THE TAXONOMY AND EPIDEMIOLOGY OF DWARF MISTLETOES PARASITIZING WHITE PINES IN ARIZONA

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Authors Mathiasen, Robert L.

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University Microfilms International 300 North Zeeb Road Ann Arbor, Michigan 48106 USA St. John's Road, Tyler's Green High Wycombe, Bucks, England HP10 8HR 78-2075 MATHIASEN, Robert Lee, 1950- THE TAXONOMY AND EPIDEMIOLOGY OF DWARF MISTLETOES PARASITIZING WHITE PINES IN ARIZONA. The University of Arizona, Ph.D., 1977 Agriculture, plant pathology

Xerox University Microfilms, Ann Arbor, Michigan 48106 THE TAXONOMY AND EPIDEMIOLOGY OF DWARF MISTLETOES

PARASITIZING WHITE PINES IN ARIZONA

by

Robert Lee Mathiasen

A Dissertation Submitted to the Faculty of the

DEPARTMENT OF PLANT PATHOLOGY

In Partial Fulfillment of the Requirements For the Degree of

DOCTOR OF PHILOSOPHY

In the Graduate College

THE UNIVERSITY OF ARIZONA

19 7 7 THE UNIVERSITY OF ARIZONA

GRADUATE COLLEGE

I hereby recommend that this dissertation prepared under my direction by Dr. RnWt t.. iWf.nn entitled The Taxonomy anil Fpi Hemi r>1 "oy nf Mi gfppfi

Parasitizing White Pines in Arii-.nna be accepted as fulfilling the dissertation requirement for the degree of Ph. D.

)issertation Director

As members of the Final Examination Committee, we certify that we have read this dissertation and agree that it may be presented for final defense.

/Jom Z? If??

do2 J•) , '77?/ ^ fill

Final approval and acceptance of this dissertation is contingent on the candidate's adequate performance and defense thereof at the final oral examination. STATEMENT BY AUTHOR

This dissertation has'been submitted in partial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to bor­ rowers under rules of the Library.

Brief quotations from this dissertation are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate Col­ lege when in his judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, permis­ sion must be obtained from the author.

SIGNED This dissertation is dedicated to Diane and Frank, the two most influential and understanding people in my life. Their friendship, encouragement, and patience gave me the strength to complete my graduate studies and their contributions to my personal and professional growth have been immeasurable.

iii ACKNOWLEDGMENTS

Ihe author wishes to express his sincerest appreciation to Dr.

F. G. Hawksworth, Forest Pathologist, U. S. Forest Service, Ft. Collins,

Colorado for his advice and encouragement throughout my graduate studies and to Dr. R. L. Gilbertson, Professor of Plant Pathology, The University of Arizona, for his help and support.

Appreciation is also expressed to the U. S. Forest Service and

The University of Arizona for financial support of these studies and to the many individuals who have contributed to this work and to ray educa­ tion.

iv TABLE OF CONTENTS

Page

LIST OF TABLES vii

LIST OF ILLUSTRATIONS ix

ABSTRACT x

CHAPTER

1. INTRODUCTION 1

2. THE DWARF MISTLETOE PARASITIZING BRISTLECONE PINE .... 3

Literature Review 3 Materials and Methods 5 Taxonomic Studies . . 5 Morphological Characters ...... 5 Physiological Characters ..... 6 Chemical Characters 9 Distribution Studies 9 Pathological Impact Studies 10 Results 10 Taxonomic Studies 10 Morphological Characters 10 ffaysiological Characters 13 Chemical Characters . 20 Distribution Studies 20 Pathological Impact Studies 23 Discussion 26 Taxonomic Status of the Bristlecone Pine Dwarf Mistletoe 26 Pathological Impact of A. microcarpum on the San Francisco Peaks 29 Geographic Variation in A. microcarpum ...... 31

3. THE DWARF MISTLETOES PARASITIZING SOUTHWESTERN WHITE PINE. 33

Literature Review 33 Materials and Methods ...... 35 Taxonomic Studies 35 Morphological Characters 35

v vi

TABLE OF CONTENTS—Continued

Page

Physiological Characters ..... 36 Chemical Characters ...... 37 Distribution Studies 37 Pathological Impact Studies ..... 38 Results 39 Taxonomic Studies 39 Morphological Characters 39 Physiological Characters 44 Chemical Characters 44 Distribution Studies 44 Pathological Impact Studies 49 Discussion -53 The Taxonomic Status of the Dwarf Mistletoes Parasitizing SW W P 53 Distribution and Pathological Impact of A. apachecum and A. blumpri in the Southwestern United States ... 62

APPENDIX A: SPECIMENS EXAMINED 65

APPENDIX B: KEY TO THE SIECIES OF ARCEUTHOBIUM PARASITIZING WHITE PINES IN ARIZONA AND NEW MEXICO 85

LITERATURE CITED . . 86 LIST OF TABLES

Table Page

1. Comparison of the height, basal diameter, habit, and color of dominant shoots of Arceuthobium microcarpum, Arceuthobium cyanocarpum. and the bristlecone pine dwarf mistletoe 11

2. Comparison of the staminate flower, fruit, and seed of Arceuthobium microcarpum. Arceuthobium cyanocarpum. and the bristlecone pine dwarf mistletoe 12

3. Comparison of the height and basal diameter of dominant shoots of the northern and southern populations of Arceuthobium microcarpum . . 14

4. Natural host range of Arceuthobium microcarpum. Arceuthobium cyanocarpum. and the bristlecone pine dwarf mistletoe 16

5. Phenolic constituents of Arceuthobium cyanocarpum. Arceuthobium microcarpum. and the bristlecone pine dwarf mistletoe as determined by paper chromatography . . 21

6. Comparison of infection and mortality in bristlecone pine dwarf mistletoe infested and non-infested mixed conifer stands on the San Francisco Peaks, Arizona .... 24

7. Mortality of bristlecone pine and Engelmann spruce in relation to the incidence of dwarf mistletoe infection on the San Francisco Peaks, Arizona 25

8. Comparison of shoot heights, basal diameters, third internodes, lateral staminate spikes, staminate flower diameters, and fruits of Arceuthobium apachecum and Arceuthobium blumeri 40

9. Geographic variation in shoot height and perianth lobe number of Arceuthobium apachecum and Arceuthobium blumeri 41

10. Phenolic constituents of Arceuthobium apachecum and Arceuthobium blumeri as determined by paper chromatography 46

vii viii LIST OF TABLES—Continued

Table Page

11. Infection and mortality rates in Arceuthobium- infested mixed conifer stands in Arizona 54

12. Mortality of southwestern white pines in Arizona • caused by Arceuthobium apachecum and Arceuthobium blumpri in relation to average dwarf mistletoe rating (D. M. R.) 55 LIST OF ILLUSTRATIONS

Figure Page

1. Approximate periods of anthesis and seed dispersal of Arceuthobium cyanocarpum. Arceuthobium microcarpum, and the bristlecone pine dwarf mistletoe . . 15

2. A dead, heavily mistletoe infected bristlecone pine near Schultz Peak, San Francisco Peaks, Arizona 18

3. The bristlecone pine dwarf mistletoe on Abies laaiocarpa var. arizonica 19

4. The bristlecone pine dwarf mistletoe on Pinus strobiformis 19

5. Approximate distribution of Pinus aristata, Arceuthobium microcarpum. and the bristlecone pine dwarf mistletoe on the San Francisco Peaks, Arizona ... 22

6. Female shoots of Arceuthobium microcarpum on Pinus aristata 27

7. Male and female shoots of Arceuthobium microcarpum on Picea engelmannii 27

8. Female shoots of Arceuthobium blumeri on Pinus strobiformis. Huachuca Mountains, Arizona 42

9. Male and female shoots of Arceuthobium apachecum on Pinus strobiformis. White Mountains, Arizona 42

10. Approximate periods of anthesis and seed dispersal of Arceuthobium blumeri and Arceuthobium apachecum 45

11. Geographic distribution of Arceuthobium apachecum and Arceuthobium blumeri ...... 47

12. Witches' brooms on Pinus strobiformis caused by Arceuthobium blumeri. Huachuca Mountains, Arizona .... 51

13. Witches' brooms on Pinus strobiformis caused by Arceuthobium apachecum. Santa Catalina Mountains, Arizona 52

ix ABSTRACT

Analyses of morphological, physiological, and chemical characters of the dwarf mistletoe parasitizing bristlecone pine (Pinus aristata Englem.) on the San Francisco Peaks, Arizona were compared with those of Arceuthobium cvanocarpum Coulter & Nelson and A. micro- carpum (Engelm.) Hawks. & Wiens. Results indicate that the dwarf mistletoe is A. microcarpum. not A. cyanocarpum as suggested previously.

A. microcarpum causes severe damage in two bristlecone pine stands on the San Francisco Peaks, but only about 12 percent of the bristlecone pine area on the Peaks is affected by the parasite. The probability of A. microcarpum spreading into presently non-infested stands is low because the majority of these are above the apparent upper elevational limits of the mistletoe. Its spread into lower populations of bristlecone pine is precluded by areas dominated by non- susceptible species.

Principal hosts of A. microcarpum on the San Francisco Peaks are Pinus aristata Engelm. and Picea engelmannii Parry. This is the second report of a North American dwarf mistletoe parasitizing species in two genera as principal hosts. Pinus strobiformis Engelm. and

Abies lasiocarpa var. arizonica (Merriam) Lemmon are rare hosts, and this is the first report of a dwarf mistletoe parasitizing four different host species at a single location.

x xi

Analysis of northern and southern populations of A. microcarpum

indicates there are geographically consistent morphological and physio­

logical discontinuities between these populations. The populations do

not at present seem to deserve taxonomic recognition because the differ­

ences may be due to environmental variation, ecotypic variation in the host populations, or possibly ecotypic variation in A. microcarpum.

Analyses of morphological, physiological, and chemical characters of the Southwestern and Mexican dwarf mistletoe populations

parasitizing Pinus strobiformis as a principal host and currently recognized as Arceuthobium apachecum Hawks. & Wiens and Arceuthobium

blimipri A. Nelson indicates there are taxonomically significant discontinuities between these populations. Geographically consistent differences in shoot color, growth habit, lateral staminate spike dimensions, and perianth lobe color were detected, but differences in

shoot size and perianth lobe number were apparently the result of geographic variation. Several additional morphological characters examined were found to be continuous. Differences in the flowering

periods of A. apachecum and A. blumeri may represent a physiological discontinuity, but some geographic variation was detected for this

character also. Additional physiological discontinuities were not

detected, but chromatographic analysis of these species did detect

some chemical differences. Both taxa consistently cause the formation of witches* brooms, contrary to previous reports. xii

The presence of geographically consistent discontinuities

between A. apachecum and A. blumeri indicates that these populations

deserve taxonomic recognition. Their classification at the subspecific

level may be more representative of their natural relationship, but

until further studies of the Series Campylopoda Hawks. & Wiens are

completed, A. apachecum and A. blumeri should be retained as species.

A. apachecum is distributed from the Santa Rita, Rincon,

Santa Catalina, and Chiricahua Mountains of southern Arizona to east-

central Arizona and west-central New Mexico, but it is not abundant within its geographic range. A. blumeri is known in southern Arizona

only from the Huachuca Mountains, but it ranges south to southern

Durango, Mexico.

Both species exclusively parasitize Pinus strobiformis and cause high mortality. The mortality rate in stands heavily infested

by A. apachecum was 30 times that of non-infested stands and that for

A. bl"mpri was 20 times greater. The economic impact of these dwarf

mistletoes in the Southwest is minimal because their hosts constitute

a small proportion of the timber volume. However, their control in recreation areas may be warranted. CHAPTER 1

INTRODUCTION

The dwarf mistletoes (Arceuthoblum spp.) are the most destructive disease agents in the forests of the Southwest. They severely damage their coniferous hosts by causing mortality, reduced growth, wood deformation, decreased seed production, and they predispose infected trees to invasion by secondary pathogens and insects. They are widespread and almost all of the conifers in the Southwest are parasit­ ized by one or more species of Arceuthobium (Hawksworth and Wiens, 1972).

Ihe Southwestern dwarf mistletoe (A. vaginatum subsp. cryptopodum

(Engelm.) Hawks. & Wiens) alone causes losses of ponderosa pine (Pinus I ponderosa Laws.) estimated at over 150 million board feet annually

(Lightle and Weiss, 1974).

Southwestern white pine (SW W P, Pinus strobiformis Engelm.) is distributed in most of the higher mountain ranges of the Southwest from approximately 6,500 to 10,500 feet (Kearney and Peebles, 1969; Critch- field and Little, 1966). It is a common member of the mixed conifer forests in this area and is an important factor in watershed protection and recreation. SW W P is often harvested with ponderosa pine since they commonly occur in mixed stands and have similar wood properties.

Arizona is estimated to have over 200 million board feet of commercial

SW W P (Shupe, 1965). Another white pine, bristlecone pine (BC P,

1 2

Pinus aristata Engelm.) is known to occur in Arizona only on the San

Francisco Peaks near Flagstaff. Because of its rarity in the state, it is considered an endangered species (McDougall, 1975) and is protected under the Arizona Native Plant Law.

Three species of dwarf mistletoe parasitize white pines in

Arizona. The Apache dwarf mistletoe (A. apachecum Hawks. & Wiens) and

A. blumeri A. Nelson (no common name) are parasites exclusively of SW W

P in the Southwest and northern Mexico (Hawksworth and Wiens, 1972).

These mistletoes cause increased mortality and deformation of standing timber, but no studies have been conducted to quantify their effect on their host. The third species, tentatively classified as the limber pine dwarf mistletoe (A. cyanocarpum Coulter & Nelson), parasitizes BC P on the San Francisco Peaks (Hawksworth, 1965;> Hawksworth and Wiens,

1972). However, the distribution of the mistletoe on the San Francisco

Peaks and the extent of the damage to this population of BC P were un­ known. Further, the taxonomic status of the dwarf mistletoes parasit­ izing white pines in the Southwest has been questioned (Kuijt, 1973) and more detailed studies of their morphological and physiological charac­ ters were needed (Hawksworth and Wiens, 1972). Therefore, these investigations were initiated in 1974 in cooperation with the U. S.

Forest Service to determine the effect dwarf mistletoes have on white pines in Arizona and to help clarify the taxonomic status of these parasites. CHAPTER 2

THE DWARF MISTLETOE PARASITIZING BRISHE CONE PINE

Literature Review

Merriam (1890) made the first detailed survey of the vegetation of the San Francisco Peaks but he did not report the occurrence of a dwarf mistletoe on bristlecone pine. This was first done by J. B.

Leiberg in 1901 who deposited voucher specimens at the U. S. National

Herbarium (Leiberg 5884). However, Leiberg, Rixon, and Dodwell (1904) did not report the dwarf mistletoe in their report on the forest condi­ tions on the San Francisco Peaks.

Coulter and Nelson (1909) described a dwarf mistletoe parasit­ izing limber pine (Pinus flexilis James) in the Rocky Mountains as

Arceuthobium cyanocarpum A. Nelson ex Rydb. This species had previously been published as Razoumofskya cvanocarpa A. Nelson by Rydberg (1906) without a diagnosis. The 1905 Vienna Botanical Congress had conserved

Arceuthobium M. Bieb. (1819) over Razoumofskya Hoff. (1808) (Nomina

Conservanda No. 2091) but many American botanists, following the rule of strict priority set forth by the American Code, continued to use

Razoumofskya. Blumer (1910) considered the dwarf mistletoe on white pines as R. cyanocarpa as did Hedgcock (1914, 1915), Wooton and Standley

(1915), Rankin (1918), Tubeuf (1919), Garrett (1921), Rydberg (1917),

Tidestrom (1925), and Hubert (1931). Abrams (1923) named the mistletoe

3 4

A. cyanocarpum (A. Nelson) Abrams sp. nov., a superfluous name.

Arceuthoblum finally replaced Razoumofskva ater the 1930 Cambridge

Botanical Congress. Gill (1935) reduced A. cvanocarpum to a host form

of A. campylopodum Engelm.: A. campylopodum Engelm. forma cyanocarpum

(A. Nelson) Gill. Gill concluded that this form could not be distin­

guished morphologically from seven other species but that they could be

separated on the basis of host susceptibility into host forms of A.

campylopodum.

An additional collection of the dwarf mistletoe parasitizing

bristlecone pine on the San Francisco Peaks was made in 1962 and depos­

ited at the U. S. Forest Service, Forest Pathology Herbarium, Ft.

Collins, Colorado (Hawksworth and Lightle 247). Hawksworth (1965) re­

ported that BC P was the only host on the San Francisco Peaks, although

several southwestern white pines grew near heavily' infected bristlecone

pines. He cited this as further evidence of the distinctness of A.

campylopodum f. cyanocarpum from A. campylopodum Engelm. f. blumeri

(Engelm.) Gill, a parasite of SW W P in southern Arizona.

Kuijt (1955, 1960a, 1960b, 1961, 1963) rejected Gill's taxo-

nomic treatment of Arceuthoblum but did not provide another system of

classification. Subsequently, Hawksworth and Wiens (1970b, 1972)

raised Gill's host form cyanocarpum to specific rank, stating that it

could be distinguished from other species based on morphology, phenology,

and host specificity. Hawksworth and Wiens (1972) then tentatively

classified the dwarf mistletoe parasitizing BC P on the San Francisco

Peaks as A. cyanocarpum Coulter & Nelson. However, they concluded that more taxonomic studies were needed before a positive identification

could be reached. They also reported four additional hosts for A.

cvanocarpum on the San Francisco Peaks; Engelmann spruce (Picea

engetnianm'i Parry) and blue spruce (Picea pungens Engelm.) were occa­

sional hosts, while corkbark fir (Abies lasiocarpa var. arizonica

(Merriam) Lemmon) and southwestern white pine were reported as rare

hosts. Hawksworth and Wiens (1972) provided detailed information on

the distribution, host range, morphology, phenology, and chemical char-

/ acters of A. cvanocarpum. They also provided similar information for

the other species of Arceuthobium known to occur in the vicinity of the

San Francisco Peaks. These are: A. douglasii Engelm., A. vaginatum

subsp. cryptopodum. A. divaricatum Engelm., and A. microcarpum (Engelm.)

Hawks. & Wiens. A. microcarpum also parasitizes Engelmann spruce on the

San Francisco Peaks (Hawksworth and Graham, 1963; Hawksworth and Wiens,

1972).

Materials and Methods

Taxonomic Studies

Morphological Characters. Measurements and observations of

morphological characters of the bristlecone pine dwarf mistletoe (BC P

D M) were made on specimens collected in 1975 from the San Francisco

Peaks or on specimens previously depostied at the U. S. Forest Service,

Forest Pathology Herbarium, Ft. Collins, Colorado (FPF) (see Appendix A,

Specimens Examined). Specimens of A. cvanocarpum collected throughout

its geographic range were examined at FPF but only additional 6 measurement? of shoot height were made for this species. All other morphological data for A. cyanocarpum are from Hawksworth and Wiens

(1972). Because A. microcarpum also parasitizes Engelmann spruce on the

San Francisco Peaks, additional measurements and observations of morpho­ logical characters were made on specimens of this taxon collected throughout its geographic range in 1975 and 1976 and on specimens previ­ ously deposited at FPF (see Appendix A, Specimens Examined).

Relatively few morphological characters are available for use in the identification of dwarf mistletoes. The following characters of the

BC P D M and A. microcarpum were compared with those of A. cyanocarpum; male and female dominant shoots (non-systemic infections only) — height, basal diameter, color, growth habit; staminate flower diameter; perianth lobes — number, length, width, color; mature fruit (dried) — length, width, length of proximal end of the bicolored fruit, color of the distal end; seed -- length, width, color.

Physiological Characters. The physiological characters analyzed were —

_ Hienology: Species of dwarf mistletoe consistently flower and dis­ perse their seed during the same period each year, although variations related to altitude, latitude, and season occur (Wiens, 1968; Hawksworth and Wiens, 1972). Observations of flowering and seed dispersal were made in the summer and fall of 1973 through 1976 for the BC P D M and A. microcarpum. Results were compared with the flowering and seed dispersal periods of A. cyanocarpum as reported by Hawksworth and Wiens (1972).

The species of mistletoe, location, and date were recorded for each field observation and flowering and seed dispersal were each ranked on

the following scale: 0 — not started; 1 — started, but not near peak;

2 — near peak; 3 -- past peak, but not completed; 4 — completed.

Phenology data were summarized by averaging all observations at 2-week-

intervals from July 1 through November 2.

Host Range: The relative consistency of a dwarf mistletoe's host

relationships makes these useful in distinguishing physiological dis­

continuities between species. Most dwarf mistletoes have at least one

host which they most frequently parasitize. Some species occur less

frequently on additional hosts, while some potential hosts are never

parasitized. Therefore, the relative susceptibility of a particular

host species distributed within a dwarf mistletoe's geographic range

can be arbitrarily ranked according to the frequency of parasitism

observed. Hawksworth and Wiens (1972) established five natural suscep­

tibility classes based on the percentage of trees infected within 20

feet of heavily infected principal hosts of a dwarf mistletoe. These

are: principal, secondary, occasional, rare, and immune, representing

90 - 100%; 50 - 90%; 5 - 50%; greater than 0%, but less than 570; and

0% infected trees, respectively.

General field observations for susceptible hosts of the BC P D M

were made on the San Francisco Peaks from 1973 through 1976. Specimens

representing the different host-dwarf mistletoe combinations observed

were collected and deposited at FPF. In addition, 27 0.25 or 0.5 acre

rectangular plots totaling 10 acres were randomly placed within the

mistletoe infested BC P areas on the San Francisco Peaks. Every conifer 8 greater than 4 inches diameter breast height within a plot was examined.

The host species, dwarf mistletoe rating (6-class system, Hawksworth,

1961), and condition (alive or dead) of each tree were recorded. An additional 5 plots totaling 2 acres were randomly placed in the Inner

Basin of the San Francisco Peaks and 13 plots totaling 5 acres were ran­ domly placed in non-infested BC P stands to the west of the infested stands. Dead trees were randomly examined for signs of secondary patho­ gens and insects.

Data from general observations were combined with plot data and. each host or potential host of the BC P D M was placed in the appropri­ ate natural susceptibility class. These groupings were then compared with the natural susceptibility classes established for A. microcarpum and A. cyanocarpum by Hawksworth and Wiens (1972).

Host Response: The first visible symptom of a dwarf mistletoe in­ fection in a stem is usually a swelling at the point of infection. The swelling becomes fusiform as it enlarges and eventually shoots of the mistletoe develop. Unusually large swellings and poor shoot development are indications of host-parasite incompatibility (Hawksworth and Wiens,

1972; Kuijt, 1964; Laurent, 1966; Tainter and French, 1967; Weir, 1918).

Infection by dwarf mistletoes often causes the development of dense masses of host branches termed witches' brooms which are of two basic types: systemic and non-systemic (Kuijt, 1960b). In the systemic type, the dwarf mistletoe's endophytic system reaches the terminal meristem of the branches and then grows at the same rate as the branches. Mistle­ toe shoots are scattered along the branch or may be more abundant at the 9 branch girdles. In non-systemic brooms, the mistletoe shoots are con­ centrated near the original point of infection and the endophytic system does not reach the terminal meristem. The type of witches' broom formed is usually consistent for a species of mistletoe within a host genus, and therefore is taxonomically significant (Hawksworth and Wiens, 1972).

Observations of host response, including stem swelling and the type of witches' broom typically formed, were made for the BC P D M and

A. microcarpum. Information on host response for A. cyanocarpum is from

Hawksworth and Wiens (1972).

Chemical Characters. Since qualitative chemical differences

(phenolics) occur among species of Arceuthobium (Hawksworth and Wiens,

1972), samples of the BC P D M, A. microcarpum. and A. cyanocarpum were analyzed chromatographically (see Appendix A, Specimens Examined), fol­ lowing the-methods of Hawksworth and Wiens (1972). Results were compared with those obtained by Hawksworth and Wiens (1972). All sam­ ples were analyzed in the first dimension only and anthocyanins were not considered.

Distribution Studies

The distribution of the BC PD M was determined by surveys in

1974 and 1975 of the larger and most of the smaller stands of BC P on the San Francisco Peaks. Kendrick Peak, approximately 15 miles to the west, was also examined for BC P.

The approximate distribution of BC P and the geographic and sle- vational limits of the BC P D M were recorded on topographic maps of the area (Humphrey's Peak and Sunset Crater West, Coconino County, Arizona, 10

U. S. G. S., 1966, 7.5 series). The approximate acerage of BC P and

mistletoe infested areas was estimated using a planimeter calibrated to

the scale of the maps.

Pathological Impact Studies

The effect of the BC P D M on the BC P population on the San

Francisco Peaks was assessed by comparing the mortality rates of infested

and non-infested BC P stands and considering the present distribution of

the mistletoe. Mortality rates of all host species were compared for in­

fested and non-infested plots as a percentage of total trees examined.

Mortality rates for BC P and Engelmann spruce were also compared as a

percentage of all trees examined for each of the following classes of

dwarf mistletoe infection: non-infested (D. M. R.; 0); lightly infested

(D. M. R.: 0.1 - 2.0); moderately infested (D. M. R.: 2.1 - 4.0);

heavily infested (D. M. R.: 4.1 - 6.0).

Results

Taxonomic Studies

Morphological Characters. Comparative measurements and observa­

tions of the morphological characters of the BC P D M, A. microcarpum,

and A. cyanocarpum are presented in Tables 1 and 2. Both A. microcarpum

and A. cyanocarpum are morphologically similar to the BC P D M, but A.

cvanocarpum differs from the BC P D M and A. microcarpum in male and fe­

male shoot color, mean fruit length, and mean seed length. The mean

heights of dominant shoots of the BC P D M were intermediate between

those of A. ttW rrfirflrpirm and A. cyanocarpum. Differences in shoot height Table 1. Comparison of the height, basal diameter, habit, and color of dominant shoots of Arceuthoblum microcarpum. Arceuthobium cyanocarpum. and the bristlecone pine dwarf mistletoe.

A. microcarpum Bristlecone Fine D. M. A. cyanocarpum

Character Mean Max. No. Meas Mean Max. No. Meas Mean Max. No..Meas

Ht. (cm) Female 5.2 12.0 232 4.2 7.0 70 3.0 5.0 94

Male 4.3 13.0 180 3.4 7.0 50 2.2 3.5 40

Basal Diam. (mm) 1.9 3.0 230 2.1 3.0 60 1.4* 2.0 80

Habit (bristlecone Shoots densely clustered Shoots densely clustered pine)

Habit (Engelmann Shoots not densely Shoots not densely spruce) clustered clustered

Color Female Green to purple Green to purple Yellow-green to bluish

Male Green to brownish Green to brownish Yellow-green

*Data from Hawksworth and Wiens, 1972. Table 2. Comparison of the stamlnate flower, fruit, and seed of Arceuthoblum mlcrocarpum. Arceuthoblum cyanocarpum. and the brlstlecone pine dwarf mistletoe.

A. mlcrocarpum Brlstlecone Pine D. M. A. cyanocarpum

Character Mean Max. Noi. Meas. Mean Max. No. Meas. Mean Max. No. M

Stamlnate Fl. 2.2 2.8 141 2.5 4.0 170 3.0* — — Diameter (mm)

Perianth Lobes: Number (%) 3 (95), 4 (4), 5 (1) 3 (85), 4 (14), 5 (1) 3 (70), 4 (30)* Length (mm) 1.2 1.4 141 1.2 1.6 170 1.4* _ 1.0 1.2 141 1.0 1.2 170 1.0* Width (mm) — — Fruit:

Length (mm) 3.1 3.6 140 3.1 3.6 135 3.5* MM

Width (mm) 2.0 2.2 140 2.0 2.3 135 2.0* Proximal End (mm) 2.2 2.6 140 2.2 2.6 135 2.0* _ Distal End Color Green to reddish-purple Green to reddish-purple Green

Seed: Length (mm) 2.4 2.8 100 2.4 2.6 100 2.0*

Width (mm) 1.0 1.2 100 1.0 1.0 100 0.9* _

*Data from Hawksworth and Wiens, 1972. 13 were detected between the northern (North Rim Grand Canyon, Kendrick

Peak, San Francisco Peaks) and southern populations (White, Mogollon, and Finaleno Mountains) of A. microcarpum (Table 3).

Hivsiological Characters. The results of the physiological characters analyzed were --

Phenology: Flowering and seed dispersal data are presented in

Figure 1. A. microcarpum and the BC P D M flower and disperse their seed at approximately the same period, while A. cyanocarpum does so slightly earlier. The northern populations of A. microcarpum flower a little earlier than southern populations, but seed dispersal is about the same.

Host Range: Bristlecone pine is the principal host of the BC P D M on the San Francisco Peaks. Engelmann spruce is also parasitized, but not as frequently as BC P. Usually 50 to 80 percent of the Engelmann spruce within 20 feet of heavily infected bristlecone pines have one or more infections, and therefore, Engelmann spruce is classified as a secondary host (Table 4).

Hawksworth and Wiens (1972) reported that blue spruce was an occasional host of the BC P D M, but it is now thought that blue spruce does not occur on the San Francisco Peaks (J. R. Jones, personal commu­ nication, 1976).

The BC P D M rarely parasitizes SW W P and corkbark fir (Hawks- worth and Wiens, 1972). Several hundred trees of these species were examined for BC P D M but only 11 infected southwestern white pines and

12 infected corkbark firs were found. Table 3. Comparison of the height and basal diameter of dominant shoots of the northern* and southern** populations of Arceuthobium microcarpum.

Northern

Character Mean Max. Min. No. Measured

Height (cm) Female 3.9 7.0 3.0 98

Male 3.2 7.0 1.5 85

Basal Diameter 1.5 2.4 0.8 100 (mm)

Specimens Examined 13 (Engelmann spruce); 1 (blue spruce) (Host)

Southern

Height (cm) Female 6.6 12.0 4.0 134

Male 5.8 13.0 3.0 95

Basal Diameter 2.0 3.2 1.0 130 (mm)

Specimens Examined 17 (Engelmann spruce); 5 (blue spruce) (Host)

* North Rim, Grand Canyon; Kendrick Peak; San Francisco Peaks.

**White Mountains; Mogollon Mountains; Pinaleno Mountains. Bristlecone pine dwarf mistletoe (37)

A. microcarpum ANTHESIS (47)

A. cyanocarpum (54)

Bristlecone pine dwarf mistletoe

A. microcarpum SEED DISPERSAL

A. cyanocarpum

15 31 15 31 15 30 15 31 July August September October

Figure 1. Approximate periods of anthesis and seed dispersal of Arceuthobium cyanocarpum, Arceuthoblum microcarpum. and the bristlecone pine dwarf mistletoe. — Peak periods are shown by solid bars; Number of observations, ( ), 16

Table 4. Natural host range of Arceuthobium microcarpum. Arceuthobium cvanocarpum, and the brlstlecone pine dwarf mistletoe.

A. microcarpum * BC. P. D. M. . A. cyanocarpum * Principal Picea engelmannii Pinus aristata Pinus aristata Picea pungens Pinus flexilis Pinus longaeva

Secondary Picea engelmannii Pinus albicaulis

Occasional Pinus monticola

Rare Abies lasiocarpa Abies lasiocarpa Picea engelmannii var. arizonica var. arizonica Pinus balfouriana Pinus strobiformis Pinus contorta subsp. latifolia Pinus ponderosa

Immune Abies concolor Abies concolor Abies lasiocarpa Abies lasiocarpa Pinus edulis var. lasiocarpa var. lasiocarpa Pinus ponderosa Pinus strobiformis** Pinus ponderosa Pseudotsuga Pseudotsuga Pinus strobiformis menziesii menziesii Pseudotsuga menziesii

*Host classification'and taxonomy is from Hawksworth and Wiens, 1972. **Based on earlier classification of the bristlecone pine dwarf mistletoe as A. cvanocarpum. Hawksworth and Wiens, 1972. 17

Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) is classified as immune to the BC P D M because non-infected Douglas-firs were common­ ly observed near heavily infected bristlecone pines. A few infected

Douglas-firs were found near the BC P D M infestations, but examination of the dwarf mistletoe shoots on these trees indicated that the patho­ gen was A. douglasii, which is morphologically distinct from the BC P D

M (Hawksworth and Wiens, 1972). A few trees each of Abies concolor

(Gord. et Glend.) Lindl. (white fir), Pinus ponderosa. and Pinus edulis

Engelm. (pinyon pine) were observed near heavily infected bristlecone

pines, but none were infected. Consequently, they are classified as immune to the BC P D M.

Host Response: The BC P D M causes the formation of large non- systemic witches' brooms on infected bristlecone pines (Figure 2), but systemic infections develop occasionally. Stem swellings are typically fusiform arid do not appear abnormally large. Shoot development is abun­ dant on BC P and often the entire branch is obscured by shoots.

The BC P D M causes the formation of dense, "round" witches' brooms on Engelmann spruce and some unusually large stem swellings were observed. Shoot development is fairly abundant, but they are not densely clustered around the host branch.

Unusually large stem swellings and poor shoot development are l characteristic of infections on SW W P and corkbark fir (Figures 3 and

4). Small non-systemic witches' brooms are formed in both of these host- parasite combinations. Neither of these rare hosts were heavily infected. Figure 2. A dead, heavily mistletoe infected bristlecone pine near Schultz Peak, San Francisco Peaks, Arizona.

i

*i i 19

3ss*

Figure 3. The bristlecone pine dwarf mistletoe on Abies lasiocarpa var. arizonica. — Note the large fusiform swelling and poor shoot development.

Figure 4. The bristlecone pine dwarf mistletoe on Pinus strobiformis. 20

Chemical Characters. The results of chromatographic analysis of the BC P D M, A. microcarpum. and A. cyanocarpum are presented in Table

5. microcarpum and the BC P D M were essentially identical chromato- graphically. A. cyanocarpum was basically similar chromatographically to A. microcarpum and the BC P D M, but it consistently lacked the A4 and B6 bands. Hawksworth and Wiens (1972)•reported that A. cyanocarpum did not consistently have the BGl, BG2, B3, and B5 bands and lacked all of the A bands. I detected the BGl, BG2, B3, B5, and the Al, A2, and A3 bands in the one sample of A. cyanocarpum I analyzed. I did not detect the B1 band in A. cyanocarpum but Hawksworth and Wiens (1972) reported its presence in some of their samples.

Distribution Studies

Bristlecone pine is the predominant species on approximately

3400 acres of the San Francisco Peaks. It is primarily distributed on the south side of the Peaks between 9000 and 11,80Q feet (Figure 5).

This pine is mainly associated with Engelmann spruce and corkbark fir, but also is found with Douglas-fir, SW W P, quaking aspen (Populus tremuloides Michx.), and occasionally ponderosa pine and pinyon pine. I did not find BC P on Kendrick Peak.

Three populations of the BC P D M were detected on the San Fran­ cisco Peaks (Figure 5). The largest population (approximately 350 acres) is located around Schultz Peak (T. 22 N., R. 7 E., Sections 2, 3, 10, and 11). A second population (approximately 50 acres) is one-half mile due west of Schultz Peak (T. 22 N., R. 7 E., Sections 3 and 10), and is apparently not continuous with the larger population. The third Table 5. Phenolic constituents of Arceuthoblum cvanocarpum. Arceuthoblum microcarpunu and the brlstlecone pine dwarf mistletoe as determined by paper chromatography.

Flavones, Flavonols, and Cinnamic Acid Ester Derivatives SAMPLE TRIALS Yl Bl BGl YO B2 BG2 A1 YG A2 B3 A3 A4 B4 A5 B5 B6

A. cvanocarpum FGH 1057 6 ++--++ ++ -- ++ ++ -- ++ ++ ++ -- ++ -- ++ MM

* H & W, 1972 ++ + + -H- -- + - - — — + -- -- ++ -- + MM m BC. P. D. M. RLM 7546 5 ++--++ ++ — ++++ — ++ ++ ++++++ — ++ ++

RLM 7549 5 ++--++ ++ — ++++ — ++ ++ ++ ++ ++ -- ++ ++

RLM 7560 4 ++ — 4+ ++ — ++ ++ — -H- ++ ++++++ — -H- ++

A. microcarpum RLM 7540 4 ++ — ++ ++ — ++++ -- ++ + -H- ++ ++ — ++ +

RLM 7542 1 ++--++ ++ -- ++ ++ -- -H- ++ ++ ++ ++ -- ++ ++

RLM 7568 4 ++--++ ++ — ++++ — ++ ++ ++++++ — -H- ++

RLM 7590 5 ++--++ ++--++++--++ ++ ++ ++ ++ ~~ ++ +

* H & W, 1972 ++ -- ++ ++ -- ++ ++ -- ++ -- ++++++ — ++ ++

++ « detected in all trials; + = sometimes not detected; — = not detected. *as reported by Hawksworth and Wiens, 1972. Figure 5. Approximate distribution of Pinus aristata. Arceuthobium microcarpum. and the bristlecone pine dwarf mistletoe on the San Francisco Peaks, Arizona. -- Areas encircled by dark lines represent Pinus aristata. Checkered areas (1 - 3) represent the bristlecone pine dwarf mistletoe. Crossed areas (4) represent Arceuthobium microcarpum. 23

population consists of ten infected bristlecone pines located in the

Inner Basin approximately 1.5 miles north of Schultz Peak (T. 23 N., R.

7 E,, Section 27). The ten trees are near Engelmann spruces heavily in­

fected with a dwarf mistletoe specifically identified as A. microcarpum

(Hawksworth and Graham, 1963; ^awksworth and Wiens, 1972). Approximately

12 percent of the total area on the San Francisco Peaks occupied by BC P

is affected with dwarf mistletoe.

The BC P D M extends as low as 9100 feet on the ridge running

southeast from Schultz Peak (T. 22 N., R. 7 E., Section 11, Figure 5).

It reaches approximately 10,300 feet on the ridge running north from

Schultz Peak (T. 22 N., R. 7 E., Section 2), but does not extend above

that elevation, although BC P is continuously present there and at

higher elevations in the area.

Pathological Impact Studies

Eighty-four percent of the bristlecone pines examined in the

Schultz Peak area were infected with BC P D M and thirty-seven percent

were dead. Most dead trees had large numbers of witches' brooms, a com­

mon symptom of dwarf mistletoe infection (Figure 2). I did not find

signs of other pathogens or insects on the dead trees I examined. Mor­

tality of BC P in the non-infested areas was one-sixth of that encoun­

tered in the mistletoe infested stands (Table 6). The percentage of

of dead trees was directly related to the amount of mistletoe infection

(Table 7).

Thirty-two percent of the Engelmann spruce examined in the

Schultz Peak area were infected with the BC P D M and only six percent 24

Table 6. Comparison of infection and mortality in bristlecone pine dwarf mistletoe infested and non-infested mixed conifer stands on the San Francisco Peaks, Arizona.

Host Species Trees/acre % Infected % Dead Ave. D. M.

Infested (10 acres)

Finus aristata 140 84 37 3.2

Ficea eneelmannii 61 32 6 0.7

Abies lasiocarpa 18 5 2 .01 var. arizonica

Finus strobiformis 32 1 2 .01

Pseudotsuga 9 0 4 0 menziesii

Pinus edulis .5 0 0 0

Non-infested (5 acres)

Pinus aristata 149 0 6 0

Picea eneelmannii 31 0 5 0

Abies lasiocarpa 4 0 5 0 var. arizonica

Pinus strobiformis 47 0 4 0

Pseudotsuga 20 0 5 0 menziesii

-*Dwarf Mistletoe Rating, Hawksworth, 1961. 25

Table 7. Mortality of brlstlecone pine and Engelmann spruce in relation to the incidence of dwarf mistletoe infection on the San Francisco Peaks, Arizona.

Level of Infection Percentage of Trees Dead Brlstlecone Pine Engelmann Spruce

Non-Infested 4.7 1.0 (0)*

Lightly Infested 3.0 3.8 (0.1 - 2.0)*

Moderately Infested 25.2 20.9 (2.1 - 4.0)*

Heavily Infested 40.6 (4.1 - 6.0)*

Number of Plots 45 40

^Average dwarf mistletoe rating, Hawksworth, 1961. 26

4 were dead. Mortality in non-infested areas was approximately the same

(Table 6). The average dwarf mistletoe rating was relatively low for

Engelmann spruce when compared to that for BC P. The few infected southwestern white pines and corkbark firs observed were not heavily in­ fected and none were dead. Their mortality rates were slightly lower in the mistletoe-infested areas (Table 6).

Discussion

Taxonomic Status of the Bristlecone Pine Dwarf Mistletoe

Gill (1935) and Hawksworth (1965) classified the dwarf mistletoe parasitizing BC P on the San Francisco Peaks as A. campylopodum forma cyanocarpum because this form encompassed those dwarf mistletoes para­ sitizing bristlecone pine, limber pine, foxtail pine (Pinus balfouriana

Grev. & Balf.), and whitebark pine (Pinus albicaulis Engelm.). When

Hawksworth and Wiens (1972) raised Gill's forma cyanocarpum to specific rank they tentatively classified this mistletoe as A. cyanocarpum. How­ ever, ray analysis of morphological, physiological, and chemical charac­ ters of the mistletoe indicates that it is A. microcarpum.

Morphologically the mistletoe resembles A. microcarpum (Figures

6 and 7), and is relatively distinct from A. cyanocarpum. Shoot heights of the BC P D M were smaller than those of A. microcarpum, but when the northern and southern populations of A. microcarpum were analyzed sepa­ rately, the shoot heights of the BC P D M were relatively similar to those of the northern populations of A. microcarpum. The shoot and fruit color variations of the BC P D M are similar to those of A. Figure 6. Female shoots of Arceuthobium microcarpum on Pinus aristata

Figure 7. Male and female shoots of Arceuthobium microcarpum on Picea engelmannii. 28

microcarpum also. Other characters of the BC P D M, such as staminate

flower diameter, perianth lobe number, fruit dimensions, and seed dimen­

sions were similar to those of A. microcarpum. but they were also similar

to those of A. cyanocarpum and it would be difficult to use them to

distinguish these taxa.

Flowering periods for southern populations of A. microcarpum are

somewhat later than for the northern populations, but seed dispersal

periods are constant throughout its range. Latitudinal and elevational

variation may account for this difference in flowering period, but it

could be indicative of a slight physiological difference between these

populations of A. microcarpum.

Few chemical differences were detected between samples of the BC

PDM and samples of A. microcarpum. A. cyanocarpum consistently lacked

two bands and occasionally lacked seven others that were consistently

detected in the BC P D M and A. microcarpum.

The presence of A. microcarpum in the Inner Basin (Hawksworth

and Graham, 1963; Hawksworth and Wiens, 1972) and the discovery of a few

infected bristlecone pines in that area also indicates the BC P D M is

A. microcarpum. The upper elevational limits of the BC P D M also sup­

ports this conclusion. Hawksworth and Wiens (1972) reported the upper

elevational limits of A. microcarpum as 10,000 feet, while Acciavatti

and Weiss (1974) rarely observed it above the same elevation on the Fort

Apache Indian Reservation, although their survey extended into Engelmann

spruce well above that elevation. The highest elevation reported by the

latter authors for A. microcarpum was 10,400 feet. The highest elevation 29

I observed for the BC P D M was 10,300 feet. The mistletoe did not ex­ tend above that limit although large numbers of its hosts were present in the area and extended above that elevation. The reasons for such a distinct elevational limit are unclear, but they are probably related to climatic conditions encountered at higher elevations. Hawksworth (1956,

1969) reported an elevational limit for Arceuthobium americanum Nuttal ex Engelm. which was several hundred feet below the upper elevational limits of its principal host in the central Rocky Mountains. Hawksworth

(1969) suggested that fruits of A. americanum may not have matured when mistletoe-infested lodgepole pines (Pinus contorta Dougl. ex Loud, subsp. latifolia (Engelm. ex Wats.) Critchf. were transplanted above the known elevational limits of A. americanum. possibly because of the shortness of the growing season. A similar situation may account for the absence of A. microcarpum above 10,400 feet in Arizona and possibly for its ab­ sence from the extensive stands of Engelmann spruce in the central and northern Rocky Mountains.

Pathological Impact of A. microcarpum on the San Francisco Peaks

A. microcarpum parasitizes Pinus aristata. Picea engelmannii.

Pinus strobiformis. and Abies lasiocarpa var. arizonica on the San

Francisco Peaks. This is the only known instance of one species of

Arceuthobium parasitizing four different hosts at a single location.

Bristlecone pine is the most severely damaged host, but only about

12 percent of the total area presently occupied by this species on the San Francisco Peaks is affected. The probability of A. microcarpum 30

spreading into the remaining non-infested BC P areas is very low because

most of the bristlecone pines on the Peaks occur above the upper eleva-

tional limits of A. microcarpum. The two largest infestations of A.

microcarpum on BC P are separated from adjacent non-infested bristlecone

pines by large areas dominated by non-susceptible species such as

Douglas-fir, ponderosa pine, and quaking aspen.

The occurrence of frequent fires on the San Francisco Peaks has

probably played an important role in determining the present distribution

'of A. microcarpum there, and may account for its absence in the BC P

populations below 10,000 feet on the south, west, and north slopes of

the San Francisco Peaks (Alexander and Hawksworth, 1975; Leiberg et al.

1904; Pearson, 1931).

Engelmann spruce is a principal host of A. microcarpum in the

Inner Basin of the San Francisco Peaks. This is the second known case

in North America of a dwarf mistletoe parasitizing species of two genera

as principal hosts. Arceuthobium tsugense (Rosendahl) G. N. Jones para­

sitizes both Pinus contorta Dougl. ex Loud, subsp. contorta and Tsuga

heterophylla (Raf.) Sarg. as principal hosts in British Columbia and

northern Washington (Orcas Island) (Wass, 1976; Smith and Wass, 1976).

Infection and mortality rates are much higher for Engelmann

spruce in the Inner Basin than in the Schultz Peak area, and consequent­

ly Engelmann spruce was classified as a secondary host in the latter '

area. These differences are probably a result of the relative abundance

of Engelmann spruce in the two areas, for it is far less abundant in the

Schultz Peak area. Most of the Schultz Peak infestations are near the V 31

elevational limits of A. microcarpum. Thus, climatic factors may also

be influencing the infection and mortality rates of Englemann spruce in

that area.

Some differences in host response were observed for Engelmann

spruce near Schultz Peak. Very dense, "round" witches' brooms were

formed instead of the "flat" witches* brooms usually formed by A. micro-

rgrpum in the Inner Basin and elsewhere. Unusually large stem swellings

were more frequent on Engelmann spruce also.

Southwestern white pine and corkbark fir were rare hosts of A.

microcarpum in the Schultz Peak area, but frequent observations of these

species in the Inner Basin failed to detect additional infections there.

These differences in host susceptibility and host response may

indicate there are slight physiological discontinuities between the

Schultz Peak population and other populations of A. microcarpum. but

further studies are needed to determine if they are taxonomically sig»>

nificant.

Geographic Variation in A. microcarpum

Analysis of morphological and physiological characters of the

northern and southern populations of A. microcarpum indicates there are

some consistent discontinuities. Shoots are larger for the southern

populations and flowering occurs slightly later. Hawksworth and Wiens

(1972) classified southwestern white pine as immune to A. microcarpum.

A. microcarpum rarely parasitizes this conifer on the San Francisco

Peaks, but my surveys in the southern populations of A. microcarpum did 32 not detect additional infections, although in those areas it is common to find SW W P in stands with heavily infected spruces.

It is not known if these differences between populations of A. microcarpum represent genetic variation, or if they are due to the in­ fluence of environmental and/or host variation. Latitudinal and eleva- tional differences may be influencing both shoot height and flowering.

The relative susceptibility of SW W P may be due to ecotypic variation within this species. Steinhoff and Andresen (1971) reported that col­ lections of SW W P from the San Francisco Peaks were morphologically intermediate between other populations of this species and limber pine.

Physiological differences may also occur among populations of SW W P which may influence its susceptibility to A. microcarpum.

Ecotypic variation in dwarf mistletoes is generally associated with parasitism of different principal hosts in various parts of a dwarf mistletoe's geographic range. These ecotypes are apparently not differ­ entiated enough to deserve taxonomic recognition (Hawksworth and Wiens,

1972). Although the discontinuities between the northern and southern populations of A. microcarpum appear to be geographically consistent, I do not believe these populations are sufficiently differentiated to warrant taxonomic recognition at this time. CHAPTER 3

THE DWARF MISTLETOES PARASITIZING SOUTHWESTERN WHITE PINE

Literature Review

Arceuthobium blumeri was described by Aven Nelson (1913) from a collection made by J. C. Blumer in 1910 from the Huachuca Mountains,

Arizona. Blumer (1910) had designated the mistletoe as Razoumofskya cyanocarpa (A. Nelson) Rydb. Razoumofskya had priority according to the

American Code of Botanical Nomenclature and therefore Standley (1916) transferred A. bl«"™»ri A. Nelson to Razoumofskya blumeri Standley.

Rankin (1918) followed Standley1s classification while Hedgcock (1915) and Tubeuf (1919) regarded all dwarf mistletoes parasitizing white pines as Razoumofskya cyanocarpa. The 1905 Vienna Botanical Congress had con­ served Arceuthobium M. Bieb. over Razoumofskya Hoff. (Nomina Conser- vanda No. 2091) but it was not until after the 1930 Cambridge Botanical

Congress that Arceuthobium finally replaced Razoumofskya.

Gill (1935) reduced several fall-flowering species of Arceutho­ bium to host forms of A. campylopodum. Those dwarf mistletoes parasit­ izing limber pine (Pinus flexilis), whitebark pine (Pinus albicaulis), bristlecone pine (BC P, Pinus aristata). and foxtail pine (Pinus balfouriana) were included under A. campylopodum forma cyanocarpum. A. campylopodum forma blumeri encompassed the dwarf mistletoes parasitizing

33 34

sugar pine (Pinus lambertiana Dougl.), western white pine (Pinus monti-

cola Dougl.) in California and Oregon and southwestern white pine (SW W

P, Pinus strobiformis) in Arizona and New Mexico. Jepson (1914) had

previously considered the dwarf mistletoe on sugar pine as A. campy-

lopodnm and later (Jepson, 1925) as A. campylopodum var. cryptopodum

Jepson, while Meinecke (1914) classified it under R. campylopoda Engelm.

On the other hand, Parish (1911) named it R. occidentale (Engelm.)

Kuntz. Gill's (1935) forma blumeri was distinguished from forma cyano- carpum by its host specificity, larger shoots, greenish color, and gen­ eral growth habit. Gill noted that f. blumeri was most often found on

sugar pine but was never abundant or seriously damaging to any host species.

Kuijt (1955, 1960a, 1960b, 1961, 1963) rejected Gill's taxo- nomic treatment of Arceuthobium and adopted an even more conservative view in which he considered A. campylopodum and A. vaginatum as a single variable species. Kuijt did not contribute a formal taxonomic treatment, however. Hawksworth and Wiens (1965) published descriptions of several new species of Arceuthobium from Mexico and stated that many of Gill's host forms could be distinguished morphologically, including A. campy­ lopodum f. cyanocarpum from f. blumeri. Hawksworth (1965) reported that

A. campylopodum f. cyanocarpum parasitizing BC P on the San Francisco

Peaks, Arizona was not found on nearby southwestern white pines. He regarded this as further evidence of the distinctness of f. cyanocarpum from f. blumeri. Hawksworth and Wiens (1970b, 1972) separated Gill's f. blumeri into three species based mainly on morphology, phenology, and 35

geographic distribution. New species were Arceuthobium californicum

Hawks. & Wiens primarily parasitizing sugar pine in California and Ore­

gon and Arceuthobium apachecum parasitizing SW W P in Arizona and New

Mexico. Arceuthobium blumeri parasitizing SW W P in southern Arizona

and northern Mexico was reinstated to specific rank. Detailed infor­

mation on the distribution, host range, morphology, phenology, and chem­

ical characters of these species was provided (Hawksworth and Wiens,

1972). A. californicum differs from A. apachecum and A. blumeri in hav­

ing much larger shoots, an earlier period of anthesis, distinct hosts,

and a more westerly distribution. A. blumeri can be distinguished from

A. apachecum by its larger shoots, shoot color, geographic distribution,

general growth habit, number of perianth lobes, and its rare induction

of witches' brooms (Hawksworth and Wiens, 1972).

Kuijt (1973) published a critical review of Hawksworth and

Wiens' taxonomic treatment of Arceuthobium where he strongly questioned

the classification of A. apachecum and A. blumeri as species. Kuijt

(personal communication, 1974) considers A. apachecum and A. blumeri to

be variable populations (perhaps ecotypes) of A. campylopodum.

Materials and Methods

Taxonomic Studies

Morphological Characters. Specimens of A. apachecum and A.

blimipri were examined which are on deposit at the U. S. Forest Service,

Forest Pathology Herbarium, Ft. Collins, Colorado (FPF) and the Univer­

sity of Arizona Herbarium, Tucson, Arizona (ARIZ). These represent an 36 estimated 90 percent of the herbaria specimens collected for these taxa.

Measurements and observations of morphological characters of A. blumeri and A. apachecum were made on 31 and 39 specimens respectively collected in 1975 and 1976 or previously deposited at FPF (see Appendix A, Speci­ mens Examined). The original measurements of shoot height and third internode dimensions made for these species by Hawksworth and Wiens

(1972) were available and were also used in arriving at maximum, mini­ mum, and mean values for these characters. Measurements and observations were made for the following morphological characters: male and female dominant shoots (non-systemic infections only)-- height, basal diameter, length and width of the third internode, color, growth habit, length and width of staminate spikes in summer; staminate flower diameter; perianth lobes— length, width, color, number; mature fruit (dried)-- length, width, color, length of the proximal end of the bicolored fruit; seed — length, width, color; pollen--length, width.

flhvsiological Characters. The physiological characters analyzed were.--

Phenology:- The methods used to determine the periods of anthesis and seed dispersal for A. apachecum and A. blumeri were described above.

Most observations for both taxa were made in Arizona from 1974 through

1976. Additional phenology data for these species were obtained from

Dr. F. G. Hawksworth who had compiled an incomplete phenology record for these taxa using the system described above.

Host Range: The taxonomic significance of a dwarf mistletoes' host range was discussed above. The methods used to determine the natural 37

host ranges of A. apachecum and A. blumeri are described under Patho­

logical Impact Studies.

Host Response: Variations in host response to dwarf mistletoe in­

fection were discussed above. Observations of host response, including

stem swelling and the type of witches' broom formed, were made for A.

apachecum and A. blumeri. as for the BC P D M.

Chemical Characters. The absence or presence of certain pheno­

lic compounds (flavonoids) has chemotaxonomic significance because

Mendelian mechanisms apparently control these qualitative differences

(Alston et al. 1965). Hawksworth and Wiens (1972) analyzed the pheno­

lic constituents (anthocyanins, flavonoids, flavones, and cinnamic acid

derivatives) of both A. apachecum and A. blumeri chromatographically.

However, they considered their results preliminary, partially because of

the small number of individuals analyzed. Therefore, additional samples

of these taxa were analyzed following the methods of Hawksworth and Wiens

(1972). All samples were analyzed in the first dimension only and

anthocyanins were not considered,. (See Appendix A, Specimens Examined.)

Distribution Studies

Hawksworth and Wiens (1972) provided the approximate geographic,

and elevational limits of A. apachecum and A. blumeri in the Southwest

and northern Mexico. Additional surveys were made in these regions by

auto and foot at various times between 1974 and 1976 to provide more in­

formation on the distributions of these species. 38

Pathological Impact Studies

The natural host ranges of A. apachecum and A. blumeri in Ari­ zona and the degree of damage they inflict upon their hosts were partially determined by randomly placing 27 rectangular 0.25 or 0.50 acre plots totaling 7.50 acres in mistletoe-infested areas in the

Santa Catalina, Santa Rita, and Huachuca Mountains of southern Arizona in 1975. Every conifer greater than 4 inches diameter breast height in a plot was examined. The host species, dwarf mistletoe rating (6-class system, Hawksworth, 1961), and condition (living or dead) of each tree were recorded. Approximately 1900 trees were examined by this method.

In 1976 line transects 200 feet apart were randomly placed in a total of eight mistletoe-infested and five non-infested mixed conifer stands in the White, Pinaleno, and Huachuca Mountains of Arizona and in the Mogollon Mountains of New Mexico. Ten to twenty circular 0.10 acre plots were located at 200 foot intervals along each transect line. Each conifer greater than 4 inches diameter breast height within a plot was examined and the host species, dwarf mistletoe rating (D. M. R.), and condition (living or dead) of each tree were recorded. Approximately

240 acres were sampled and 5941 trees were examined.

General observations were also made in the field for hosts of A. apachecum and A. blumeri from 1974 through 1976. Specimens of host ma­ terial for use in identification were collected where uncertainty exist­ ed regarding the taxonomic status of the host. This information was combined with plot data and each host of A. apachecum and A. blumeri was placed in one of the five natural susceptibility classes established by 39

Hawksworth and Wiens (1972). Data on the Immune species of both taxa are from Hawksworth and Wiens (1972).

Infection and mortality rates were compared on a percentage basis for every host-dwarf mistletoe combination observed in the plots.

Mortality rates for SW W P were also-compared as a percentage of all trees examined for each of the following classes of dwarf mistletoe in­ fection: non-infested (D. M. R.; 0); lightly infested (D. M. R.; .0.1

- 2.0); moderately infested (D. M. R.; 2.1 - 4.0); heavily infested (D.

M. R.; 4.1 - 6.0).

Results

Taxonomic Studies

Morphological Characters. Mean heights of male and female dom­ inant shoots of A. blumeri were approximately 2 cm. larger than those of

A. apachecum, and maximum shoot heights of A. bliimeri were approximately twice those of A. apachecum (Table 8). Analysis of mean and maximum shoot heights of separate populations from east-central Arizona to south­ ern Durango, Mexico indicates that shoots are smaller in the northern populations of both species (Table 9).

The mean basal diameter and third internode dimensions of A. blinneri were larger than those of A. apachecum but these differences are directly related to differences in shoot heights. Distinct color dif­ ferences exist between shoots of these species. A. blumeri varies from light green to straw or gray, while A. apachecum varies from yellow-green to blue or reddish (Figures 8 and 9). Both species parasitize SW W P Table 8. Comparison of shoot heights, basal diameters, third internodes, lateral staminate spikes, staminate flower diameters, and fruits of Arceuthoblum apachecum and Arceuthoblum blumerl

A. apachecum A. blumerl Character Mean Max. Min. No. Measured Mean Max. Min. No. Meat Height: Female 4.6 9.5 2.5 234 6.7 18.0 3.0 188 (cm) Male 3.8 7.5 2.0 174 5.5 16.0 2.0 •87

Basal Diameter 1.8 4.4 0.8 224 2.2 3.4 1.2 173 (mm)

ttiird Internode: (mm) Length 6.5 13.0 2.0 185 9.1 20.0 4.0 180

Width 1.3 3.0 0.4 185 1.5 2.0 1.0 180

Lat. Staminate 7 x 1 95 12 x 2 35 Spikes (L x W mm) / Staminate Flower 2.9 4.2 2.2 296 3.3 4.4 2.0 146 Diameter (mm)

Fruit: Length 3.3 4.0 2.6 310 3.5 4.0 2.0 175 (mm) Width 1.9 2.4 1.4 310 2.0 2.4 1.6 175

Proximal End 2.3 3.0 1.6 310 2.2 2.8 2.0 175 Table 9. Geographic variation in shoot height and perianth lobe number of Arceuthoblum apachecum and Arceuthoblum blumeri.

A. apachecum Shoot Ht. (cm) Female Shoot Ht. (cm).Male Perianth Lobe Number (%)

Population Mean Max. No. Meas. Mean Max. No. Meas. 3 4 5 6 No. Counted

White Mt8., Az. 3.5 5.0 31 3.0 4.3 34 81 19 0 0 390

Pinaleno Mts., 4.1 5.0 16 3.8 4.4 15 68 30 2 0 50 Az.

Chiricahua 5.0 6.0 11 4.4 5.0 7 42 54 4 0 50 Mts., Az.

Santa Catalina 5.8 7.5 67 4.4 6.1 66 54 42 4 0 480 Mts., Az.

Santa Rita 6.4 9.5 84 4.8 7.5 66 43 48 8 0 500 Mts., Az.

A. blumeri

Huachuca Mts., 5.7 8.5 56 4.2 8.0 49 30 53 16 1 700 Az.

Chihuahua, 6.5 11.5 26 4.8 8.0 8 40 58 2 0 50 Mexico

Durango, 8.0 18.0 96 7.6 16.0 36 55 44 1 0 100 Mexico 42

Figure 8. Female shoots of Arceuthobium blumeri on Pinus strobiformis, Huachuca Mountains, Arizona.

Figure 9. Male and female shoots of Arceuthobium apachecum on Pinus strobiformis. White Mountains, Arizona. 43 but their general growth habit is different on this host. A. apachecum

shoots are consistently densely clustered around infected branches and

may even completely obscure a branch. A. blumpri shoots are not usually densely clustered.

Mean lateral staminate spikes are larger for A. blumeri (Table

8); this character is apparently geographically consistent. The mean staminate flower diameter of A. blumeri is larger than that of A. apachecum, but their size range is approximately the same. Perianth lobe dimensions are continuous, but their color varies. Perianth lobes of A. apachecum are the same color as the male shoots, but perianth lobes of A. blumeri are darker brown than the male shoots. The number of perianth lobes for each species varies also. A. apachecum is predom­ inantly 3-raerous (65%), occasionally 4-merous (33%), and rarely 5- merous (2%), A. blumeri is predominantly 4-merous (53%), occasionally

3 or 5-merous (31% and 15% respectively), and rarely 6-merous (1%).

Comparison of perianth lobe number by populations from east-central

Arizona to southern Durango, Mexico indicates that 3-merous staminate flowers predominate in northern populations of A. apachecum and gradual­ ly decrease until the 4-merous condition predominates in most of the southern populations of this species (Table 9). The few counts made of

A. blumeri in Mexico indicate that there may be a shift to 3-merous staminate flowers predominating in the extreme southern populations of this species. Flowers with six lobes were found only in the Huachuca

Mountain population of A. blumeri. 44

Mean fruit dimensions and size ranges are approximately the same for both species (Table 8). The proximal end of the bicolored fruit was light green for both taxa and the color of the distal end was usually the same color as the female shoots. Seed dimensions averaged 2.6 x 1.1 mm. for A. blumeri and 2.3 x 1.0 mm. for A. apachecum. Seeds of A. blumeri are dark green while seeds of A. apachecum are light green, but seeds of Mexican populations of A. blumeri were not examined. Pollen grains were approximately the same for both species: 21 x 19 jam. for A. apachecum and 21 x 20 jam. for A. blumeri.

Physiological Characters. The results of the physiological characters analyzed were —

Phenology: Flowering and seed dispersal data are presented in

Figure 10.

Host Range: Results are presented under Pathological Impact Studies

Host Response: Results are presented under Pathological Impact

Studies.

Chemical Characters. The results of chromatographic analysis of A. apachecum and A. blumeri are presented in Table 10.

Distribution Studies

A. apachecum is distributed from east-central Arizona (White

Mountains) and central New Mexico (Mangas, Gallo, San Mateo, Magdalena,

Mogollon, and Capitan Mountains) into southern Arizona and New Mexico

(Pinaleno, Black Range, Chiricahua, Rincon, and Santa Catalina Mountains

Figure 11). It is also known from the Sierra del Carmen in northern ANTHESIS

A. blumeri

A. apachecum

SEED DISPERSAL

A. blumeri

A. apachecum

15 31 15 31 15 30 15 31 July August September October

Figure 10. Approximate periods of anthesis and seed dispersal of Arceuthobium blumeri and Arceuthobium apachecum. -- Peak periods are shown by solid bars; Number of observations, ( ). Table 10. Phenolic constituents of Arceuthobium apachecum and Arceuthobium blumerl as determined by paper chromatography.

Flavones, Flavonols, and Cinnamic Acid Ester Derivatives SAMPLE TRIALS Yl Bl BGl YO B2 BG2 A1 YG A2 B3 A3 A4 B4 A5 B5

A. apachecum RLM 7556 4 ++ — ++++ — ++ — — — ++ — ~ ++ — ++

RLM 7557 3 ++ -- ++ -H- — ++ ++--++ ++ ++ + ++ — ++

RLM 7558 3 ++ — ++++ — ++ ++--++ ++ ++ + ++ ~ ++

RLM 7576 3 ++ — ++++ — ++ ++ — ++ ++ ++ ++++-- ++

* H & W, 1972 ++ — ++++ — ++ ++ — ++ ++ ++ ++ ++ — ++

A. blumerl RLM 7552 4 ++ + + ++ ++ ++ -H- -- ++ ++ ++ ++++-- ++

RLM 75111 1 ++ — + ++ ++ ++ ++ -- ++ ++ ++ ++++++ ++

RLM 75120 4 +++ — ++ ++ 4+ ++--++ ++ ++ ++ ++ — ++

* H & W, 1972 +++ — ++ + + ++ — ++ ++ ++ ++ ++ ++ ++

++ ° detected in all trials; + •= sometimes not detected; 8 not detected. *as reported by Hawksworth and Wiens, 1972. 47

A. blumerl

Figure 11. Geographic distribution of Arceuthobium apachecum and Arceuthobium blunffiri. 48

Coahuila, Mexico (Hawksworth and Wiens, 1972), but has not been found- elsewhere in Mexico.

Ify studies indicate that the dwarf mistletoe population in the

Santa Rita Mountains of southern Arizona is also A. apachecum. and not

A. blumeri as reported by Hawkworth and Wiens (1972). I could find no evidence of both taxa occurring in this mountain range. However, the

Santa Rita population of A. apachecum does have some morphological and

physiological characteristics which are intermediate between those of A. bl"T"pri and other A. apachecum populations. The Santa Rita population has slightly larger shoots, flowers earlier, and has a slightly higher

proportion of 5-merous staminate flowers than the more northern popula­ tions of A. apachecum, but it is similar to these populations in all other characters.

Surveys in northern New Mexico (Jemez, Sangre de Cristo, Cebol- ieta, and Zuni Mountains), southern Colorado (San Juan Mountains), and east-central Arizona (Mogollon Rim area west of Showlow, and Pinal

Mountains) did not disclose additional populations of A. apachecum al­

though SW W P was present in these areas.

The elevational range of A. apachecum is from 6500 feet in the

Santa Rita Mountains of Arizona to 9800 feet in the San Mateo Mountains of New Mexico. The specimen I examined from the Sierra del Carmen was

very similar to A. apachecum specimens from Arizona and New Mexico.

A. blri is distributed from southern Durango, Mexico, north

through the Sierra Madre Occidental to the Huachuca Mountains of southern

Arizona (Figure 11). Although it has not been collected from Sonora, 49' Mexico, it can be expected to occur there in the higher mountain ranges.

It is also known from Cerro Potosjt in Nuevo Leon, Mexico. Field obser­ vations of the Cerro Potosf population indicated that it is very similar to the A. blumeri populations of the Sierra Madre Occidental.

The known elevational range of A. blumeri reported by Hawksworth and Wiens (1972) was from 7100 to 9800 feet, but it occurs as high as

10,600 feet on Cerro Potosf.

Pathological Impact Studies

A. apachecum and A. blumeri parasitize SW W P exclusively. Be­ cause other conifers distributed within the geographic ranges of these dwarf mistletoes are apparently not parasitized, they are classified as immune. Species immune to A. apachecum are: Abies concolor (white fir)

Abies lasiocarpa var. arizonica (corkbark fir), Picea pungens (blue spruce), Pinus edulis (pinyon pine), Pinus engelmannii Carr. (Apache pine), Pinus ponderosa Laws. var. arizonica (Engelm.) Shaw (Arizona pine), Pinus ponderosa Laws. var. scopulorum Engelm. (ponderosa pine), and Pseudotsuga menziesii (Douglas-fir). Species immune to A. blumeri are: Abies concolor. Abies durangensis Martinez, Abies veiarii Martinez

Pinus cooperi C. E. Blanco (Cooper pine), Pinus engelmannii. Pinus leiophylla Schiede & Deppe var. leiophylla. Pinus ponderosa var. arizonica. Pinus ponderosa var. scopulorum. and Pseudotsuga menziesii,

• A few cones collected from SW W P infected by A. blumeri in

Chihuahua and Durango, Mexico were over 15 cm. long and strongly resem­ bled cones described for Pinus ayacahuite var. brachyptera Shaw (Shaw,

1909; Martinez, 1948; Loock, 1950). However, foliage of these collections was typtcal for SW W P (Sargent, 1897; Soto, Barrett, and

Little, 1962; Steinhoff and Andresen, 1971). Pinus ayacahuite var. brachyptera is generally considered to be synonymous with Pinus strobi- formis (Gausen, 1960; Soto, Barrett, and Little, 1962; Critchfield and

Little, 1966; Andresen and Steinhoff,. 1971; Mirov, 1967) and until the taxonomic status of the white pines of northern Mexico is investigated in more detail, host populations of A. blumeri in this region should be designated as Pinus strobiformjs.

Hawksworth and Wiens (1972) reported that A. apachecum consis­ tently caused formation of witches' brooms and that A. blumeri rarely did so. Observations indicate that A. blumeri rarely causes brooms at lower elevations in the Huachuca Mountains, but consistently causes them at higher elevations (Figure 12). Witches' brooms also are caused by A. blumeri at higher elevations in Chihuahua, Durango, and Nuevo Leon.

Witches' brooms are less common at lower elevations in the Santa Rita

Mountains, but other populations of A. apachecum appear to consistently cause formation of witches' brooms (Figure 13). Both species usually produce non-systemic infections, but may rarely cause systemic infec­ tions. Swelling of infected stems is not unusually large for either species and shoot development is generally abundant, but the shoots of

A. apachecum are usually more densely clustered around the infected branch.

Transect data indicate that in Arizona mixed conifer stands in­ fested with A. vaginatum, A. douglasii, and A. apachecum or A. blumeri. the intensity~of infection and mortality of white pines is greater than 51

Figure 12. Witches' brooms on Pinus strobiformis caused by Arceuthobium blumeri. Huachuca Mountains, Arizona. 52

Figure 13. Witches' brooms on Pinus strobiformis caused by Arceuthobium apachecum. Santa Catalina Mountains, Arizona.

j'

!•: 53 that of the principal hosts of A. vaginatum and A. douglasii (Table 11).

The percentage of dead trees greatly increases for SW W P as the inten­ sity of dwarf mistletoe infection (as indicated by average D. M. R.) increases (Table 12). The mortality rate of SW W P in heavily infested plots (average D. M. R.: 4.1 - 6.0) with A. apachecum was approximately thirty times greater than for non-infested (average D. M. R.: 0) and lightly infested plots (average D. M. R.: 0.1 - 2.0) (Table 12). The mortality rate of both moderately (average D. M. R.: 2.1 - 4.0) and heavily infested plots with A. blumeri was approximately four times greater than lightly infested plots and twenty times greater than non-infested plots.

A. apachecum was usually sympatric with A. vaginatum and/or A. douglasii. A. apachecum and A. blumeri were more common in mixed conifer stands where SW W P was one of the predominant species.

Discussion

The Taxonomic Status of the Dwarf Mistletoes Parasitizing SW W P

Gill (1935) designated forms of A. campylopodum exclusively on the basis of host relationships because he recognized few morphological differ­ ences between these taxa. Hawksworth and Wiens (1970a, 1970b, 1972) main­ tained that Gill's host forms were morphologically and physiologically separable and constituted discrete species. Geographically consistent morphological and physiological discontinuities have been found between the

Southwestern and Mexican dwarf mistletoe populations exclusively parasit­ izing Plnus strobiformis. These two populations are currently Table 11. Infection and mortality rates in Arceuthoblum-lnfested mixed conifer stands in Arizona.

Trees Infected Dead Avg. D. M. R,* Area Sampled Conlfer-Arceuthobium sp. In plots "L % (acreal

Plnus oonderosa-A. vaelnatum 2964 46.8 4.0 1,2 240

Pseudotsuga menziesll- A. 2353 49.1 4.9 1,2 " douglasii

Plnus strobiformi8- A. 1284 46.5 11.6 1,7 " apachecum

Abies concolor- A, douglasii 648 0,1 0.1 0,1 11

Picea eneelmannli- A. 345 9,9 2.0 0,2 " mlcrocarpum

Plnus strobiformis- A. 324 - 30.4 11,4 1.8 38 blumeri **

*Hawksworth, 1961.

**Data from the Huachuca Mountains only. 55

Table 12. Mortality of southwestern white pines in Arizona caused by Arceuthobium apachecum and Arceuthobium blumeri in relation to average dwarf mistletoe rating (D. M. R.).

A. apachecum A. blumeri D. M. R.* %** ~ %*** 0 0.8 0

0.1 - 2.0 1.2 5.1

2.1 - 4.0 12.9 22.2

4.1 - 6.0 31.6 19.8

Mean 11.6 11.4

*Hawksworth, 1961. **Total trees examined - 2899 in 329 plots. ***Total trees examined = 863 in 42 plots. 56 designated as A. apachecum and A. blumeri by Hawksworth and Wiens

(1970b, 1972). However, the taxonomic significance of discontinuities between these species has been questioned (Kuijt, 1973).

A. apachecum and A. blumeri are very similar morphologically.

The most geographically consistent discontinuities between these taxa are male and female shoot color, growth habit, lateral staminate spike dimensions, and perianth lobe color. Shoot size and perianth lobe num­ ber also appear to be discontinuous. However," analysis of these characters indicates that geographic variations occur. Although average shoot heights are different for these species, shoot sizes are smallest in the northern populations of A. apachecum. largest in the southern populations of A. blumeri. and approximately the same near the geographic boundary between these taxa. Variations in the number of perianth lobes appears to follow a geographic pattern also, although more information is needed for Mexican populations of A. blumeri.

A. blumeri flowers slightly earlier than A. apachecum in Arizona, but the Santa Rita Mountain population of A. apachecum flowers at approx­ imately the same time as A. blumeri. Information on the flowering period of A. blumeri in Mexico is inadequate, but it appears to flower at about thp samp time as the Arizona population. There is no evidence of lati­ tudinal flowering variation for A. apachecum and A. blumeri, but altitudinal variations occur. Scharpf (1965) reported that fall- flowering sppcies of Arceuthobium flpwered earlier at higher elevations in California, but the opposite is true for both A. apachecum and A. blumeri. Lower populations flower earlier than higher populations in 57

the same mountain range. The variation in flowering period between

Arizona populations of A. apachecum and A. blumeri may represent a tax-

onomically significant physiological discontinuity between these taxa.

However, the occurrence of an A. apachecum population, which flowers at

approximately the same time as A. blumeri, near the geographic boundary

separating these species, indicates that this discontinuity may not be genetically constant. When doubt exists about the genetic fixity of a character it is advisable not to use it in the delimitation of taxa

(Davis and Heywood, 1963). Variation in flowering periods of dwarf mistletoes is a complex phenomenon that deserves more study before it is heavily considered in delimiting species of Arceuthobium.

Consistent formation of witches' brooms by A. apachecum and the rare formation of brooms by A. blumeri was considered a taxonomically significant discontinuity between these taxa by Hawksworth and Wiens

(1972). Some populations of A. blumeri and A. apachecum rarely form witches' brooms at lower elevations, but brooms are common at higher elevations in the same area. The reasons for this apparent elevational relationship to broom formation are not known, but this character does not represent a significant physiological discontinuity between these dwarf mistletoes.

Chromatographic analysis of these species disclosed some chem­ ical differences. Only one compound was consistently present in A. blumeri while completely absent in A. apachecum. The presence of two compounds varied in A. blumeri, but were consistently absent from A. apachecum and one compound consistently found in A. apachecuta was 58 occasionally detected in A. blumeri. These were the only differences detected and when compared to the chemical differences between other species of Arceuthobium (Hawksworth and Wiens, 1972) they appear to rep­ resent a relatively small discontinuity between the two species under study.

The exclusive parasitism of a single host species by both taxa is unique in Arceuthobium (Hawksworth and Wiens, 1972) and represents a significant physiological continuity between A. apachecum and A. blumeri.

Some of the apparent discontinuities between A. apachecum and A. blumeri are a result of geographic variation along a north-south gradi­ ent. Therefore, these variations might be considered to represent eco- typic variation. However, ecotypic variation in dwarf mistletoes is generally associated with parasitism of different principal hosts in various parts of a dwarf mistletoes' geographic range (Hawksworth and

Wiens, 1972). Significant morphological differences are usually not found between such ecotypes. Therefore, the dwarf mistletoe populations parasitizing SW W P do not conform to the general concept of ecotypes in

Arceuthobium. The morphological and perhaps physiological differences detected between these populations may be caused by environmental modi­ fications or ecotypic variation within the host population. Ecotypic variation in populations of SW W P has been suggested by Steinhoff and

Andresen (1971) and the various taxonomic treatments of Pinus strobi- formis in different parts of its geographic range (Andresen and Stein­ hoff, 1971) may reflect such variation in this species. Dwarf mistletoe 59

shoot size is directly associated with host vigor (Hawksworth and Wiens,

1972). Therefore, this character as well as other morphological and

physiological characters could well be influenced by ecotypic variation

within a host species. A. cyanocarpum. another parasite of white pines .

(Pinus flexilis and Pinus longaeva D. K. Bailey), is morphologically and

physiologically similar to A. apachecum. The most common principal host of A. cyanocarpum (P. flexilis) is closely related to Pinus strobiformis

(Steinhoff and Andresen, 1971) and variations between these hosts could

be influencing the discontinuities detected between A. cyanocarpum and

A. apachecum (Hawksworth and Wiens, 1972). Further studies are needed

to determine the influence that different hosts or geographic variation

within a host population can have on the morphological and physiological characters of a dwarf mistletoe.

I believe several of the morphological discontinuities between

the Southwestern and Mexican dwarf mistletoe populations parasitizing

Pinus strobiformis are taxonomically significant and indicate that these

populations should be given taxonomic recognition. These populations

may represent intermediate stages of gradual evolutionary divergence and

perhaps their recognition at the subspecific level would be more repre­ sentative of their natural relationship. Hawksworth arid Wiens (1972) defined subspecies of Arceuthobium as "geographically restricted popula­

tions, delimited by relatively few but consistent variations." The

taxonomic treatment of the mistletoes parasitizing Pinus strobiformis is dependent then, on what is considered to be "relatively few but consis­

tent variations." This decision must be based on a comparison of the 60 discontinuities used to delimit other species and subspecies of Arceu- thobium.

Examination of the discontinuities separating currently recog­ nized subspecies of Arceuthobium gillii Hawks. & Wiens and A. vaginatum

(Hawksworth and Wiens, 1965, 1972) indicates there are more differences between these taxa than between A. apachecum and A. blumeri. However, several species in the Series Campylopoda Hawks. & Wiens (Hawksworth and

Wiens, 1970b, 1972), including A. apachecum and A. blumeri, are delim­ ited by relatively few discontinuities, so the classification of taxa in this Series is relatively consistent. Consistency in the classification of a group is desirable and changes in the rank of taxa for motives of consistency or for achieving a more balanced natural classification are justified (Davis and Heywood, 1963). Since species and subspecies of

Arceuthobium differ only in the number of discontinuities between them

(Hawksworth and Wiens, 1972), the elevation to specific level of cur­ rently recognized subspecies of Arceuthobium would alleviate the apparent inconsistency I feel exists in the current classification of

Arceuthobium. Changes in the rank of tribes, sections, or subspecies are generally less confusing and inconvenient than changes in the rank of higher taxonomic categories (Davis and Heywood, 1963). Additional field studies of the subspecies of Arceuthobium have been conducted and results indicate that some changes in their rank would create a more natural classification of Arceuthobium (F. G. Hawksworth, personal com­ munication, 1977). 61

Hawksworth and Wien's species concept in Arceuthobium may appear to "stretch" the generally accepted concepts of plant species, but if characteristics of this group available for taxonomic analysis are con­ sidered, their delimitation of species appears reasonable. The dwarf mistletoes have undergone extreme morphological reduction due to their parasitic habit and a relatively small number of morphological charac­ ters are available for use in their classification. Therefore, the emphasis on the use of life cycles and physiological characters, in the classification of Arceuthobium advocated by Hawksworth and Wiens (1970a,

1972) is needed and it is valid as long as the discontinuities detected between these characters can be shown to be genetically constant. How­ ever, it is often difficult to distinguish between environmental modification and genetically fixed variations in the absence of experi­ mental evidence, particularly when small differences in physiological characters exist between taxa. Determination of the relative genetic compatibility between dwarf mistletoes through artificial cross pol­ lination studies should provide information concerning the genetic fixity of physiological variations between taxa. Cross pollination studies using A. apachecum and A. blumeri are in progress and should be expanded to include additional species. These and additional taxonomic studies of the other species of Arceuthobium in the Series Campylopoda will provide more information concerning the natural relationships of these taxa. Therefore, a change in the rank of A. apachecum or A. blumeri should not be considered at this time. 62

These investigations may indicate that the creation of addition­

al species or subspecies of Arceuthobium is necessary to create a more

natural classification of this group. Stability in the classification

of such an economically important group is desirable, yet it is doubtful

that the classification of Arceuthobium will stabilize for some time be­

cause very little is known about the distributions and natural relation­

ships of the recently discovered Mexican and Central American dwarf

mistletoes (Hawksworth and Wiens 1965, 1970b, 1972). More than one-half

of the taxa now recognized have been described in the last 10 to 15

years and a great deal of critical work on the entire genus is required

before a "stable" classification system can be evolved.

Distribution and Pathological Impact of A. apachecum and A. blumeri in the Southwestern United States

A. apachecum and A. blumeri are not as widespread geographically

as the two most damaging dwarf mistletoes in the Southwest., A. douglasii

and A. vaginatum subsp. cryptopodum (Andrews and Daniels, 1960; Graham,

1961; Hawksworth, 1961; Hawksworth and Wiens, 1972; Lightle and Weiss,

1974). A. apachecum is not found north or west of the White Mountains,

Arizona or north of the Gallo, Mangas, and Magdalena Mountains in New

Mexico. These northern limits of A. apachecum are at approximately the

same latitude and indicate that A. apachecum may be restricted from more

northern habitats by climatic factors, since its host extends much

further north. A. apachecum ranges south to the Finaleno, Chiricahua,

Santa Catalina, Rincon, and Santa Rita Mountains of southern Arizona.

It has not been reported from the Final and Galiuro Mountains of 63 south-central Arizona or from the Sacramento, Guadalupe, or Animas

Mountains of southern New Mexico, although Pinus strobiformis occurs in these areas (Critchfield and Little, 1966; Hawksworth and Wiens, 1972).

A. blumeri is only found in the United States in the Huachuca Mountains of southern Arizona, but it ranges south to southern Durango, Mexico.

These studies indicate that A. apachecum is not abundant within its geographic range. Reports (Gill, 1935) and dwarf mistletoe surveys

(Andrews and Daniels, 1960; Gottfried and Embry, 1977) also indicate that it is not abundant. However, an earlier listing of A. apachecum as an endangered species by the U. S. Department of the Interior, Fish and Wildlife Service, Threatened or Endangered Fauna or Flora, Vol. 40,

No. 127»(July, 1975) is not a valid representation of the abundance of this dwarf mistletoe. Mixed conifer stands infested with A. apachecum generally had an unusually high abundance of SW W P. The relatively low abundance of A. apachecum may be related to the normal low abundance of its host in Southwestern mixed conifer forests (Gottfried and Embry,

1977; Jones, 1974).

A. apachecum and A. blumeri severely damage SW W P in a few areas in Arizona. Mortality in these areas is directly related to the intensity of dwarf mistletoe infection. Moderately and heavily infested

* areas have significantly higher mortality rates than non-infested and lightly infested areas. SW W P is not an important commercial species in the Southwest and since A. apachecum and A. blumeri are not abundant in this region, their economic impact is minimal. Control of these dwarf mistletoes alone would seldom be practical, but they are commonly 64 sympatric with other dwarf mistletoes whose control is often a principal consideration of the forest manager in the Southwest (Jones, 1974). A. apachecum can cause damage in high-value recreation areas and its con­ trol in these areais may be beneficial. The development of forest management recommendations .to control dwarf mistletoes in Southwestern recreation areas should have a high priority because public recreation is a major use of Southwestern National Forests. Heavily infected trees are unsightly and are often invaded by secondary pathogens, including butt and root rots, which predispose them to windthrow, thereby creating a possible safety hazard. The gradual removal of infected southwestern white pines along with favoring the regeneration of immune species .could eventually eradicate A. apachecum from an area without causing an abrupt change in the vegetation. In areas where A. apachecum is sympatric with other damaging dwarf mistletoes control procedures would be dependent on the mistletoes present, their relative abundance, and the ecological characteristics of the area. APPENDIX A

SPECIMENS EXAMINED

Hie dwarf mistletoe specimens examined In these studies are listed: the collector, collection number, host, location, and date are given for each specimen. An asterisk after a collection number denotes a specimen used In the morphological analyses and two asterisks after a date denotes a specimen used in the chromatographic analyses.

Collection numbers followed by FPF or ARIZ are housed at the U. S.

Forest Service, Forest Pathology Herbarium, Ft. Collins, Colorado or at the University of Arizona Herbarium, Tucson, Arizona, respectively.

Four collector abbreviations are used in the specimens listed: RLM «

R. L. Mathiasen, H = F. G. Hawksworth, 1 • P. C. Lightle, and W • Del

Wiens.

/

65 1. Arceuthoblum apachecum

Specimens examined: all on Pinus stroblformls'

Collector Number Location Date Arizona

RLM 7504* Onion Saddle, Chiricahua Mountains 7-8-75

RLM 7543* FPF Big Lake, White Mountains 8-18-75

RLM 7502 FPF Wattmid Ridge, Chiricahua Mountains 7-7-75

RLM 7556* FPF Baldy Saddle, Santa Rita Mountains 8-24-75**

RLM 7557* 4 mi. from Madera Canyon on old Mt. Wrightson 8-24-75** trail, Santa Rita Mountains

RLM 7558* FPF Top of Mt. Lemmon, Santa Catallna Mountains 8-28-75**

RLM 7559* Bear Wallow, Santa Catallna Mountains 8-28-75

RLM 7567* Big Lake, White Mountains 9-2-75

RLM 7569* 2 ml. E. of Green Peak, White Mountains 9-3-75

RLM 7576 1.2 mi. above Josephine Saddle, Santa Rita Mtns. 9-11-75**

RLM 7592* 4 mi. E. of Hospital Flat, Pinaleno Mountains 9-23-75

RLM 7595* Bear Wallow, Santa Catallna Mountains 9-25-75

RLM 75102* .4 mi. S. of Hospital Flat, Pinaleno Mountains 10-4-75 Collector Number Location Date

RLM 7624* 1.2 mi. above Josephine Saddle, Santa Rita Mtns. 7-30-76

RLM 7626* Bear Wallow, Santa Catalina Mountains 7-31-76

RLM 7629* 2 mi. E. of Green Peak, White Mountains 8-17-76

RLM 7630* 5 mi. S. of Gagar on road to Big Lake, White Mtns. 8-17-76

RLM 7633* Bear Wallow, Santa Catalina Mountains 8-19-76

RLM 7637* Top of Mt. Lemmon, Santa Catalina Mountains 8-21-76

RLM 7640* Baldy Saddle, Santa Rita Mountains 8-24-76

RLM 7644* 2 mi. G. of Green Peak, White Mountains 8-26-76

RLM 7651* .4 mi. S. of Hospital Flat, Pinaleno Mountains 9-1-76

H 796* FPF Mt. Wrightson Trail, 4 mi. from end of road in 6-15-65 Madera Canyon, Santa Rita Mountains

H 1453 FPF 4 mi. N. of Reno Lookout on new road to Black 6-73 River, White Mountains

H 822 FPF Ca. .2 mi. E. of Big Lake on Springerville road, 5-18-62 White Mountains

L 64-21 FPF 1 mi. S. of Mogollon Rim on U. S. 666, White Mtns. 9-17-64 ARIZ

H & L 156* FPF .25 mi. S. of Onion Saddle, Chiricahua Mountains 4-1-62 Collector Number Location Date

H & L 1105 FPF .5 mi. G. of Hospital Flat, Pinaleno Mountains 9-11-68 ARIZ

H & L 1107* FRF Onion Saddle, Chiricahua Mountains 9-12-68 ARIZ

H & L 228* FPF .5 mi. E. of Hospital Flat, Pinaleno Mountains 7-4-62

R. A. Morrow 7501* FPF Bear Wallow, Santa Catalina Mountains 9-13-75

Tom Ela FPF Mica Mountain, Saguaro National Monument, 7-14-68 Rincon Mountains

H & L & R. L. 1110* FPF ISOTYIE - Near summit of Mt. Lemmon, Santa 9-13-68 Gilbertson Catalina Mountains

H & L 167* FPF Bear Wallow, Santa Catalina Mountains 4-3-62

RLM 7427 FPF .75 mi. below Josephine Saddle on old Mt. 10-13-74 Wrightson trail, Santa Rita Mountains

RLM 7428 FPF 1.6 mi. above Josephine Saddle on Mt. Wrightson 10-13-74 trail, Santa Rita Mountains

New Mexico

H & L 105 FPF 2 mi. E. of Capitan Gap on Capitan Trail road, 3-27-62 Capitan Mountains

H & L 220* FPF 7 mi. E. of Mogollon on Route 78, Mogollon 7-3-62 Mountains CTv 00 Collector Number Location Date

H & L 212* FPF Summit 6 mi. S, of Luna on U. S. 260, White Mtns. 7-2-62

H & L 892 FPF Just N. of Rocky Creek Campground on State 61 7-6-66

H & L 929 FPF 1 mi. E. of Fox Mountain 7-11-66

H & L 1098 FPF .5 mi. E. of Capitan Gap, Capitan Mountains 9-9-68

H & L 1102 FPF .25 mi. W. of Emory Pass, Black Range 9-10-68

H & L 1117 FPF 13.2 mi. S. of U. S. 60 on State 52, San 9-15-68 Mateo Mountains

65-36* FPF 12 mi. S. of U. S. 60 on State 52, San Mateo 8-24-65 Mountains

H 1687 FPF 6 mi. above Water Canyon Campground on road 11-18-75 to Langmuir Laboratory, Magdalena Mountains

L 66-19 FPF North Mount Baldy, Magdalena Mountains 6-20-66

L 65-40 FPF 17 mi. N. of Mimbres Ranger Station on Route 8-25-65 67, Pinos Altos Range

H & R. Scharpf 696* FPF On road .5 mi. below Mangas Mountain Lookout, 9-5-64 Mangas Mountains

L. S. Gill, D. FP 89490* FPF Below 7 Cabins Canyon, Capitan Mountains 7-25-38 Ellis, & Hackelman

L. S. Gill, D. FP 89492* FPF Below 7 Cabins Canyon, Capitan Mountains 7-27-38 Ellis, & Hackelman Collector Number Location Date Mexico

H, L, & F. Munoz 1032 FPF Approximately 4 mi. W. of Asseradero Maderas 4-4-67 Del Carmen, Sierra Del Carmen, Coahuila

2. Arceuthobium blumeri

Specimens examined: all on Pinus strobiformis

Arizona

RLM 7518* .4 mi. from Carr Peak on Carr Peak Trail, 8-7-75 Huachuca Mountains

RLM 7519* 1.2 mi. W. of Reef Mine, Huachuca Mountains 8-7-75

RLM 7521* FPF 1 mi. W. of Reef Mine, Huachuca Mountains 8-7-75

RLM 7551* FPF 1.2 mi. W. of Reef Mine, Huachuca Mountains 8-22-75

RLM 7552* 1 mi. W. of Reef Mine, Huachuca Mountains 8-22-75**

RLM 7553* Just above Bathtub Spring, Huachuca Mountains 8-23-75

RLM 7577* .4 mi. from end of Carr Canyon Road on Carr 9-13-75 Peak Trail, Huachuca Mountains

RLM 7596* .5 mi. W. of Carr Peak on Carr Peak Trail, 9-28-75 Huachuca Mountains

RLM 7622* 1.2 mi. W. of Reef Mine, Huachuca Mountains 7-29-76 Collector Number Location Date

RLM 7635* 1 mi. W. of Carr Peak, Huachuca Mountains 8-20-76

RLM 7636* .5 mi., W. of Carr Peak, Huachuca Mountains 8-20-76

H & L 235* FPF 1 mi. W. of Reef Mine, Huachuca Mountains 7-5-62

H & L 1109* FPF 1.2 mi. W. of Reef Mine, Huachuca Mountains 9-12-68 ARIZ

& RLM 1468* FPF 1 mi. W. of Reef Mine, Huachuca Mountains 8-29-73

MEXICO

Chihuahua

RLM 75105* 20 mi,, W. of Tomachic on Route 16 11-8-75

H 1650* FPF 20 mi,. W. of Tomachic on Route 16 11-8-75

H & W 296* FPF 36 mi. SW. of La Junta 3-18-63

H & W 314* FPF 13 mi. SW. of El Vergel 3-20-63

H & W 475* FPF 13 mi. SE. of Mesa Huracan on Chico Road 7-16-63

H & W 493* FPF 65 mi. SW. of Matachic on road to Ocampo 7-18-63

Durango

RLM 75111* FPF Puerto Buenos Aires, 34 mi. W. of El Salto 11-10-75** ^ » on Route 40 1-1 Collector Number Location Date

RLM 75120* FPF 16 ml. W. of El Salto on Route 40 11-11-75**

H & W 350* FPF 15 ml, W. of El Salto on Route 40 3-22-63

H & W 516* FPF 48 ml. S. of Durango on road to La Flor 7-21-63

H & W 530* FPF 15 ml. W. of El Salto on Route 40 7-24-63

H & W 536* FPF 19 ml. W. of Santiago Papisquiaro 7-25-63

H, R. Scharpf, & 1421* FPF 34 mi. W. of El Salto on Route 40 8-15-72 D. Knutson

R. S. Peterson 72-169* FPF 50 mi. S. of Hidalgo del Parral Airport 6-23-72 turnoff on the Cendradillas Road

Nuevo Leon

RLM 75132* 15 km. from Villa "18 de Marzo" on road to 11-15-75 Relay Tower, Cerro Potosf

W 7531* FPF 15 km. from Villa "18 de Marzo" on road to 11-15-75 Relay Tower

H & W 392* FPF 16 km. from "18 de Marzo" on road to Relay 11-15-75 Tower ' 3. Arceuthoblum cyanocarpum

Collector Number Host Location Date California

H & R. Scharpf 671* FPF Plnus flexilis 17 mi. W. of Bishop on Sabrina 7-11-64 Lake Road, Inyo County

W 3617 FPF 11 11 Saddle N. of Tahquitz Peak, San 7-12-64 Jacinto Mountains

Miller & Bynum - FPF Plnus monticola High Camp Creek, 5 mi. WNW. of Mt. 9-6-74 Eddy, Siskiyou County

Root & Gooding -* FPF Pinus albicaulis Summit of Black Butte, Siskiyou 8-18-32 County

H & W 642* FPF 11 " Summit of Black Butte, Siskiyou 7-4-64 County

D. Bailey 72-39* FPF Pinus balfouriana Summit of Lookout on Lake 9-13-72 Mountain, Siskiyou County

Colorado

H 689* FPF Pinus flexilis 1.3 mi. E. of Eldora on Nederland 8-21-64 Road, Boulder County

H 540* FPF 11 5 mi. S. of junction near Bruin Inn 9-6-63 on Gold Camp Road, Pikes Peak

H 1057* FPF " 11 7 mi. NW. of Idaho Springs 7-31-67 \

Collector Number Host Location Date

H 1055 FPF Plnus flexilis 1.6 mi. E. of Pingree Park, 6-20-67 Larimer County

H 827 FPF " " 1 mi. SW. of Tolland, Gilpin 6-2-65 County

H 829 FPF " " 4.3 mi. S. of Wyoming border 6-9-65 on Ranch Road, Larimer County

T. Hinds - * FPF " 11 4 mi. W. of Eaton Resevoir, 8-22-62 Larimer County

H & J. Laut 1327 FPF 11 " 7 mi. NW. of Manitou Springs on 5-26-71 Rampart Range Road, El Paso County

H & J. Laut 1317 FPF " " 8 mi. SW. of U. S. 50 on Hayden 12-11-70 Pass Road, Fremont County

H, J. Laut, T. 1498 FPF " " .3 mi, W. of Silver Mountain, 10-21-74 Hinds, & D. Leatherman Heurfano County

H, J. Laut, T. 1497 FPF Pinus aristata .3 mi. W. of Silver Mountain, 10-21-74 Hinds, & D. Leatherman Heurfano County

Idaho

R. S. Peterson 62-53* FPF Pinus flexilis Craters of the Moon National 5-29-62 Monument

R. S. Peterson 65-370 FPF ii ii Ridge S. of Bloomington Lake, 9-12-65 W. of Bloomington, Bear Lake County -«i Collector Number Host Location Date Montana

W 3257* FPF Pinus flexills 7 mi. E. of Bozeman Pass on 7-22-76 Highway 90, Gallatin County

W 3865 FPF ii ii Ca. 5 mi. W. of Red Lodge on 8-30-65 road to Rock Creek, Carbon County

J. Weir 3218* FPF it it Mount Haggin near Anaconda, 1914 Deerlodge County

G. Gregory FPF II II Rotten Grass Drainage, Big Horn 8-22-69 Mountains

D. Brown FPF II II Near S. boundary of Custer Nat. 9-69 Forest, Crooked Creek

Nevada

H fie W 575* FPF Pinus flexilis 12 mi. SE. of Lamoille, Ruby Mtns., 6-25-64 Elko County

Clolrey 5430* FPF II II Peak Trail, Charleston Mountains 8-8-35

H, T. Hinds, & 1379* FPF Pinus albicaulis Copper Mountains 9-18-71 W. Mark

Utah

H 571* FPF Pinus flexilis 25.5 mi. SW. of Duchense on 6-24-64 Indian Canyon Road, Duchense County Collector Number Host Location Date

H 255* FPF Pinus flexllls .5 ml. S. of Main Lodge, Bryce 7-15-62 Canyon National Park

H 679 FPF it ii 16.5 mi. E. of Cedar City on 7-13-64 Route 14, Iron County

Garrett - * FPF II II Bryce Canyon National Park, 8-13-21 Headquarters

R. S. Peterson 65-339 FPF II II 8 mi. S. of Belknop Guard 8-23-65 Station, Piute County

H & J. Laut 1162 FPF N. shore of Navajo Lake, Kane 5-10-69 County

R. S. Peterson 62-75 .25 mi. NW. of Tony Grove Lake, 7-3-62 Cache County

D. Bailey 74-07 FPF II II Deep Creek Mountains 6-18-74

Wyoming

J. Weir 9884* FPF Pinus flexllls Cody Canyon, Park County 9-16-18

H 85 FPF 7 mi. SW. of Tie Siding, 7-10-61 Albany County

H 277 FPF W. Fork of Long Creek, Fremont 9-15-72 County

H 1627 FPF 1.5 mi. N. of Route 28 on Louis 6-9-75 Lake Road, Fremont County Collector Number Host Location Date

H & A. Landgraf 279* FPF Plnus flexllls Ca. 2 ml. S. and 1 ml. W. of ' 9-16-62 Crook Gap, Green Mountains

H & D. Bailey 1008 FPF n it Ca. 3 mi. S. of Pilot Hill on W. 10-26-66 Pilot Hill Road, Albany County

J. Dunder FPF ii II NE. slope of Whiskey Gap, Ferris 9-23-69 Mountains

J. Stewart FPF Dry Fork Drainage on Sunlight 8-10-67 Basin Road, Park County

4a. Brlstlecone Pine Dwarf Mistletoe (Arceuthoblum microcarpum)

Arizona

RLM 7524* Plnus aristata Top of Schultz Peak, San Francisco 8-13-75 Peaks

RLM 7525* .25 mi. N. of Schultz Peak 8-13-75

RLM 7527* .25 mi. S. of Schultz Peak 8-13-75

RLM 7528*. .5 ml. SE. of Schultz Peak 8-13-75

RLM 7535 FPF .3 mi. S. of the Flagstaff City 8-15-75 Water Camp, Inner Basin, San Francisco Peaks •vj -j Collector Number Host Location Date

RLM 7536* Plnus arlstata .3 mi. S. of Flagstaff City 8-15-75 Water Camp, Inner Basin

RLM 7537 FPF " " .3 mi. S. of Flagstaff City 8-15-75 Water Camp, Inner Basin

RLM 7538* . 11 " Near the top of Schultz Peak 8-15-75

RLM 7544* 11 " .25 mi. W. of Schultz Peak 8-19-75 .

RLM 7545* " " .25 mi. E. of Schultz Peak 8-19-75

RLM 7546* 11 " .1 mi. W. of Schultz Peak 8-19-75**

RLM 7549* 11 " .2 mi. N. of Schultz Peak 8-19-75**

RLM 7550* " " .1 mi. S. of Schultz Peak 8-19-75

RLM 7560* " " Top of Schultz Peak 8-31-75**

RLM 7581* 11 " • .2 mi. N. of Schultz Peak 9-16-75

RLM 7569* " " Ridge running E. of Schultz Peak 9-3-75

RLM 7575* " " Top of Schultz Peak 9-8-75

RLM 7582* " 11 Ridge running E. of Schultz Peak 9-17-75

RLM 7583* " " .2 mi. S. of Schultz Peak 9-18-75

H & RLM 1462* FPF " " Ca. .5 mi. E. of Weatherford 8-25-73 Road, San Francisco Peaks Collector Number Host Location Date

H & L 1357* PPF Pinua aristata Fremont Saddle Road on the San 8-29-71 Francisco Peaks

H & L 247 FPF " 11 6 mi. N. of Schultz Pass Road, 7.9.72 San Francisco Peaks

H & L 1404 FPF " " Weatherford Road to Fremont Pass, 3-20-72 San Francisco Peaks

RLM 7550* Plcea engelmannit ,2 mi. N. of Schultz Peak 8-19-75

RLM 7580* !' " .1 mi. N. of Schultz Peak 9-16-75

H & RLM 1463 FPF " " .1 mi. N. of Schultz Peak 8-25-73

RLM 7513 FPF Pinus strobiformts .2 mi. N. of Schultz Peak 7-30-75

RLM 7510 11 " .1 mi. W. of Schultz Peak 7-30-75

RLM 7578 ' " » .2 mi. E. of Schultz Peak 9-15-75

H & L 1361 FPF " " Fremont Saddle Road on the 8-29-71 San Francisco Peaks

H & RLM 1464 FPF " " Ca. .5 mi. E. of Weatherford 8-25-73 Canyon, San Francisco Peaks

H, L, M. Weiss, 1280 FPF " " 6 mi. N, of Schultz Pass Road 7-15-70 R. Gilbertson, & on Fremont Saddle Road, San A. Buddington Francisco Peaks

^1 VO Collector Number Host Location Date

RLM 7529 FPP Abies laslocarpa .2 mi. E. of Schultz Peak 8-13-75 var. arizonlca

RLM 7512 " " .1 mi. N. of Schultz Peak 7-30-75

H & L 1360 FPF 11 " Fremont Saddle Road on the San 8-29-71 Francisco Peaks

H, L, M. Weiss, 1282 FPF 6 mi. N. of Schultz Pass Road on 7-15-70 R. Gilbertson & Fremont Saddle Road, San Francisco A. Buddlngton Peaks

4b. Arceuthobium microcarpum

Arizona

RLM 7531* Picea engelmannii .2 mi. E. of the Lookout Tower on 8-14-75 Kendrick Peak, Coconino County

RLM 7532* FPF " " .3 mi. E. of the Lookout Tower on 8-14-75 Kendrick Peak

RLM 7533* FPF " " .1 mi. E. of the Lookout Tower on 8-14-75 Kendrick Peak

RLM 7534* FPF 11 11 Inner Basin, San Francisco Peaks 8-15-75

RLM 7535* FPF " " Inner Basin, San Francisco Peaks 8-15-75 Collector Number Host Location Date

RLM 7536* Picea engelmatmll Inner Basin, San Francisco Peaks 8-15-75

RLM 7540* 11 " Hannagan Meadows on U. S. 666 8-18-75

RLM 7541* " " 1 mi. N. of Hannagan Meadows on 8-18-75 U. S. 666

RLM 7542* " " .6 mi. W. of Big Lake on road to 8-18-75** Eagar

RLM 7561* " 11 3.2 mi. S. of entrance to North . 9-1-75 Rim, Grand Canyon National Park

RLM 7563* 11 " Junction of Point Royal and Point 9-1-75 Imperial roads, North Rim, Grand Canyon National Park

RLM 7564* " 11 2 mi. from Route 67 on Point 9-1-75 Imperial road, North Rim, Grand Canyon National Park

RLM 7571* 11 " Big Lake, near end of Route 273 9-2-75

RLM 7572* " 11 .3 mi. W. of Coulter Resevolr on 9-2-75 Route 273

RLM 7588* FPF " " Webb Peak, Pinaleno Mountains 9-22-75

RLM 7589* " " Soldier Creek Campground, Pinaleno 9-22-75 Mountains

RLM 7590* FPF 11 " Columbine Work Center, Pinaleno 9-22-75** oo Mountains M Collector Number Host Location Date

RLM 7591* FPF Plcea engelmannli Hospital Flat, Pinaleno Mountains 9-22-75

RLM 7594* 11 " High Peak, Pinaleno Mountains 9-23-75

RLM 75101* " " .2 mi. S. of Hospital Flat, 9-23-75 Pinaleno Mountains

H 253* FPF 11 " 2 mi. E. of State 64 on Point 7-14-62 Imperial Road, North Rim, Grand Canyon National Park

H & L 249* FPF " 11 Flagstaff Water Camp, 9 mi. N. of 7-9-62 Schultz Pass Road, San Francisco Peaks

H & RLM 1465* FPF 11 " Kendrick Peak, on ridge ca. .5 mi. 8-26-73 E. of Lookout Tower

H & L 207 FPF " " 20 mi. W. of Eagar on State 73 7-2-62

S. Peterson 62-165* FPF " " On U. S. 666 N. of Gobbler Point 9-13-62

H & L 225* FPF 11 " Soldier Creek Campground, 7-4-62 Pinaleno Mountains

H & L 224* FPF " 11 3 mi. N. of Columbine Road on 7-3-62 High Peak road, Pinaleno Mtns.

RLM 7652* 11 11 Hospital Flat, Pinaleno Mtns. 9-1-76

H & RLM 1487* FPF 11 " Ca. .5 mi. W. of Flagstaff Water 7-24-74 Camp, Inner Basin, San Francisco Peaks Collector Number Host Location Date

64-20 FPF Plcea englemannii 3 ml. N. of Hannagan Meadows on 9-17-64 U. S. 666

G. W. Barr & 64-533 ARIZ II II Near Big Lake, White Mountains 9-22-64 R. J. Barr

R. J. Barr & 64-459 ARIZ II II Near Big Lake, White Mountains 8-21-64 J. M. Welch

R. A. Darrow, 1173 ARIZ II II Webb Peak, Pinaleno Mountains 9-4-44 W. s. Phillips, & L. M. Pultz

Kearney & 14135 ARIZ " Near Hospital Flat, Pinaleno Mtns. 8-21-38 Peebles

RLM 7539* Plcea pungens 8 mi. S. of Alpine on U. S. 666 8-17-75

RLM 7584 it ii Near Sierra Blanca on road to 9-19-75 Big Lake

H & L 900 FPF II II 6 mi. NE. of Maverick, Fort 5-7-66 Apache Indian Reservation

H & L 1083 FPF II II Ca. .5 mi. S. of Horseshoe 9-19-67 Cienega Lake, White Mountains

H & R. Scharpf 700* FPF II it 4.8 mi. SW. of Alpine on U. S. 9-5-64 666

R. S. Peterson 43-61* FPF II II 2.4 mi. from main road on Point 5-30-61 Royal Road, North Rim, Grand ^ Canyon National Park w 4

Collector Number Host Location Date

D. J. Stouffer & FP 68291 FPF Abies laslocarpa Columbine Work Center, Pinaleno 7-21-34 L. S. Gill var. arizonlca Mountains

New Mexico

RLM 7586* Picea engelmannii Bearwallow Lookout Road, Mogollon 9-21-75 Mountains

R&L 897* FPF 4.2 mi. W. of Route 78 on 5-6-66 Bearwallow Lookout Road, Mogollon Mountains

RLM 7585* Plcea pungens Gillita Campground, Mogollon Mtns. 9-20-75

RLM 7587* ii ii Willow Creek Campground, Mogollon 9-20-75 Mountains

H & L 219* FPF Willow Creek Campground, Mogollon 7-3-62 Mountains

00 APPENDIX B

KEY TO THE SPECIES OF ARCEUTHOBIUM PARASITIZING WHITE PINES IN ARIZONA AND NEW MEXICO

Shoots green to purple; plants averaging 4 to 6 cm., but up to 13 cm.; perianth lobes 3, rarely 4 or 5, same color as shoots; anthesis from late August through September; parasitic on Picea engelmannli. Picea pungens. and Pinus arlstata, rarely on Abies lasiocarpa var. arizonica and Pinus strobiformis:

A. microcarpum

Shoots yellow-green, light green, straw or gray to blue or reddish; plants averaging 4 to 5 cm., but up to 8 or 9 cm. in Arizona and New Mexico; perianth lobes 3, 4, or 5, rarely 6, same color or darker than the shoots; anthesis from mid July to late September; parasitic on Pinus strobiformis exclusively:

B.

B. Shoots yellow-green to blue or reddish; plants averaging 4 cm., up to 9 cm., densely clustered around the host branch; perianth lobes 3 or 4, rarely 5, same color as the shoots; anthesis from late July to late September; Chiricahua and Santa Rita Mtns., north to east-central Arizona and New Mexico;

A. apachecum

B. Shoots straw or gray to light green; plants averaging 4 to 6 cm. up to 8 cm. (18 cm. in Durango, Mexico), not densely clustered around the host branch; perianth lobes 3, 4, or 5, rarely 6, darker than the shoots; anthesis from mid July to late August; Huachuca Mountains of southern Arizona, south into northern Mexico:

A. blumeri

85 LITERATURE CITED

Abrams, L. 1923. Illustrated flora of the Pacific States. Univ. of Calif. Press, Berkeley. 666 p.

Acciavatti, R. E. and M. J. Weiss. 1974. Evaluation of dwarf mistletoe on Engelmann spruce, Fort Apache Indian Reservation, Arizona. Plant Dis. Reptr. 58: 418-419.

Alexander, M. E. and F. G. Hawksworth. 1975. Wildland fires and dwarf mistletoes: A literature review of ecology and prescribed burning. U. S. D. A. For. Serv. Gen. Tech. Report RM-14. 12 p.

Alston, R. E., H. Rosier, K. Naifeh, and T. J. Mabry. 1965. Hybrid components in natural interspecific hybrids. Nat. Acad. Sci. Proc. 54: 1458-1465.

Andresen, S. R. and R. J. Steinhoff. 1971. The taxonomy of Pinus flexilis and Pinus strobiformis. Phytologia 22: 57-70.

Andrews, S. R. and J. P. Daniels. 1960. A survey of dwarf mistletoes in Arizona and New Mexico. U. S. D. A. For. Serv., Rocky Mt. Forest and Range Exp. Station, Station Paper 49. 17 p.

Blumer, J. C. 1910. Mistletoe in the Southwest. Plant World 13: 240- 246.

Cohen, L. I. 1968. Development of the staminate flower in the dwarf mistletoes, Arceuthobium. Amer. J. Bot. 55: 187-193.

Coulter, J. M. and A. Nelson. 1909. New manual of botany of the cen­ tral Rocky Mountains. American Book Co., New York. 646 p.

Critchfield, W. B. and E. L. Little. 1966. Geographic distribution of the pines of the world. U. S. D. A. Misc. Publ. 991. 97 p.

Davis, P. H. and V. H. Heywood. 1963. Principles of angiosperm taxon­ omy. Oliver and Boyd, Princeton, N. J. 556 p.

Garrett, A. 0. 1921. Forest tree diseases. Trans. Utah Acad. Sci. 2: 183-190.

86 87

Gausen, H. 1960. Les Gymnospermes. Actuelles et fosslles. Fascicule VI, Chapter XI. Generalities. Genre Pinus Travaux ce Laborataire Forestier du Toulouse, Sec. 1, Vol. 2, part a. 272 p.

Gill, L. S. 1935. Arceuthobium in the United States. Trans. Conn. Acad. Sci. 32: 111-245.

Gottfried, G. J. and R. S. Embry. 1977. Distribution of Douglas-fir and ponderosa pine dwarf mistletoes in a virgin Arizona mixed coni­ fer stand. U. S. D. A. For. Serv., Rocky Mtn. Forest and Range Exp. Station, (in press).

Graham, D. 1961. Dwarfmistletoe of Douglas-fir. U. S. D. A. For. Serv. Forest Pest Leaflet 54. 4 p.

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