Refine
Year of publication
Document Type
- Article (19)
Language
- English (19) (remove)
Has Fulltext
- yes (19) (remove)
Is part of the Bibliography
- no (19) (remove)
Keywords
- invasion (19) (remove)
Institute
1. Both direct and indirect competition can have profound effects on species abundance and expansion rates, especially for a species trying to strengthen a foothold in new areas, such as the winter moth (Operophtera brumata) currently in northernmost Finland. There, winter moths have overlapping outbreak ranges with autumnal moths (Epirrita autumnata), who also share the same host, the mountain birch (Betula pubescens ssp. czerepanovii). Competitive interactions are also possible, but so far unstudied, are explanations for the observed 1–3 years phase lag between the population cycles of the two moth species. 2. In two field experiments, we studied host plant-mediated indirect inter-specific competition and direct interference/exploitation competition between autumnal and winter moths. The experimental larvae were grown either with the competing species or with the same number of conspecifics until pupation. Inter-specific competition was judged from differences in pupal mass (reflecting lifespan fecundity), larval development time and larval survival. 3. Larval performance measurements suggested that neither direct nor indirect interspecific competition with the autumnal moth reduce the growth rate of winter moth populations. Winter moths even had a higher probability of survival when reared together with autumnal moths. 4. Thus, we conclude that neither direct nor indirect inter-specific competition is capable of suppressing the spread of the winter moth outbreak range and that both are also an unlikely cause for the phase lag between the phase-locked population cycles of the two moth species.
Sphingosine‐1‐phosphate lyase 1 (S1P lyase or SGPL1) is an essential sphingosine‐1‐phosphate‐degrading enzyme. Its manipulation favors onset and progression of colorectal cancer and others in vivo. Thus, SGPL1 is an important modulator of cancer initiation. However, in established cancer, the impact of retrospective SGPL1 modulation is elusive. Herein, we analyzed how SGPL1 siRNA affects malignancy of the human colorectal cancer cells DLD‐1 and found that in parallel to the reduction of SGPL1 expression levels, migration, invasion, and differentiation status changed. Diminished SGPL1 expression was accompanied with reduced cell migration and cell invasion in scratch assays and transwell assays, whereas metabolic activity and proliferation was not altered. Decreased migration was attended by increased cell–cell‐adhesion through upregulation of E‐cadherin and formation of cadherin‐actin complexes. Spreading cell islets showed lower vimentin abundance in border cells. Furthermore, SGPL1 siRNA treatment induced expression of epithelial cell differentiation markers, such as intestinal alkaline phosphatase and cytokeratin 20. Hence, interference with SGPL1 expression augmented a partial redifferentiation of colorectal cancer cells toward normal colon epithelial cells. Our investigation showed that SGPL1 siRNA influenced tumorigenic activity of established colorectal cancer cells. We therefore suggest SGPL1 as a target for lowering malignant potential of already existing cancer.
Like most jurisdictions, Australia is managing a broad range of invasive alien species. Here, we provide the first holistic quantification of how much invasive species impact Australia’s economy, and how much Australia spends on their management. In the 01–02 financial year (June to July), the combined estimated cost (economic losses and control) of invasive species was $9.8 billion, rising to $13.6 billion in the 11–12 financial year. Approximately $726 million of grants funded through the Commonwealth of Australia (i.e. federal funding) was spent on invasive species management and research between 1996 to 2013. In 01–02, total national expenditure on invasive species was $2.31 billion, rising to $3.77 billion in 11–12. Agriculture accounted for more than 90% of the total cost. For 01–02 and 11–12, these expenditure figures equate to $123 and $197 per person per year respectively, as well as 0.32 and 0.29% of GDP respectively. All values provided here are most likely to be underestimates of the real values due to the significant constraints of the data obtainable. Invasive species are clearly a significant economic burden in Australia. Given the extent of the issue of invasive species globally, there is a clear need for better quantifications of both economic loss and expenditure in more jurisdictions, as well as in Australia.
We argue that human-mediated invasions are part of the spectrum of species movements, not a unique phenomenon, because species self-dispersing into novel environments are subject to the same barriers of survival, reproduction, dispersal and further range expansion as those assisted by people. Species changing their distributions by human-mediated and non-human mediated modes should be of identical scientific interest to invasion ecology and ecology. Distinctions between human-mediated invasions and natural colonisations are very valid for management and policy, but we argue that these are value-laden distinctions and not necessarily an appropriate division for science, which instead should focus on distinctions based on processes and mechanisms. We propose an all-encompassing framework of species range expansion. This does not detract from the importance of invasion biology as a discipline, but instead will help bring together research being conducted on multiple taxa, and by multiple disciplines, including epidemiology, that are often focused on an identical phenomenon: colonisation.
In our recent Discussion paper, we presented our view that the only real distinction between biological invasions and natural colonisations is the human element. We agree that invasion science is a very important science, not only to better understand the role that human mediation plays for colonisation, but also for many other science fields. We agree with all invasion researchers that the human influence can result in spectacular differences, including in rates of species movement, rates of successful colonisation, the particular species being moved, the biogeography of dispersal pathways and rates of any resulting ecological disturbance and biodiversity loss. Our deep point is that that species dispersed by human-mediation or natural colonisation are all subject to the same basic laws and rules of ecology, identical to many other phenomenon that occur naturally and can be greatly influenced by people. The human dimension is merely a mechanistic distinction, albeit important because it exposes insights about the colonisation process that cannot be seen by the study of natural colonisations alone. We provide 10 hypotheses that can be scientifically tested to determine whether biological invasions and natural colonisations are two separate processes or the same process being influenced by different mechanisms.
Islands are particularly noteworthy for global conservation because of the high number of species they host, the high levels of species endemism, and the large number and proportion of species at risk of extinction. Much of the conservation threat on islands is from invasive species. Whilst biosecurity is an increasing focus of attention for authorities globally, species are continuing to establish in new locations outside of their native ranges. Among invasive species, ants are a prominent taxon, especially on islands. Over the past decade, following the detection of one of the world’s worst invasive ant species, African big-headed ant Pheidole megacephala, the environmental management authority on world-heritage-listed Lord Howe Island has focused attention on invasive ants. This detection influenced the creation of biosecurity measures to prevent further incursions of exotic species, particularly ants. Despite these efforts, over the following decade numerous ant species were collected on the island for the first time, indicating a serious biosecurity problem. Here, we investigate the chronosequence of ant introductions to Lord Howe Island to quantify the extent and nature of the island’s ant biosecurity problem. A total of 45 species have been collected on the island and of these, 12 are considered to be endemic, and a further seven are possibly native. Nineteen of the 26 introduced species (42% of the total fauna and 73% of the introduced fauna) were only found for the first time in the last 15 years. All but two of the species that are not native to Lord Howe Island are native to the Australian mainland, indicating that the biosecurity threat comes from the transport of goods from the Australian mainland. We suggest that the pattern of accelerating ant species accumulation on Lord Howe Island is probably not an isolated phenomenon, and that it is probably occurring on most islands globally that are habitable by ants and visited by people.
RITA, the RBP‐J interacting and tubulin‐associated protein, has been reported to be related to tumor development, but the underlying mechanisms are not understood. Since RITA interacts with tubulin and coats microtubules of the cytoskeleton, we hypothesized that it is involved in cell motility. We show here that depletion of RITA reduces cell migration and invasion of diverse cancer cell lines and mouse embryonic fibroblasts. Cells depleted of RITA display stable focal adhesions (FA) with elevated active integrin, phosphorylated focal adhesion kinase, and paxillin. This is accompanied by enlarged size and disturbed turnover of FA. These cells also demonstrate increased polymerized tubulin. Interestingly, RITA is precipitated with the lipoma‐preferred partner (LPP), which is critical in actin cytoskeleton remodeling and cell migration. Suppression of RITA results in reduced LPP and α‐actinin at FA leading to compromised focal adhesion turnover and actin dynamics. This study identifies RITA as a novel crucial player in cell migration and invasion by affecting the turnover of FA through its interference with the dynamics of actin filaments and microtubules. Its deregulation may contribute to malignant progression.
Understanding the diverging opinions of academic experts, stakeholders and the public is important for effective conservation management. This is especially so when a consensus is needed for action to minimize future risks but the knowledge upon which to base this action is uncertain or missing. How to manage non-native, invasive species (NIS) is an interesting case in point: the issue has long been controversial among stakeholders, but publicly visible, major disagreement among experts is recent. To characterize the multitude of experts’ understanding and valuation of non-native, NIS we performed structured qualitative interviews with 26 academic experts, 13 of whom were invasion biologists and 13 landscape experts. Within both groups, thinking varied widely, not only about basic concepts (e.g., non-native, invasive) but also about their valuation of effects of NIS. The divergent opinions among experts, regarding both the overall severity of the problem in Europe and its importance for ecosystem services, contrasted strongly with the apparent consensus that emerges from scientific synthesis articles and policy documents. We postulate that the observed heterogeneity of expert judgments is related to three major factors: (1) diverging conceptual understandings, (2) lack of empirical information and high scientific uncertainties due to complexities and contingencies of invasion processes, and (3) missing deliberation of values. Based on theory from science studies, we interpret the notion of an NIS as a boundary object, i.e., concepts that have a similar but not identical meaning to different groups of experts and stakeholders. This interpretative flexibility of a concept can facilitate interaction across diverse groups but bears the risk of introducing misunderstandings. An alternative to seeking consensus on exact definitions and risk assessments would be for invasive species experts to acknowledge uncertainties and engage transparently with stakeholders and the public in deliberations about conflicting opinions, taking the role of honest brokers of policy alternatives rather than of issue advocates.
Integrin receptors contribute to hepatocellular carcinoma (HCC) invasion, while AKT-mTOR signaling controls mitosis. The present study was designed to explore the links between integrins and the AKT-mTOR pathway and the CDK-Cyclin axis. HCC cell lines (HepG2, Huh7, Hep3B) were stimulated with soluble collagen or Matrigel to activate integrins, or with insulin-like growth factor 1 (IGF1) to activate AKT-mTOR. HCC growth, proliferation, adhesion, and chemotaxis were evaluated. AKT/mTOR-related proteins, proteins of the CDK-Cyclin axis, focal adhesion kinase (FAK), and integrin-linked kinase (ILK) were determined following IGF1-stimulation or integrin knockdown. Stimulation with collagen or Matrigel increased tumor cell growth and proliferation. This was associated with significant alteration of the integrins α2, αV, and β1. Blockade of these integrins led to cell cycle arrest in G2/M and diminished the number of tumor cell clones. Knocking down the integrins α2 or β1 suppressed ILK, reduced FAK-phosphorylation and diminished AKT/mTOR, as well as the proteins of the CDK-Cyclin axis. Activating the cells with IGF1 enhanced the expression of the integrins α2, αV, β1, activated FAK, and increased tumor cell adhesion and chemotaxis. Blocking the AKT pathway canceled the enhancing effect of IGF on the integrins α2 and β1. These findings reveal that HCC growth, proliferation, and invasion are controlled by a fine-tuned network between α2/β1-FAK signaling, the AKT-mTOR pathway, and the CDK–Cyclin axis. Concerted blockade of the integrin α2/β1 complex along with AKT-mTOR signaling could, therefore, provide an option to prevent progressive dissemination of HCC.
Although the mechanistic target of rapamycin (mTOR) inhibitor, everolimus, has improved the outcome of patients with renal cell carcinoma (RCC), improvement is temporary due to the development of drug resistance. Since many patients encountering resistance turn to alternative/complementary treatment options, an investigation was initiated to evaluate whether the natural compound, sulforaphane (SFN), influences growth and invasive activity of everolimus-resistant (RCCres) compared to everolimus-sensitive (RCCpar) RCC cell lines in vitro. RCC cells were exposed to different concentrations of SFN and cell growth, cell proliferation, apoptosis, cell cycle, cell cycle regulating proteins, the mTOR-akt signaling axis, adhesion to human vascular endothelium and immobilized collagen, chemotactic activity, and influence on surface integrin receptor expression were investigated. SFN caused a significant reduction in both RCCres and RCCpar cell growth and proliferation, which correlated with an elevation in G2/M- and S-phase cells. SFN induced a marked decrease in the cell cycle activating proteins cdk1 and cyclin B and siRNA knock-down of cdk1 and cyclin B resulted in significantly diminished RCC cell growth. SFN also modulated adhesion and chemotaxis, which was associated with reduced expression of the integrin subtypes α5, α6, and β4. Distinct differences were seen in RCCres adhesion and chemotaxis (diminished by SFN) and RCCpar adhesion (enhanced by SFN) and chemotaxis (not influenced by SFN). Functional blocking of integrin subtypes demonstrated divergent action on RCC binding and invasion, depending on RCC cell sensitivity to everolimus. Therefore, SFN administration could hold potential for treating RCC patients with established resistance towards everolimus.