NeoBiota 25
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Lantana camara L., considered among the world’s worst invaders is in identity crisis and contentiously referred as Lantana camara L. (sensu lato). Taxonomic ambiguity in L. camara L. (sensu lato), a species complex is one of the grim caveats behind incompetence of its management efforts. Recognizing the extent of variability within the complex, we aim to highlight the need to circumscribe its composition to bring effective management and control efforts into practice. There is a need for clear terminology to examine weedy, naturalized and/or invasive complex constituents that have been placed under the contentious umbrella of 'L. camara L. (sensu lato)'. The time is ripe for invasion ecologists, cytogeneticists and conservationists to collaboratively focus on disentangling the complex and integrate their knowledge and expertise into management and control programs.
Recent critics of invasion biology advocate reduced efforts against nonnative species, arguing that attempts to manage invasions are often costly and futile and that managers are indiscriminately managing species regardless of their impact. Whether this criticism has affected ground-level operations is unknown. A survey of land stewards of a major conservation NGO reveals that this plea has not been heeded; in fact, managers report that they would increase nonnative species management if more resources were available. While respondents overwhelmingly listed nonnative, invasive species as their highest priority for management, we found little evidence supporting the criticism that practitioners focus on nonnative species with minimal ecological impact. Additionally, we found that more conservation practitioners reported managing problematic "weedy" native species over nonnative species that are not invasive. Our results indicate that these managers are selective rather than profligate, targeting species that are having a demonstrable impact or are likely to do so. They feel hamstrung by resource shortages despite their rigorous target selection. Why the increasing literature calling for changed treatment of nonnatives has not led to changed operations is uncertain. Possible reasons are that the critics are not prescriptive or unified about management prioritization, or that these managers simply reject the proposed new paradigm.
The impacts of invasive alien species are greatest when they become dominant members of a community, introduce novel traits, and displace native species. Invasions by alien mollusks represent a novel context by which to compare trait differences between generalist native and introduced herbivores in terrestrial ecosystems. Here, we determined the abundance, habitat, feeding preferences, as well as the metabolic rate of the native Pacific banana slug (Ariolimax columbianus) and the alien black slug (Arion rufus) in the coastal forests of British Columbia, Canada. Through a series of observational and experimental studies, we found that alien slugs are more abundant, differ in their habitat preferences, and consumed more fungi (mushrooms) than native banana slugs. Conversely, in an enclosures experiment we found that herbivory damage by native slugs was higher compared to enclosures with alien only and control enclosures. Finally, metabolic rates were similar for both slug species. These results suggest that alien black slugs possess a suite of traits that make them functionally different from native banana slugs.
Numerous fast growing and highly competitive exotic crops are being selected for production of renewable bioenergy. Tolerance of poor growing conditions with minimal inputs are ideal characteristics for bioenergy feedstocks, but have attracted concern for their potential to become invasive. Miscanthus × giganteus is one of the most promising bioenergy crops in the US, but grower adoption is hindered by high establishment costs due to sterility. Newly developed fertile tetraploid M. × giganteus may streamline cultivation while reducing establishment costs. However, fertile seed dramatically increases the potential propagule pressure, and thus probability of off-site plant establishment. To empirically evaluate the invasive potential of fertile M. × giganteus in the Southeastern US, we compared fitness and spread potential relative to ten grass species comprising 19 accessions under both high and low levels of competition and disturbance. We chose species known to be invasive in the US (positive controls: Arundo donax, naturalized M. sinensis, M. sacchariflorus, Phalaris arundinacea, Sorghum halepense) and non-invasive (negative controls; Andropogon gerardii, ornamental M. sinensis, Panicum virgatum, Sorghum bicolor, Saccharum spp.). This novel design allows us to make relative comparisons of risk among species with varying invasiveness. After three years of establishment and growth in Blacksburg, Virginia, neither aboveground disturbance nor interspecific weed competition influenced fitness for fertile M. × giganteus or our positive and negative control groups. Fertile M. × giganteus produced 346% and 283% greater aboveground biomass than our positive and negative species, respectively. However, fertile M. × giganteus produced 74% fewer inflorescences m-2 than our positive controls and 7% and 51% fewer spikelets inflorescence-1 than the positive and negative control species. After 18 months of growth, we observed the vegetative and seedling spread of three of our positive control species (S. halepense, P. arundinacea, and M. sacchariflorus) outside the cultivated plot into receiving areas of both high and low competition. After 24 months of growth, numerous species were observed outside the cultivated plot including fertile M. × giganteus and 50% of negative control species. Notably, in three years sterile M. × giganteus ‘Illinois’ and Arundo donax never moved from the cultivated plot. The addition of fertile seed appears to increase the potential for offsite movement, but within the geographic confines of our empirical evaluation, fertile M. × giganteus seedlings are more similar to native P. virgatum and were not nearly as fast growing or as competitive as our positive control S. halepense. The use of numerous species providing relative comparisons allow us to draw important conclusions which may help prepare for widespread commercialization, while providing novel methodology for ecological risk assessment of new species.
Identifying factors that underlie invasive species colonisation and change in density could provide valuable insights into the mechanisms of biological invasions and for invasive species management. We examined a suite of factors potentially influencing the landscape-level invasion of Lantana camara L., one of the most ubiquitous invasive species in South Asia. These factors included disturbance factors like forest fires, historical habitat modification, and edge effects, in addition to factors like propagule pressure and habitat suitability. We examined the relative importance of these factors on the colonisation and change in density of L. camara in the Biligiri Rangaswamy Temple Tiger Reserve, Western Ghats, India. We used extensive (1997–2008) datasets tracking the presence and abundance of L. camara and combined these with corresponding data on disturbances, propagule pressure, and habitat suitability. We used an information-theoretic model selection approach to determine the relative importance of each factor on the colonisation and change in density of L. camara. Colonisation was mainly a function of proximity to already established populations (i.e. propagule pressure), whereas increase in L. camara density appeared to be constrained by high fire frequency. Research and management efforts need to recognize the multidimensional nature of mechanisms underlying L. camara’s success during different invasion phases when strategizing interventions to mitigate its effects.
