Arceuthobium divaricatum

Engelmann in J. T. Rothrock

Rep. U.S. Geogr. Surv., Wheeler, 253. 1879.

Common names: Pinyon dwarf mistletoe
Synonyms: Razoumofskya divaricata (Engelmann) Coville
Treatment appears in FNA Volume 12. Treatment on page 428. Mentioned on page 425.

Plants usually forming localized local infections only, sometimes forming small nonsystemic witches brooms. Stems olive green, orange, or reddish-brown, glaucous; secondary branching fanlike, branches 8 (–13) cm, slender, third internode 6–15 × 1–2 mm, dominant shoot 1.5–4 mm diam. at base. Staminate pedicels absent. Staminate flowers radially symmetric, lenticular in bud, 2.5 mm diam.; petals 3, light yellowish green. Berries proximally olive or grayish to bluish green, distally olive green to brown, glaucous, 3.5 × 2 mm. Seeds ellipsoid, 2 × 0.9 mm, endosperm bright green. 2n = 28.


Phenology: Flowering Aug–Sep; fruiting Sep–Oct.
Habitat: Pinyon-juniper woodlands.
Elevation: 1200–3000 m.

Distribution

V12 24-distribution-map.jpg

Ariz., Calif., Colo., Nev., N.Mex., Tex., Utah, Mexico (Baja California)

Discussion

Meiosis occurs in July, with fruits maturing 13 months after pollination.

Arceuthobium divaricatum is parasitic only on pinyon pines. Its principal hosts are Pinus edulis and P. monophylla, but it can also parasitize P. californiarum, P. cembroides, P. discolor, and P. quadrifolia. Most infections are localized; however, over time small witches’ brooms can form that are cryptic given the shrubby habit of the host tree. Pinyon dwarf mistletoe was classified in sect. Campylopoda (F. G. Hawksworth and D. Wiens 1972) as was another parasite of pinyons from Mexico, A. pendens (Hawksworth and Wiens 1980). Isozyme data first showed that these species are not part of sect. Campylopoda (D. L. Nickrent 1996) and this was later confirmed with DNA evidence (Nickrent et al. 2004). Moreover, the two pinyon dwarf mistletoes are not closely related to each other; A. divaricatum is close to A. douglasii, and A. pendens is sister to A. guatemalense Hawksworth & Wiens of Mexico and Guatemala.

Selected References

None.

Lower Taxa

None.
... more about "Arceuthobium divaricatum"
Daniel L. Nickrent +
Engelmann in J. T. Rothrock +
grayish +  and bluish green distally olive green +
3.5 cm35 mm <br />0.035 m <br /> (?) +
2 cm20 mm <br />0.02 m <br /> (?) +
scale-like +
8 cm80 mm <br />0.08 m <br /> (13 cm130 mm <br />0.13 m <br />) +
slender +
8 cm80 mm <br />0.08 m <br /> (?) +
Pinyon dwarf mistletoe +
spikelike +
Ariz. +, Calif. +, Colo. +, Nev. +, N.Mex. +, Tex. +, Utah +  and Mexico (Baja California) +
1200–3000 m. +
globose +  and pyriform +
2.5 cm25 mm <br />0.025 m <br /> (?) +
lenticular +
Pinyon-juniper woodlands. +
terminal +  and axillary +
bisexual +  and unisexual +
0.1 cm1 mm <br />0.001 m <br /> (0.2 cm2 mm <br />0.002 m <br />) +
connate +
scale-like +
pinnate +  and entire +
articulated +
asymmetric +  and symmetric +
green +  and light yellowish +
connate +  and distinct +
deltate +  and triangular +
Flowering Aug–Sep +  and fruiting Sep–Oct. +
2[-3]-carpellate +
Rep. U.S. Geogr. Surv., Wheeler, +
mucilaginous +
2 cm20 mm <br />0.02 m <br /> (?) +
ellipsoid +
0.9 cm9 mm <br />0.009 m <br /> (?) +
0.15 cm1.5 mm <br />0.0015 m <br /> (0.4 cm4 mm <br />0.004 m <br />) +
3 +  and 4 +
reddish-brown;orange;reddish-brown;orange;olive green +
pendulous +  and erect +
fanlike +
undifferentiated +
Razoumofskya divaricata +
Arceuthobium divaricatum +
Arceuthobium +
species +
spikelike +
mucilaginous +
evergreen +  and perennial +