How effective were mangroves as a defence against the recent tsunami?

Whether or not mangroves function as buffers against tsunamis is the subject of in-depth research, the importance of which has been neglected or underestimated before the recent killer tsunami struck. Our preliminary post-tsunami surveys of Sri Lankan mangrove sites with different degrees of degradation indicate that human activity exacerbated the damage inflicted on the coastal zone by the tsunami.     

Did brain-specific genes evolve faster in humans than in chimpanzees?

One of the most distinctive characteristics of humans among primates is the size, organization and function of the brain. A recent study has proposed that there was widespread accelerated sequence evolution of genes functioning in the nervous system during human origins. Here we test this hypothesis by a genome-wide analysis of genes that are expressed predominantly or specifically in brain tissues and genes that have important roles in the brain, identified on the basis of five different definitions of brain specificity. Although there is little overlap among the five sets of brain-specific genes, none of them supports human acceleration. On the contrary, some datasets show significantly fewer nonsynonymous substitutions in humans than in chimpanzees for brain-specific genes relative to other genes in the genome. Our results suggest that the unique features of the human brain did not arise by a large number of adaptive amino acid changes in many proteins.     

Does attraction to frugivores or defense against pathogens shape fruit pulp composition?

Fruit traits evolve in response to an evolutionary triad between plants, seed dispersers, and antagonists that consume fruits but do not disperse seeds. The defense trade-off hypothesis predicts that the composition of nutrients and of secondary compounds in fruit pulp is shaped by a trade-off between defense against antagonists and attraction to seed dispersers. The removal rate model of this hypothesis predicts a negative relationship between nutrients and secondary compounds, whereas the toxin-titration model predicts a positive relationship. To test these alternative models, we evaluated whether the contents of nutrients and secondary compounds can be used to predict fruit removal by mutualists and pathogens in 14 bird-dispersed plants on a subtropical island in São Paulo state, southeastern Brazil. We selected eight to ten individuals of each species and prevented fruit removal by covering four branches with a net and left fruits on four other branches available to both, vertebrate fruit consumers and pathogens. The persistence of ripe fruits was drastically different among species for bagged and open fruits, and all fruit species persisted longer when protected against seed dispersers. We found that those fruits that are quickly removed by vertebrates are nutrient-rich, but although the attack rate of pathogens is also high, these fruits have low contents of quantitative defenses such as tannins and phenols. Thus, we suggest that the fruit removal rate by seed dispersers is the primary factor selecting the levels of fruit defense. Likewise, nutrient-poor fruits have low removal of seed dispersers and low probability of attack by pathogens. These species retain ripe fruits in an intact condition for a prolonged period because they are highly defended by secondary compounds, which reduce overall attractiveness. However, this strategy might be advantageous for plants that depend on rare or unreliable dispersers.     

Did protein kinase regulatory mechanisms evolve through elaboration of a simple structural component?

Statistical analysis of the functional constraints acting on eukaryotic protein kinases (EPKs) and on distantly related kinases suggests that EPK regulatory mechanisms evolved around an ancient structural component whose most distinctive features include the HxD-motif adjoining the catalytic loop, the F-helix, an F-helix aspartate, and the DFG-motif adjoined to the activation loop. The HxD-histidine constitutes a convergence point for signal integration, as conserved interactions link it to key catalytic residues, to the F-helix aspartate, and to both ends of the DFG-motif. These and other conserved features appear to be associated with DFG conformational changes and with coordinated movements possibly associated with phosphate transfer and ADP release. The EPKs have acquired structural features that link this core component to likely substrate-interacting regions at either end of the F-helix (most notably involving an F-helix tryptophan) and to three regions undergoing conformational changes upon kinase activation: the activation segment, the C-helix, and the nucleotide-binding pocket.     

Helminth anti-oxidant enzymes: a protective mechanism against host oxidants?

Highly reactive oxygen species potentially represent a powerful effector mechanism against parasites. They are produced during normal cellular metabolism, especially by activated phagocytes, and also by some anti parasitic drugs. From studies to date, all protozoan and helminth parasites appear to have one or more anti-oxidant enzymes able to scavenge or quench the reactive oxygen species, and there is strong evidence that such enzymes play a crucial role in protecting against the host response. This detailed review, which summarizes studies on the major anti-oxidant enzymes of helminths, clearly illustrates that methods to block or overcome anti-oxidant protection may be a fertile field in the search for improved ways to inhibit parasite survival.     

How much is a lot? Seed dispersal by white-faced capuchins and implications for disperser-based studies of seed dispersal systems

The quantity of seeds dispersed is considered one of several means to determine the dispersal effectiveness of an animal. However, there is little consistency in the manner in which quantities are measured or presented. Here, we quantify seed dispersal by white-faced capuchin monkeys (Cebus capucinus) in Santa Rosa National Park, Costa Rica by measuring: degree of frugivory, number of plant species consumed, the number of seeds consumed per unit time, the number of seeds dispersed intact per unit time, and the number of seeds dispersed intact per unit space. Forty-nine percent of C. capucinus diet is composed of the fruit of 39 species, 4 of which constitute 82% of the frugivory. Seventy-four percent of consumed fruits contain seeds that pass intact through the capuchin digestive system. Capuchins pass a mean of 15.7 seeds of a mean of 1.3 species per defecation, and defecate 25.4 times per 12-h day. These numbers are compared with extant data for C. capucinus, and possible reasons for discrepancies among results between studies are discussed. We propose a standardization of quantitative measures of seed dispersal so that quantifications of seed dispersal can be compared within species, and eventually across species.     

Did internal transport,rather than directed locomotion,favor the evolution of bilateral symmetry in animals?

The standard explanation for the origin of bilateral symmetry is that it conferred an advantage over radial symmetry for directed locomotion. However, recent developmental and phylogenetic studies suggest that bilateral symmetry may have evolved in a sessile benthic animal, predating the origin of directed locomotion. An evolutionarily feasible alternative explanation is that bilateral symmetry evolved to improve the efficiency of internal circulation by affecting the compartmentalization of the gut and the location of major ciliary tracts. This functional design principle is illustrated best by the phylum Cnidaria where symmetry varies from radial to tetraradial, biradial and bilateral. In the Cnidaria, bilateral symmetry is manifest most strongly in the internal anatomy and the disposition of ciliary tracts. Furthermore, the bilaterally symmetrical Cnidaria are typically sessile and, in those bilaterally symmetrical cnidarians that undergo directed locomotion, the secondary body axis does not bear a consistent orientation to the direction of locomotion as it typically does in Bilateria. Within the Cnidaria, the hypothesized advantage of bilateral symmetry for internal circulation can be tested by experimental analysis and computer modeling of fluid mechanics. The developmental evolution of symmetry within the Cnidaria can be further explored through comparative gene expression studies among species whose symmetry varies.     

Could Tyrannosaurus rex have been a scavenger rather than a predator? An energetics approach.

Arguments on whether Tyrannosaurus rex was likely to have been an active predator or a scavenger have been based on evidence from jaw morphology and/or dentition. Here, we adopt an entirely novel approach, using energetic arguments to estimate the minimum productivity that would be required for an ecosystem to support a scavenger of the size of T. rex. We argue that an ecosystem as productive as the current Serengeti would provide sufficient carrion for such a scavenger. Hence, T. rex need not have been an active predator and could have found sufficient food purely by scavenging.     

May photoinhibition be a consequence, rather than a cause, of limited plant productivity?

Photoinhibition in leaves in response to high and/or excess light, consisting of a decrease in photosynthesis and/or photosynthetic efficiency, is frequently equated to photodamage and often invoked as being responsible for decreased plant growth and productivity. However, a review of the literature reveals that photoinhibited leaves characterized for foliar carbohydrate levels were invariably found to possess high levels of sugars and starch. We propose that photoinhibition should be placed in the context of whole-plant source–sink regulation of photosynthesis. Photoinhibition may represent downregulation of the photosynthetic apparatus in response to excess light when (1) more sugar is produced in leaves than can be utilized by the rest of the plant and/or (2) more light energy is harvested than can be utilized by the chloroplast for the fixation of carbon dioxide into sugars.     

Working for a dustbath: are hens increasing pleasure rather than reducing suffering?

Dustbathing is one of the major behavioural systems of domestic fowl that is constrained by commercial caging systems. Although research conducted over the last 20 years has revealed a great deal about causation of dustbathing, attempts at measuring the importance to hens of having access to dustbathing substrate have proven difficult. Various economic techniques, operant conditioning and learning trials have been used to determine whether hens have a 'need' for dustbathing substrate or 'think' about dustbathing in the absence of substrate. In this study, we measured hens' willingness to work to obtain substrate for dustbathing using a vertically swinging door to which weights could be added. Hens were trained to push through the door to enter a goal box containing peat moss. The hens were subjected to two series of trials to compare the maximum weight that they would push to open the door when living in a cage and deprived of dustbathing substrate, with the maximum weight that they would push when living in a pen furnished with litter and a dustbath (non-deprived). Of the 10 hens that opened the door for access to peat moss, six hens pushed more weight when deprived, three hens pushed more weight when non-deprived and one hen pushed an equal amount of weight. Overall, the hens tended to push more weight (860+/-95.6 vs. 682.5+/-83.3 g; P<0.10, one-tailed paired t-test) and tended to make more attempts to open the door (P<0.10) when they were deprived than when they were non-deprived. Significantly more trials resulted in dustbathing when hens were deprived (P<0.01) suggesting that following deprivation, the hens were, in fact, more motivated to dustbathe. The results of these trials indicate that although deprived hens may be more motivated to dustbathe, and that most hens may be willing to work to obtain a dusty substrate when they can see it, they are not necessarily willing to work harder when they are in a state of deprivation than when they have recently dustbathed. These results are very difficult to explain using a 'needs' model of motivation in which deprivation leads to a state of suffering. They are much more consistent with an 'opportunity' model of motivation in which performance of the behaviour, when the opportunity presents itself, leads to a state of pleasure.     

Could poor seed dispersal contribute to predation by introduced rodents in a Hawaiian dry forest?

Dry forests are among the most diverse, yet threatened, communities in Hawai’i. Dry forests throughout the archipelago suffer from a lack of natural regeneration of trees. Two factors that may limit tree recruitment include poor seed dispersal and seed predation by rodents. Poor or limited dispersal of fleshy-fruited species results in seeds and fruits falling directly under parents. Dispersed and non-dispersed seeds may differ in their vulnerability to predation. We tested effects of seed location (under/away from parent trees) and pulp (presence/absence) on predation of four native species that suffer from limited dispersal and one readily-dispersed alien species in Kanaio Natural Area Reserve, Maui. Three natives (Diospyros sandwicensis, Pleomele auwahiensis, Santalum ellipticum), had significantly more seeds removed under parent trees than in exposed sites away from trees. For the one alien (Bocconia frutescens) and two native trees (D. sandwicensis, P. auwahiensis) that were evaluated, significantly more intact fruits were removed than were cleaned seeds. Presence of teeth marks and gnawed seed husk fragments indicate introduced rodents are destroying many of the seeds they remove. These results suggest that seed predation is disproportionately concentrated among poorly-dispersed seeds and may contribute to recruitment failure.     

Nestling discrimination without recognition: a possible defence mechanism for hosts towards cuckoo parasitism?

One of the great evolutionary puzzles is why hosts of parasitic birds discriminate finely against alien eggs, but almost never discriminate against parasitic chicks. A theoretical model has shown that an adaptive host response to alien eggs can be based on learning. However, learned nestling discrimination is too costly to be favoured by selection in hosts of evicting parasites, such as the European cuckoo (Cuculus canorus). Indeed, parasitic chick rejection has never been reported for any European cuckoo host species. As learned nestling discrimination is maladaptive, one can expect that a viable alternative for hosts would be to use discrimination mechanisms not involving learning and/or recognition. We suggest that hosts may starve and desert cuckoo chicks that require higher amounts of food than an average host brood at fledging (i.e. feeding rates to a parasite are outside the normal range of host behaviour in unparasitized nests). Our observations of the reed warbler (Acrocephalus scirpaceus) at parasitized nests indicate that such behaviour could possibly work in this host species.     

Natural folding of airborne fungal spores: a mechanism for dispersal and long-term survival?

Analysis of numerous air samples has indicated that dormant, viable fungal spores are highly present, which suggests that aerial dispersion is important for fungi. Whereas the majority of the spores may travel only very short distances, there is indication that a notable number of them cover much longer distances. Harmomegathy is a terminology coined by Wodehouse (1935) describing the natural folding of pollen to accommodate controlled and reversible water loss. Here, we discuss evidence that this concept may also apply to airborne fungal spores that face similar challenges and have to survive periods of drought and low temperatures while retaining viability to germinate after deposition upon a suitable moist substrate. In fact, (air)dried conidia, appear collapsed, survive for much longer times compared to spores in liquid, that deteriorate in time. This indicates that for some types of fungal spores, true dormancy is reached in the desiccated state. For these airborne spores this might be regarded as a pre-adaptation that supports long-distance transport of viable cells through air. We state that spores are naturally folded during transport in air if the humidity is low enough. We hypothesize that this is a pre-adaptation supporting release, dispersal and survival of airborne spores. Moreover, the smaller size of dry naturally-folded spores may also be relevant, e.g. for the opportunistic pathogenic fungus Aspergillus fumigatus reduced spore size supports deposition within the alveoli in the lung.     

Mass-dependent predation risk as a mechanism for house sparrow declines?

House sparrow (Passer domesticus) numbers have declined rapidly in both rural and urban habitats across Western Europe over the last 30 years, leading to their inclusion on the UK conservation red list. The decline in farmland has been linked to a reduction in winter survival caused by reduced food supply. This reduction in food supply is associated with agricultural intensification that has led to the loss of seed-rich winter stubble and access to spilt grain. However, urban house sparrows have also declined, suggesting that reduced food supply in farmland is not the sole reason for the decline. Here, we show that changes in house sparrow mass and thus fat reserves are not regulated to minimize starvation risk, as would be expected if limited winter food were the only cause of population decline. Instead, the species appears to be responding to mass-dependent predation risk, with starvation risk and predation risk traded-off such that house sparrows may be particularly vulnerable to environmental change that reduces the predictability of the food supply.     

Evolution of fruit traits in ficus subgenus Sycomorus (Moraceae): to what extent do frugivores determine seed dispersal mode?

Fig trees are a ubiquitous component of tropical rain forests and exhibit an enormous diversity of ecologies. Focusing on Ficus subgenus Sycomorus, a phenotypically diverse and ecologically important Old World lineage, we examined the evolution of fruit traits using a molecular phylogeny constructed using 5 kilobases of DNA sequence data from 63 species (50% of global diversity). In particular, we ask whether patterns of trait correlations are consistent with dispersal agents as the primary selective force shaping morphological diversity or if other ecological factors may provide a better explanation? Fig colour, size and placement (axial, cauliflorous, or geocarpic) were all highly evolutionarily liable, and the same fruit traits have evolved in different biogeographic regions with substantially different dispersal agents. After controlling for phylogenetic autocorrelation, we found that fig colour and size were significantly associated with fig placement and plant-life history traits (maximum plant height and leaf area, respectively). However, contrary to prevailing assumptions, fig placement correlated poorly with known dispersal agents and appears more likely determined by other factors, such as flowering phenology, nutrient economy, and habitat preference. Thus, plant life-history, both directly and through its influence on fig placement, appears to have played a prominent role in determining fruit traits in these figs.     

Inhibitory potential of proanthocyanidins from the fruit pulp of Clausena lansium (Lour.) Skeels against α-glucosidase and non-enzymatic glycation: Activity and mechanism

Inhibiting the activity of α-glucosidase and glycosylation of protein is an important way to treat diabetes mellitus and its complications. In this study, we investigated the anti-α-glucosidase activity, anti-glycation potential and structure of proanthocyanidins from fruit pulp of Clausena lansium (Lour.) Skeels. C. lansium fruit pulp proanthocyanidins showed a remarkable inhibition against α-glucosidase activity with IC₅₀ vaule of 0.26 ± 0.01 μg/mL in a competitive manner, and quenched the fluorescence of α-glucosidase by forming proanthocyanidin-α-glucosidase complex. Furthermore, compared to positive agent aminoguanidine (AG), the proanthocyanidins were the more significant inhibitors of non-enzymatic glycation by strongly inhibiting the formation of α-dicarbonyl compounds and advanced glycation end products. In addition, the structure of the proanthocyanidins was characterized in detail. These compounds were mainly composed of prodelphinidins, and their gallates. The main extender units, gallocatechin epigallocatechin and their gallates, were critical factor of the strong anti-α-glucosidase and anti-glycation activity. Therefore, this study authenticated a efficient α-glucosidase inhibitors and antiglycation agents, which would contribute to the development of anti-diabetic drug.     

Are large frugivorous birds better seed dispersers than medium‐ and small‐sized ones? Effect of body mass on seed dispersal effectiveness

Frugivorous birds vary in seed dispersal effectiveness (SDE) depending on their body mass. It has been suggested that large birds are more effective dispersers than small ones because they consume a large number of fruits, disperse seeds of distinct sizes, and transport seeds over long distances. Yet, few studies have evaluated the impact of body mass on SDE of birds. In this study, we compiled one database for the quantity (i.e., frequency of visits to plants and number of seeds removed per visit) and quality (i.e., germination of seeds after gut passage and gut retention time of seeds) of seed dispersal by frugivorous birds to evaluate the impact of body mass on SDE. In addition, we compiled data on plant characteristics such as life‐form, fruit type, number of seeds per fruit, and size of seed to evaluate their influence on the quantity and quality of seed dispersal. Data were analyzed with linear mixed effects models and quantile regressions to evaluate the relationship between body mass of birds and quantity, quality, and SDE, in addition to the influence of plant characteristics on SDE. The body mass of birds was negatively related to the frequency of visits to plants. Furthermore, it was positively related to the number of seeds removed per visit, although negatively related to seed size. The life‐form of plants was the only factor explaining the germination of seeds after gut passage. Yet, the body mass of birds was positively related to the gut retention time of seeds. Small and medium birds have a relatively higher SDE than large birds. These results differ from the assertion that large birds are more effective dispersers of plants. Small and medium birds are also effective dispersers of plants that should be preserved and protected from the impact of human activities.