Download Silphium albiflorum (white rosinweed) is an endemic limestone

Silphium albiflorum population viability in Tandy Hills 2014-2015
Axelrod A, Charon K, Duran J, Metcalf T, Perez A, Scribner M, Thomas M, Trejo M & Benz B
Texas Wesleyan University, Department of Biology
Abstract
Results
Results & Conclusions
Figure 1: Shows RO values for metapopulations in Tandy Hills in
2014 & 2015 (Kruskal-Wallis One-Way ANOVA P < 0.05)
Figure 3: Seed investment per metapopulation in 2015 < 2014.
(Kruskal-Wallis One-Way ANOVA P < 0.05)
Silphium albiflorum (white rosinweed) is an endemic
limestone-loving perennial herb of North Central Texas.
Census in Tandy Hills from 2014-2015 suggests that
seed and leaf production are competing functions
associated with the constraints of water availability.
Background
Previous research suggests that the S. albiflorum
population in Tarrant County is declining and
threatened with extinction. Only 25% of all
metapopulations in Tarrant county have stable or
increasing net reproductive rates (Arreola, et al., 2015).
In 2014, RO is > 1 (stable or increasing) in 30% of 97
Tandy Hills metapopulations. In 2014, Tandy Hills S.
albiflorum metapopulations generated 12.2 seeds on
average.
A census of three other localities in 2014 showed
considerable disparity in demographic parameters. The
other Tarrant County localities’ RO values tended to be
less than 10 on average, and RO for one locality was
effectively 1 or less.
We determined that the Tandy Hills metapopulations
do not have RO values that indicate stability.
Reproductive viability is > 1 for 6 of 79
metapopulations in 2015 and is > 1 for 29 of 97
metapopulations in 2014.
Tandy Hills natural area posted the second highest seed
production and second greatest average RO values of all
four localities in Tarrant County in 2014.
The number of leaves produced per metapopulation in
2015 is greater than in 2014.
Methods
The decrease in seed production and increase in leaf
production from 2014 to 2015 appears to be a result of
higher levels of precipitation in 2015 following
prolonged drought conditions in North Central Texas.
Census was performed in Tandy Hills in October and
November of 2015. All metapopulations (collections of
individuals within 1.5 meters) were located with
handheld GPS, individuals were tallied according to
leaf number, presence/absence of flowering stalk, and
total number of flowers and seeds per flowering stalk.
This information was organized into a static life table.
Reference
Figure 2: Leaf investment per metapopulation in 2014 < 2015.
(Kruskal- Wallis One-Way ANOVA P < 0.05)
Arreola M, Coronado P, et al. 2015. Viability of Silphium
albiflorum in Tarrant County. Post Oak and Prairie
Journal. 1 (3): 14-18.