Nonrandom processes maintain diversity in tropical forests

An ecological community's species diversity tends to erode through time as a result of stochastic extinction, competitive exclusion, and unstable host-enemy dynamics. This erosion of diversity can be prevented over the short term if recruits are highly diverse as a result of preferential recruitment of rare species or, alternatively, if rare species survive preferentially, which increases diversity as the ages of the individuals increase. Here, we present census data from seven New and Old World tropical forest dynamics plots that all show the latter pattern. Within local areas, the trees that survived were as a group more diverse than those that were recruited or those that died. The larger (and therefore on average older) survivors were more diverse within local areas than the smaller survivors. When species were rare in a local area, they had a higher survival rate than when they were common, resulting in enrichment for rare species and increasing diversity with age and size class in these complex ecosystems

Colon perforation during antiangiogenic therapy for malignant glioma

Antiangiogenic drugs have emerged as effective treatment options for patients with recurrent malignant gliomas (MGs). Though this class of drugs is generally well tolerated, rare life-threatening complications, including thromboembolism, hemorrhage, and gastrointestinal (GI) perforation, are reported. We describe six cases of GI perforation among 244 glioma patients (2.5%) during treatment with antiangiogenic agents in combination with chemotherapy and corticosteroids. Two patients succumbed to this complication, and the others recovered. Because GI perforation is a life-threatening yet treatable complication, neurooncologists must have a low threshold to consider it in patients on antiangiogenic drug therapy who present with abdominal pain and other GI complaints

Predicting species diversity in tropical forests

A fundamental question in ecology is how many species occur within a given area. Despite the complexity and diversity of different ecosystems, there exists a surprisingly simple, approximate answer: the number of species is proportional to the size of the area raised to some exponent. The exponent often turns out to be roughly 1/4. This power law can be derived from assumptions about the relative abundances of species or from notions of self-similarity. Here we analyze the largest existing data set of location-mapped species: over one million, individually identified trees from five tropical forests on three continents. Although the power law is a reasonable, zeroth-order approximation of our data, we find consistent deviations from it on all spatial scales. Furthermore, tropical forests are not self-similar at areas ≤50 hectares. We develop an extended model of the species-area relationship, which enables us to predict large-scale species diversity from small-scale data samples more accurately than any other available method