Human talus bones from the Middle Pleistocene site of Sima de los Huesos (Sierra de Atapuerca,Burgos, Spain)

Here we present and describe comparatively 25 talus bones from the Middle Pleistocene site of the Sima de los Huesos (SH) (Sierra de Atapuerca, Burgos, Spain). These tali belong to 14 individuals (11 adult and three immature). Although variation among Middle and Late Pleistocene tali tends to be subtle, this study has identified unique morphological characteristics of the SH tali. They are vertically shorter than those of Late Pleistocene Homo sapiens, and show a shorter head and a broader lateral malleolar facet than all of the samples. Moreover, a few shared characters with Neanderthals are consistent with the hypothesis that the SH population and Neanderthals are sister groups. These shared characters are a broad lateral malleolar facet, a trochlear height intermediate between modern humans and Late Pleistocene H. sapiens, and a short middle calcaneal facet. It has been possible to propose sex assignment for the SH tali based on their size. Stature estimates based on these fossils give a mean stature of 174.4 cm for males and 161.9 cm for females, similar to that obtained based on the long bones from this same site.     

New and little known cladocerans (Crustacea: Anomopoda) from southeastern Mexico

Mexico represents a transitional area in which two biogeographic regions meet. A survey of the cladocerans collected in true tropical waterbodies from the country revealed a diverse fauna. The environments examined included temporary pools in the forest, rivers, permanent lagoons and karstic sinkholes. New records or little known taxa include: Diaphanosoma brevireme, D. fluviatile, Pseudosida ramosa, Simocephalus mixtus, Onchobunops tuberculatus,Guernella raphaelis, Chydorus nitidilus, Notoalonacf. globulosa, Alonella brasiliensis and Leydigiopsis curvirostris. In contrast to high altitude systems, with clear nearctic affinity, the lowlands of southeastern Mexico showed a striking resemblance with the South and Central American cladoceran fauna. Apparently, orographic barriers control the distribution of the cladoceran taxa in this region.     

Lethal Interpersonal Violence in the Middle Pleistocene

Evidence of interpersonal violence has been documented previously in Pleistocene members of the genus Homo, but only very rarely has this been posited as the possible manner of death. Here we report the earliest evidence of lethal interpersonal violence in the hominin fossil record. Cranium 17 recovered from the Sima de los Huesos Middle Pleistocene site shows two clear perimortem depression fractures on the frontal bone, interpreted as being produced by two episodes of localized blunt force trauma. The type of injuries, their location, the strong similarity of the fractures in shape and size, and the different orientations and implied trajectories of the two fractures suggest they were produced with the same object in face-to-face interpersonal conflict. Given that either of the two traumatic events was likely lethal, the presence of multiple blows implies an intention to kill. This finding shows that the lethal interpersonal violence is an ancient human behavior and has important implications for the accumulation of bodies at the site, supporting an anthropic origin.     

CD43 Promotes Cells Transformation by Preventing Merlin-Mediated Contact Inhibition of Growth

In normal tissues, strict control of tissue size is achieved by regulating cell numbers. The mechanism that controls total cell number is known as contact inhibition of growth and it depends on the NF2/Merlin pathway. Negative regulation of this pathway by deleterious mutations or by oncogenes results in cell transformation and tumor progression. Here we provide evidence that the CD43 sialomucin cooperates with oncogenic signals to promote cell transformation by abrogating the contact inhibition of growth through a molecular mechanism that involves AKT-dependent Merlin phosphorylation and degradation. Accordingly, inhibition of endogenous CD43 expression by RNA interference in lung, cervix and colon human cancer cells impaired tumor growth in vivo. These data underscore a previously unidentified role for CD43 in non-hematopoietic tumor progression.     

Does genetic diversity reduce intraspecific competition in rotifer populations?

As a result of reduced intraspecific competition, genetically diverse populations may have higher relative fitness than genetically uniform populations. To test this hypothesis, we compared polyclonal (i.e., genetically diverse) versus monoclonal (i.e., composed of a single clonal genotype) experimental populations of the rotifer Brachionus plicatilis (Müller, 1786) growing separately and in competition. We estimated the following fitness components: intrinsic growth rate; carrying capacity; proportion of sexual females; diapausing egg production per sexual female and total egg production. Polyclonal populations showed similar dynamics to monoclonal populations and no statistical difference between their fitness components was detected. Therefore, results do not support the hypothesis that genetically diverse populations reduce competition through diversification in resource use. Instead, results suggest that B. plicatilis is a generalist consumer whose polyphagy does not depend on genetic differences, but on the broad diet of each genotype. However, clones showed significant differences in almost all fitness components demonstrating among-clone variation in life-history traits. We found a trade-off between sexual ratio and carrying capacity, highlighting the cost of sex in cyclical parthenogenetic rotifers. We discuss the mechanisms that could maintain the observed among-clone genetic variation in natural populations, and speculate on results implication for sex maintenance in rotifers.     

Effect of experimental methodology on estimation of density at sex initiation in cyclically parthenogenetic rotifers

Sexual reproduction is density-dependent in several cyclically parthenogenetic rotifer species and induced by a chemical signal produced by the rotifers. As population density increases, the chemical accumulates in the medium until reaching a threshold that triggers sex. The density threshold for sex initiation is of ecological and evolutionary importance due to the large impact that timing of sex has on fitness in cyclical parthenogenetic rotifers. Here we study the effects of experimental methodology in combination with intrinsic features of the biological system on the estimation of the density required to produce enough of this chemical to initiate sex (i.e., density threshold). We have developed a theoretical model describing the dynamics of both population density and the concentration of the chemical signal. Model analysis showed that the time at which sex is recorded in an experiment, the initial density (i.e., experimental volume) and the population growth rate can affect the estimation of density thresholds. Results from an experiment in which density at sex initiation was tested for 29 clones of Brachionus plicatilis at two culture volumes, revealed that density threshold is negatively dependent on the experimental volume. We conclude that in order to estimate density thresholds so that they are comparable across studies, experimental methodology should be standardized.     

Fire effects and ecological recovery pathways of tropical montane cloud forests along a time chronosequence

Tropical montane cloud forests (TMCFs) harbour high levels of biodiversity and large carbon stocks. Their location at high elevations make them especially sensitive to climate change, because a warming climate is enhancing upslope species migration, but human disturbance (especially fire) may in many cases be pushing the treeline downslope. TMCFs are increasingly being affected by fire, and the long‐term effects of fire are still unknown. Here, we present a 28‐year chronosequence to assess the effects of fire and recovery pathways of burned TMCFs, with a detailed analysis of carbon stocks, forest structure and diversity. We assessed rates of change of carbon (C) stock pools, forest structure and tree‐size distribution pathways and tested several hypotheses regarding metabolic scaling theory (MST), C recovery and biodiversity. We found four different C stock recovery pathways depending on the selected C pool and time since last fire, with a recovery of total C stocks but not of aboveground C stocks. In terms of forest structure, there was an increase in the number of small stems in the burned forests up to 5–9 years after fire because of regeneration patterns, but no differences on larger trees between burned and unburned plots in the long term. In support of MST, after fire, forest structure appears to approximate steady‐state size distribution in less than 30 years. However, our results also provide new evidence that the species recovery of TMCF after fire is idiosyncratic and follows multiple pathways. While fire increased species richness, it also enhanced species dissimilarity with geographical distance. This is the first study to report a long‐term chronosequence of recovery pathways to fire suggesting faster recovery rates than previously reported, but at the expense of biodiversity and aboveground C stocks.     

Production and quality of conidia by <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> var. <Emphasis Type="Italic">lepidiotum</Emphasis>: critical oxygen level and period of mycelium competence

Mycoinsecticides application within Integral Pest Management requires high quantities of conidia, with the proper quality and resistance against environmental conditions. Metarhizium anisopliae var. lepidiotum conidia were produced in normal atmospheric conditions (21 % O₂) and different concentrations of oxygen pulses (16, 26, 30, and 40 %); conidia obtained under hypoxic conditions showed significantly lower viability, hydrophobicity, and virulence against Tenebrio molitor larvae or mealworm, compared with those obtained under normal atmospheric conditions. Higher concentrations of oxygen (26 and 30 %) improved conidial production. However, when a 30 % oxygen concentration was applied, maximal conidial yields were obtained at earlier times (132 h) relative to 26 % oxygen pulses (156 h); additionally, with 30 % oxygen pulses, conidia thermotolerance was improved, maintaining viability, hydrophobicity, and virulence. Although conidial production was not affected when 40 % oxygen pulses were applied, viability and virulence were diminished in those conidia. In order to find a critical time for mycelia competence to respond to these oxidant conditions, oxygen pulses were first applied either at 36, 48, 60, and 72 h. A critical time of 60 h was determined to be the best time for the M. anisopliae var. lepidiotum mycelia to respond to oxygen pulses in order to increase conidial production and also to maintain the quality features. Therefore, oxygen-enriched (30 %) pulses starting at 60 h are recommended for a high production without the impairment of quality of M. anisopliae var. lepidiotum conidia.