Differences in egg hatching time between cyclical and obligate parthenogenetic lineages of aphids

Many aphid species exhibit a variation in reproductive mode which is influenced by winter climate regimes,with cyclical parthenogenetic (CP)lines dominating in cold winter areas (because they produce cold-resistant eggs)and obligate parthenogenetic (OP) ones in mild winter regions (because of their parthenogenetic overwintering).Genetic studies on several aphid species have shown that the OP trait can be transmitted during sexual events involving the 2 types of lines.This genetic system could be considered as a local safeguarding mechanism for OP alleles in case severe frost would have killed all parthenogenetically overwintering individuals.However,this strategy would only be efficient in restoring local polymorphism in breeding systems if the newly hatched OP recombinants remain competitive over their CP counterparts.In this study we compared egg hatching sequences of CP and OP F1 clones from several crosses obtained for 2 cereal aphid species,Sitobion avenae (constant 5℃,8 h of light)and Rhopalosiphum padi (winter outdoor conditions).For S.avenae,we obtained F1 offspring from 6 crosses, involving 4 clones while in R.padi F1 were obtained from 11 crosses involving 14 clones. We showed that in both species proportions of OP clones were higher in the first half of the progeny relative to the second half.In addition,F1 OP clones hatched in the mean about a week earlier than their CP sibs,which gives them a demographic advantage at the start of the growth season.We then discussed the consequences of this fitness advantage for the maintenance and spread of the OP trait in aphid populations.     

Brain organization of gorillas reflects species differences in ecology

Gorillas include separate eastern (Gorilla beringei) and western (Gorilla gorilla) African species that diverged from each other approximately 2 million years ago. Although anatomical, genetic, behavioral, and socioecological differences have been noted among gorilla populations, little is known about variation in their brain structure. This study examines neuroanatomical variation between gorilla species using structural neuroimaging. Postmortem magnetic resonance images were obtained of brains from 18 captive western lowland gorillas (Gorilla gorilla gorilla), 15 wild mountain gorillas (Gorilla beringei beringei), and 3 Grauer's gorillas (Gorilla beringei graueri) (both wild and captive). Stereologic methods were used to measure volumes of brain structures, including left and right frontal lobe gray and white matter, temporal lobe gray and white matter, parietal and occipital lobes gray and white matter, insular gray matter, hippocampus, striatum, thalamus, each hemisphere and the vermis of the cerebellum, and the external and extreme capsules together with the claustrum. Among the species differences, the volumes of the hippocampus and cerebellum were significantly larger in G. gorilla than G. beringei. These anatomical differences may relate to divergent ecological adaptations of the two species. Specifically, G. gorilla engages in more arboreal locomotion and thus may rely more on cerebellar circuits. In addition, they tend to eat more fruit and have larger home ranges and consequently might depend more on spatial mapping functions of the hippocampus. Am J Phys Anthropol 156:252–262, 2015. © 2014 Wiley Periodicals, Inc.     

Signal Transduction by BvgS Sensor Kinase: BINDING OF MODULATOR NICOTINATE AFFECTS THE CONFORMATION AND DYNAMICS OF THE ENTIRE PERIPLASMIC MOIETY*

The two-component sensory transduction system BvgAS controls the virulence regulon of the whooping-cough agent Bordetella pertussis. The periplasmic moiety of the homodimeric sensor kinase BvgS is composed of four bilobed Venus flytrap (VFT) perception domains followed by α helices that extend into the cytoplasmic membrane. In the virulent phase, the default state of B. pertussis, the cytoplasmic enzymatic moiety of BvgS acts as kinase by autophosphorylating and transferring the phosphoryl group to the response regulator BvgA. Under laboratory conditions, BvgS shifts to phosphatase activity in response to modulators, notably nicotinate ions. Here we characterized the effects of nicotinate and related modulators on the BvgS periplasmic moiety by using site-directed mutagenesis and in silico and biophysical approaches. Modulators bind with low affinity to BvgS in the VFT2 cavity. Electron paramagnetic resonance shows that their binding globally affects the conformation and dynamics of the periplasmic moiety. Specific amino acid substitutions designed to slacken interactions within and between the VFT lobes prevent BvgS from responding to nicotinate, showing that BvgS shifts from kinase to phosphatase activity in response to this modulator via a tense transition state that involves a large periplasmic structural block. We propose that this transition enables the transmembrane helices to adopt a distinct conformation that sets the cytoplasmic enzymatic moiety in the phosphatase mode. The bona fide, in vivo VFT ligands that remain to be identified are likely to trigger similar effects on the transmembrane and cytoplasmic moieties. This mechanism may be relevant to the other VFT-containing sensor kinases homologous to BvgS.     

A link between host dispersal and parasite diversity in two sympatric cichlids of Lake Tanganyika

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Application of the Bang and Ramm age at death estimation method to two known‐age archaeological assemblages

The Bang and Ramm method uses root dentine translucency (RDT) length in sectioned or unsectioned teeth as a sole indicator of chronological age at death in adult human remains. The formulae have been tested on modern remains of known age and on modern and archaeological remains of unknown age. This is the first published study of the method on known‐age archaeological specimens and tests whether RDT is a good indicator of chronological age in buried human remains. We applied the Bang and Ramm equations to two 18th and 19th century assemblages excavated from the crypt of Christ Church, Spitalfields, and the cemetery of All Hallows by the Tower. Translucency was defined by shining a light through the external unsectioned root surface and was measured from digital images of 583 and 83 nonmolar roots from 126 Spitalfields and 12 All Hallows individuals, respectively, aged 21–81 years. Average absolute difference between real age and estimated age was 10.7 years and 8.4 years for Spitalfields and All Hallows individuals, respectively, with 58% and 75% estimated within 10 years of known age, and 29% and 33% estimated within five years of known age. These estimations are comparable to results from other ageing methods applied to the Spitalfields collection. Ages from both populations were estimated largely to the middle ranges, with younger individuals overestimated and older individuals underestimated. This is a common occurrence when using inverse calibration, where age is treated as the dependent variable and the ageing feature as the independent variable. Am J Phys Anthropol 155:332–351, 2014. © 2014 Wiley Periodicals, Inc.     

Filling the gaps in stream size spectra: using electroshocking to collect large macroinvertebrates

Studies of stream benthic macroinvertebrate size distributions describe assemblages from random small area samplers or cobbles. Large organisms are often underestimated in these samples because of their mobility or low densities. This study compared the performance of cobble collection and a Hess sampler with electrobugging (using a backpack electroshocker to collect macroinvertebrates) to determine whether electrobugging could improve estimates of the biomass of large organisms. We sampled 12 stream sites, collecting cobbles and Hess samples and conducting 3–4 consecutive electrobugging passes (repeating until attrition was observed, following with kick samples). Electrobugging collected more biomass of mobile taxa than cobble or Hess samples, and collected greater taxonomic richness, particularly at sites with low algal biomass. However, it was less effective at collecting attached and immobile taxa. Electrobugging extended the size distribution range by up to eight size classes by collecting larger macroinvertebrates than the cobble or Hess methods, and collected significantly more taxa per size class. Size distributions created from only cobble or Hess samples clearly do not represent the entire benthic community, but our results indicate that electrobugging provides a means to improve estimates of the biomass of large, mobile taxa, providing a more accurate estimate of body size distributions.     

Chilling and heat requirements for leaf unfolding in European beech and sessile oak populations at the southern limit of their distribution range

With global warming, an advance in spring leaf phenology has been reported worldwide. However, it is difficult to forecast phenology for a given species, due to a lack of knowledge about chilling requirements. We quantified chilling and heat requirements for leaf unfolding in two European tree species and investigated their relative contributions to phenological variations between and within populations. We used an extensive database containing information about the leaf phenology of 14 oak and 10 beech populations monitored over elevation gradients since 2005. In parallel, we studied the various bud dormancy phases, in controlled conditions, by regularly sampling low- and high-elevation populations during fall and winter. Oak was 2.3 times more sensitive to temperature for leaf unfolding over the elevation gradient and had a lower chilling requirement for dormancy release than beech. We found that chilling is currently insufficient for the full release of dormancy, for both species, at the lowest elevations in the area studied. Genetic variation in leaf unfolding timing between and within oak populations was probably due to differences in heat requirement rather than differences in chilling requirement. Our results demonstrate the importance of chilling for leaf unfolding in forest trees and indicate that the advance in leaf unfolding phenology with increasing temperature will probably be less pronounced than forecasted. This highlights the urgent need to determine experimentally the interactions between chilling and heat requirements in forest tree species, to improve our understanding and modeling of changes in phenological timing under global warming.