The Cerrado is a wide Neotropical savanna with tremendously high endemic diversity. Yet, it is not clear what the prevalent processes leading to such diversification are. We used the Cerrado-endemic lizard Norops meridionalis to investigate the main abiotic factors that promoted genetic divergence, the timings of these divergence events, and how these relate to cryptic diversity in the group. We sequenced mitochondrial and nuclear genes from 21 sites of N. meridionalis to generate species tree, divergence time estimations, and estimate species limits. We also performed population-level analysis and estimated distribution models to test the roles of niche conservatism and divergence in the group diversification. We found that N. meridionalis is composed by at least five cryptic species. Divergence time estimations suggest that the deepest branches split back into the early-mid Miocene, when most of the geophysical activity of the Cerrado took place. The deep divergences found in N. meridionalis suggest that beta anoles invaded South America much earlier than previously thought. Recent published evidence supports this view, indicating that the Panama gap closed as early as 15 mya, allowing for an early invasion of Norops into South America. The spatial pattern of diversification within N. meridionalis follows a northwest-southeast direction, which is consistent across several species of vertebrates endemic to the Cerrado. Also, we found evidence for non-stationary isolation by distance, which occurs when genetic differentiation depends on space. Our preliminary data in two out of five lineages suggest that niche conservatism is an important mechanism that promoted geographic fragmentation in the group.
Oxidative stress has been related to aging. Recent evidences suggest that a genetic dimorphism that encodes for either alanine or valine in superoxide dismutase (SOD2) is involved with oxidative stress. However, the current literature is still controversial, and the potential role of the Ala16Val polymorphism in human aging needs to be established. Here we investigated the role of the SOD2 polymorphism in: a) age-related mortality, b) morbidity (breast and prostate cancer), c) immunological markers, and d) DNA damage in peripheral blood cells. We did not find an association between SOD2 polymorphisms and mortality. However, the AA genotype was associated with increased risk for prostate and breast cancer, immunosenescence profile, as well as DNA damage. These data suggest that SOD2 presents characteristics that support the free radical theory of aging.
Propylene polymerization was performed using homogeneous and supported rac‐SiMe2(2‐Me‐Ind)2ZrCl2 catalysts. The supports used were commercial sodic bentonites from different sources. The influence of polymerization time and nature of catalyst support on the nanocomposites syntheses and the consequent properties of obtained composites, were evaluated at two different reaction temperatures and with two cocatalyst systems (MAO and a mixture of MAO/TIBA). The highest catalytic activities were obtained at 60 °C with the cocatalyst mixture MAO/TIBA in the reaction medium. Polymerization rate profiles were obtained as well as melting and crystallization temperatures, crystallinity degree, isotactic index, and number‐average molecular weight. The polypropylene produced with the supported catalyst pretreated with TIBA instead of MAO showed higher crystallinity degree, melting and crystallization temperatures, however, it presented lower catalyst activity. Clay exfoliation was verified by the absence of diffraction peak in the range of 2θ from 2.5° to 7° of X‐ray diffractometry analyses and by transmission electron microscopy. The thermogravimetric analyses showed an increase of PP degradation temperature of above 70 °C when synthesized with clay supported catalysts in relation to the PP obtained by means of homogeneous system.
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