Larix potaninii var. australis A. Henry ex Handel-Mazzetti

Pollination from April to May; seed maturity in October.

Larix potaninii var. australis is close relative of Larix potaninii var. potaninii, but differs from the latter in its seed cones 5-7.5 × 2.5-3.5 cm (vs. 3-5 × 1.5-2.5 cm), seed scales 75-90 (vs. 35-65), thick, 1.4-1.6 cm (vs. thin, 0.8-1.3 cm), short branchlets stout, glabrous or subglabrous (vs. slender, densely hairy at apex).

Larix potaninii var. australis is occurring in SW Sichuan, SE Xizang, NW Yunnan of China.

The intra- and intergenomic heterogeneity of the nrDNA internal transcribed spacer (ITS) region were examined for four varieties of Larix potanini (Wei et al., 2003). Two clones with more than a 100-bp deletion in ITS1 were detected in Larix potaninii var. chinensis and Laris potaninii var. australis, respectively. The deletion resulted in the loss of most part, including the motif sequence, of subrepeat 1 (SR1). Sequence divergence and phylogenetic analyses showed that some clones would be pseudogenes given their low GC content, high substitution rates, unique positions in the phylogenetic trees, or significant length variation. These clones might represent orphons or paralogues at minor loci resulting from large-scale gene or chromosome reorganization. Some recombinants characterized by chimeric structure and discordant phylogenetic positions in partitioned sequence analyses indicate that unequal crossing-over plays an important role in the process of nrDNA concerted evolution. In addition, some varieties of Laris potaninii might have experienced an nrDNA founder effect parallel to their geographical isolation.

Trees to 50 m tall; trunk to 1 m d.b.h.; bark gray or gray-brown, rough, longitudinally fissured; crown conical; long branchlets reddish brown or purplish brown, rarely initially yellowish brown, finally dark gray; short branchlets stout, 4-8 mm in diameter, glabrous or subglabrous; first-year long branchlets red-brown, purplish brown, or yellowish brown. winter buds brown or dark brown, glossy, ovoid. Leaves 1.2-3.5 cm long, 1-1.5 mm broad, keeled on both sides. Seed cones reddish or purplish, maturing purplish brown or light gray-brown, cylindric or ovoid-cylindric, 5-7.5 cm long, 2.5-3.5 cm broad. Seed scales 75-90, thick, 1.4-1.6 cm, ± tuberculate and pubescent abaxially, apex truncate or obtuse-rounded. Bracts often exserted, purplish brown, oblong-lanceolate, straight, apex acute or acuminate. Seeds light brown with irregular purplish spots, obliquely obovate, obliquely obovoid, 7-10 mm including wing.

The chromosomal number of Larix potaninii var. australis is 2n = 24 (Wang, 1980; Hizume, 1988; Li, 1993; Shi and Wang, 1994).

Growing in mountains; 2900-4300 m.

Larix potanini is reported be lower risk/least concern (Conifer Specialist Group, 1998).

The timber of Larix potaninii var. australis is used for construction, pit props, railway sleepers, and making furniture, and the bark yields tannins. The species is also used for afforestation.