Agriculture Reference
In-Depth Information
Allelopathy as a mechanism for resisting invasion:
the case of
Polygonella myriophylla
Jeffrey D. Weidenhamer
1
and John T. Romeo
2
1
Department of Chemistry, Ashland University, Ashland, Ohio 44805, USA
2
Department of Biology, University of South Florida, Tampa, FL 33620, USA
Overview
Studies of the mechanisms by which grasses and herbs are excluded from the
Florida scrub provide evidence that allelopathy by perennial shrubs in this
community plays a primary role in preventing invasion of neighboring species.
The Florida scrub serves as a compelling counter-example to recent papers
linking the success of certain invasive plants to allelopathy, and suggests that
the role of allelopathy as a mechanism in plant invasions is more complex than
has been appreciated. This perspective deserves special emphasis given the
current dominance of the viewpoint that invasive species are superior allelo-
chemical species.
Polygonella myriophylla
and resistance to invasion
Characteristics of the scrub community
The Florida sand pine scrub occurs on well-drained sandy soils along Florida's
central Lake Wales ridge and coastal dunes. This community contains a num-
ber of perennial shrubs (e.g.,
Polygonella myriophylla
(Small) Horton,
Conradina canescens
(Torr. & Gray) A. Gray,
Ceratiola ericoides
Michx.,
Chrysoma pauciflosculosa
(Michx.) Greene, and
Calamintha ashei
(Weatherby) Shinners) for which there is evidence of allelopathic interference
toward invasive grasses of the adjacent sandhill community. Scrub vegetation
is vulnerable to fire, and sandhill grasses such as wiregrass (
Aristida stricta
Michx.
var. beyrichiana
(Trin. & Rupr.) D.B. Ward) and little bluestem
(
Schizachyrium scoparium
(Michx.) Nash) would provide fuel for fires if they
became established. Richardson and Williamson [1] proposed that allelopath-
ic interference by the fire-sensitive scrub species deters invasion by fire-prone
grasses, herbs, and pines of the neighboring fire-adapted sandhill community.
The work on allelopathy in the Florida scrub has been the subject of a number
of reviews [2-5]. Key points will be highlighted here.
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