New and Exciting in PLoS this week

Distorted Views of Biodiversity: Spatial and Temporal Bias in Species Occurrence Data:

Historical as well as current data on species distributions are needed to track changes in biodiversity. Species distribution data are found in a variety of sources but it is likely that they include different biases towards certain time periods or places. By collating a large historical database of ~170,000 records of species in the avian order Galliformes, dating back over two centuries and covering Europe and Asia, we investigate patterns of spatial and temporal bias in five sources of species distribution data: museum collections, scientific literature, ringing records, ornithological atlases, and website reports from "citizen scientists." Museum data were found to provide the most comprehensive historical coverage of species' ranges but often proved extremely time-intensive to collect. Literature records have increased in their number and coverage through time, whereas ringing, atlas, and website data are almost exclusively restricted to the last few decades. Geographically, our data were biased towards Western Europe and Southeast Asia. Museums were the only data source to provide reasonably even spatial coverage across the entire study region. In the last three decades, literature data have become increasingly focussed towards threatened species and protected areas, and currently no source is providing reliable baseline information--a role once filled by museum collections. As well as securing historical data for the future and making it available for users, the sampling biases will need to be understood and addressed if we are to obtain a true picture of biodiversity change.

Secondary Prevention of Suicide:

Suicide prevention can be primary, secondary, or tertiary. Primary suicide prevention aims to reduce the number of new cases of suicide in the general population [5]. Secondary suicide prevention aims to decrease the likelihood of a suicide attempt in high-risk patients [5]. Tertiary suicide prevention occurs in response to completed suicides and attempts to diminish suicide contagion (clusters of suicides in a geographical area that occur predominantly among teenagers and young adults) and copy-cat suicides [5],[6].

Secondary suicide prevention is particularly important but not always given the attention that it deserves, in part because research into secondary prevention is only just starting to be applied to clinical practice. In this article, we discuss recent research on the evaluation of suicidal risk and on different kinds of secondary suicide prevention interventions that aim to reduce that risk. We also indicate how these interventions are currently being applied and what additional research is needed.

Multi-Way Multi-Group Segregation and Diversity Indices:

How can we compute a segregation or diversity index from a three-way or multi-way contingency table, where each variable can take on an arbitrary finite number of values and where the index takes values between zero and one? Previous methods only exist for two-way contingency tables or dichotomous variables. A prototypical three-way case is the segregation index of a set of industries or departments given multiple explanatory variables of both sex and race. This can be further extended to other variables, such as disability, number of years of education, and former military service. We extend existing segregation indices based on Euclidean distance (square of coefficient of variation) and Boltzmann/Shannon/Theil index from two-way to multi-way contingency tables by including multiple summations. We provide several biological applications, such as indices for age polyethism and linkage disequilibrium. We also provide a new heuristic conceptualization of entropy-based indices. Higher order association measures are often independent of lower order ones, hence an overall segregation or diversity index should be the arithmetic mean of the normalized association measures at all orders. These methods are applicable when individuals self-identify as multiple races or even multiple sexes and when individuals work part-time in multiple industries. The policy implications of this work are enormous, allowing people to rigorously test whether employment or biological diversity has changed.