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4 May 2011 Density and Elevational Distribution of the San Francisco Peaks Ragwort, Packera franciscana (Asteraceae), a Threatened Single-Mountain Endemic
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Abstract

Packera franciscana (Greene) W. A. Weber and A. Löve is endemic to treeline and alpine habitats of the San Francisco Peaks, Arizona, USA and was listed as a threatened species under the Endangered Species Act in 1983. Species abundance data are limited in scope, yet are critical for recovery of the species, especially in light of predictions of its future extinction due to climate change. This study defined baseline population densities along two transects which will allow the detection of future population trends. Packera franciscana ranged from 3529 to 3722 m elevation along the outer slope transect and densities were 4.18 and 2.74 ramets m−2 in 2008 and 2009, respectively. The overall P. franciscana 2009 density estimate for both transects was 4.36 ramets m−2 within its elevational range of occurrence, 3471–3722 m. The inner basin density was higher, 5.62 ramets m−2, than the estimate for outer slopes, 2.89 ramets m−2. The elevation of the 2009 population centroid for both transects was at 3586 (±10 SE) m with the inner basin centroid significantly lower than the outer slopes centroid: 3547 (±7 SE) m vs. 3638 (±7 SE) m, respectively. In mid-September, 6–9% of the P. franciscana ramets were flowering and/or fruiting in 2008–2009. These results and our estimate of >36,000 P. franciscana ramets in <2% of its range would suggest that the species is locally abundant, persisting and reproducing.

James F. Fowler and Carolyn Hull Sieg "Density and Elevational Distribution of the San Francisco Peaks Ragwort, Packera franciscana (Asteraceae), a Threatened Single-Mountain Endemic," Madroño 57(4), 213-219, (4 May 2011). https://doi.org/10.3120/0024-9637-57.4.213
Published: 4 May 2011
JOURNAL ARTICLE
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