A NEW SPECIES OF DIRCA (THYMELAEACEAE) FROM THE SIERRA OF NORTHEASTERN MEXICO

9 Pages·1995·5.4 MB·English

by  Guy L Nesom

NEW
(THYMELAEACEAE)
A OF DIRCA
SPECIES
FROM THE NORTHEASTERN MEXICO
OF
SIERRA
GUYL NESOM MARKH.
MAYl
.D
and El
PI
.
Depart we Botany
of
;;/
Umversi Texas
ty
of
TX
Amttn, 78715, U.S. A.
A newly scovered po pulation of Dmv?:from the Siern Madre One.ntalofTam
di 1
mexkana
D. nov.Ite xpands the
vlexico, de^ illustrated here as sp.
IS
^
Me
The new
nown
liree species and It TfiiSt of the genus k to occui in xico. s]
:
d
.imilar to D. pa/»sim of the eastern Unite States in it: long c alyx tube with .
i
ncted D.
kring limb, ,.a
1
Dmc
)f the San Fnmcisco Bay region in west-ce ntral Californ la. / Illt'Xlanu, resem
atter in its bi th whitish pubesa.nee, sessile flc)wers an d fruiits, distinct
'
oung
and twigs abaxi surfaces.
;alyces, .ersistenc pt ai id al le;if
p
from D. na ger, nar rowe r tube, shot
.pecies differs
Una pobla.cion de Di ra, reci enteimente Jescub ieria en la Sie
(
mexk.
Tamauli Mexico, d escribe iconografiElaquic:omo D.
,pas, se e
numero gen ;ndo esta pr
eleva a trese d< especi es er el ero, si( la
1 - I
Lan ecea de
Mexico. ueva especu D. pal.'turn. este los
;lel
(
mbo
bade con anado, pero su
caliz ab
li
1
con restnngi,da D. :ciden tain de la reg ion de la Bahia
es y
0,
1:
G
de parece a esta u
i-oeste
yem; con pubescenci a blanq la, flores y frut
las is iLiecir
[
y la pub escen ciapersisterite en laIS ranlas jove nes y eia el enves'de las
mn
mas
tubo largo
ocadentalis flores y
I
i
masc imen mas cortos Los dos sisten-
lobulos ;ortos, y esti lo y fib tos
.
masde25C Dtna
separadi pot iO kilometre; mexica na esta alejada
:)s s. ,
Dma
The genus has previously included only two species, D. palustris
L.
United and adjacent
scattered but widespread in the eastern States
L.,
Canada, and D. occidentals A. Gray, endemic to six counties of the San
&
(McMinn
Bay Forderhase 1935;
region west-central California
Francisco in
On
NevUng
Vogelman 1962; various manuals; Fig. a
1953; floristic 1).
botanical reconnaissance September 1994 Madre
in in the Sierra Oriental
of Tamaulipas, Mexico, we observed a population of low shrubs that we
recognized as Dtrca, but the plants were and not
sterile identifiable to spe-
March we
cies. In early 1995 were able to study the population peak
at
flowering and beginning of The Mexican most
fruit. plants closely resemble
D. but
occidentalis, there are several consistent morphological
differences
between them and
they are geographically disjunct by more than 2500
kilometers (California/Tamaulipas, The known
see Fig. closest popula-
1).
tions o{ Dirca palustns, at the southwestern corner of range in eastern
its
Louisiana, Arkansas, and southeastern Oklahoma, more than 1100
are
ki-
We
lometers disjunct from the Mexican
plants. believe that
justifiable
it is
and
desirable to recognize this Mexican population
as a species distinct
from both more
of northern
its relatives.
&
Nesom
exicana
Mayfield,
sp. (Fig.
2)
.
Woody dm
6-20
shrubs dm,
averaging 16 from
tall, ca. a single
t
branched near the base, with spreading, flexuous branches, the stem
cm
wide
3(-5) near the bcise of the plant, the ultimate branches 2-3
wide, bark smooth and gn
grayish reddish-brown,
to the current
year's
opened
gle flower,
462
SiDA 16(3) 1995
persistently loosely and sparsely pubescent, glabrous below. Leaves
deciduous, alternate, entire, at maturity broadly elliptic to slightly ovate,
mm
4-8 cm
basally rounded, long, 2.5-6.0 wide, 1.3-1.7 times longer
than wide, the largest distally situated on the branchlets, glabrous above,
the lower surface persistently sparsely strigose-sericeous on the lamina and
mm
along the veins, petioles 1-2 long. Buds covered by the enlarged peti-
mixed
(Rowers and
ole base, leaves), the apical apparently falsely terminal,
bud
the 4 scales whitish-sericeous, forming a foliaceous, deciduous involu-
cre to the dowers. Flowers appearing before or concurrently with the
leaves,
sessile in axillary and apical fascicles, deflexed to somewhat more nodding
at full anthesis, the axillary fascicles invariably producing 3 flowers, the
sometimes
apical apparently "twinned" with
fascicles (5-)6
flowers; corolla
mm
absent, not represented by infracalycular structures; calyx (7-)8-10
mm
long, petaloid, the tube narrow but widening 5-7
slightly
distally,
mm
long, abruptly expanded into a flaring limb 2-4 long, the tube/limb
mm
ratio (of length) (1.5-)1. 7-3.0, the 4 calyx 1.5-3.0
lobes long, the
and limb
lobes yellow, the tube lighter yellow and drying creamy; stamens
filaments inserted within the calyx tube
8, essentially at a single level (at
mm
mm
the throat, 2.0-3.5 below the lobe apex), the longest exserted 2-3
mm
above the calyx lobes, those inserted below the lobes 1-2 longer than
mm
below
those inserted the sinuses, the thecae 0.4-0.8 long, basifixed;
"hypogynous Heinig
disc" or "disc" (sensu 195 a ring of connate, irregu-
1)
mm
lar, slightly fleshy scales ca. 0.2-0.4 high and wide, basally adnate to
the inner surface of the calyx base; stigma minutely capitate, above the
level of the pre-dehiscent anthers on a fully elongated style, equalled or
slightly surpassed by the dehiscing anthers. Fruits drupaceous,
-seeded,
1
pyriform when
to ovoid, sessile, green young, mature fruits not observed.
MEXICO.
Typf,: Tamaulipas, Municipio. Hidal^i;(K mountainous road from
al.,n,^ Sra.
Nombres
Engracia (Tamaulipas) Dnlces (Nuevo
to LL'on)/Arro\o Ohscuro, 2.0 road mi
NE
of Los Caballos toward Canada El Mimbre, 15.0 road mi w'of lowermost crossing of
Mimbre,
arroyo El 23"59'()9"N, 99"28'37"W, 1800 m, Mar 7863
ca. S 1995, G/iy Nesoiii
with Mark Mayfieldand Greg Anderson MEXU; AAU, ANSM, ARIZ,
(hoi.otyfi;: isotvpfs:
ASU, BH, BRIT, CAS, CHAP, COLO, CONN, DAV, DUKE, ENCB,
FSU, FTG, GA,
F,
GH, GUADA, KANU,
lEB, K, LSU, M, MICH, MO, MSC, NCU, NLU, NY, OBI, OKL,
RM, TENN, UARK,
OS, OSC, USA, TEX, UAT, UC, UCR, UNL, VDB,
US, WIS,
P, S,
MEXICO.
exammed:
jllection Tamaulipas: type
locality, [sterile,
le
m,
Nesom
MayfieU/2()85 with (TEX).
—
The which Dina
of the locality. site at mexuzana was obser
m
(Arroyo Obscuro)
a steeply sloping, nooh-facing,
is
I
ding rocky The
a watercourse. area limes tone with kar
is
^he elevation near the road 1800 met but plant
is ca. ers,
a
Nesom and Mayfield, new species of Dirca from Mexico 463
Dirca extend 20 meters (elevation) above the road and to at
to at least ca.
we
may
80 meters below They well occur over a broader area than
least
it.
where
investigated, particularly downslope, but this the only locality
is
from Engracia
Dirca was encountered along the 35 kilometer road Sta. to
Dulces Nombres. Indeed, we found no other site along this road with a
and
similar physical floristic definition.
The dominant canopy trees at the site are Carya ovata (P. Miller) K.
&
Koch, Pmuspatula Schlecht. Cham., Pseudotsuga menziesii (Mirb.) Franco,
&
20-25
and Quercus launna H. B. Large trees of these reach about meters
height, with Pseudotsuga perhaps reaching 30 meters. Judging from
in tall
stumps in the area, particularly large individuals (presumably o^ Pseudotsuga
and Pmus) have been removed by logging. Large trees oiCarpinus caroliniana
Uqmdambar the but do not
Walt, and styraciflua L. are scattered at locality
The woody understory includes the
reach the height of the canopy.
full
Garrya
Muell.-Arg.,
Cornus urbimana Rose, Croton virletianus
following:
macrophylla Benth., rubra Wats., Litsea pringki Bartlett, Persea
Ilex aff. S.
Most
Hu, and Taxus Schlecht.
pododaema Blake, Philadelphus caldcolus globosa
bud
and were beginning break
of the canopy species are deciduous just to
predominance evergreen
the understory includes a of species.
at this site;
conspicu-
Arboreal bromeliads, including three species of Tillandsia, are
among
the
Ferns form a major part of the herbaceous flora at this site;
ous.
common
most are species of Adiantum, Woodivardia, Botrychium,
common
and Polystkhum. Other herbs include
Phanerophlebta, Polypodium,
and
Chmaphila, Chiropetalum, Goodyera, Sisyrinchium, Stachys.
species o^
—
We
and observed
population biological observations.
Characteristics of the
800-1000 plants (by estimate) at the Dirca site, where they occur for about
300 meters along the road and adjacent slopes on the east side of the water-
more open-canopy
They microsites,
tend be densely clustered in
course. to
We
more did not unearth any plants,
singly and scattered over a larger area.
A
but there was no indication that they reproduce clonally. report of rhi-
&
(McMinn
zome Forderhase 1935) has not
production D,
in occidentalis
more (Spongberg comm.).
been corroborated by recent observations pers.
synchronous
The population of Dirca mexicana strongly in
entire is
we would
flowering. Had we arrived 3 or 4 days later, it is likely that have
appear wither quickly
been unable to observe floral features, as the flowers to
The appear be weakly
with the onset of fruit maturation. flowers to
may
protogynous and there evidence that they also be self-compatible.
is
before development of the calyx, the style (with apical stigma)
Initially, full
At time, the stigma
usually elongated past the level of the anthers. this
is
we
appears slightly moist and presumably receptive; also observed that
many
at this stage appear to have pollen attached. At anthesis, the
full
filaments have raised the open anthers to the level of the stigma or slightly
beyond
Further, there time separating
it. is little intial receptivity of the
stigma and
dehiscence of the anthers, and distance between the stigma
little
and open
anthers.
mm
Visiting the flowers were one species of bee (individuals
7 in
ca.
and
length)
at least four species of butterflies. Pollination effective, judg-
is
from
ing the apparently ubiquitous deposition of pollen on the stigmata of
pre-staminate flowers. Bees and were probing
butterflies inside the flowers,
and although seems
highly likely that nectar was available them (prob-
it to
ably produced by hypogynous
the production was
disc), not evident
its in
numerous flowers that we examined. Nor could we any
detect fragrance
(D. ocddentalis was noted by Howell [1970} to be fragrant). Fruit matura-
tion was beginning only on a few plants and we were unable make an
to
estimate of the success of fruit and seed production.
We
did not determine what
feature or features account for the remark-
able o^ Dirca
rarity mexicana. All of the other species yet identified from
—
Arroyo Obscuro
are found in other sites in the same general area none
Dina
except the could be considered (but comments below
rare see regard-
ing Viburnum). however,
Rarity, also is a feature of both other species of the
genus, particularly D. D'ma
occtdentalts (Stebbins 1942; Johnson
1994).
uncommon
palustns widespread but
of
occurrence.
is —
Morphological amipansons. Dirca mexicana resembles D. most
ocddentalis in
of the features that have been used to distinguish the from D.
latter palustris
(Vogelmann
1953; see key below): vestiture, presence or absence of pe-
a
duncle and pedicel, and the morphology The
distal of the calyx. flowers of
D. mexicana, however, more
are similar in general configuration to those of
D. palustris: both have a relatively long and narrow tube with
a shorter,
abruptly widening
limb,
the staminal filaments are inserted above the
middle
of the calyx, and the and
style anthers are exserted for a relatively
short length. In D. occidentalism the tube shorter than the broadly funnel-
is
form
limb, the staminal filaments are inserted below the middle of the
calyx, and the and stamens Vogelman
style are long-exserted.
(1953, 80)
p.
emphasized
the taxonomic
usefulness of the of filament which
level insertion,
turn
in is indicative of the throat position and flower shape: "In most
in-
stances this character alone sufficient to distinguish the two
is species."
The
comparative
illustrations furnished by Vogelmann, however, do
not
accurately represent this difference, nor does the detailed illustration of D.
Holm
Cronquist
palustris in (1981, p. 635); those by (192 are more simi-
1)
own
lar to our observations. Differences between the new species and D,
Bud wn own young twigs nd both
with bro or reddish-br piibescence;
scales ai
whole
leaf surfaces complfitely glabrous; 3wers ind fruirs pedicellate, th.e
fl. I
ma
pedun merely crenulate-undulate with-
cluster often .culate; calyx rgin
;,
United D, palu.
out distinct lobes;.=astern St:ates...
Bud with whitish pubescence youn, twigs and abaxial leaf:surfaces
scales g
;
and anc[deeply
persistently pubesci;nt; flowers fruits se ssile; calyx distinctly
Bay region of Califori or northeastern Mexic
iia
nm 4-
imb
Calyx tube 2-4 long, broade ned a broadly funnelform
2. inl:o
r 1
mm
6 long; stanamal filaments uiserred below the middle of the calyx.
mm
and
3_4(-5) at)ove th flower at maturity; st yle
.e
mm
Bay
stigma (l-)2-4 above the nthers maturity; San Franci SCO
a at
—
seem point provide
Bwgeographk does not possible at this to
pattern. It
among
morphologically based hypothesis of relationship the three spe-
a
ofDirca, because the genus appears to be relatively isolated, its closest
cies
(and thus the evolutionary polarity of character states) difficult to
relatives
Domke Nevhng
surprising to find a
1934; 1959).
specify (see Still, it is
view
between D. mexicana and D. in
greater overall similarity occidentalism
between
of the well-known pattern of close relationship and disjunction
species of the eastern and southeastern United States and the sierra of north-
&
Graham immediate
Mexico (Miranda Sharp 1950; 1973). In the
eastern
from
numerous disjunct their
area of Dirca mexicana are species that are
Carya
United Carpinus caroliniana,
primary range the eastern States
in (e.g.):
W. Desmodium (Muhl. ex
Barton, glutinosum
Chimaphila umbellata
ovata, (L.)
and
Willd.) Wood, Liquidambar styraciflua, Pedicularis canadensis L.,
and
(Michx.) Schott. In addition, there a rare yet
Polystichum acrostichoides is
(Nesom
undescribed species oi Viburnum in prep.) in the close vicinity that
V
most obovatum Walt, of the southeastern
apparently closely related to
is
from same
United Another recently recognized, disjunct species the
States.
Nesom
(May and submitted),
area of Tamaulipas, Scrophularia sp. nov. field
and
closely similar to marilandica L. of the eastern U.S. species S.
S.
is
&
Cham. Taxus one of the
Schlect. of the Pacific region. globosa,
californica
widely separated
understory species at the Dirca site, also has close relatives
and western United
the eastern States.
in
Biotic disjunctions between the eastern and western United States, similar
common
known
well though not particularly (e.g.,
to that in Dirca, are
Wood added
Sharp 1951; 1970), and other examples can easily be (e.g.,
This pattern emphasized by the recent discovery of
Sericocarpus, lonactis). is
(
466
SiDA 1995
16(3)
a second species ofNeu^isia in California (Shevock et 1992), both species
al.
extreniely rare. In contrast, clearly established disjunctions of extant plants
from the western United States to the Sierra Madre Oriental of Mexico
are
unknown Numerous
to us. disjunctions exist between the Sierra Madre
Oriental and S.M. Occidental, but most or all of these appear to be deriva-
McVaugh
tives of the general pattern described by where
(1952), the evo-
A
lutionary antecedents occupy a more southern position. few Mexican
species have a broken but somewhat continuous from
still distribution the
through
eastern sierra northern Coahuila into the mountains of southwest-
New
ern Texas and southeastern Mexico
Populus Michx.,
(e.g., tremuloides
Nesom
Pseudotsuga menziesii [Mirb.} Franco, and see 1993).
Dm-^
In the broadest view of the origin of mexicana, the simplest hy-
pothesis that belongs the element with
is it to floristic closest evolu-
its
tionary ties to the flora remaining in the southeastern United States, the
geographic continuity between them probably established during the middle
Miocene (Graham The
to late 1973). disjunction between D. and
palustns
may
D. ocadmtaln be considerably
older, as a vegetation probably includ-
ing these species was spread across North America through much of the
Tertiary, beginning as early as the Eocene (Graham 1972, 1993). In a con-
Axelrod
trasting view, (1975) hypothesized
that the closely related dis-
juncts found in eastern Mexico, the Appalachians, and the West coast of
United
the States represent remnants of continuous
a forest earlier spread
Mexico and more
into simultaneously fragmented
as a result of a spreading
dry climate in the mid-Oligocene. Evaluation of the theory
latter
diffi-
is
cult at present because of the lack of evidence northern temperate
for
ele-
ments American
in Latin prior to the Late Tertiary. These elements have
not been rec covered from the Oligo-Mi ocene Sim ojove Group of Chiapas,
1
M
Mexico; appe Panam;
Q^uereus first ars in a in the 10-Pli ocene, aiid in South
America
arrives by about one mi Uion ago nd
A//,ins years a Q^uen.us not until
Many Ame
about 340, )()() years age east(;rn North rica disj uncts were
).
Mc
present in eastern _^xico by th< middle Plio cene, nd global
a
;
M
paleotemper ature history suggests that cooling in the middle iocene may
have been appropriate time
ar for principal introduction.
thei:
1 r
We
thank Greg Anderson
help with
for collecting, observations on
floral
new We
biology of the species and his comments on the manuscript.
are
grateful to Billie Turner, Steve Spongberg, Alan Graham, and Simpson
Beryl
comments
for on the manuscript, John Gene Wofford and Bob
to Taylor,
Krai, and Sidney McDaniel information on Oklahoma,
for Dirca Ten-
in
and
nessee, Mississippi, Linda Vorobik
respectively, to for the illustration,
and to Jaime Hinton for his encouragement and company on and spring
fall
fDircafromMex
and example
the of
illecting trips for his
nuing
vigor.
New
York
Press
y
1934 Untersucliun^en die stem itischeundgeographischeGhederun^
Liber
s>
1972 Outhnt ot tlu oiuin in historit d reLo^ninon of flonstic iffinitie:
1
AmeiRi A Crihim
Asii ind eastern Noirh In (cd rionstics ind paieo-
)
_
197^ Historv the irboitscuu tempLrite element in the northern Latir
ol
md
bioti In A Grihim cd Vci^etuion Ve^et ition History ol Northerr
nLeuh
JOHNSC \ lU, 199 PliUuolthe\Ve-,tL.
1
M
A
new
4LSOM Submitted
ind
,) I [
,
Mex
^'Trom
>
Dma
McMiN ^
[OR DLRHAS, 19.5 on ouidentalis
N u.d Jotes
1 }
1 1 I I
Midiono 120
Gra>
>
Vm
M< tP,u.u
sttd phyiot^env
n'.'h'AmuK Hut
1
M
A Ch^ru
1950
Mi'iMN, 'ind Rr tenstic
1
)
199''
'
NLs'ni "(Vj' nirc e species ot Astc I A^ste
!
Coalnull Mexico Fhyi ologia 74 296-3 04
onofthegenusD^/;^#i/
m
196/ The
tlie
'
Dina
(Thymeleaceae).
ouidentalts
J
the southern Appalachians and
;n