Erin Vander Stelt
Abstract for Student Grant Proposal: Factors influencing population dynamics in Isoëtes
butleri, an endangered wetland species
Human actions in the U.S. are reducing wetland size and function. This reduction leads to
decreased plant diversity, especially among rare and endangered species. We need to
conserve these species in the interest of conserving biodiversity and learning more about
their contribution to ecosystem functions. Isoëtes butleri Engelm. (butler’s or limestone
quillwort) is an endangered wetland lycopod, and in Illinois it is suffering population
declines. It currently exists in four populations in Will and DuPage counties, but
managers hope to increase current population sizes and reintroduce it to new habitat. This
study addresses four factors that potentially influence I. butleri population dynamics:
population genetics, soil properties, associated vegetation, and litter accumulation. First,
many species of Isoëtes have exhibited inbreeding and population differentiation. I
hypothesize I. butleri populations in Illinois are also inbred and highly structured. I will
use microsatellite markers to genetically describe these populations. Second, I. butleri
inhabits thin-soiled, ephemeral wetlands over dolomite bedrock. I hypothesize soils
inside Illinois I. butleri populations are wetter, shallower, higher in Mg and Ca, and lower
in P, K, and N than soils outside I. butleri populations. I will analyze soil chemistry
(using PRS soil probes), soil moisture, and soil depth, and determine if soil properties
influence population boundaries. Third, I. butleri grows in stands with other small,
herbaceous plants. I hypothesize community composition is different between inhabited
and uninhabited areas, with fewer and smaller species inhabiting I. butleri plots. Using
modified Whitaker plots, I will measure species presence and cover in I. butleri
populations. Finally, Isoëtes butleri inhabits areas with exposed soil, gravel, and bedrock.
I hypothesize that removing litter will increase I. butleri recurrence, recruitment, and size.
In 2012, I applied a litter removal treatment and control to one population. I expect the
removal treatment to increase the individual size of I. butleri. Until more is known about
I. butleri, every action should be taken to preserve it in the interest of conserving wetland
plant diversity and function.