Taxonomic resources are essential for the effective management of invasive plants because biosecurity strategies, legislation dealing with invasive species, quarantine, weed surveillance and monitoring all depend on accurate and rapid identification of non-native taxa, and incorrect identifications can impede ecological studies. On the other hand, biological invasions have provided important tests of basic theories about species concepts. Modern taxonomy therefore needs to integrate both classical and new concepts and approaches to improve the accuracy of species identification and further refine taxonomic classification at the level of populations and genotypes in the field and laboratory.
lnstitute oj Applied Ecology CS-281 63 Kostelec nad Èerný/ni lesy, Czechoslovakia JIØÍ LIŠKA Botanical Institute, Czechoslovak Academy oj Scie/lces CS-252 43 Prùhonice, Czechoslovakia AB,5TRACT The population or Sibba/dia lelra/ldra, a cushion plant, on thc scrcc slape at 3800 m a.s.l. in thc Pamiro-Alai Mountains consists or isolatcd individuals with positivcly ske\Ved size distribution. Direct competition among isolated individuals is improbable. The dirrerences in cushion size are due mainly to the age or individuals and the local síle quality. Linear relationship between the growth in height or a cushion and its latcral growth \Vas round. Frost injuries are more extensive in the small cushions, bul the proportion or arrlicted plants is greater in the large ones. Slightly contagious spatial pattern resulting rrom the environmental heterogeneity was detccted. Seventeen specics were observed to invade the cushions. Total biomass or intruding species is highly correlated with the cushion volume as \Vel I as with biomass. Species diversity increases with cushion area. A 10g-linear relationship between the number or invading species and cushion area \Vas round. Both the number and cover or the species occurring outside or the Sibba/dia letrandra cushions are negatively correlated with the cover or Sibba/dia tetrandra. The spatial pattern or Sibba/dia populations dirrers considcrably bet\Vcen the study plot on a flat site and lhal on the screc slape. On thc flat sitc, Sibba/dia rorms a carpet consisting or individuals which cannot bc clearly distinguishcd rrom cach othcr. Thcrc also, thc numbcr and covcr or the othcr species incrcases, and the most succcssrul spccics are those \Vhich are capable or colonizing Sibba/dia cushions.
An increasing threat to U.S. waterways is the establishment and spread of invasive and injurious fishes. A species may be designated by the U.S. Fish and Wildlife Service (USFWS) as federally "injurious" under the Lacey Act (18 U.S.C. 42) either if that species causes harm (injury) without establishing and spreading (not invasive), or if that species causes harm after establishment and spread (invasive). Species designated as injurious are prohibited from being imported, which is a highly effective way of preventing invasions by nonnative species. We developed a decision-support, riskassessment system to aid USFWS's prioritization of species for injuriousness. Our system is based on USFWS's evaluation criteria of a species' potential injuriousness and consists of a semi-quantitative, rapid-assessment procedure called the Ecological Risk Screening Summary (ERSS) and a quantitative probability network model called the Freshwater Fish Injurious Species Risk Assessment Model (FISRAM). ERSS provides information on a species' history of invasiveness elsewhere in the world, and on its biology and ecology, potential or known effects of introduction, global and domestic distribution, and climate associations, and provides conclusions on potential risk of invasiveness. FISRAM calculates expected probability of injuriousness as a function of species potential establishment, spread, and harm, based on probable effects on native species and ecosystems, suitability of climate and habitat in introduced areas, ease of dispersal and transport, and harm to humans. FISRAM is used to assess risk probability when ERSS categorizes invasion risk as uncertain. We calibrated and updated the probability structure of FISRAM using a data set of 50 species with known invasiveness outcomes. We demonstrate the use of these two models for risk assessment and decision-support in identifying and documenting species for potential risk management actions, such as listing wildlife as injurious under the Lacey Act.
Aridity and intensive grazing have been confirmed to affect the
facilitative effects of dryland shrubs. However, their combined effects
on plant-plant interactions have rarely been tested. To test how these
two factors affect relations between plants, we analyzed 144 plots
(under shrub canopy vs. open areas) at 12 sampling areas established in
the conditions of two grazing regimes (high grazing vs. low grazing
intensity) and two different climatic regions (arid vs. semi-arid) in
northeastern Iran. A dominant shrub, Artemisia kopetdaghensis, was
selected as the model species. Further, we studied changes in plant life
strategies along the combined grazing and aridity stress gradients. We
used relative interaction indices to test the outcomes of plant-plant
interactions, calculated for species richness, Shannon diversity and
species abundances. Then we compared them using linear mixed-effect
models (LMM). The indicator species analysis was used to identify
species typical for the under-canopy of shrub and for the adjacent open
areas. The combination of stress factors affected the type and intensity
of plant-plant interactions and plant life strategies (CSR) of the
indicator species. Artemisia kopetdaghensis showed the highest
facilitation effect under the most intensive stress conditions (high
aridity/high grazing), which turned into competition under the low
stress conditions (low aridity/low grazing). In the arid region, the
canopy of shrub protected ruderal annual forbs and grasses with SR and
R-strategy, respectively, in both high (high aridity/high grazing) and
low grazing intensity (high aridity/low grazing). In the semi-arid
region and high grazing intensity (low aridity/high grazing), the shrubs
protected perennial forbs with C-strategy. Our FINDINGS highlight the
importance of context-dependent shrub management in the restoration of
vegetation damaged by intensive grazing.
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