DISTRIBUTION AND MORPHOLOGICAL CHARACTERISTICS OF ARCEUTHOBIUM HONDURENSE AND A. NIGRUM (VISCACEAE) IN MEXICO

2012·5.7 MB·English

by  Robert L Mathiasen

AND MORPHOLOGICAL OF
CHARACTERISTICS
DISTRIBUTION
AND MEXICO
HONDURENSE NIGRUM
(VISCACEAE) IN
ARCEUTHOBIUM
A.
Shawn
Mathiasen Kenaley Brian Reif
C.
Robert P.
L.
School ofForestry Department of Plant Pathology School ofForestry
and Plant-Microbe Biology Northern Arizona University
Arizona University
Northern
Arizona 860
86011 Cornell University Flagstaff, U.S.A.
Arizona U.S.A. 1 1
Flagstaff,
New
York 14853 [email protected]
[email protected] Ithaca, U.S.A.
[email protected]
ABSTRACT
RESUMEN
&
Tfe genus (Hawksworth Wiens 1996) that are
Arceuthobium (Santalales: Viscaceae) consists of 42 species
aenal Many commonly known as dwarf mistletoes, are
parasites of Pinaceae or Cupressaceae. of the species,
&
cognized Morphological
Wiens Mathiasen 2008).
as serious pathogens (Hawksworth 1996; et al.
forest
characters produced on male and female plants, leaves
consistent throughout the genus include small flowers
&
Wiens The
reduced (Hawksworth 1996).
to squamate
^ scales, and morphologically similar bi-colored fruits
8enus extreme morphological reduc-
long been group because of the
considered a taxonomically difficult
&
’'°n dialed (Hawksworth
between species
with the parasitic habit and the morphological similarities
lens 1996 amount of variation in
Factors and identification include a large
)- that complicate classification
Two
morphology
species
and occasionally overlap.
periods that
geographic flowering
distributions as well as
exem
' 1 Phfy morphologically similar dwarf mistletoes
the problems with identification of
associated field
^
&
in southern Hawksw. Wiens (Honduran dwarf mistle-
and
hondurense
central Mexico: Arceuthobium
106 3ndA &
"igrum Hawksw.
Wiens dwarf
- (black mistletoe).
Journal of the Botanical Research Institute of Texas
6(2)
&
Honduras (Hawksworth
from Wiens
was described central
Arceuihobium hondurense originally 1970)
and
and thought to be extremely rare, even on the verge of extinction due to rapid extensive harvesting of
its
&
was
Honduran dwarf found
pine hosts (Hawksworth Wiens 1972). However, mistletoe later to occur from
northern Nicaragua, through much of Honduras into Chiapas, Mexico and as far north as central Oaxaca (Ma-
&
Mathiasen Mathiasen
thiasen et 2001; Mathiasen et al. 2002a; Mathiasen et al. 2003; et al. 2006; Melgar
al.
Wiens Mathiasen Another dwarf mistletoe, originally described as A. hawfesworthii Wiens
1977; et al. 2003).
and C.G. Shaw (Hawksworth’s dwarf mistletoe), was recombined as a subspecies of A. hondurense (Mathiasen
2007). Therefore, A. hondurense presently consists of two subspecies: A. hondurense subsp. hondurense which
occurs from Nicaragua north Oaxaca, Mexico (Mathiasen et 2010) and A. hondurense subsp. hawksworthu
to al.
&
(Wiens C.G. Shaw) Mathiasen which primarily distributed in the Mountain Pine Ridge area of Belize
is
(Mathiasen 2007), but also has been reported from central Honduras (Mathiasen et al. 2002b).
Because plants of Arceuthobium hondurense subsp. hondurense (hereafter referred to as A. hondurense) art
similar in size and color to those of A. nigrum, determining the geographic distribution of these species in
&
southern Mexico has been (Hawksworth Wiens 1989, 1996; Mathiasen et 2001, 2002a, 2003,
difficult al.
Although nigrum was thought be from northern Durango, Mexico into southern Mexi-
2010). A. to distributed
&
co (Hawksworth Wiens 1996), it is now thought to be distributed only as far south as central Mexico (Ma-
We
bloom
thiasen et 2010). Further, both A. hondurense and A. nigrum produce red flowers that in the fall.
al.
we
have collected additional morphological data for A. hondurense and A. nigrum since 1998. Here report our
findings and discuss the distribution of these dwarf mistletoes in Mexico based on our field observations and
morphological measurements. Because (Mathiasen Nickrent 2004) have success-
prior studies et al. 2003; et al.
A
DNA
fully used ribosomal (rDNA) sequence information to discriminate between A. hondurense and ni-
we
grum, conducted additional analyses of the internal transcribed spacer (ITS) region for several populations
may
of both species, particularly populations in central Mexico where these species be sympatric (Nickrent et
2004). In addition, because A. vaginatum (Willd.) Presl subsp. vaginatum (Mexican dwarf mistletoe) is also
al.
we
morphologically similar to A. hondurense as well as A. nigrum, and often confused with them, have provided
on how how-
information to distinguish these species from A. vaginatum. The primary objective of this study,
—
ever, was to provide additional data on how to discriminate A. hondurense from A. nigrum and vice versa-
and in so doing, better determine their geographic and host ranges. Morphological data and ITS sequences for
A. vaginatum were taken from Hawksworth and Wiens (1996) and obtained from GenBank, respectively.
MATERIALS AND METHODS
Morphology and
Phenology
To compare morphological characters we sampled 16 populations of Arceuthobium hondurense (two fro®
Oaxaca, Mexico, one from Nicaragua, and 13 from previous work by Mathiasen and 14 populations
(2007))
both
A. nigrum from throughout its geographic range (Fig. Plants were measured from the type locality for
1).
&
population,
mistletoe species (Hawksworth Wiens and From each
1965, 1970, 1977) (Fig. locations 6 23).
1;
10-20 male and 10-20 was used for
female plants were collected and the dominant shoot from each infection
morphological measurements. Wiens (1996) far
Characters measured were those used by Hawksworth and
taxonomic and color
classification of Arceuthobium: and width,
height, basal diameter, third internode length
width
of male and and
female mature
plants; fruit length, width, and color; seed length, width and color; length
of staminate stamina*
spikes; staminate flower diameters for 3- and 4-merous length and width of
flowers;
2
flower within
petals; and, anther diameter and measured
anther from were
distance
the petal Plants
tip.
micromeW
hours
after collection using a digital caliper and a Bausch and Lomb 7X hand equipped with a
lens
Staminate spike and flower measurements were made during peak and and seed measure-
the of anthesis fruit
ments were made exam-
during the peak of seed One-way (ANOVA) was used to
dispersal. analysis of variance
between
ine the variance in the above
characters for A. hondurense and A. nigrum and significant differences
s»
means
were determined using = All
a Tukey’s honestly 0.05).
significant difference (HSD) post-hoc test (a
tistical analyses were performed usingJMP
8.0.2 software (SAS NC).
Institute, Cary,
601
Because Arceuthobium hondurense and A. nigrum are poorly
the times of flowering and seed dispersal for
& made
known were
(Hawksworth Wiens observations of the phenology of these taxa dur-
additional
1996),
ing the during the early spring of 2011.
spring and and 2010 as well as
fall of 1999, 2003, 2005, 2007, 2008,
DNA
Extraction and
ITS Sequencing
^nples of DNA were obtained from and specimens, each representing a geographically separate popu-
six
five
!ati°n, of and voucher number for each speci-
Arceuthobium Locality
hondurense and A. nigrum respectively.
,
DNA DNeasy™
"•en (bold was extracted using the Plant
print) are presented For each specimen, total
in Fig.
1.
DNA
MlruKit purity and concentration
(Qiagen, CA) manufacturer’s instructions.
Valencia, according to the
Were
Wilmington, DE).
quantified NanoDrop ND-1000 (Thermo Fischer Scientific,
for each sample using a
^'kngth, ITS rDNA and ITS2) were PCR-amplified using the primer
sequences gene,
(comprising ITS1, 5.8S
P® pL
1 IBS PCR were carried out in 25 reaction
1830for and amplifications
26S 40rev (Nickrent 2004).
et al.
pL
"jhuures Mix Biosystems, Foster City, CA), 0.5
containing pL 2X AmpliTaq Gold® Master (Applied
12.5 of
ofeach20pM DNA.
genomic
pL 8-78 ng/pL) of
-2-18 ng of
primer, pL and (0.25
11.25 nuclease-free water,
602
PCRs were performed in an Eppendorf Mastercycler® pro thermal cycler (Eppendorf, Westbury, NY) with the
following cycling parameters: initial hold for 6 min. at 95°C; 5 cycles at 94°C for 30s, 55°C for 30s, and 72°C for
min.; 33 cycles at 94°C for 30s, 48°C for 30s, and 72°C for 1 min.; and, a final extension step of 72°C for 10 min.
1
Blank reactions minus genomic DNA) were run concomitantly to check for contamination of the reagents.
(i.e.,
The of each PCR product (bp) was checked separately by ultraviolet fluorescence after 1.2% agarose
size
TAE and with GelRed™ (Phenix Research Products, Candler, NQ.
gel electrophoresis in 0.5x buffer staining
pL pL
Amplification products were purified directly from reactions using ExoSAP-lT (0.4 per of reaction prod-
USB OH) and normalized 130 ng per sequencing reaction. Sequencing was carried
Cleveland, to out
uct; Inc.,
DNA
DNA
using a BigDye terminators sequencing kit (Applied Biosystems), ABI 3730 sequencer, and the
above forward and reverse primers. PCR products were sequenced in both directions. Sequences were proof-
read and assembled in CodonCode Aligner (CodonCode Corporation, Dedham, MA). Boundaries to the 5-
and 3'-region of ITS1 and ITS2, respectively, were previously identified by Nickrent et al. (1994). ITS sequences
GenBank.
for A. hondurense (n=5) and A. nigrum (n=6) produced in this study were deposited in
Phylogenetic Analysis
GenBank
and from
ITS sequences Arceuthobium hondurense and A. nigrum obtained in this study (A. hondu-
for
rense AY2888263 and A. nigrum AY288271) as well as A. vaginatum subsp. vaginatum (AY288286 and
AY288287) and A. douglasii Engelmann (L25687; outgroup) were included in the dataset. Sequences were
CodonCodon
aligned using ClustalX ver. 2 (Larkin et 2007) and visually edited as necessary in Aligner.
al.
DNA
Maximum PAUP* The
Likelihood (ML) were constructed using 4.0bl0 (Swofford 2003). substitu-
trees
tion model TIM2 and the parameter estimates for tree reconstruction were determined using the Akaike Infor-
were
mation Criterion (AIC; Akaike 1974) as implemented in jModelTest 0.1.1 (Posada 2008). All nucleotides
were
included in the phylogenetic analysis; gaps were treated as missing characters. Heuristic searches per-
formed with 200 replicates of random sequence addition and tree bisection-reconnection (TBR) branch swap-
ping. Branch support was evaluated using 1000 bootstrap and 10 random additions of sequences per
replicates
pseudo-replicate. Inter- and intraspecific genetic distances were also examined using Kimura’s two-parameter
model (K2P; Kimura 1980) for base substitution as implemented in PAUP*.
&
was The
Bayesian analysis also performed using MrBayes (Huelsenbeck Ronquist 2001). best-fit
3.1.2
DNA
model for substitution was determined as described previously; however, Hasegawa-Kishino-Yano (HKY;
Hasegawa et al. 1985) model and parameter estimates were determined using the Bayesian Information Crite-
rion (BIC; Schwarz 1978). One cold and three heated Markov chain(s) were run, and samples were taken every
6 model
100 generations over 5.0 x 10 generations. The potential scale reduction factor (PSRF) for each of the
parameters was > 1.0 when the program was terminated. Stationarity was accessed by examining the average
using
standard deviations of frequencies and Bum-in was determined
split likelihood values. value (10%)
&
Drummond
Tracer vl.5 (Rambaut The emaining 50% majority rule
2009). r trees were used to calculate a
consensus and determine
tree to the posterior
probabilities.
AND
RESULTS
DISCUSSION
Our by
measurements
of Arceuthobium hondurense indicate forms larger plants than previously reported
it
ma»-
Hawksworth and Wiens cm
with a
(1970, 1996); they reported plant heights averaged approximately 14
mum
We
height of 21 cm, but we measured plants (male and female combined) averaged 22 cm. found
that
maximum
some male
plants in Chiapas, Mexico were cm in
that over 65 in height (Table The discrepancy
1).
Honduras
heights probably Hawksworth
is related to and Wiens only measuring specimens from central
A*
where plants were generally smaller than in southern Mexico Mathiasen 2007).
(Mathiasen 1999;
et al.
ap
mean
basal diameter of dominant shoots was the same as reported by Hawksworth and Wiens (1996);
mm. Hawk'
we
proximately 5 However, measured some mm, while
shoots with 13
basal diameters of nearly
m^
mm
sworth and Wiens maximum
(1996) only reported a of 9 The means and ranges for
for this character.
& W*®
5
of the remaining morphological
characters were (Hawksworth
similar to those previously reported

by Arceuthobium
Previously, Mathiasen et al. (2003) listed the pines parasitized hondurense in Central
America and Chiapas, Mexico. Our observations support their findings, except that A. hondurense also
parasit-
&
we
Schiede ex Schlechtendal Chamisso in central Oaxaca. Although have only
ized Pirns teocote observed
A. hondurense infecting this pine in one location north of Ixtlan (Fig. location 13), the level of infection
1,
(>
was
90%) indicated Pinus teocote was a principal host. This population misidentified as A. vaginatum subsp.
vaginatum by Hawksworth and Wiens (1996), as our morphological and ITS analyses indicated this population
brown
was indeed A. hondurense. Mistletoe plants on P. teocote at this location were dark to black, similar
in
color to A. vaginatum, but male plants flowered in the fall producing dark red flowers. Large male plants at this
P
locality also had swollen nodes and parasitized tecunumanii Eguiluz et P. Perry, a principal host of A. hon-
J.
was
durense elsewhere in southern Mexico (Mathiasen et ai. 2003). In addition, A. hondurense found parasitiz-
&
ing lawsonii Roezl ex Gordon Glendining in central and northern Oaxaca. Although Hawksworth and
P.
Wiens (1977, 1996) reported A. hondurense (but identified as A. nigrum parasitizing Pinus oaxacana Mirovand
)
&
we
patula Schiede ex Schlechtendal Chamisso in Chiapas, did not observe these host-mistletoe combina-
P.
tions during our work in southern Mexico.
field
Arceuthobium nigrum is morphologically very similar to A. hondurense. Both species produced relatively large,
&
A
dark brown to black plants on their pine hosts (Hawksworth Wiens 1996). Male and female plants of
ni-
cm
grum
averaged nearly 25 and 18 in height, respectively, but were not significantly larger than A. hondurense
(Table 1). It is difficult to compare our results for plant heights with those of Hawksworth and Wiens (1996)
maximum
because they only provided a range of heights for A. nigrum (15-35 cm, = 45 cm). However, the larg-
We
est plant we measured for A. nigrum was a male over 53 cm from Puebla, Mexico. also found that the
tall
two-mm mm) mm,
basal diameter of shoots averaged larger (7.6 than that previously reported (5 Hawksworth
&
maximum
Wiens
1996) with a basal diameter nearly twice that described by Hawksworth and Wiens. Mea-
mm)
surements of the third intemode widths also indicated that A. nigrum produced thicker plants (about 5
than what Hawksworth and Wiens mm)
reported (about 4 mm). The means the basal diameters of male (7
for
A
mm)
and
female and
plants (7.8 third intemode widths ofA. nigrum were significantly greater than those for
hondurense mean
(Table 1). Furthermore, the length of the third internode of female plants of A. nigrum (16.5
mm)
was mm)
significantly longer than those of A. hondurense (13.8 but not the mean length of the third inter-
node male
of
plants.
The
only flower characteristics Hawksworth and Wiens reported Arceuthobium nigrum was the diam-
for
eter of 3-merous flowers mm), which was mean 3-merous flowers
(3.5 sUghtly larger than the diameter for the
we
measured mm). Our
(3.2 observations indicated that A. nigrum commonly produced 4-merous flowers also,
we mm
sampled
thus, these flowers and found the
they averaged nearly 5 in diameter (Table Collectively,
1).
mean
diameters of 3 and 4-merous flowers of A. nigrum were than those of A. hondurense.
significantly larger
&
were
Petal sizes also when (Hawksworth
relatively large for A. nigrum compared to other dwarf mistletoes
We mm A
Wiens
1996). found
petals longer than 2 and than those for
nearly as wide, both significantly larger
hondurense (Table Another key geo-
throughout
1). characteristic of A. nigrum flowers that was consistent its
graphic range, was ob-
that the adaxial surface of its petals was dark red. While this characteristic was easily
&
and
served, is similar to flowers for A. hondurense, a review of the (Hawksworth Wiens 1989, 1996)
literature
on
nigrum
A. revealed
that the petal color, as a diagnostic character, had never been mentioned before,
Arceuthobium
nigrum were remarkably dwarf mistletoes
glaucous and compared other
large to
The mean
length was mm, we found
nearly 7 which what Hawksworth However,
f it and Wiens
is reported.
mm
fruits 8.8 in length compared width
rr to 9.0 by Hawksworth and Wiens the average
In contrast,
(1996).
of we amined was mm) We
fruits
larger than mm).
(4.1 that reported by Hawksworth and Wiens
(3.5
were
lat shorter, but wider on Wiens (1996)
average than those examined by Hawksworth and
ho*
fruit length and width
• of A. nigrum were hondurense,
significantly larger than those of A.
and
length width
of seeds were
i similar for both species (Table
1).
,
605
we
phenology of A. nigrum requires additional observations as were unable to confirm the incidence
The
—
by
periods one in March-April and one in September-October—as reported previously
flowering
two
of
We
and Wiens (1989, 1996). examined male plants of A. nigrum at several localities in mid- to
Hawksworth
during 2003, 2005, and 2007 as well as in early April 2011 and never observed open flowers. Fur-
late-March
Our
March
staminate flowers did not appear to be approaching anthesis in late or early April. field
thermore,
November
however, indicated that flowers beginning in mid-September and continued into in
observations, it
and
Mexico, while in central Mexico, A. nigrum flowers in late-September continued into at least
Durango,
Mex-
Peak flowering was in early October in Durango; however, the peak flowering period in central
January.
poorly understood. Seed dispersal initiated in early September and peaked in mid-October continu-
ico is still
mid-November in Durango and elsewhere in central Mexico.
ing to
Our observations of pines infected by Arceuthobium nigrum in Mexico did not reveal any additional
field
&
The principal hosts of A. nigrum in Durango were clearly Pinus leiophylla Schiede ex Schlechtendal
hosts.
&
P
Engelmann by
Robinson Femald, and chihuahuana as reported
Chamisso, lumholtzii B. L. P. teocote,
P.
Engelmann and
Hawksworth and Wiens (1996). This mistletoe also been reported to rarely infect P. arizonica
&
we on
Mexico (Hawksworth Wiens but have not observed these infre-
Blanco in northern 1996), it
cooperi
P.
&
P Chamisso was
quent hosts. In central Mexico its principal host was teocote. Pinus patula Schlechtendal a
we
secondary host at several locations in Hidalgo and Puebla. While agree with the classification of P. pseu-
&
we
(Hawksworth Wiens were unable to verify
dostrobus Lindley as an occasional host of A. nigrum 1996),
P
whether P montezumae A. B. Lambert was also an occasional host. Moreover, we did not observe any mont-
ezumae at the location where Hawksworth and Wiens reported an infestation of A. nigrum in Hidalgo nor in
P
Veracruz where we found mistletoe-free montezumae growing near teocote severely-infected with A.
large, P.
Hawksworth
Although
montezumae nigrum needs further study.
nigrum. Therefore, the susceptibility of to A.
P.
nigrum
and Wiens (1989, 1996) reported that both P. lawsonn and P. oaxacana Mirov were principal hosts of A.
Oaxaca and
by hondurense in
this host susceptibility classification was based on infection of these pines A.
Chiapas, (Mathiasen
respectively et 2003).
al.
DNA
Analyses
DNA
and vaginatum occurred in
nigrum, A.
sequence analysis demonstrated that Arceuthobium hondurense, A.
and nigrum
hondurense A.
three well supported clades All samples identified morphologically as A.
(Fig.
2).
yielded a 627 and 623 bp fragment, consisting of the 3'end of the 18S (4 bp), complete ITS1-5.8S-
respectively,
HS2 were
sequence (604 and 600 and the 5'end of the 26S (19 bp). Four of five sequences for A. hondurense
bp),
identical (mean K2P value= however, RLM 98107 differed by an A/G nucleotide change at positions 22
0.0017);
K2P
and 40 (mean value= 0.0018); except
in 1TS1. Similarly, ITS sequences for A. nigrum were nearly identical
649
for A/T nucleotide changes 508 The alignment for phylogenetic analyses consisted of
position in ITS2.
at
characters including those of A. douglasii and A. vaginatum. Of these characters, 574 were constant, 50 were
tree supported >98% and posterior probability values equal
three with bootstrap values
distinct clades
(Fig. 2)
nigrum
to morphometric data as A. hondurense or A.
1.00, respectively. Each plant identified according to
(DLN
formed a (RLM Nickrent 2004) or A. nigrum 2019,
distinct clade with either A. hondurense 0136, et al.
Nickrent hondurense and A. vaginatum by ap-
et al. 2004). Sequences of A. nigrum differed from those of A.
mean
proximately 43 = mean K2P value= 0.0775). Likewise, the
nucleotides (mean nucleotide difference 43.07,
number was (mean K2P value= 0.0224).
of and vaginatum 13.0
nucleotide changes between hondurense A.
A.
(GenBank
Nickrent Veracruz based on molecular data
hondurensemay occur in
etal. (2004) reported thatA.
accession no. L25693; voucher DLN but our results did not support this. Plants collected south of Sierra
2018),
A
de DLN
comm.),
Ua (RLM 2018 Nickrent, pers.
A (D.
where Nickrent collected
1083), the approximate location
RLM
Were
from 1083
sequences generated
morphologically As the ITS
suspected,
similar those ofA. nigrum.
to
not shown),
identical to L25693 not shown). However, in a separate phylogenetic analysis (data
(data
these GenBank accessions of A. du-
collections/sequences were nigrum (AY288271) as well as
unrelated A.
to
r &
&
®«go«eHawksw. and vaginatum. Nickrent previously
A.
Wiens, Hawksw. Wiens, A. hondurense,
A. gUlu

607
nigrum Mexico
A. in
DLN 2018 (L25693) as either A. vaginatum (Nickrent et 1994) or A. hondurense (Nickrent et al.
al.
identified
DLN
(RLM and
1083 and remains unresolved
The species identity of this mistletoe 2018), therefore,
2004).
further study.
requires
SUMMARY
and
Arceuthobium hondurense, A. nigrum, and A. vaginatum are morphologically similar often diffi-
Although
distinguish from each other in situ, there are several diagnostic characteristics that can be used to iden-
to
cult
m Mexico where they may be sympatric. Our results support the classification of these taxa
he in central
tify t
and the principal morphological and physiological characters that can be used to distin-
species
distinct
as
summarized in Table While the overall height of male and female plants and their
guish these species are 2.
cannot be used to easily separate these species, A. hondurense is a more slender plant than both A. nigrum
color
and vaginatum. also has swollen, rounded nodes, particularly near the base of older plants. This character-
A. It
rounded nodes
most evident on older, male plants. In contrast, A. nigrum and A. vaginatum lack swollen,
istic is
near the base of plants.
Another key of A. hondurense that separates from the other dwarf mistletoes is the width
characteristic it
staminate spikes. While the length of staminate spikes often is too variable to be of any diagnostic value,
of its
mm)
compared nigrum
(mean those of A.
the width of the staminate spikes of A. hondurese are thinner 1.7 to
mm) nigrum and hondurense gener-
andA. vaginatum mm). Furthermore, the staminate spikes ofA. A.
(2.9 (2.0
do not form secondary branches, while those of A. vaginatum typically do.
ally
Arceuthobium hondurense primarily forms 3-merous flowers, and occasionally 4-merous flowers, but A.
nigrum andA. vaginatum commonly form both 3- and 4-merous flowers. Although the adaxial surface of petals
of male flowers for A. hondurense andA. nigrum is distinctively dark red, the 3-merous flowers ofA. hondurense
are smaller (2.5 mm) on average than those of A. nigrum (3.5 mm). The color of male flower petals of A. vagina-
mark-
turn, however, is dark brown to green. While the fruits of both A. hondurense and A. nigrum are usually
vaginatum. Addition-
edly glaucous, the fruits of A. nigrum are larger than those of A. hondurense as well as A.
August through September and October, but A.
ally, A. hondurense and A. nigrum primarily flower from late
&
Wiens Additional observations of
vaginatum from March (Hawksworth 1965, 1996).
flowers through April
Hawksworth and Wiens
by
A. nigrum spring as reported
are necessary determine flowers in the
still to if it
Durango, Mexico, do not sup-
(1989, 1996). Our observations of A. nigrum over multiple seasons and years in
can be
port a spring flowering period for A. nigrum. Furthermore, our analyses confirm that these species
readily distinguished using ITS-rDNA sequences as previously demonstrated by Nickrent et al. (1994, 2004).
on Mexico. In
The host may help separate them, depending the locality in
specificity of these mistletoes
Arango, Arceuthobium nigrum and vaginatum both parasitize teocote, but P. teocote is less susceptible to A.
A. P.
P
&
vaginatum vaginatum does not parasitize
Wiens Moreover, A.
secondary (Hawksworth
(a host) 1996).
Iftophylla, P A. nigrum. In central Mexico, the
lumholtzii, nor chihuahuana, which are all highly susceptible to
P.
Now
hondu-
Principal host by A. vaginatum there. that A.
of A. nigrum but patula also infected
is P. teocote, P. is
rense has been P Oaxaca, Mexico, infection of this pine cannot be used
discovered in
severely infecting teocote
and
10 distinguish both flower in the have red flowers,
A. nigrum from A. hondurense, since these mistletoes fall,
are the best char-
similar in and and staminate spikes, therefore, are likely
size color. The width of internodes
acters and will also assist in dis-
for distinguishing between The 3-merous flowers, petals, fruits
them. size of
tln
guishing
A. nigrum and from A. hondurense (Table 2).
(larger flowers fruits)
Based on of the dwarf mistletoes in
our and measurements of plant characteristics
field observations
**thern Mexico, we do nigrum or A. vaginatum occur in Oaxaca or Chiapas,
not agree that Arceuthobium
hese Mexico and north into
species are primarily distributed along the Central Volcanic Cordillera of central
Durango. Madre Occidental
Chihuahua in the Sierra
Arceuthobium
vaginatum extends as far north as central
&
and
as far north Madre (Hawksworth Wiens 1996). However, the
as southern Oriental
Coahuila in the Sierra
graphic and extends north
Central Cordillera
distribution of A. nigrum centered on the eastern side of the
is
&
rato (Hawksworth
Durango Mexico
with nigrum in central
(Fig. Arceuthobium vaginatum sympatric A.
1). is
. .
Journal of the Botanical Research Institute of
Texas6(2)
608
Wiens 1996) and since also extends as far north as Chihuahua, it is probably sympatric with A. nigrum in
it
Durango.
&
which was once thought be near extinction (Hawksworth Wiens
Honduran dwarf to
mistletoe, 1972),
Mexico Our
now known be distributed from northern Nicaragua to northern Oaxaca, (Fig. 1). surveys in
to
is
Oaxaca we now
northern location so know
2010 confirmed thatArceuthobiumhondurense occurs in (Fig. 1, 16),
species occurs almost to Veracruz and Puebla in central Mexico. Moreover, it has only been found in
this
throughout geographic range and therefore, should not be considereda
widely-scattered, small populations its
0
nigrum Guatemala
common pine should also be noted that the reports of A. in and
parasite of its hosts. It
&
Salvador (Hawksworth Wiens 1977, 1989, 1996) should be considered as reports of A. hondurense. In addi-
vaginatum from
sinf-p our results demonstrated that at least one of the populations of A. north-central
tion,
Oaxaca was misidentified by Hawksworth and Wiens (1996) and is indeed A. hondurense (Fig. 1, location 13),
we suspect the southern distribution of A. vaginatum only extends into Puebla and not Oaxaca. Further inves-
Oaxaca
however, are warranted to assess whether A. vaginatum occurs in as several collections of this
tigations,
species have been made in the Sierra Juarez near Ixtlan. While all of these were classified as A. vaginatum by
A
we
Hawksworth and Wiens page suspect these collections represent additional populations of
(1996, 370),
hondurense in Oaxaca, but this needs to be confirmed.
ACKNOWLEDGMENTS
The field assistance provided by Carolyn Daugherty and earlier reviews of the manuscript by Carolyn Daugh-
We
erty, Dan Nickrent, and Job Kuijt are greatly appreciated. also appreciate the help of Gustavo Perez, Socorro
Gonzalez-Elizondo, and Juan Tun Garrido with reviews and Spanish translation for the Resumen.
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