New Species of Phoradendron ( Viscaceae ) from Mexico and Guatemala and a Synopsis of Species in Section

As presently interpreted Phoradendron sec tion Pau cifiorae consists of 15 spec ies. These mistletoes parasitize primarily conifers. We describe seven new spec ies . make sta tus changes for four species, and provide information on the hosts and di str ibution of all members of the sec tion. New species described are: Phoradendron abietinurn Wiens, on Abies durangen si s in Chihuahua, Durango, and Jalisco, Mexico; P. acuminatum Wiens, on Cupress us lusitanica in Gu atem ala; P. flavomarginatum Wiens, on Juniperus fiaccida in Nuevo Leon , Mexico; P. lta wksworthii Wien s. on Juniperus in New Mexico, west Texas, and Coahuila, Mexico; P. olivae Wien s, on Cupressus lusitanica in Colima and Jalisco, Mexico; P. rufescens Wiens, on Juniperus spp . in San Lui s Potosf, Mexi co ; and P. sedifo lium Wiens on Cupressus /usitanica in Chiapas, and Hidalgo. Mexico. Three taxa previ ousl y recognized as subspecies are raised to specific rank: P. densum Torr. ex Trel ., P. paucifi orum Torr., and P. /ibocedri (Engelm.) Howell. Also P. saltillense Trel. , which had been placed in synonymy und er P. botleanum subsp. densum, is accorded species status, In addition, three new epiparasit ic speci es of Ph oradendron are described. Epiparastic mistletoes are known to para sit ize only other spec ies of mistletoesin this instance Phoradendron or Cladocolea (Loranthaceae).


populations o
P. densum occurring in central Arizona on Cupres sus, and perhaps various population systems of the widespread P. saltillense in northern Mexi co.


MATERIALS AND METHODS

The morphological differences most useful in the construction of keys for separating the species, often leaf size, are notoriously variable ch ara cters.Nonetheless, leaf size tends to fall out statistica lly, as well as internode length, since the latter is generally a correlate of overall plant size.Characters, suc h as stature and size, are not especially useful for con structing keys , but are still important feature s in defining the species, along with host differences.The specifics of these quantitative features are de scribed in Wiens (1964), or in the descriptions o f the new species presented herein.The problem is well illu strated by the relationship between P. juniperinum and P. libocedri.

The latter pe cies has internodes that are significantly longer than those of P. juniperinum, and long internodes are correlated with the distinctive pendulous habit.Yet neither morphology nor molecul ar data (Ashworth 2000) identify clear-cut interspecifi c differences.

In addition to the description of new species in sect.Pauciflorae, we also include descriptions of three new species of epiparasitic spe cie s of Phoradendron, i.e., mistletoes that are known to parasitize only other mistletoes.In this instance the host mistletoes are either other species of Phoradendron or Cladocolea (Loranthaceae).The subject of epiparasitism is a fascinating phenomenon deserving of further study.More detailed

formation on the subje
t is available in Wiens and Calvin (19 87), and in Polhill and Wien s (1998 ).

Unfortunately, Kuijt (pers. cornrn ., 1996 ) has indicated that there are potential nomenclatural difficulties with the maintenance of the name Pau cifiorae as a section of Phoradendron sen su Wiens (1964) .This issue will not be addressed here , as there is no question of the species involved or the cohesiveness of the group, regardless of what name is ultimately a ttac hed to it.


RESULTS AND DI SCUSSION

The species of section Pau ciflorae (Wiens 1964) parasitize primarily Juniperus, Cup res sus, a nd to a lesser extent, Abies.Members of the group are typically reduced in terms of thei r overall size, as well as their flora and vegetative features, when compared to most other members of Phoradendron.Overall the spec ies are rarely over 0.5 m high (exceptions are P. acuminatum and P. olivae, which may be over 1 m).Reduced overall size is typically correlated with shortened internode lengths an widths (mostly < 25 X 4 mm ).The leaves are likewise either comparativel y sm all (mostly < 25 X 8 mm) or redu ced to scales.The len gth of the inflorescence, the number of fertile internodes produced, and the number of flowers per fertile internode are also relatively s ma ll in comparison with species in other sections.Th e staminate inflorescen ce s are usually < 10 mm long with mostly 1-2 (3) fertile internodes, with each fertil e internode commonly bearing < 20 flowers.The pistillate inflorescences typically have I (2) fertile in ernodes, and consi stently produce only two flow ers per fert ile internode; two pist illate flowers per fert ile internode is the best single morphological feature defining sec t.Pauciflorae.In addition to the morphological and host affinities that characterize the group, Ashworth (2000) showed that mol ecular data also confirm the uniformity of the group, as well as its monophyleti

origin.


CHANGES I N TA
ONOMI C ST ATUS

Specimens are cited only for tho se species for which we have significant new distribution al data.For di stributional information of other spe cies, see Wien s (1964 ).1964).


Ph oradendron densum

We now consider P. libocedri a distinct species.It is an obligate parasite of Calocedrus (Libocedrus) decurrens, and it co-occurs in the Lake Tahoe region of California with P. juniperinum, which infects Juniperus occidentalis; each mistletoe is restricted to its particular host in this area.Also, P. libocedri becomes pendulous with age, and is a larger plant than P. juniperinum.This size difference is reflected in the longer internodes of P. libocedri (> 10 mm) (Wiens 1964) .We give species status to this taxon because it differs from P. densum in a number of features : leaf size, color, hosts, and distribution (Wiens 1964) .The distributional range of P. pauciflorum extend s from the central Sierra Nevada of California (Calaveras County) southward to the Transverse Ranges of southern California and to the Sierra San Pedro Martfr in Baja California.Throughout its distribution it is a consistent parasite of Abies , especially A. concolor.An extreme outlying population occurs in southern Arizona in the Santa Catalina Mountains (Pima County) and it ha s also been recorded in the nearby Rincon Mountains (Bowers and McLaughlin 1987) .Abies concolo r is the typical host of P. pauciflorum throughout its range, but i

the Sierra San Pedro Martir in
aja California it rarely parasitizes Cupressus montana, where this tree is associated with infected Abies concolor (Hawksworth and Wiens 1966).There is also a report of autoparasitism in this species (Fel

1970), which is an u
common phenomenon among mistletoes in general.

The known elevational range is 1400-2600 m .(Wiens 1964) wa s based on collections now transferred to P. hawksworthii.The known elevational range is 1900 -2500 m.


Phoradendron saltillense

In the section, P. bolleanum is unique because it commonly parasitizes two diverse hosts , a conifer (Juniperus spp.) and an angiosperm (Arbutus) (Wie ns 1964;Hawksworth and Wiens 1966).We know of no other instance where a mistletoe is restricted to two such di verse hosts.Trelease (1916) questioned whether the same mistletoe actually occurred on two su ch di stantl y related species.Without experimental evidence the question remains moot.We find , however, no morphological basi s for a separation of the two populations on the two hosts.Although infection of Juniperus and Arbutus frequently occurs together, we have also ob served a number of instances from Chihuahua to Jalisco, where only one of the two hosts is parasitized, ev en though the other host is pre sent.For example, in Jalisco we have found P. bolleanum only on Arbutus (al so occ asionally on associated Arctostaphylos), but Juniperu s also occurs in the same area (C hazaro per s. comm., 1989).This sugges ts the pos sibility of two host races, and areas where both hosts are infected may simply represent instances of the co-occurrence of the two host races.Such morphologi cally indistingui shable host races are known in the related dwarf mistletoes (Arceuthobium) (Hawksworth and Wien s 1996).Controlled cross-inoculation e xpe iments are nec essary to resolve the problem.

bright brownish, some greenish populat
ons were observed in central Chihuahua (Ha wks wo rth and Cibrian 1985).


Phoradendron capitellatum (Torr.) ex Trelease

This highly distinctive parasite of junipers is characterized by it s small , densel y stell ate-pubescent leaves.Th e distribution of P. capitellatum is restricted to central and southeastern Arizona, southwestern New Mexico, northeastern Sonora, and northwestern Chihu ahua.The known elevational ran ge is 8 0-1700 m.

The ho sts of P. capitellatum include Juniperus deppeana, 1. ery throca rpa, J. m onosperma, and J. osteosperma.Typically, P. cap ite llatum occurs at elevations below P. juniperinum, but the two species sometimes co -occur, and rarely parasitize the sa me host tree , e.g ., on the south side of the Santa Catalina Mountain s, Pima County, Arizona (Gilbertson pers .co rnrn.. 1978).For whatever reason, P. cap itellatum tends to be under-collected, so we cite a number of collectio ns to gi ve a better understanding of its distribution .Ph oradendron juniperinum Engelm.

This distin ctive sca le-lea ved spec ies has the bro adest distribution of any member of section Pauciflorae, and ranges from Oregon so uthward and eastward to Californi a, Nev ada, Utah, western Colorado, Arizon a, New Mexico, and western Texa s into Ch ihu ahua and Durango in northwestern Mexico.It occurs in the Chiso s Mts, but has not been reported from adjacent Coahuila.The known elevational range is 1000-1600 m.

Common host s of P. juniperinum include Juniperus californica, 1. deppeana, 1. erythrocarpa, 1. flaccida, 1. monosp erma, 1. occidentalis, J. osteosperma, and J. scopulorum.Cupressus a rizonica is commonl y parasitized in central Chihuahua, but this ho st is only rarely infected in Ari zon a (Ha wks wo rth and Wiens 1966) .Other rare ho sts are Cupre sus baked in C alifornia (Hawksworth and Wiens 1966 ) and Chamaebatia ria millefolium (Rosaceae) in Arizona (H awksworth 1952;Hawksworth and Mathiase

1978).

Geographi cally, P. juniperinum co-occ
rs with P. cap itella tum in Arizona, with P. hawksworthii in New Mex ico , and with P. densum in California.Natural hybrids between P. d en sum X P. juniperinum that are apparentl y sterile F, plants are known in the Inyo Mts. of California (Wiens and DeDecker J 972) and San Bernardino Mts.(Vasek per s. cornm., 1973).Th se are amo ng the few reports of natural hybridization for mistletoes.


Phoradendron minutifolium Urb an

In 1959 thi s mistletoe was known only from the type locality near Perote, Sierra Madre Oriental, Veracruz, Mexico.Phoradendron minutifolium, however, is now known to have a wide, but apparently localized, distribution in Mexico.It is most common in central Mexico (Tlaxcala and Veracruz) and in the Sierra Madre Occidental in southern Chihuahua and Durango.A widely disjunct population occurs in the Sierra del Carmen of northern Coahui

, where it co-occurs with P. salti
lense on junipers and the two mistletoes have been found parasitizing the same tree.The Sierra del Carmen is just across the border from Big Bend National Park, Texas, and P. minuufolium might be expected to occur there.The known elevational range is 2000-2750 m.

The closest relative of P. minutifoliuni appears to be P. olivae.Phoradendron olivae has even smaller leaves (ca. 2 mm)-but these are still expanded (as opposed to scales)-whereas P. minutifoliuni typically has leaves ca.The occurrence of a mistletoe specific to such a rare tree as Abies durangensis presents an interesting evolutionary situation.Although the host tree is known from only a few widely scattered localities in the Sierra Madre Occidental (Martinez 1963), all the populations of A. durangensis we have surveyed are parasitized by P. abietinum.The dispersal of host specific mistletoes between small, highly disjunct populations would appear to be difficult.T us, the occurrence of this mistletoe on A. durangensis is perhaps best explained in terms of the parasite becoming evolutionarily "stranded" along with its host.In fact, the presence of a host specific mistletoe on such a rare species supports the proposition that the host at one time had a larger, more continuous distribution.Plantae maturae massas pendulas usque ad 2 m longas efforman-te s, furca tae, d ioec iae , aca ta phy llae

inte rno d ia 15-25 mm longa; fol
a linearia, 15-20 mm longa, c a. 2 mm lata, abaxial iter app lanata, ada x ia lite r rotund at a, ad basim ses sili a , ad apicem acum inat a ; inflore scentia starninat a ign ota: infloresc e nti a pistillata ca. 5 mm longa, pendunculo ca .I mm longo praedita, in se g rne nta fenili a 1-2 dec ussa tirn dispositi s di vi sa: segmento qu oque flores 2 ferente se gmentis e bra cti s minute ciliatis navi cularibus flores par ce s upe ra ntibus subtent is ; a nthesis pr ob ab ilit e r Juli-Septembro; fructu s ro seoa lb id us, orbicul ari s, 4-5 mm d iam ; in Cupresso et Jun ipero par asiticurn.

Hosts: Cupressus lusitanica, rarely Juniperus spp.Distribution: Broadleaf-coniferous woodlands of northern Guatemala; pos sibly also in souther Mexico.The known elevational range is 2500-3150 m.

Discussion: Morphologically this species is most closely related to P. sedifolium, a parasite on Cupressus in the Chiapas and Hidalgo highlands, Mexico.Th e two species are readily distinguished, however, by the short (mean = 9.3 mm long), markedly succ ule nt, glaucous leaves of P. sedifolium.In P. acuminatum the leaves are longer (mean = 16.0 mm long ) and lack significant succule nce or glaucousness.Al so , P. acu- minatum is a much larger plant often a meter or more high, whereas P. sedifo ium is a s malle r plant rarely larger than 5 dm high.The berries of P. acuminatum are pink, and larger (ca. 4 mm) than those of P. sedifolium which are white and smaller (ca. 3 mm).

Phoradendron acuminatum also shows so me morphological resemblance to P. abietinum, but differs from that species by its occurrence primarily on Cu - pressus (secondarily on Junipe rus), whereas P. abietinum is known only from A bies ; P. acuminatum is also a larger plant than P. abietinum, sometimes forming masses a meter or more in length and characteristically producing severe infestations in Cupressus, where it may occupy a larg e proportion of the crown in host tree s.Phoradendron abietinum is a relatively small plant producing globose bushes 2-5 dm in dia mete r.In P. acuminatum, the leaves are mostly a dull, brownish green, generally les s than 3 mm wide and the internodes fuscous, whereas in P. ab ietinum, the lea ves are usually more than 3 mm wid e and both the blades and internodes are yellowish gre en.

An interesting characteristic of P. acuminatum is its role as a host for two epiparasitic species of Phoradendron, i.e., species that para sitize only other species of mistletoes: cf.P. auriculatum Trel.and P. calyculatum Trel.Infrageneric epiparasitism in Phoradendron is a fascinating phenomenon; for further detail s see the discussion under new epiparasitic species of Phoradendron.

E. Clark (pers.com rn., 1973) found that thi s mistletoe causes frequent mortality in cypress in Guatemala, particularly in the Department of San Marcos.Plantae usque J m a ha , bre ve pubescentes ; di oe ci ae , acataph yll ae: ca ules in rnaturitat e lign e scentes.et terete s; inte rno d ia ca.18 mm lo nga ; folia linearia-oblon ga , sessil ia ca .25 (35) mm lon g a , 3 mm lat a; infl orescentia s ta m ina te ca.6-8 mm longa , segrneruis 1-2 .c um 8-15 floribus; inflorescent ia pistillate ca . 2 mm longa, segmentis I, c um 2 flores; anthe sis Jul i (?) -5e ple m bro ; fruc tus ovatus, a lbus, 4 -5 rnrn: in Juniperus fi accida parasiticum, Ho sts: known onl y on Junipe rus fla ccida.Distribution: known only from several populations near the type locality, where it is locally abundant.

Discussion: Ph oradendron fla vomarginatum is separated elevationall y and by host from P. saltillense, which is the common Phoradendron at lower elevation s in thi s region .There is considerable variation in P. saltillense throughout its extensi ve distribution .These two species appear separable on the basi s of morphology as well as host and elevation.Phoradendron fiavomarginatum can become a large, brownish plant and becomes pendulous with age (I m long), whereas P. saltillen se is typically ca.3-4 dm high , more or less globose, as well as yellow-green , the common color of most species of sect.Pauciflo rae.The leaves of P. flavomarginatum are generally longer (ca.25 mm) than tho se of P. saltillense (ca.15 mm) and ha ve a pal e yellow margin (hand lens needed ).Th e leaves of P. flavomarginatum tend to become oblanceol ate , while tho se of P. saltillense are generally linear-oblong.When living, the leaves of P. flavomarginalum are also thinner by about 2!J than tho s of P. saltille nse, wh ose leaves are also slightly succulent.Preliminary ob ser vations in September suggest that P. saltillense produces continuous, success iona l cro ps of flowers, a fe ature not presently known among species of sect.Pau ciflorae.This po ssibility requires further study.Plant a e 1-2.5 dm altae , dioeciae, acataphyllae ; ba se s ram orum in rnat urita te lignosae .g labrae vel in partibus junioribus puberulent ae ; interno dia 6-12 mm lon ga, folia oblanceolate-Iinearia, subse ssili a ve l sessi lia, 6-25 mm longa, 1.5-3 mm lata, ad apicem obtusa vel rotundat a ; inflorescentia staminate e segmento uno floribus 3-6 pra ed ito con siitut a ; inflorescenti staminata e segmento uno floribus 3-6 prae dit o co nstituta; inflorescentia pistillata e segmento uno cum flor ibu s 3 co ns tituta ; anthesis paene Julio--Septembro; fructus albus ve l roscolu s, orbicularis, 4 mm lata; in Junipero parasiticum.


Phoradendron hawksworthii

The species is named for Frank G. Hawksworth, life-long student of mistletoes, particularly the genus A rceuthob ium.

Hosts: Juniperus ashei, 1. deppeana, 1. erythrocarpa, J .jiaccida, 1. monosperma, and J .pinchotii.

Distribution: Juniper-pinyon woodlands; common in west Texas, but localized in southern New Mexico, and known from only one locality in Coahuila.Phorade nd ron ha wks worthii wa s reported from NW of Carrizoz o , Lin coln Co. , New Me xico, but attempts to locate this popul ation were un successful, and no ex tant populations re pre sently known in Lin coln County.

The known e lev atio nal range is 1550-2000 m.

Discu ssion : Ph oradendron hawks worthii shows affinities to P. bolleanum, P. densum.and P. saltillense.It differs from P. den sum, with whi ch it has been confused in the past , by its shorter internodes (mean 9.0 rnm , range 6-I2 mm, ver sus a mean of 11 mm and a range of 6-17 mm in P. densum) .Su h differences in internode length are generally positively correlated with tot al plant size.Finally, the number of fertile internodes per staminate inflorescence is apparently only one in P. hawksworthii, an uncommon characteristic in the section.Phoradendron typically has two fertile internodes on the staminate inflorescences.

Ph oradendron hawksworthii is distinguishable from P. sa ltille nse primarily by its narrower leaves (ca. 2 mm wide).Occasionally the young leaves of P. hawksw orthii also show a tendency toward tereteness, with old er leaves becoming flattened adaxially, but rounded a bax ially.In P. saltille nse the leaves are typically flatten ed dorsi ventrally and usually exceed 3 mm in width .In P. hawks worthii young leaves are often mucronulate in the ex treme, the mucro itself being o nly 0 .2-0.3 mm lon g.Newly emerging lea ve s ge nerally do not exh ibit thi s feature , whi ch apparently ori ginates during mid-ontogeny.Th e mu cro is also fugacious, and is la rgely ab sent on mature lea ves ; howev er, the apex of old leaves often exhibits a minute scar at the tip , presumably resulting from the los s of the mucro.Geographicall y, P. ha wksworthii a nd P. saltillen se approach each other in the Sierra del Carmen, but do not appea r to co-occ ur there.

Ph o radendron cap ite llatum is also a parasite of junipers in southern New Mexico, but its distributional range doe s not appear to overlap with that of P. hawksworthi i. Ph oradendron cap itellatum occurs from the Cook and Florida Mountains westward to central Arizon a, whereas P. hawksworthii is found in New Mexico only east of the Rio Grande Valley in the San Andreas, Cornudas, and Sacramento Mountains.

Ph o raden dron juniperinum usually occurs at elevations above that of P. hawksworthii, but these two mistletoes sometimes co-occur, and rarely infect the same host tree , wh ich was o bse r ved in La Luz Canyon, Otero County, New Me xico.

I decu ssatim d ivisa; segmento quoque flores ferente segmentis e bractis minut e cili ati s na vicularibus, flores parce superantibus subtenti s; anthes is prob abiliter December-Januario; fructus rose o-albidus , orbiculari s, 4-5 mrn , in C upress o parasiticum.
The species is named for Hector Oliva Rivera of the University of Veracruz, Cordoba, and student of M xican mistletoes.

Host: Cupressu s lusitanica.Distribution: Known only from the VICinity of EI Sauz and Terrero, Sierra de Marnitlan, Jalisco, and in adjacent Colima.The known elevational range is 2000-2300 m.

Discussion: The species most closely resembles P. minutifolium, but is distinguishable from that species by (1) its smaller, almost scale-like leaves ca. 2 mm long, whereas the leaves of P. minutifolium ar 3-5 mm long; (2) its much larger size, and open habit, forming pendulous ma sses over I m long, as compared to P. minutifolium whi ch is rarely larger than 0.5 m high .This size difference is again reflected by the internode lengths, averaging 18 mm in P. olivae, but only 8 mm in P. minutifolium; (3) the ho st d ifference-P.olivae is known only on Cupressus and P. minutifolium is known to parasitize only Juniperus; and (4) the known distribution of P. olivae is far to the west and south of P. minutifolium and occurs at higher elevations.Plantae usque ad 6-7 dm altae, dioeciae, acataphyllae ; ca ules in maturitate lignescentes et eretes, breve pubescentes, leniter sca brellae; internodia 15-25 mm longa; folia linearia usque subl an ceol ata, 7-15 mm long a, 1.5-2 .5 mm lata, minute et breviter pubescenti a, in maturitate appl an ata, sed in juventate adaxialiter subrotundata, ad basim sessil ia, ad apicem acuta usque rotundara, interdum mucronulata ; inflore scenti a srarninata ca .10 mm longa, segmentis du obi s 6-17 flore s ferent ibu s, pedunculo 3-4 mm longa; inflorescent ia pistillata ca. 10 mm lon ga, seg mentis fertilibus flores duas ferentibu s, pedunculo ca. 3 mm longo, segmentis perianthii in sexibus ambis con sp icue rufis, anthes is in mensibus Januario-Februario (? ); fructus orbi cularis, 4-5 mm d iam ., rufo-roseus; in Jun ipero parasiticum.

Hosts: Juniperus fiaccida and J .deppeana.Distribution: Juniper-pinyon woodl and s of San Luis POtOSI, Queretaro, and Hidalgo.The known elevational range is 2100-2200 m.

Di scussion: This is one of the mo st distinctive spe ie s in section Pauciflorae.It is perhaps most closely related to P. bolleanum, from which it is ea sily distingui shed by the rusty-brown color of the perianth segments, and the dense short pubescence, whi ch give the plants a somewhat scabrous c harac ter.The berries are bright, reddish-pink.Plantae 3-4 cm altae, dio eci ae , acataphy llae; bases caulorum solum in rnaturitate lign escentes, teretes usque pa um applanatae, glabrae; internodia 6-15 mm long a ; foli a linearia usqu e sub la nceo lata, 6-12 mm longa, 2-3 mm lata, in vivo va lde succosa; incrementum novum conspicue griseo-glaucum, abaxia liter applanaturn sed partern proximam versus leniter e leva tum, adax ia lite r rotundaturn, ad basim sessile, ad apicem ac uturn usque rotundaturn, interdum mucronulatum, margine in juventate interdurn minute ciliato; inflorescenti a staminata ca. 4 mm longa, segmento uno (raro 2) 6-7 flores ferente , pendu culo 1-1.5 mm longo; inflore scent ia pistillate ca. 3 mm longa, segmento uno flares du as ferente , pedunculo 1-1.5 mm on go ; anthes is in mensibus Januario-Febru aria ; fructus ovatus albus, 3 mm diam.; in Cupresso par asiticum.

Hosts: Known only on Cupressus lusitanica.Distribution: Broad-leaf coniferous for sts of the Chiapan and Hidalgan highlands.The known elevationa I range is 1850-2200 m.

Discussion: This species most closely resembles P. acuminatum from Guatemala, but is readily separated from that species (even though they occur on the same host) by the characteristics mentioned in the discussion under P. acuminatum.Phoradendron sedifolium is also a host for one of the epiparasitic species of Phoradendron (P.calyculatum) which also regularly parasitizes P. acuminatum.Plantae maturitata pendulas usque ad 2 m longa effor rnant es, d ioeciae, acataphyllae : inte rnodia 80-120 mm longa, 3-4 mm lata, fo lia lanceolata, falc ate , 120-130 ( 165) mm longa, 15-45 mm lata ; inftores centia staminate 90 -110 mm lon ga, 2 mm lat a, se gment is 3-5; inflor esc e nt ia pist illate ca .35 mm lo nga , 3-4 mm lata, seg me ntis 3-5; fructu s a lbus , 3 mm a lta .In Phoraden dron longifolium par asiticum.

The speci es is named for Prof. Clyde L. Calvin, lifelong student of mistl etoe anatomy, particul arly the haustorial systems.

Host: P. longifol ium , but also occasionally on P. cf. reichenbachianum.

Distribution: Known only from the type locality .Discussion: Th is a mazing species parallels the size of the large epiparasite, P. ca lyculatum, forming huge, pendulous mas ses exceeding 2 m in length and parasitizing primarily P. lon g ifolium, and to a lesser exte nt another spe cies with whi ch it co-occurs.Ph oradendron calvinii is readily distinguished from P. caly culatum, with which it als o co-occurs, by its long, thin staminate inflorescence s that reach lengths up o 110 mrn, but are only 2 mm wid e.These inflorescence s are borne on peduncles ca .15 mm long and comprise 3-5 fertile segments, each bearin g hundreds of flowe rs.

The fr it s are sma ll (ca . 2 mm ) as are the see ds, wh ich is typical of all epiparasitic Viscaceae so far known .The fruits of P. calvi nii are also distinguished by the persistent sepals that form a short coll ar ( I mm) around the minute « 0.5 mm) style.Host : Known only from Cladocolea g raha mii (Loranthaceae)


Phoradendron chazaro i

Distribution : Western Jalisco Discussion: The plant s branch profusely from a "basal cushion" w hen young, but the "cushion " becomes obscure in older plants.The young shoots are quadrangular, and often occ ur in whorl s of 3-6, w ith the basal internode of each shoot bearing a shea thi ng ca taphyll ca. 3 mm high .The infloresce nces are often whorled with 3-8 infloresce nces per nod e, with 2-3 fertile segments bearing 12-16 flowers.The type collection made on 30 July had berries that were just beginning dev elopment, but were probably destined to turn reddish at maturity.Some old seeds at the type collection site were seen on othe r plants and they appeared to be sma ll « 2 mm ), as is typi cal of all e piparasites of Viseum and Phoradendron seen by us in Africa, Asia, Australia and Latin America.

At the time of collection no sta minate flow er s could b found in approx imately 35 plants examined.The speci es is no doubt monoecious and the sta minate flowers had likel y dehi sced at this time.If this is the case, the inflo escences likel y bear relativel y few staminate flow er s, since most of the flowers on the sp ikes appeared to be developing fruit s.In monoecious species of Afri can Vise um , the rat io of pistillate to stamin ate flow ers is oft en highl y skewe d (at least 4 : I ) in favor of pistill ate flowe rs (Po lhi II and Wien s 1998), o ften to the point that it is difficult to find stami nate flowers.Be cau se the early collec tors had onl y a few pressed samples available for study, at least one suc h s pec ies was ori gin ally de scribed as being dioecious.App arentl y P. chazaroi also has highly s kewe d flower ratios in favor of pistillate flower s.The e volut ionary implications o f such skewed flower ratios sho uld be stud ied further.The reproductive advantages of high seed production for pioneering species, suc as these parasites, would see m obvious .A mong dio ecious spec ies of vari ous mistl etoes, the re are a number of examples o species in whi ch the sex ra tio is a lso highl y skewed tow ard pistill te plants (Wie ns et al. 1996).

Specim ens examined: MEXICO: J ALI SC O : 14 km S of Tequ ila on Rd to Volcan de Teq uila, on Cladocol ea g raham ii, whi ch in turn was parasitizing Querc us cas tanea.e leva tio n 1860 rn, W ien s e t a l.707 8 in 1989 (IB UG ).C ha za ro (pers. comm ., 1989)  Host: P. lon g ifolium; P. du ran gen se was not obse rved on ass oci ated P. schumannii.

Distribution : Collected only from the typ e locality, but numerous young plants obse rved near a microwave station on the ridg e top ca .10 km W of EI Palmito .

Di scussion : Morphologicall y, P. durangen se superficially resembles P. calyculatum, a wid espread nd commo n e pi paras itic species with a distribution from the Volcan de Tequila, northern Jali sco, to northern Guatemala.Herbarium spec imens of P. d urangense could be co nfused with P. calyculatum, but a number of ch aracteri sti cs sepa rate the two species: P. ealyeulatum is a mu ch larger plant , oft en form ing pendulous ma sses over 2 m long , where as P. duran gen se is commonly an erect plant , ca .0 .5 m high.Phoradendron calyculatum is gray ish-green, due perh ap s to the den se, short pubescence typical of the spec es, whereas P. duran gen se is brownish-green.Th e nod es of both speci es a re dil ated, but those of P. calyculatum are about tw i e the w idth o f thos e of P. duran gen se (ca .20 mm vs. 10 mm ).The inflorescen ces o f both se xes of P. calycula tum are approximately twi ce the length of those of P. durangense: staminate ca .80 mm vs. 40 mm ; pistillate ca.60 vs. 30 mm.Each fertile segment of the inflorescences of P. calyculatum probably bear tw ice the number of flowers as thos e of P. duran gen se, e .g., the fertile pistillate seg me nts of P. ealyculatum are ca.12 mm long, ver sus ca .6 mm in P. durangen se.

Th e re is also a signifi cant distributional difference between the species, but further coll ect ions might alt er th is situat ion.Presen tly P. duran gense is the mo st northward ranging of any of the epipar asitic species of Ph oradendron.



Not eworthy co lle ct ions ex am ined.-U.S .A .ARIZONA.Coch ise C o.: Guad alupe Mts, Gua dalupe Cy n, on 1. erythroca rpa, Gi lbe rtso n 75 6 in 1967 (FPF); Chiri cahua Mts.Parad ise.Blumer 1524 in 1906 (M O ); Gil a C o .: 5 rni S of Pay son , Wien s 2707 in 1960 (RSA ); Tont o Nati onal Monument , Strong 118 in 1961 (A SU); Pin al Co.: 5 mi E o f Superior on Hwy 60, o n J. eryt hrocarpa, Hawksworth 2 149 in 1986 (FPF); Gr aham Co .: Gr ah am Mts.Tripp C yn. on J. deppeana.Hawk sw orih & Lightl e 145 in 1962 (FPF); Galiu ro Mts.I mi N of Deer Cr Cabin, o n J. dep peana.Mathi asen 770 2 in 1977 (FPF): Pel oncillo Mts, Microwave Tower.11.5 a ir mile s WNW of Dun can .Holmgren & Holm gren 7073 in 1973 (WT U); G ree nlee Co .: 8 mi NE o f G uthrie on Rte 78, o n 1. erythrocarpa.Hawk sworth & Bailey 1771 in 1977 (FPF); near Clifton .Gre en e in 1880 (MO); Pim a Co .: Sa nta Ca ta lina Mts.Molina Basin , on J. ervt hrocarpa.Hawk sworth & G ilbertson 1808 in 1977 (FPF); Sant a Cruz Co .: Pajarito MIS.. 1.7 mi S o f Pajarito Peak, o n 1. deppeana, Van Deve nde r & Tool in s.n. in 198 1 (A RIZ .FPF ); Yav apai Co .: 8 mi W of Se do na.on Hwy 89.Wiens 26 92 in 1960 (RSA); 10 mi E of Camp Verd e o n Pin e Rd .Wiens 26 99 in 1960 (RSA).NEW MEX-IC O. Gr an t Co .: S ummit Mrs. 10 mi E o f Duncan on Eas t Mine Cam p Rd , o n J. ery throcarp a, Hawksworth & Bailey 1772 in 1977 (FPF); Hidalgo Co.: Steins Pas s.Toumey in 1895 ( UC ; Guadalupe C yn , on J. erv thro carpa, Hawk sworth 1624 in 197 5 (FPF); Lightning Dock Min, 18 mi S o f Lord sburg, o n 1. erythrocarpa.Hawksworth s.n. in 1985 ( FPF); Lun a Co .:Florida Mts.N s lope, o n J. eryth rocarpa, Mathiasen 75-5 3 in 1975 (FPF) ; Cro ok Mts, near C rook Peak , on J. e ryt h ro carpu, Hawksworth & Bailey 1762 in 1977 (FPF) .-MEXICO.CHIHUAHUA : Si rra de Moscos , Chaing et a l.385 I in 1979 (FPF, TEX ).SONORA: Palm Cyn , 13 mi SE of Magdalen a, o n J. dep peana, Mathi asen 760 in 1976 (FPF).




Specimen s exam ined : GUATEMALA: HUEH UETENANGO: 2 5 km N of Hu ehuetenango, on Rd 10 Chemal, on C. sta ndleyi, Wien s & Hawkswonh 4408 in 196 (FPF); Paquix, on J .standley i. Clark & R amirez s .n. in 1972 (FPF).SAN MAR COS : Mpio Bosque del As rilero , EI Ca scajo , o n C. lusitanica , Clark s.n. in 1972 (F PF); between Cumbre C otz ic a nd Se rc h il, o n C. lusitanica, Clark & Ramirez s.n. in 1972.SOLOLA : 10 km W of N ah ual a, o n C. lusit an ica , Cl ark & Ramirez s.n. in 1972 (FPF).Ph oradendron flavomarginatum Wien s, sp.nov.Holotype (US): MEXICO: NUEVO LEON: Rd to San Francisco, 10.8 mi E of Hwy 61 turnoff at km 80, N of the town of Doctor Arroyo, elevation 2400 m, parasite on Juniperus fiaccida, Wien s 7779 in 1995.Isotypes: MEXU, UC , MO.




Wien s, sp .no v.Phoradendron bolleanum su bs p .hawksworthii Wiens, in Manual of Vascul ar Plants of Texas, 1970, p. 504, nom.nud .Holotype (US): TEXAS : BREWSTER CO: Big Bend National Park, Chi so s Mts, The Basin (near campground), oak-juniper woodland, ele vation 1650 m.Parasite on Juniperus fla ccida, but also on J. dep-peana and J. pinchotii.Hawksworth, Lightle, & Lampi 1044 in 1967 .Isotypes: ARIZ, CAS , COLO, ENCB , FPF, GH , RS A, UC , UTe.




Sp ecimens ex am ine d : MEXICO: JALISCO: Mpi o Minatitlan , Sierra de Marnitl an , 2 km de EI Terrero hacia el Sauz, Ch azaro, et al. 4479 in 1987 (IBUG) .COLIMA: Mpio de Toliman, km 14 sobre camino Sauz-Terrero.de la Rosa.Villareal, & Tamayo 1677 in 1988 (lBUG ).Phoradendron rufescens Wiens, sp .nov .Holotype (US): MEXICO: SAN LUIS POTOSI: 22 km E of Zaragosa on Rd to La Cuevas mine, elevation 2150 m, on Juniperus fiaccida, Wiens, Ha