Habitat fragmentation and large-scale conservation: what do we know for sure?

We review the ecological effects of habitat fragmentation, comparing the theoretical approaches that have been taken to understanding it with the existing evidence from empirical studies. Theory has emphasized the spatial aspects of fragmentation and the role of dispersal among patches, and has generated interesting predictions such as a nonlinear relationship between the amount of remaining habitat and the probability of species persistence. However, while the few available large-scale empirical studies of fragmentation all tend to show that it has major effects, these documented effects tend to be relatively simple ones such as the degradation of habitat quality within fragments. There is good reason to be cautious of any claim that corridors or the spatial configuration of remaining habitat can compensate for the overall loss of habitat.
This is an invited Minireview on the occasion of the 50th anniversary of the Nordic Ecological Society Oikos.     

Consequences of habitat fragmentation for plant species: Do we know enough?

Habitat fragmentation is one of the most important causes for the decline of plant species. However, plants differing in phylogeny, habitat requirements and biology are likely to respond differently to habitat fragmentation. We ask whether case studies on the effects of habitat fragmentation conducted so far allow generalizations about its effects on the fitness and genetic diversity of populations of endangered plant species. We compared the characteristics of plant species endangered in Germany whose sensitivity to habitat fragmentation had been studied with those of the endangered species that had not been studied. We found strong discrepancies between the two groups with regard to their taxonomy and traits relevant to their sensitivity to habitat fragmentation. Monocots, graminoids, clonal, abiotically pollinated and self compatible species were underrepresented among the studied species, and most study species were from a few habitat types, in particular grasslands. We conclude that our current knowledge of the effects of habitat fragmentation on plant populations is not sufficient to provide widely applicable guidelines for species management. The selection of species studied so far has been biased toward species from certain habitats and species exhibiting traits that probably make them vulnerable to habitat fragmentation. Future studies should include community-wide approaches in different habitats, e.g. re-visitation studies in which the species pool is assessed at different time intervals, and population-biological studies of species from a wide range of habitats, and of different life forms and growth strategies. A more representative picture of the effects of habitat fragmentation would allow a better assessment of threats and more specific recommendations for optimally managing populations of endangered plants.     

Measures to reduce population fragmentation by roads: what has worked and how do we know?

Roads impede animal movement, which decreases habitat accessibility and reduces gene flow. Ecopassages have been built to mitigate this but there is little research with which to evaluate their effectiveness, owing to the difficulty in accessing results of existing research; the lack of scientific rigor in these studies; and the low priority of connectivity planning in road projects. In this article, we suggest that the imperative for improving studies of ecopassage effectiveness is that road ecology research should be included from the earliest stages of road projects onwards. This would enable before-after-control-impact (BACI) design research, producing useful information for the particular road project as well as rigorous results for use in future road mitigation. Well-designed studies on ecopassage effectiveness could help improve landscape connectivity even with the increasing number and use by traffic of roads.     

Skin and diabetes mellitus: what do we know?

Diabetes mellitus (DM) is becoming increasingly prevalent worldwide. Although major complications of this condition involve kidney, retina and peripheral nerves, the skin of diabetic patients is also frequently injured. Hence, interest is mounting in the definition of the structural and molecular profile of non-complicated diabetic skin, i.e., before injuries occur. Most of the available knowledge in this area has been obtained relatively recently and, in part, derives from various diabetic animal models. These include both insulin-dependent and insulin-resistant models. Structural work in human diabetic skin has also been carried out by means of tissue samples or of non-invasive methods. Indications have indeed been found for molecular/structural changes in diabetic skin. However, the overall picture that emerges is heterogeneous, incomplete and often contradictory and many questions remain unanswered. This review aims to detail, as much as possible, the various pieces of current knowledge in a systematic and synoptic manner. This should aid the identification of areas in which key questions are still open and more research is needed. A comprehensive understanding of this field could help in determining molecular targets for the prevention and treatment of skin injuries in DM and markers for the monitoring of cutaneous and systemic aspects of the disease. Additionally, with the increasing development of non-invasive optics-based deep-tissue-imaging diagnostic technologies, precise knowledge of cutaneous texture and molecular structure becomes an important pre-requisite for the use of such methods in diabetic patients.     

Spatial dynamics in model plant communities: what do we really know?

A variety of models have shown that spatial dynamics and small-scale endogenous heterogeneity (e.g., forest gaps or local resource depletion zones) can change the rate and outcome of competition in communities of plants or other sessile organisms. However, the theory appears complicated and hard to connect to real systems. We synthesize results from three different kinds of models: interacting particle systems, moment equations for spatial point processes, and metapopulation or patch models. Studies using all three frameworks agree that spatial dynamics need not enhance coexistence nor slow down dynamics; their effects depend on the underlying competitive interactions in the community. When similar species would coexist in a nonspatial habitat, endogenous spatial structure inhibits coexistence and slows dynamics. When a dominant species disperses poorly and the weaker species has higher fecundity or better dispersal, competition-colonization trade-offs enhance coexistence. Even when species have equal dispersal and per-generation fecundity, spatial successional niches where the weaker and faster-growing species can rapidly exploit ephemeral local resources can enhance coexistence. When interspecific competition is strong, spatial dynamics reduce founder control at large scales and short dispersal becomes advantageous. We describe a series of empirical tests to detect and distinguish among the suggested scenarios.     

UV radiation: what we know and do we protect ourselves adequately?

Chronic sun exposure causes degenerative changes in the skin that are recognized as photoaging, immunosuppression and photocarcinogenesis. Sun is necessary for life, so total sun avoidance is impossible. Sun exposure during the first 15 years of life and blistering sunburns before age 20 have been linked to an increased risk of melanoma. Individuals who have outdoor lifestyles, live in sunny climates, and are lightly pigmented will experience the greatest degree of photoaging. In our study, performed four years ago, we have shown the knowledge of more than 4000 people about the effects of UV rays on the skin. The results show us that sun exposure is still exaggerated and uncontrolled due to the lack of knowledge about this topic. Encouraging photoprotection and improving the awareness of the general public about the harmful effects of too much sun exposure must be the leading preventative health strategy.     

Sexual selection and environmental change:what do we know and what comes next?

Anthropogenic environmental change is the most significant threat to biodiversity in the 21st century.Animal populations are experi-encing rapid changes in thei...     

Microplastics and freshwater microalgae: what do we know so far?

The constant entry of microplastics in several environmental matrices has been of great concern to the scientific community and to society in general, mainly due to the mysteries that surround the implications of this pollutant in the environment. Freshwater ecosystems are resources especially susceptible to variations in environmental quality, and the lack of data on the impacts caused by plastic fragments exacerbates the vulnerability of this environment. Considering the results of other studies, which demonstrate the increasing entry of polymeric fragments in the aquatic environment can lead to algae growth inhibition, an investigation was carried out to determine the current state of research on the interaction between microplastics and freshwater microalgae. In total, 20 scientific articles were analyzed. Different species were subjected to toxicological tests under controlled conditions in the laboratory with small microplastics (size range between 0.1 and 1000 µm), primary and secondary microplastics of different types of polymer. Four toxicity class of indicators were chosen to assess the microalgae response to exposure to microplastic in the selected studies: growth inhibition; photosynthetic activity; pigment analysis; and enzymatic activity and oxidative stress. In this review, a critical analysis is made on the effects of the shape, size, concentration, and duration of exposure to microplastics and research gaps are identified to guide future research priorities in this area of study.

     

Candida pneumonia: What we know and what we don’t

The diagnosis of Candida pneumonia is a difficult one to make, and some experts often question whether the entity truly exists. This article assimilates the information currently available regarding Candida pulmonary infection to elucidate the presentation of the disease and the hosts in which it occurs. It also describes how to interpret the presence of Candida in respiratory secretions from both immunocompetent and immunocompromised patients. Finally, it describes how the diagnosis of Candida pneumonia can be made, which patients with suspected disease should be treated, and which antifungal agents should be used.     

Dying with dementia: what do we know about it?

Death with dementia is increasingly common, yet research on end of life with dementia and end-of-life care for such patients has been sparse. This article reviews recent studies in this area, most of which were done in US nursing homes. Research focused on five domains: prognosis, decision making, treatment, patient's health and suffering, and family's circumstances and satisfaction with care. Prognostication focused on developing risk scores for mortality within 6 months or a year, and while decision making was usually studied qualitatively, the other three domains were largely covered by a series of small, retrospective studies. Future direction in research is discussed, including the ongoing CASCADE project in Boston and the Dutch End of Life with Dementia Study (DEOLD). Both of these prospective studies in nursing home residents assess decision making, as well as factors associated with family's satisfaction and patient suffering. These studies will provide insight into interventions that are most likely to improve end of life care of patients with dementia in the respective countries and elsewhere.     

Host cell invasion by apicomplexans: what do we know?

Apicomplexan zoites enter host cells by forming and actively moving through a tight junction (TJ) formed between the parasite and host cell surfaces. Although the TJ was first described decades ago, its molecular characterization has proved difficult mainly because of its transient existence during an internalization process that lasts only seconds. In the past 7 years, work has led to a model of the TJ in which the association between AMA1 and RON proteins structures the TJ and bridges the cytoskeletons of the two cells. However, more recent work questions this view. Here, we critically discuss the current model and speculate on alternative models of the AMA1-RON association and of the apicomplexan TJ.