December 2012 Number 1 - Utah Native Plant Society

Calochortiana December 2012 Number 1
Figure 1. Range of Penstemon clutei (Sunset Crater beardtongue) in northern Arizona.
ages of sister taxa within the Penstemon clade had bootstrap
values above 70%, which is the generally accepted
value for moderate to strong support. The contradictory
results are likely due to hybridization and/or rapid speciation
among penstemons. Wolfe and her co-authors
(1998) have documented hybridization among some
Penstemon species and have also demonstrated that pollen-mediated
gene flow occurs via hummingbird vectors.
Many narrow endemics are found in extreme edaphic
conditions, including recent volcanic soils (Lesica et al.
2006). Characteristic of many of these species are high
population growth rates but poor dispersal rates. Their
restricted ranges may in some cases be due more to recent
evolution than to ecological tolerance: it may simply
be the case that some species have not yet had time
to spread across the landscape and may therefore be
relatively young (neoendemics) (Lesica et al. 2006).
Neoendemism is common in intermountain regions of
western North America, and P. clutei is likely a fairly
recently evolved species.
Little is currently known about the ecology of P. clutei,
and information in the scientific literature is sparse.
It is believed to be a short-lived perennial like many
other taxa in the genus Penstemon, perhaps living five
to seven years on average. No long-term population
studies following individual plants have been conducted
to date in its natural habitat, so estimates of its longevity
are purely speculative at this time. Observations in the
field have suggested a link to disturbances. Prolific
growth was observed following the Burnt Fire in 1973
(Goodwin 1979) and the Hochderffer Fire in 1996 (Fulé
et al. 2001). It has also been observed growing in large
numbers in the path left by a tornado (Crisp 1996) as
well as surrounding Pinus edulis (pinyon pine) trees that
were killed by drought and bark beetles in 2002-2003
(J.D. Springer, personal observations, 2008 and 2009).
Phillips and others (1992) noted vigorous plants and
high seedling numbers in areas of past disturbance, especially
from logging operations. Plants were particularly
prevalent near decaying logs and stumps. Large
numbers of reproductively mature plants are also sometimes
found in a ring surrounding recent Pinus ponderosa
(ponderosa pine) snags (Fulé et al. 2001).
Because plants had been noted to emerge in abundance
following wildfire, two prescribed burning studies
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