Saturday, August 10, 2013

Polemonium chartaceum way out of range at Donner Pass, Nevada County, California

Polemonium chartaceum (CHSC3180) at Donner Pass
I hereby record that I did not relocate a Polemonium at Crater Lake, on the western flank of Boreal Ridge, Nevada County (ca. 7500 feet elevation), visited on Friday last.  The terse label on the specimen suggests that it was gathered on an ascent to the lake from Norden, to the south.  I obtained Crater Lake by driving to the summit of Boreal Ridge, thence to the lake and vicinity from the ridge proper. 

The immediate vicinity of the Crater Lake is an odd geologic setting in that the andesite (?) locally forms blocky (ca. 2 dm average diameter) patches largely barren of vegetation – not unlike typical habitat for the tufted-alpine polemoniums (Grant 1989)

The record CHSC3180 filed as Polemonium eximium is worthy of more study.  

First, the elevation of this record is an extreme low-elevation outlier, being located several thousand feet in elevation below the lowest known records for Polemonium eximium, which as you know is one of the highest-elevation limit vascular plants in the Sierra Nevada alpine.

Secondly Polemonium CHSC3180 has the membranous/chartaceous leaf bases which characterize P. chartaceum and its sister taxon P. eddyense, which are poorly developed in P. exemium    

Third, the geographic location is essentially distant from either taxon,  in being removed ca. 130 km from the population of P. chartaceum (proximal in the Sweetwater Mountains, Mono County), or, 300 km from P. eddyense on Mt Eddy, largely on the Siskyou County side, in far northwestern California.

An ascent and search from Norden is suggested.  My working hypothesis is that CHSC3180 is the sole collection of an undescribed taxon in the P. chartaceum-P. eddyense clade, geographically and mid-Pleistocene era isolated from its congeners.

Grant, Verne.  1989. Taxonomy of the Tufted Alpine and Subalpine Polemoniums (Polemoniaceae). Botanical Gazette Vol. 150, No. 2, pp. 158-169

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