Molecular phylogeny and diversification history of Prosopis (Fabaceae: Mimosoideae)

The genus Prosopis is an important member of arid and semiarid environments around the world. To study Prosopis diversification and evolution, a combined approach including molecular phylogeny, molecular dating, and character optimization analysis was applied. Phylogenetic relationships were inferred from five different molecular markers ( mat K- trn K, trn L- trn F, trn S- psb C, G3pdh, NIA). Taxon sampling involved a total of 30 Prosopis species that represented all Sections and Series and the complete geographical range of the genus. The results suggest that Prosopis is not a natural group. Molecular dating analysis indicates that the divergence between Section Strombocarpa and Section Algarobia plus Section Monilicarpa occurred in the Oligocene, contrasting with a much recent diversification (Late Miocene) within each of these groups. The diversification of the group formed by species of Series Chilenses, Pallidae, and Ruscifoliae is inferred to have started in the Pliocene, showing a high diversification rate. The moment of diversification within the major lineages of American species of Prosopis is coincident with the spreading of arid areas in the Americas, suggesting a climatic control for diversification of the group. Optimization of habitat parameters suggests an ancient occupation of arid environments by Prosopis species.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 621–640.     

Innovative social behavior in chimpanzees (Pan troglodytes)

We present evidence of agonistic buffering in captive chimpanzees, recorded from 1993 until 2005, mainly from ad libitum sampling in over 2000 hr of observation. A total of 33 agonistic buffering episodes were analyzed for context and effects of this complex social behavior. Agonistic buffering was directed at the whole chimpanzee colony as they supported an individual who initially received aggression from the alpha male, independently of the victim's age, sex or social rank. Chimpanzee agonistic buffering behavior is compared with that in other nonhuman primate species, and we describe some particularities of chimpanzee agonistic buffering: the status of the buffers used-socially important offspring such as those from the alpha female-and the social rank of the adult male responsible for the buffering episode-alpha male. Possible functions for this behavior in chimpanzees are suggested as appeasement of group members in a particularly crowded captive setting, and/or as a "forced reconciliation" mechanism. Chimpanzees exhibit behavioral flexibility by adapting themselves to new social and physical situations and use novel behavior to achieve social benefits.     

Prospectives for applying molecular and genetic methodology to improve wheat cultivars in drought environments

With the advent of molecular biotechnologies, new opportunities are available for plant physiologists to study the relationships between wheat traits and their genetic control. The functional determinations of all genes that participate in drought adaptation or tolerance reactions are expected to provide an integrated understanding of the biochemical and physiological basis of stress responses in wheat. However, despite all the recent technological breakthroughs, the overall contribution of genomics-assisted breeding to the release of drought-resilient wheat cultivars has so far been marginal. This paper critically analyses how biotechnological, genetic and information tools can contribute to accelerating the release of improved, drought-tolerant wheat cultivars. Armed with such information from established models, it will be possible to elucidate the physiological basis of drought tolerance and to select genotypes with an improved yield under water-limited conditions.     

Stability of Model Membranes in Extreme Environments

The first forms of cellular life required a source of amphiphilic compounds capable of assembling into stable boundary structures. Membranes composed of fatty acids have been proposed as model systems of primitive membranes, but their bilayer structure is stable only within a narrow pH range and low ionic strength. They are particularly sensitive to aggregating effects of divalent cations (Mg+2, Ca+2, Fe+2) that would be present in Archaean sea water. Here we report that mixtures of alkyl amines and fatty acids form vesicles at strongly basic and acidic pH ranges which are resistant to the effects of divalent cations up to 0.1 M. Vesicles formed by mixtures of decylamine and decanoic acid (1:1 mole ratio) are relatively permeable to pyranine, a fluorescent anionic dye, but permeability could be reduced by adding 2 mol% of a polycyclic aromatic hydrocarbon such as pyrene. Permeability to the dye was also reduced by increasing the chain length of the amphiphiles. For instance, 1:1 mole ratio mixtures of dodecylamine and dodecanoic acid were able to retain pyranine dye during and following gel filtration. We conclude that primitive cell membranes were likely to be composed of mixtures of amphiphilic and hydrophobic molecules that manifested increased stability over pure fatty acid membranes.     

Prokaryotic diversity in Tuz Lake, a hypersaline environment in Inland Turkey

Tuz Lake is an inland thalassohaline water body located in central Anatolia that contributes to 60% of the total salt production in Turkey per year. The microbiota inhabiting this lake has been studied by FISH, denaturing gradient gel electrophoresis of PCR-amplified fragments of 16S rRNA genes, and 16S rRNA gene clone library analysis. Total cell counts per milliliter (1.38 × 10⁷) were in the range of the values normally found for hypersaline environments. The proportion of Bacteria to Archaea in the community detectable by FISH was one to three. 16S rRNA gene clone libraries indicated that the archaeal assemblage was dominated by members of the Square Haloarchaea of the Walsby group, although some other groups were also found. Bacteria were dominated by members of the Bacteroidetes , including Salinibacter ruber -related phylotypes. Because members of Bacteroidetes are widely present in different hypersaline environments, a phylogenetic analysis of 16S rRNA gene sequences from Bacteroidetes retrieved from these environments was carried out in order to ascertain whether they formed a unique cluster. Sequences retrieved from Tuz Lake and a group of sequences from other hypersaline environments clustered together in a branch that could be considered as the 'halophilic branch' within the Bacteroidetes phylum.     

Introduction of captive breeders to the wild: Harmful or beneficial?

This work focuses on the consequences on thegenetic load and the risk of extinction when anendangered population is exposed to recurrentintroductions from a captive population whereselection is somewhat relaxed. Our findingssuggest that, although selection pressuresmight be reduced in captivity, which leads tohigher frequency of deleterious alleles innatural populations (Lynch and O'Hely 2001),such a population structure could have positiveeffects on population fitness when threeconditions are met: (i) the time length of thesupplementation program does not exceed areasonable time frame, e.g., 20 generations (ii)introduction of captive individuals is kept ata low level, i.e., one or two individuals pergeneration (iii) the size of the captivepopulation is reasonably large, e.g., more than20 individuals. The positive effect is due tothe fact that the supplementation programdelays the increase of homozygosity of thenatural population. When migration from thewild towards captivity is also allowed, thebenefits with regard to genetic load increasesignificantly even for larger numbers ofcaptive immigrants and a higher number ofgenerations. We also worked out a model withexplicit demographic considerations(fluctuating population sizes, captive migrantsincrease the size of the wild population),which shows that the probability of extinctiondecreases significantly with the number ofintroduced individuals when short-termsupplementation programs are applied (up totwenty generations). Furthermore, anappropriate genetic management of the captivepopulation, such as the equalization of familysizes, could enhance the positive effects ofsuch supplementation programs.     

Phosphorylation of Nucleotide Molecules in Hydrothermal Environments

Phosphorylation of AMP into ADP and ATP, that can outrun their hydrolysis, was made possible in a simulated hydrothermal environment when trimetaphosphate was used as the phosphate source. The best yields of phosphorylated products were obtained when the reaction fluids whose temperature was set at about 100 degrees centigrade was injected into the cold environment maintained at 0 degree in a recycling manner. Hydrothermal environments in the primitive ocean could also have served as prebiotic sites for phosphorylation, among others.     

Current perspectives in pulmonary surfactant — Inhibition, enhancement and evaluation

Pulmonary surfactant (PS) is a complicated mixture of approximately 90% lipids and 10% proteins. It plays an important role in maintaining normal respiratory mechanics by reducing alveolar surface tension to near-zero values. Supplementing exogenous surfactant to newborns suffering from respiratory distress syndrome (RDS), a leading cause of perinatal mortality, has completely altered neonatal care in industrialized countries. Surfactant therapy has also been applied to the acute respiratory distress syndrome (ARDS) but with only limited success. Biophysical studies suggest that surfactant inhibition is partially responsible for this unsatisfactory performance. This paper reviews the biophysical properties of functional and dysfunctional PS. The biophysical properties of PS are further limited to surface activity, i.e., properties related to highly dynamic and very low surface tensions. Three main perspectives are reviewed. (1) How does PS permit both rapid adsorption and the ability to reach very low surface tensions? (2) How is PS inactivated by different inhibitory substances and how can this inhibition be counteracted? A recent research focus of using water-soluble polymers as additives to enhance the surface activity of clinical PS and to overcome inhibition is extensively discussed. (3) Which in vivo, in situ, and in vitro methods are available for evaluating the surface activity of PS and what are their relative merits? A better understanding of the biophysical properties of functional and dysfunctional PS is important for the further development of surfactant therapy, especially for its potential application in ARDS.     

圈养繁殖在大熊猫保护生物学中的作用

栖息地的日益恶化、片段化和种群孤岛化已成为保护大熊猫的严重障碍。尽管就地保护濒危物种是最有希望的措施,但对于大熊猫而言,研究表明圈养繁殖也是保护这一极危物和中的有效手段之一,对保护遗传多样性起以了重要作用,是延缓绝灭速率的保证。本文阐述了大圈养繁殖的必要性及其在保护生物学中的作用。