research.html
Prior
to my doctoral dissertation research, the basic biology of rare plant Polemonium vanbruntiae (Eastern
Jacob's ladder) was unknown.
Because of this, conservation management policies for remaining
populations of this globally threatened species were ineffective and
uninformed.
Mating
system, pollen limitation, and offspring performance
In 2004-2005, I conducted a series of hand-pollination experiments
in
both the lab and the field to determine the mating system and the
extent of pollen
limitation for P. vanbruntiae.
Populations are not limited by pollen probably because of this
species ability to self-fertilize. I determined that P. vanbruntiae is self-compatible,
but selfing reduces offspring performance. I also found that
hybrid offspring resulting from crosses between distant sites
exhibit hybrid vigor (heterosis) compared to selfed offspring.
Although
Polemonium vanbruntiae
is self-compatible, its floral characteristics promote
outcrossing. The
stamens become functionally mature prior to maturation of the pistil,
and as
the
corolla opens, the unreceptive stigma surpasses the corolla by 5
– 7
mm.
After discovering that populations of
P.
vanbruntiae are not limited by
pollen-receipt,
I tested whether plants can self-fertilize. I
bagged a series of treatment plants
with breatheable organdy fabric to exclude pollinators and
hand-pollinated receptive stigmas with
within-plant self-pollen. Contrary to our initial assumptions,
P. vanbruntiae is self-compatible.
Population viability analysis of Polemonium
vanbruntiae
I collected four years (2004-2007) of demographic data from 9
sites within the Green Mountain National Forest in central Vermont.
With these data, I built matrix population models to
project population growth rate and extinction risk. I determined that
both white-tailed deer herbivory and habitat type (forest seep and wet
meadow) significantly influence long-term population growth, but deer
herbivory poses a far more significant threat to P. vanbruntiae populations.
I individually flagged and tagged P.vanbruntiae ramets
and collected
annual data on the population vital rates
(survival, growth, and reproduction).
Life cycle graph for
Polemonium
vanbruntiae.
Last modified February 01 2009 11:40 AM
