taken from lierbarlum specimens and greenhouse-grown
dried,
and mounted aluminum
individuals onto stubs and sputter-coated with gold-
:
Manos, Trichomc Quercus 395
VLiriation in
*^
^ f ^ ^j -r-'v if ^^
;^^i
^'' I . I
^ii^ >.V ^•y:#<
^ ^
..J
-*t
»' -^
.t
Si.
1-
r
>
^
<.'
x ''.: ;^--.iK.-«3
4f^*fr .:^*J-^ •^'^'^ '^..^W^ :-^
-'
.W
' r^^:^^
<
-:*
—
"^^
^
m
Fig. SEM photographs. A) Appressed-fasciculate, Q. cedrosensis, scale bar = 100 |im; B)
2.
appressed-fasciculace, Q, ceclrosemis, scale bar = 100 (Jm; C) appressed-fasciculatc, Q. cedrosensis,
scale bar = 50 |im; D) fasciculate and stellate, Q. tommtellct, scale bar = 300 |Jiti; E) fasciculate,
Q.palmeri, scale bar = 200 yxny, F) fasciculate, O.pcdmeri, scale bar = 100 |im.
396
siDA iyy3
15(3):
palladium for 4 minutes in a Balzers Union Sputtering Device. All material
leaf
was prepared without prior treatment or point drying. Trichomes
critical
SEM
pictured with using the simple procedure outlined here do not deviate from
AMR
An
LM.
SEM
RESULTS
The
which
descriptions follow are representative of the mature condition of
and
adaxial ab^Lxial leaf surfaces since mature leaves are most often collected for
purposes of
identification.
The
currently recognized within
species section
FrotobaJaniis
{Q. ccclroseusis
Mull,
Liebm., Engelm.
Q, chrysolepis Q. pcdmeri chmnii KelL], Q
[Q.
Engelm., and
were by
'ella Q. vaLximfolia Kell.) distinguished non-glandu-
lick-walled trichome types. The distinction between and
Q. dvjsolepis Q
was the weakest and based on observations trichomes of Q
ifolici tliat
predominantly
ifolici are stellate, whereiis trichomes of Q. chjsolepis exclu-
rw
and
Q. ceclrosemis, Q. tome?/ el/a, Q
f
SEM
The
non-glandular trichome complements
on both and
adaxial abaxlal leaf
within
surfaces species of section Protoba/a/i/zs were similar, and typically only
One
differed in density exception noteworthy The trichomes of the abaxial
is
H)
surface (Fig. 2 ofQ. vaainijolia have fewer rays than those of the adiixial surface
(Fig. 2 G). Table lists, by species, the type(s) of trichome and includes
1
descriptions of morphology.
their respective
The
golden glandular trichomes ("branched
uniseriate" sensu Jones 1986;
''siniple branched" sensu Hardin 1976) commonly seen on the abaxial leaf
twigs and
surface, cupules ofg. chysolepis-And thin-walled and
Q^,pcd)ucytiv:(^ often
collapse after drying (Fig. 2 F). Their absence in Q- cechosmsis and
Q. vcuxnufolui,
combined
with
other characters, is taxonomically useful to discriminate each
from The
0. dnysokp/s. long solitary trichomes (Hardin 976) were observed
also
1
on some specimens
of all species; they are not taxonomically informative.
Descriptions of foliar trichomes of each species
Quercus
cedrosensis C.H.
Miill.
ai/ax/af: kvif glabrous to pubcrulenc; Typos: apjM-csscd-fasciculace; no glandular tricliomcs.
c
A-C):
i?/;t/.VA//(Fit;s. 2 leaf pubcruleut wich (.'picucicuhir wax; Types: appressed-fasciculate and
no
solitary; i^landnlar trichomes.
Appressed-fasciculate trichomes, persistent on the were diag-
abcixial surfiice
This type from
nostic. clearly differs the appresscd-lateral described by
tyjie
Hardin
(1976). Appressed-fasciculate trichomes have not been reported
in
:
397
Manos, Trichome Variation in Quercus
M. .^ :^>
W.
.,^
«i-«.
l-*/-^.
v_.
^.
A:?
r."
I ^^ i;
^^.
'm*
:,<-
-!'.
^
V
j>*r
^j
'^
^...'^
t^^
%^^r^„ ^
—
^1.. J.^-Am^^-1^1
._^
.^^i-.
jf^JV
3^-^^
"TT
^ ma^^ ^- ^+
>.
if.
>^^.^ v-^
-:j-
'
^ ,-rvj'
-^r'
•M-\ J
^: ^
V
.^'^....
^
^'
;^^^.r
S-. '-
V. ""i :^s:
. ^
^ ^ \ •I*'
^>r
-.^
X"
^Jr
r
=:^& ^ -^-i 5.0^
-^^:
-^..-tf-
+--
:^'
.j£,
^I^ ^-*h_:^^^^->. ^.r^ r^
-J
:iir
(\
^W
^^^'ra^^V -ii^
,^'
^^
m-nm
—
^^.>*-_-s'iSv>iS^'.i*?.-. *tCft^.^- .tv't>\4 .^vjSS
Um
and
D) E) multiracliate
ummnella\ C) rosuhite, Q. cbrysohpis; mulciracliate, Q. chrysokp/s;
stellate, Q.
G) and
simple-branched glandular, chrysokpis\ stellate
multiradiatc, Q.
simple, Q. chrysolepis; F)
H)
mukiradiatc, Q. vaainifolta\ stellate, Q. vacaniji^lia.
398
SiDA 1993
15(3):
A
LM,
Q/^ercm. cellular wall, only visible with was observed between
the
rays of
each 2-rayed These might
unit. paired trichomes otherwise
apjx^ar to represent
a single-celled
unit.
Quercus
palmeri Engelm.
{Q. palmeri Kell.}
aclaxhd
{V\)^<,. 2 E, F): k-aves puberiilcnt; Ty]x's: fascicularc, and
solitary,
^^laixlLilar.
abaxhih leaves puberulenc to tomenrosc with epicuticular wax; Types: and
fasciculace
glaiulLilar.
Fcxsciculate trichomes, mostly on
persistent the adaxial were diagnos-
surflice
The
tic. rays are erect, splay-out, twist near the apex, and on
insert a distinct
pedestal formed by
the epidermis. Jones 986)
characterized type having
(1 this as
rays that are joined only the
at base.
Qiicrcus tomentella Engelm.
culaxidL leaf sparsely tomenrose, mostly
near the midrib;
Tyjx's: foscicalate, multiradiate
to
and
stellate, solitary, glandular.
D,
r74/x/^/(F]gs. 2 3 A, B): densely tomencose; Types:
fliSLiculate, nuiltiradiate to stellate, and
scilitary.
and
Fasciculate multiradiate
to stellate trichomes with long on
rays, persistent
A
the adiLxial surface were diagnostic. weak distinction between
the types can
made
by comparing
the longer, erect Eisciculate and multiradiate with
rays the
of
rays the stellate type that are shorter and diverge one The
laterally in plane.
designation of the trichome complement
somewhat
in this species
arbitrary,
is
because they appear to vary continuously, but
this feature alone diagnostic
for
is
The
Q. tomeutdla. rays of these types are longer than those observed on
the leaves
of other species of section Protohakmns.
Quercus
chrysolepis Liebm.
cubxhil{Y'i^ C~E):
3 leaf puberulenc; Types: multiradiate, rosulate, simple, and glandular.
uhuxhd
(Fig. 3 leaf puberulent to lightly romentose with
19: epicuticular wax; Types:
muluradiare, and
solitary, glandular.
Multiradiate and
rosulate trichomes, persistent mostly on
the adaxial
surface,
were The
diagnostic. multiradiate type was described by Hardin and
(1976)
Jones 986) being composed
(1 as of approximately S-1 2 rays that radiate more
in
than one plane from common
rounded The
a typically
base. rosulate type
also
observed seems
in this species to represent smaller and
especially thin-walled
multiradiate trichomes
that collapse drying They
after (Fig. 3 C). are most
common
on
the adaxial surfice of immature
leaves that have been
dried.
Quercus
vaccinifolia
Kell.
adaxial
(Fig 3 G): leaf glabrous to puberulent; Types:
stellate to slightly multiradiate; no
glandular trichomes.
399
Manos, Tnchome Variation Qucrcus
in
abaxial (Fig. 3 H): leaf glabrous to pubcrulent with epicuticular wax; Types: srellatc; no
glandular trichomes.
trichomes were diagnostic, with an occasional upright ray, that
Stellate
chjsokp
Q.
^fQ,chr}^soiep
on were diagnostic (Fig. H).
observed the abaxial surface also 3
fewer rays 4)
(ca.
trichomes
The trichomes was within the range observed for the
length of these
ray
of the adaxial surface. The vestiture on the leaves and twigs of this species is often
On
glandular trichomes
wanting or off soon after leaf expansion. occasion,
falls
This
were found on individuals collected from lower elevations. feature is
The
4-
(Myatt
with 1975)-
presumably the result of hybridization Q. chiysokpis
distinguished from those of Q.
trichomes of species are easily
rayed this
stellate
The
two of two-rayed trichomes.
which often occur as adjacent pairs
cedrosemis,
Q. vaccinifoL
Q
:edrosensis.
C
DISCUSSION
Species delimitation
The non-glandular trichomes of section Protohalam/s are useful taxo-
Q/zmy/.i"
taxonomic
Q
of
identifying the species seci
Q and Q
vacdnifoli
chy-ysokph
.
.
but rather on a strong trend toward stellate trichomes with shorter rays
difference,
Q. vaccinifoL
(Manos can be used to
1992),
of populations within section Protohcdanus tliat corre-
diagnose distinct clusters
spond taxonomic units as defined upon application of a phylogenetic species
to
Wheeler
variation
Intraspecific
Q
Mohlenb
Many trichome complement; therefore, devia-
oak species possess a diagnostic
from complement can be used as an indicator of either
a particular
tions
Tucker 1963; Hardin 1975) or presence of a cryptic species
hybridization
(e.g.
Nixon and
Steele 1981).
(e.g.
Pwtohalanm
The trichome complements obsen.'ed for each species of section
uniform although variation in density and ray length, as
were type,
relatively in
400
SiDA
1993
15(3):
well as occasional intergradation between was
certain types observed
(see
Q.
Hardin
toimnteUci). (1979a) discussed trichome
variation in relation to habitat
and
difFerences suggested that the oaks of North American showed
eiisrern
Among
greater pubescence
in drier habitats. species of section
Protobi/hnu/s,
cedrownh and
Q. Q
if
jsolep.
L
Mult
2- civysolep
Point
locality of Reyes, California, the trichomes were more dense than and
usual
had
longer accounting
rays for the higher values of ray length within the
species,
but were
otherwise
similar to the typical multiradiate type. The trichomes of
individuals of were from
Q. cedroseusis identical habitats on Cedros and
Island
inland Baja 3000
California and from more mesic on
(ca. ft) sites the coast of Baja
California 300
(ca. feet). In section Protohcdamis, greater density of non-glandular
Q
^ki
density of non-glandular The
trichomes. example
best demonstrating
the
correlation of greater density of non-glandular trichomes and mesic
habitats
in
section would be
ProtohciLui/is Q. UmiemelLi, the island oak.
The
taxonomic
identities of populations from
the extremes of the range of
section
Protolkdan/zs are critical to establishing the limits of species boundaries,
in addition to the discovery of where may One
these boundaries down.
break
example
that Muller (1962) alluded
to the putative
is Q. chtysolepis of the Sierra
Mexico
s
and
Q. cedmsem/s, small, thin cupules resembling Q
those of
-fi-
multiradiate trichomes of
0. chry.solepis; therefore, this pattern of morphological
variation is best considered intraspecihc, and similar to other extreme forms
inmore
observed
northern
fQ
hi'
the result of past hybridization, no
as there is evidence of either a combination of
trichome complements
or intermediate
types.
Hybridization
Q
1960;Myattl9
11
Q. chrysolepis, Q.
t
Q
&
analysis of vegetative characters (Tucker Haskell I960; Manos and
1992)
allozyme (Manos
characters Examination
1992). of the trichomes present on
numerous
specimens
throughout
collected region
this also supports the conclu-
sion that "pure" Q. pcdmeri is absent, as only the multiradiate trichomes of
Q.
chrysolepis were observed. Based on other morphological &
characters (Tucker