A call for an end to calls for the end of invasion biology

Calls for the end of invasion biology are misguided. There is no evidence that modern invasion biology has progressed slowly in its short life. Although some aspects of biological invasions fit comfortably in the framework of ecological succession, many others do not. Some native species, particularly in the wake of various anthropogenic impacts, behave like invasive non‐native species, but the probability and degree of harmful impact are greater for non‐native than for native species. Neither native nor non‐native species suffer lack of attention and research by virtue of the fact that invasion biology focuses on the latter. Basing management solely on current observed impact is highly risky because impacts may be subtle but nonetheless important, and impacts often change, as they are contingent on the physical or biotic environment. The known harmful impacts of many non‐native species suggest that recent introductions warrant attention even if impacts are not evident. Neither is the focus of modern invasion biology on non‐native species motivated by xenophobia. Rather, it reflects the recognition of their likelihood of harmful impact. A related call for the end of traditional restoration ecology shares many features with calls to terminate invasion biology, not least because management of invasive non‐native species is a key component of restoration ecology. Such species are a dominant element in generating the ‘novel ecosystems’ that are said to render traditional restoration ecology obsolete. The argument that both invasion management and traditional restoration are largely futile endeavors is contradicted by substantial and growing successes in both fields.     

A theorem for the invasion triangle and its applicability for invasion biology

The triangle conceptual model is a construct that is foundational across several fields of the natural sciences including the study of diseases, invasive species, and fire. The invasion triangle incorporates the complex ecological and evolutionary interactions between the qualities of the abiotic environment, the invader, and the biotic interactions that describes or predicts the impacts of the invasive species. Although the triangle concept is widely used among fields, to date there has not been an analytical implementation of the model. Current modelling in invasion biology often only considers the effects of one or two factors on the outcomes of species introductions. A mathematical implementation of the triangle model will allow a more comprehensive consideration of the various ecological factors. Here, we provide the first mathematical theorem for an interpretation of the invasion triangle that allows for the consideration of time. This new analytical development of the triangle is flexible, and can be used to model the spatial and temporal population dynamics observed in invasions. We also describe the conditions under which invasion is maintained when factors change with opposing effects. In this interpretation, the lower limits for invasion are explicitly defined and each component can move independently. The complexity of the interactions between factors contributing to invasions is integrated into the single model, such as those suggested by major invasion hypotheses. We briefly describe how the theorem can be applied to account for various phenomena in range dynamics using rapid range expansion and the time lag in invasions as examples. Future work can explicitly define the interdependence among components to suit more specific questions.     

A role for immunology in invasion biology

Invasive species are of increasing conservation and economic concern, yet mechanisms underlying invasions remain poorly understood. We propose that variation in immune defences might help explain why only some introduced populations become invasive. Introduced species escape many of their native diseases, but also face novel pathogens that can induce costly, and sometimes deadly, immune responses in na?ve hosts. Therefore, favouring less resource-demanding and dangerous defence mechanisms and allocating a greater proportion of resources to growth and reproduction should favour invasion. Specifically, we argue that successful invaders should reduce costly systemic inflammatory responses, which are associated with fever and metabolic and behavioural changes, and rely more heavily on less expensive antibody-mediated immunity. Here we provide supporting arguments for this hypothesis and generate predictions that are testable using tools from the growing field of ecological immunology.     

Cell biology and invasion of the microsporidia

Microsporidia are amitochondrial eukaryotic obligate intracellular parasites. They are reported to infect every animal group from protists to vertebrates, including humans. Microsporidia are of interest as opportunistic pathogens in humans and for certain characteristics which raise questions about their evolution and phylogenetic position. This review describes the basic biology and invasion mechanisms of microsporidian species infecting humans.     

Restoring physiology to the undergraduate biology curriculum: a call for action

The National Research Council-sponsored report, BIO 2010: Transforming Undergraduate Education for Future Research Biologists, describes a number of significant changes that should be made to the undergraduate biology curriculum if we are to adequately train students to become the researchers of the 21st century. What should be of concern to the physiology community is the lack of identifiable physiology in the proposed revisions. This article describes the report and suggests some steps that physiologists can take to enhance our discipline in the undergraduate biology curriculum.     

Logical fallacies and invasion biology

Leading invasion biologists sometimes dismiss critics and criticisms of their field by invoking “the straw man” fallacy. Critics of invasion biology are also labelled as a small group of “naysayers” or “contrarians”, who are sometimes engaging in “science denialism”. Such unfortunate labels can be seen as a way to possibly suppress legitimate debates and dismiss or minimize reasonable concerns about some aspects of invasion biology, including the uncertainties about the geographic origins and complex environmental impacts of species, and the control programs against species perceived as “invasive”. In assessing the quality of the debate in this area, we examine the validity of the use of various strategies, including the “straw man” concept, and explore a range of potential logical fallacies present in some recent prominent discussions about invasion biology and so-called “invasive” species. The goal is to add some clarity to the concepts involved, point out some problematic issues, and improve the quality of the debates as the discussions move forward.     

A review of the critics of invasion biology

Herein, I review existing criticisms of the field of invasion biology. Firstly, I identifiy problems of conceptual weaknesses, including disagreements regarding: (i) definitions of invasive, impact, and pristine conditions, and (ii) ecological assumptions such as species equilibrium, niche saturation, and climax communities. Secondly, I discuss methodological problems include the misuse of correlations, biases in impact reviews and risk assessment, and difficulties in predicting the effects of species introductions or eradications. Finally, I analyse the social conflict regarding invasive species management and differences in moral and philosophical foundations. I discuss the recent emergence of alternatives to traditional invasion biology approaches, including the concept of novel ecosystems, conciliation biology, and compassionate conservation. Understanding different value systems will be the first step to reconciling the different perspectives related to this controversial topic.     

Specific oligonucleotide invasion into the end of DNA duplex

Phenomenon of the interaction of a double-stranded DNA fragment with an oligonucleotide complementary to the end of the duplex strand was demonstrated to occur via formation of three-stranded DNA structure with an oligonucleotide invasion. It was shown that oligonucleotides complementary to the duplex ends inhibit Holliday junction formation in solutions of homologous linear DNA fragments. This effect depends on the oligonucleotide concentration, sequence and their complementarity to the duplex ends. Formation of three-stranded complexes was demonstrated using radiolabeled oligonucleotides by agarose gel-electrophoresis followed by autoradiography. Analysis of three-stranded DNA structures by chemical cleavage of non-canonical base pairs revealed that oligonucleotide invades into duplex ends via a sequential displacement mechanism and that the level of the invasion may vary considerably.     

The problem of prediction in invasion biology

Invasion biology is a relatively young discipline which is important, interesting and currently in turmoil. Biological invaders can threaten native ecosystems and global biodiversity; they can incur massive economic costs and even introduce diseases. Invasion biologists generally agree that being able to predict when and where an invasion will occur is essential for progress in their field. However, successful predictions of this type remain elusive. This has caused a rift, as some researchers are pessimistic and believe that invasion biology has no future, whereas others are more optimistic and believe that the key to successful prediction is the creation of a general, unified theoretical framework which encompasses all invasion events. Although I agree that there is a future for invasion biology, extensive synthesis is not the way to better predictions. I argue that the causes of invasion phenomena are exceedingly complex and heterogeneous, hence it is impossible to make generalizations over particular events without sacrificing causal detail. However, this causal detail is just what is needed for the specific predictions which the scientists wish to produce. Instead, I show that a limited type of synthesis (integration of data and methods) is a more useful tool for generating successful predictions. An important implication of my view is that it points to a more pluralistic approach to invasion biology, where generalization and prediction are treated as important yet distinct research goals.     

The biology of the receptor for advanced glycation end products and its ligands

Receptor for advanced glycation end products (RAGE) is a multiligand member of the immunoglobulin superfamily of cell surface molecules whose repertoire of ligands includes advanced glycation end products (AGEs), amyloid fibrils, amphoterins and S100/calgranulins. The overlapping distribution of these ligands and cells overexpressing RAGE results in sustained receptor expression which is magnified via the apparent capacity of ligands to upregulate the receptor. We hypothesize that RAGE-ligand interaction is a propagation factor in a range of chronic disorders, based on the enhanced accumulation of the ligands in diseased tissues. For example, increased levels of AGEs in diabetes and renal insufficiency, amyloid fibrils in Alzheimer's disease brain, amphoterin in tumors and S100/calgranulins at sites of inflammation have been identified. The engagement of RAGE by its ligands can be considered the 'first hit' in a two-stage model, in which the second phase of cellular perturbation is mediated by superimposed accumulation of modified lipoproteins (in atherosclerosis), invading bacterial pathogens, ischemic stress and other factors. Taken together, these 'two hits' eventuate in a cellular response with a propensity towards tissue destruction rather than resolution of the offending pathogenic stimulus. Experimental data are cited regarding this hypothesis, though further studies will be required, especially with selective low molecular weight inhibitors of RAGE and RAGE knockout mice, to obtain additional proof in support of our concept.     

Progress in invasion biology: predicting invaders

Predicting which species are probable invaders has been a long-standing goal of ecologists, but only recently have quantitative methods been used to achieve such a goal. Although restricted to few taxa, these studies reveal clear relationships between the characteristics of releases and the species involved, and the successful establishment and spread of invaders. For example, the probability of bird establishment increases with the number of individuals released and the number of release events. Also, the probability of plant invasiveness increases if the species has a history of invasion and reproduces vegetatively. These promising quantitative approaches should be more widely applied to allow us to predict patterns of invading species more successfully.     

网络理论在入侵生物学中的应用研究现状

生物入侵是一个动态有序的过程,其发生和危害存在异质性,通常由来源地、入侵地和它们之间的连接构成的系统中的自然、生物、社会等因素所决定。网络理论是研究复杂系统的一种新方法,本质是从复杂的信息中抽象出规律、揭示系统的结构特征共性。近20年,网络理论已被应用于生物入侵研究。本研究综述了网络理论在生物入侵研究中的应用进展,明确了主要的研究方向和前沿热点,认为:2000年以来国际上已开展的研究集中在评估外来物种入侵风险和入侵后对生态系统影响2个方面;外来物种随运输网络入侵的风险评估和景观连接性对入侵物种扩散的影响、外来物种入侵对本地物种间互作网络的影响及生态群落可入侵性是网络理论应用的热点;研究热点具有明显的时间发展特征,2013年以前多是对生态系统的影响,近10年来主要是风险评估。我国利用网络理论研究外来物种入侵较少且集中于对生态系统的危害,未来应加强对外来物种的时空定量传入和扩散风险评估,为我国制定和提升外来入侵物种早期监测预警、阻止新的入侵、抑制进一步扩散的管理措施提供依据。     

Telomere biology: a new player in the end zone

Yet another protein has been added to the crowd of players found at the ends of chromosomes. Known variously as PTOP, PIP1 or TINT1, this negative regulator of telomere length connects some of the key proteins already known to be present - TRF1, TIN2, POT1, and TRF2 - and adds even more complexity to telomere protein interactions.