Army ants harbor a host-specific clade of Entomoplasmatales bacteria

In this article, we describe the distributions of Entomoplasmatales bacteria across the ants, identifying a novel lineage of gut bacteria that is unique to the army ants. While our findings indicate that the Entomoplasmatales are not essential for growth or development, molecular analyses suggest that this relationship is host specific and potentially ancient. The documented trends add to a growing body of literature that hints at a diversity of undiscovered associations between ants and bacterial symbionts.     

Biogeography and morphological evolution in a Pacific island ant radiation

While insular radiations are documented for many terrestrial arthropods, few examples are known for eusocial insects. This study seeks to ascertain whether the spinescence observed among Fijian Pheidole ants was inherited from an oversea ancestor or is evidence of ecological release from interspecific competitors. We broaden our understanding of morphological convergence, insular radiation and Pacific biogeography by testing three hypotheses proposed previously for the Fijian Pheidole roosevelti group: (i) the group is monophyletic; (ii) spinescence is a plesiomorphic trait inherited from an overseas ancestor; and (iii) the group is closely related to spinescent New Guinean relatives. The analysis included the fragments of two mitochondrial genes (COI, cytb) and two nuclear genes (H3, EF1α-F2) from 66 taxa, including all members of the roosevelti group, representatives from the spinescent subgenus Pheidolacanthinus, Fijian congeners and widespread Pacific congeners. Our results yield new insights into the biogeographic history of Fiji, reveal a fascinating example of convergent evolution and serve as a novel example of ecological release occurring within an insular eusocial insect lineage. These findings recover the history of a presumably unremarkable ant species that colonized a remote oceanic archipelago in the Miocene (17-10 Ma) and radiated across the emerging islands into niche-space occupied elsewhere in the Pacific by distantly related spinescent congeners. We propose the radiation of Fijian Pheidole into spinescent morphotypes was the consequence of ecological opportunities afforded by the absence of competing ant lineages with conspicuous epigaeic foraging strategies.     

Assessing Google flu trends performance in the United States during the 2009 influenza virus A (H1N1) pandemic

Background

Google Flu Trends (GFT) uses anonymized, aggregated internet search activity to provide near-real time estimates of influenza activity. GFT estimates have shown a strong correlation with official influenza surveillance data. The 2009 influenza virus A (H1N1) pandemic [pH1N1] provided the first opportunity to evaluate GFT during a non-seasonal influenza outbreak. In September 2009, an updated United States GFT model was developed using data from the beginning of pH1N1.

Methodology/Principal Findings

We evaluated the accuracy of each U.S. GFT model by comparing weekly estimates of ILI (influenza-like illness) activity with the U.S. Outpatient Influenza-like Illness Surveillance Network (ILINet). For each GFT model we calculated the correlation and RMSE (root mean square error) between model estimates and ILINet for four time periods: pre-H1N1, Summer H1N1, Winter H1N1, and H1N1 overall (Mar 2009–Dec 2009). We also compared the number of queries, query volume, and types of queries (e.g., influenza symptoms, influenza complications) in each model. Both models'' estimates were highly correlated with ILINet pre-H1N1 and over the entire surveillance period, although the original model underestimated the magnitude of ILI activity during pH1N1. The updated model was more correlated with ILINet than the original model during Summer H1N1 (r = 0.95 and 0.29, respectively). The updated model included more search query terms than the original model, with more queries directly related to influenza infection, whereas the original model contained more queries related to influenza complications.

Conclusions

Internet search behavior changed during pH1N1, particularly in the categories “influenza complications” and “term for influenza.” The complications associated with pH1N1, the fact that pH1N1 began in the summer rather than winter, and changes in health-seeking behavior each may have played a part. Both GFT models performed well prior to and during pH1N1, although the updated model performed better during pH1N1, especially during the summer months.     

Design and Use of Multiplexed Chemostat Arrays

Chemostats are continuous culture systems in which cells are grown in a tightly controlled, chemically constant environment where culture density is constrained by limiting specific nutrients.^1,2 Data from chemostats are highly reproducible for the measurement of quantitative phenotypes as they provide a constant growth rate and environment at steady state. For these reasons, chemostats have become useful tools for fine-scale characterization of physiology through analysis of gene expression^3-6 and other characteristics of cultures at steady-state equilibrium.⁷ Long-term experiments in chemostats can highlight specific trajectories that microbial populations adopt during adaptive evolution in a controlled environment. In fact, chemostats have been used for experimental evolution since their invention.⁸ A common result in evolution experiments is for each biological replicate to acquire a unique repertoire of mutations.^9-13 This diversity suggests that there is much left to be discovered by performing evolution experiments with far greater throughput. We present here the design and operation of a relatively simple, low cost array of miniature chemostats—or ministats—and validate their use in determination of physiology and in evolution experiments with yeast. This approach entails growth of tens of chemostats run off a single multiplexed peristaltic pump. The cultures are maintained at a 20 ml working volume, which is practical for a variety of applications. It is our hope that increasing throughput, decreasing expense, and providing detailed building and operation instructions may also motivate research and industrial application of this design as a general platform for functionally characterizing large numbers of strains, species, and growth parameters, as well as genetic or drug libraries.     

Investment in higher order central processing regions is not constrained by brain size in social insects

The extent to which size constrains the evolution of brain organization and the genesis of complex behaviour is a central, unanswered question in evolutionary neuroscience. Advanced cognition has long been linked to the expansion of specific brain compartments, such as the neocortex in vertebrates and the mushroom bodies in insects. Scaling constraints that limit the size of these brain regions in small animals may therefore be particularly significant to behavioural evolution. Recent findings from studies of paper wasps suggest miniaturization constrains the size of central sensory processing brain centres (mushroom body calyces) in favour of peripheral, sensory input centres (antennal and optic lobes). We tested the generality of this hypothesis in diverse eusocial hymenopteran species (ants, bees and wasps) exhibiting striking variation in body size and thus brain size. Combining multiple neuroanatomical datasets from these three taxa, we found no universal size constraint on brain organization within or among species. In fact, small-bodied ants with miniscule brains had mushroom body calyces proportionally as large as or larger than those of wasps and bees with brains orders of magnitude larger. Our comparative analyses suggest that brain organization in ants is shaped more by natural selection imposed by visual demands than intrinsic design limitations.     

Climate change effects on animal and plant phylogenetic diversity in southern Africa

Much attention has been paid to the effects of climate change on species' range reductions and extinctions. There is however surprisingly little information on how climate change driven threat may impact the tree of life and result in loss of phylogenetic diversity (PD). Some plant families and mammalian orders reveal nonrandom extinction patterns, but many other plant families do not. Do these discrepancies reflect different speciation histories and does climate induced extinction result in the same discrepancies among different groups? Answers to these questions require representative taxon sampling. Here, we combine phylogenetic analyses, species distribution modeling, and climate change projections on two of the largest plant families in the Cape Floristic Region (Proteaceae and Restionaceae), as well as the second most diverse mammalian order in Southern Africa (Chiroptera), and an herbivorous insect genus (Platypleura) in the family Cicadidae to answer this question. We model current and future species distributions to assess species threat levels over the next 70 years, and then compare projected with random PD survival. Results for these animal and plant clades reveal congruence. PD losses are not significantly higher under predicted extinction than under random extinction simulations. So far the evidence suggests that focusing resources on climate threatened species alone may not result in disproportionate benefits for the preservation of evolutionary history.     

Kinetic mechanism of myosinV-S1 using a new fluorescent ATP analogue

We have used a new fluorescent ATP analogue, 3'-(7-diethylaminocoumarin-3-carbonylamino)-3'-deoxyadenosine-5'-triphosphate (deac-aminoATP), to study the ATP hydrolysis mechanism of the single headed myosinV-S1. Our study demonstrates that deac-aminoATP is an excellent substrate for these studies. Although the deac-amino nucleotides have a low quantum yield in free solution, there is a very large increase in fluorescence emission ( approximately 20-fold) upon binding to the myosinV active site. The fluorescence emission intensity is independent of the hydrolysis state of the nucleotide bound to myosinV-S1. The very good signal-to-noise ratio that is obtained with deac-amino nucleotides makes them excellent substrates for studying expressed proteins that can only be isolated in small quantities. The combination of the fast rate of binding and the favorable signal-to-noise ratio also allows deac-nucleotides to be used in chase experiments to determine the kinetics of ADP and Pi dissociation from actomyosin-ADP-Pi. Although phosphate dissociation from actomyosinV-ADP-Pi does not itself produce a fluorescence signal, it produces a lag in the signal for deac-aminoADP dissociation. The lag provides direct evidence that the principal pathway of product dissociation from actomyosinV-ADP-Pi is an ordered mechanism in which phosphate precedes ADP. Although the mechanism of hydrolysis of deac-aminoATP by (acto)myosinV-S1 is qualitatively similar to the ATP hydrolysis mechanism, there are significant differences in some of the rate constants. Deac-aminoATP binds 3-fold faster to myosinV-S1, and the rate of deac-aminoADP dissociation from actomyosinV-S1 is 20-fold slower. Deac-aminoATP supports motility by myosinV-HMM on actin at a rate consistent with the slower rate of deac-aminoADP dissociation.     

PrimRglo: a multiplexable quantitative real-time polymerase chain reaction system for nucleic acid detection

We report the development of a new real-time polymerase chain reaction (PCR) detection system that uses oligonucleotide "tagged" PCR primers, a fluorophore-labeled "universal" detection oligonucleotides, and a complementary quenching oligonucleotide. The fluorescence signal decreases as PCR product accumulates due to the increase in detection/quencher hybrid formation as the tagged primer is consumed. We use plasmids containing the influenza A matrix gene and the porA and ctrA genes of Neisseria meningitidis as targets for developing the system. Cycle threshold (Ct) values were generated, and the sensitivity of the new system (dubbed "PrimRglo") compared favorably with the commonly used SYBR green and Taqman detection systems and, unlike the latter system, does not require the design of a new dual-labeled detection oligonucleotide for each new target sequence.     

Correlated genetic and ecological diversification in a widespread southern African horseshoe bat

The analysis of molecular data within a historical biogeographical framework, coupled with ecological characteristics can provide insight into the processes driving diversification. Here we assess the genetic and ecological diversity within a widespread horseshoe bat Rhinolophus clivosus sensu lato with specific emphasis on the southern African representatives which, although not currently recognized, were previously described as a separate species R. geoffroyi comprising four subspecies. Sequence divergence estimates of the mtDNA control region show that the southern African representatives of R. clivosus s.l. are as distinct from samples further north in Africa than they are from R. ferrumequinum, the sister-species to R. clivosus. Within South Africa, five genetically supported geographic groups exist and these groups are corroborated by echolocation and wing morphology data. The groups loosely correspond to the distributions of the previously defined subspecies and Maxent modelling shows a strong correlation between the detected groups and ecoregions. Based on molecular clock calibrations, it is evident that climatic cycling and related vegetation changes during the Quaternary may have facilitated diversification both genetically and ecologically.