Diversity and productivity peak at intermediate dispersal rate in evolving metacommunities

Positive relationships between species diversity and productivity have been reported for a number of ecosystems. Theoretical and experimental studies have attempted to determine the mechanisms that generate this pattern over short timescales, but little attention has been given to the problem of understanding how diversity and productivity are linked over evolutionary timescales. Here, we investigate the role of dispersal in determining both diversity and productivity over evolutionary timescales, using experimental metacommunities of the bacterium Pseudomonas fluorescens assembled by divergent natural selection. We show that both regional diversity and productivity peak at an intermediate dispersal rate. Moreover, we demonstrate that these two patterns are linked: selection at intermediate rates of dispersal leads to high niche differentiation between genotypes, allowing greater coverage of the heterogeneous environment and a higher regional productivity. We argue that processes that operate over both ecological and evolutionary timescales should be jointly considered when attempting to understand the emergence of ecosystem-level properties such as diversity-function relationships.     

Resource competition and social conflict in experimental populations of yeast

Understanding the conditions that promote the maintenance of cooperation is a classic problem in evolutionary biology. The essence of this dilemma is captured by the 'tragedy of the commons': how can a group of individuals that exploit resources in a cooperative manner resist invasion by 'cheaters' who selfishly use common resources to maximize their individual reproduction at the expense of the group? Here, we investigate this conflict through experimental competitions between isogenic cheater and cooperator strains of yeast with alternative pathways of glucose metabolism, and by using mathematical models of microbial biochemistry. We show that both coexistence and competitive exclusion are possible outcomes of this conflict, depending on the spatial and temporal structure of the environment. Both of these outcomes are driven by trade-offs between the rate and efficiency of conversion of resources into offspring that are mediated by metabolic intermediates.     

Collaborative genome-wide association analysis supports a role for ANK3 and CACNA1C in bipolar disorder

To identify susceptibility loci for bipolar disorder, we tested 1.8 million variants in 4,387 cases and 6,209 controls and identified a region of strong association (rs10994336, P = 9.1 x 10(-9)) in ANK3 (ankyrin G). We also found further support for the previously reported CACNA1C (alpha 1C subunit of the L-type voltage-gated calcium channel; combined P = 7.0 x 10(-8), rs1006737). Our results suggest that ion channelopathies may be involved in the pathogenesis of bipolar disorder.