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Society for Conservation Biology 16th
Annual Meeting July 14-July 19 2002
co-hosted by DICE and the British Ecological Society
Abstracts for Alien and Invasive Species
Session One
Monday 15th July, 13.30 - 15.00, Grimond
Lecture Theatre 2
Chair: Alan Tye
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timetable
(BLOCK CAPITALS indicate the presenting author)
13.30 - 13.45
JENKINS, CLINTON N. and Stuart L. Pimm. Department of Ecology and Evolutionary
Biology, University of Tennessee, Knoxville, TN 37996, USA, <Rontavius@utk.edu>
(CNJ); Center for Environmental Research and Conservation, Columbia University, 1200
Amsterdam Ave., New York, NY 10027 USA (SLP).
HOW BIG IS THE GLOBAL WEED PATCH?
We cannot defend against an enemy without knowing our vulnerable areas. In the battle
against invasive species, we know that disturbed ecosystems are vulnerable. The degree
of vulnerability and which species might invade depends on the ecosystem and the
disturbance. Our global analysis comparing original and current landcover shows that
the most disturbed areas were formerly temperate or subtropical forests with moderate
rainfall. People favour areas with mild climates. A finer scale analysis shows that
the disturbance is not random. We disturb the lowlands first and create lots of edge.
What remains are some large, high-elevation fragments, and many small, lowland fragments,
most of which suffer from edge effects. It is these places, the mild lowlands, where
invasive species may present the biggest problem and be most difficult to stop.
13.45 - 14.00
TYE, ALAN. Department of Botany, Charles Darwin Research Station, Isla Santa
Cruz, Galapagos, Ecuador, <atye@fcdarwin.org.ec>.
INCREASE OF INTRODUCED PLANT SPECIES IN GALAPAGOS: CAN WE INFER ISLAND INTRODUCTION
RATES FROM INVENTORY DATA?
Galapagos probably has one of the best-documented introduced floras of any oceanic
archipelago, due to its relatively late discovery. The rate of introduction of alien
plant species to the islands has been suggested to be exponential, paralleling the
rise in the human population of the archipelago. However, a re-analysis of the historical
data, along with the addition of more recent records, reveals that a two- or three-stage
linear model better describes the historical progress of floral inventory research
in Galapagos. The floral data reflect the rate of discovery rather than the true
introduction rate, and the numbers of introduced species reported represent more
closely the changing botanical interests and research effort over the last 200 years.
An initial phase of collection and description of the native flora during the 19th
century was followed by increased reporting of naturalised introductions up to about
1970, and finally the inclusion of cultivated species since that date. What has been
reported as an increasing rate of introduction actually better represents these changing
interests and increasing research effort. The confounding effect of these factors
prevents drawing precise or reliable conclusions about changing introduction rates
from the floral inventory data.
14.00 - 14.15
VON HOLLE, BETSY. University of Tennessee, Department of Ecology & Evolutionary
Biology; Knoxville, TN 37996-1610, USA, <hvon@utk.edu>.
TESTING ELTON’S BIOTIC RESISTANCE HYPOTHESIS: DOES PLANT INVASION SUCCESS DEPEND
UPON SPECIES DIVERSITY OF THE RECIPIENT COMMUNITY?
‘Biotic resistance’ is the hypothesis that the key to the success of an invader is
the degree of resistance by the resident biota and that this resistance is somewhat
predictable. I investigated the role and importance of biotic diversity in resistance
to plant invaders in a floodplain forest in south-western Virginia, USA. I lowered
plot diversities while leaving control plots with their original complement of species.
All plots remained at their original densities. These plots were then planted with
adult plants (<1/2m) of 10 randomly chosen native and introduced species commonly
found throughout the floodplains of Big Stony Creek. Success of an invasion was measured
by total biomass and survivorship of the invader. Multiple regressions were conducted
with invasion success as the dependent variable and diversity and density of the
recipient plots as the independent variables. Survivorship is negatively correlated
with density and positively correlated with diversity of the recipient plots. This
is contrary evidence for the notion of biotic resistance rising with increasing community
diversity. Density is an important factor that should be analysed simultaneously
with diversity of recipient plots, in order to separate their disparate contributions
to invasion resistance.
14.15 - 14.30
MINCHINTON, TODD E. and Mark D. Bertness. Department of Environmental Biology,
University of Adelaide, SA 5005, Australia, <todd.minchinton@adelaide.edu.au>
(TEM), and Department of Ecology and Evolutionary Biology, Brown University, Providence,
RI 02912, USA, (MDB).
EUTROPHICATION AND DISTURBANCE FACILITATE INVASION OF COASTAL MARSHES BY PHRAGMITES
AUSTRALIS
A leading explanation for the recent invasion of coastal tidal marshes in New
England, USA by the common reed, Phragmites australis, is that anthropogenic
development along the coast is producing environmental conditions conducive to its
colonisation and expansion. Two major alterations along the terrestrial-marsh ecotone
have been recognised as potentially important: nutrient enrichment and physical disturbance
(e.g., clearing of marsh vegetation). Given these observations, we predicted that
the colonisation and expansion of P. australis in coastal marshes is dependent
on the intensity of competition with the other marsh plants as mediated by the availability
of nutrient resources. To test this prediction, we did field experiments where we
added nutrients and cleared vegetation in plots at natural borders between stands
of P. australis and the other dominant plants along the upper border of the
marsh. We then monitored the natural vegetative expansion of P. australis
and the establishment success of propagules of P. australis that we
added to the manipulated plots. Results showed that marsh vegetation could resist
and buffer the invasion of P. australis, even under conditions of nutrient
enrichment. In contrast, clearing vegetation facilitated the colonisation and expansion
of P. australis, which was further promoted by nutrient enrichment.
14.30 - 14.45
BROWN, CARRIE J. and Bernd Blossey. Department of Natural Resources, Fernow Hall,
Cornell University, Ithaca, NY 14853, USA <cjb37@cornell.edu>
PLANT INVASIONS AND AMPHIBIAN DECLINES: ARE THEY LINKED?
Invasive non-indigenous plants are responsible worldwide for alterations in ecosystem
function and loss of native species, yet how such alterations affect amphibian populations
is unknown. The Eurasian plant purple loosestrife (Lythrum salicaria) has
successfully invaded North American wetlands where it alters physical, chemical,
and biological wetland properties. To assess effects of purple loosestrife on amphibians,
we compared American toad (Bufo americanus) tadpole survival, growth, and
development in purple loosestrife and native cattail (Typha spp.) dominated
mesocosms for two consecutive years. We hypothesized tadpoles in purple loosestrife
would experience lower survival, development, and growth than cattail reared tadpoles.
The first year following mesocosm construction resulted in no fitness difference
between cattail and purple loosestrife reared tadpoles. However, in the second year
when plants had become established, purple loosestrife reared tadpoles had significantly
lower survival rates. Results from year two were consistent with our results from
an in situ experiment in natural cattail and purple loosestrife dominated
marshes where purple loosestrife reared tadpoles displayed significantly lower survival,
growth, and development. Our data support the hypothesis that invasive non-indigenous
plants threaten amphibian populations and the mesocosm experiment further suggests
that time since establishment of non-indigenous plants affects the magnitude of the
response.
14.45 - 15.00
MOORE, ROBIN D. and Richard A. Griffiths. Durrell Institute of Conservation and
Ecology, University of Kent at Canterbury, Canterbury, Kent, CT2 7NS, UK, <rdm1@ukc.ac.uk>.
THE IMPACT OF INTRODUCED PREDATORS ON ISLANDS: A CASE OF UNNATURAL SELECTION IN THE
MALLORCAN MIDWIFE TOAD
On islands, extinctions often result from a lack of coevolution between introduced
predators and prey, as endemic species will lack appropriate defences when confronted
by novel predators. Although alien predators will still impose a significant selective
force on prey species, the consequences of such unnatural selection are poorly understood.
We studied how the endemic midwife toad of Mallorca has responded to predation by
the introduced viperine snake. Morphological variation between populations of toad
tadpoles was related to the presence or absence of snakes. When snakes were present,
tadpoles possessed more streamlined bodies, with narrower fins but thicker tail muscles.
Moreover, these characters developed in under 30 days when bags of snakes were introduced
to a pool of tadpoles, and regressed within a similar period of time when snakes
were removed from another pool. These morphological changes therefore represent a
plastic phenotypic character that has evolved under variable predation pressure.
Such features may enable rapid escape in the presence of predators, but carry a cost
of reduced feeding and growth. The physical removal of predators from an island may
therefore avert extinction, but it make take much longer for costly anti-predator
traits to be selected out.
The SCB2002 pages are maintained by Christine Eagle
email: C.M.Eagle@ukc.ac.uk
Conference email: scb2002@ukc.ac.uk
Last updated: 30.06.02