Pinaceae

Pinus flexilis var. reflexa Engelm.

A rare variety of the more widespread limber pine. Major potential threats include white pine blister rust and mountain pine beetles.

Distribution

Recorded from the southwestern USA (Arizona, New Mexico, SW Texas) and extending into northern Mexico in scattered localities in Chihuahua, Coahuila, Nuevo León and NE Sonora.

This taxon is much more scattered than var. flexilis which occurs to the north of it, and is restricted to the highest altitudes of the mountains in northern Mexico and the southwest of the

USA. Populations are accordingly disjunct and often small.

Habitat and Ecology

Pinus flexilis var. reflexa is a conifer tree of subalpine habitats on the highest mountains within its range. Occurs between 1,900 and 3,000 m asl. The species is one of several in the genus Pinus of western North America that can withstand extreme conditions of climate on bare rock or scree without any other vegetation cover. On these sites it occurs either alone or with Pinus aristata in the SE and P. longaeva in the SW. The seeds, which only have rudimentary wings, are mostly dispersed by rodents and birds.

Human Uses

No uses have been recorded for Pinus flexilis var. reflexa. It is probably too rare and remote for it to be of commercial value.

Conservation Status

Global Status

Near Threatened

Global Rationale

Pinus flexilis var. reflexa is a rare variety limited to five known locations with a small area of occupancy less than 2,000 km2. There is no evidence of continuing decline at present hence this variety is assessed as Near Threatened (almost qualifies as threatened under criterion B2ab(iii,v)). White Pine Blister Rust (WPBR) caused by the non-native pathogen Cronartium ribicola does not appear to have reached the isolated subpopulations of this variety. Likewise, no epidemics of Mountain Pine Beetle (MPB) have been reported yet. However, as soon as either of these threats starts to impact this variety, it will quickly qualify for a more threatened category. The combination of WPBR with the MPB epidemic compromises the regeneration cycle of the pine populations and reduces their resilience to recover from this and any other disturbances. Extirpation of subpopulations is probable. See the species account for full details on the impacts of these two threats. Regular monitoring is required.

Conservation Actions

The variety is probably present in some protected areas. See the species account for details on the ongoing research into the threats. The population of this variety should be regularly monitored to detect the presence of WPBR or MPB.

Entry information:

Entry author:

P.Thomas ·

Entry last edited:

4 Nov 2019

Recommended Citation:

P.Thomas, 2019, Pinus flexilis var. reflexa, from the website: ‘Threatened Conifers of The World’ (https://threatenedconifers.rbge.org.uk/conifers/pinus-flexilis-var-reflexa-engelm). Downloaded on 2 July 2022.

Categorised in:

Near Threatened, Northern Mexico / SW USA, Invasive species and Pinaceae