Editors' Choice

Science  25 Sep 2015:
Vol. 349, Issue 6255, pp. 1501
  1. Evolutionary Ecology

    Successional specialism in forests

    1. Andrew M. Sugden

    The types of tree species present in forests evolve over time

    PHOTO: FRANS LANTING/NATIONAL GEOGRAPHIC CREATIVE

    In forests, different tree species tend to occupy different stages of ecological succession, a process whereby the species structure of a particular habitat changes over time. However, scientists do not fully understand the evolutionary relationships behind these patterns. Letcher et al. studied this in tropical forest tree species across a gradient of precipitation. Specialism for particular stages of succession tended to be more conserved in related species in wet forest species than in dry forest species. More extreme environmental differences between early and late successional habitats in wet forest than in dry forest may cause this pattern, leading to successional niche similarity within species-rich rainforest tree lineages.

    J. Ecol. 103, 1276 (2015).

  2. Development

    A wild hair day for mice

    1. Beverly A. Purnell

    Petting your cat backward will probably elicit a not-so-friendly response. This is because a cat's fur grows from hair follicles that have a specific orientation. Proteins that make up the planar cell polarity (PCP) signaling pathway, which regulate the polarization of groups of cells on a plane, help orient hair follicle growth in many vertebrates. Chang et al. now report on an intriguing mouse strain that has a ridge of hair across their backs where the hair follicles are oriented in the opposite direction. Mutations in the genes that encode Frizzled 6, a PCP protein, and Astrotactin2, known for its role in guiding migrating neurons, are responsible for giving the mice such a wild hairdo.

    PLOS Genet. 10.1371/journal.pgen.1005532 (2015).

  3. Ecology

    Traffic noise effects on birds

    1. Julia Fahrenkamp-Uppenbrink

    Traffic noise repels and degrades the fitness of birds like the MacGilivray's warbler

    PHOTO: JIM ZIPP/SCIENCE SOURCE

    Bird populations decline near roads, but teasing apart the reasons for these declines can be difficult. To identify how road noise affects migratory bird species, Ware et al. used traffic noise playbacks to create a “phantom road” in a road-free area in Idaho. Overall bird numbers were 31% lower at the phantom road site than at a quiet control site. Birds that stayed at the phantom road site had a lower body condition index, an indicator of fitness. One reason for the body condition changes is the need for increased vigilance in a noisy environment, reducing the time available for foraging. The noise levels used in the experiment are similar to those in suburban neighborhoods and in many protected areas. Noise reduction is thus of crucial importance for conservation.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1504710112 (2015).

  4. Energy Economics

    Uncovering site selection bias

    1. Brad Wible

    Despite internal validity and massive replication, program evaluations may bias out-of-sample predictions and thus misinform policy discussions. Allcott analyzed 111 randomized controlled trials (RCTs) of the Opower energy efficiency intervention, involving 8.6 million U.S. households. Large-scale replication is intended to ensure external validity across RCT sites, populations, contexts, etc., but energy utilities were not all equally willing and able to participate. Utilities having more environmentalist customers were more inclined to partner earlier and to target their most high-consuming customers. Thus, earlier interventions, despite many replications, overestimated impacts relative to effects realized in later trials.

    Quart. J. Econ. 10.1093/qje/qjv015 (2015).

  5. Virology

    Giant virus varieties keep growing

    1. Barbara R. Jasny

    Transmission electron micrograph of a Mollivirus particle

    PHOTO: M. LEGENDRE ET AL., PNAS PLUS (8 SEPTEMBER 2015) © PNAS

    A recent fascinating development in basic virology has been the discovery of “giant” viruses that are visible by light microscopy. Legendre et al. now report a fourth type of giant virus called Mollivirus sibericum. Like its cousin Pithovirus sibericum, it can still infect acanthamoeba (a common soil protozoan) after being found in 30,000-year-old Siberian permafrost. Its diameter spans 0.6 µm, with a 623-kb genome, but it differs from other giant viruses in how it replicates, how its genome is organized, and in the proteins it encodes. Nearly 65% of the proteins encoded by Mollivirus have no known homologs.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1510795112 (2015).

  6. Geophysics

    Broadening the source for hot spots

    1. Brent Grocholski

    Certain volcanoes are fed by plumes of hot material originating at the very base of Earth's rocky mantle. Dynamic arguments suggest that the conduits feeding these hot-spot volcanoes should be narrow, because of the relatively small areas over which they erupt. French and Romanowicz use an improved whole-mantle seismic imaging technique to show that plumes are actually quite broad. Their surprising results imply that plumes are long-lived and may have a thermochemical origin. The vertical orientation of conduits suggests sluggish convection deep within the mantle.

    Nature 10.1038/nature14876 (2015).

  7. Liver Cancer

    Suspicious behavior by a harmless virus

    1. Paula A. Kiberstis

    Every year doctors diagnose over 700,000 people worldwide with liver cancer. The most common risk factors are alcohol abuse and chronic infection with hepatitis B or hepatitis C viruses. A new study hints at a possible nefarious role of adeno-associated virus type 2 (AAV2), which infects about half of all adults with no obvious adverse effects. Nault et al. sequenced the genomes of 193 liver tumors and found that 11 harbored AAV2 sequences integrated near genes previously linked to cancer development. The viral sequences altered the expression of these genes, but whether the integration events contributed causally to tumorigenesis is unclear. Because modified versions of AAV2 are used as gene therapy vectors, answering this question is a priority.

    Nat. Genet. 10.1038/ng.3389 (2015).