The coevolution of altruism and punishment: role of the selfish punisher

Punishment is an important mechanism promoting the evolution of altruism among non-relatives. We investigate the coevolution of altruism and punitive behavior, considering four possible strategies: the altruist punisher (AP, a cooperator who punishes defectors), the altruist non-punisher (AN, a pure cooperator), the selfish punisher (SP, a defector who punishes defectors), and the selfish non-punisher (SN, a pure defector). The SP uses a paradoxical strategy as it punishes other defectors. We analyse the effects of SP and AN on the coevolution of altruism and punishment. We study both the score-dependent viability model (whereby the game's score affects survivorship only) and the score-dependent fertility model (whereby the score affects fertility only). In the viability model of a completely mixed population, SP first drives out SN, and hence it helps cooperators (AP and AN) to evolve. In contrast, in the fertility model of a completely mixed population, neither SP nor AN helps the evolution of cooperation. In both the viability and fertility models of a lattice-structured population, SP promotes the spread of AP. In contrast, AN discourages the evolution of AP. These results can be understood that punishment is a form of spite behavior, paying a cost to reduce the fitness of the opponents, and that different models give different magnitude of advantage to spite behavior.     

Homomeric and heteromeric interactions of the extracellular domains of death receptors and death decoy receptors

Death receptors (DRs) can induce apoptosis by oligomerization with TRAIL, whereas death decoy receptors (DcRs) cannot, due to their lack of functional intracellular death domains. However, it is not known whether DRs and DcRs can interact with one another to form oligomeric complexes prior to TRAIL binding. To address this issue, the extracellular domains (ECDs) of DR4 (sDR4), DR5 (sDR5), DcR1 (sDcR1), and DcR2 (sDcR2) were expressed in a soluble, monomeric form, and their binding interactions were quantified by surface plasmon resonance. The purified sDRs and sDcRs exhibited native-like secondary structure and bound to TRAIL with binding affinities in the nanomolar range (K(D)= approximately 10-62 nM), suggesting that they were properly folded and functional. The soluble receptors interacted homophilically and heterophilically with similar micromolar range affinities (K(D)= approximately 1-9 microM), with the exception that sDR5 did not interact with the sDcRs. Our results suggest that most DRs and DcRs can laterally interact through their ECDs to form homomeric and/or heteromeric complexes in the absence of TRAIL binding.     

Effect of the presence of empty sites on the evolution of cooperation by costly punishment in spatial games

Cooperation and spiteful behavior are still evolutionary puzzles. Costly punishment, for which the game payoff is the same as that of spiteful behavior, is one mechanism for promoting the evolution of cooperation. A spatially structured population facilitates the evolution of either cooperation or spite/punishment if cooperation is linked explicitly or implicitly with spite/punishment; a cooperator cooperates with another cooperator and punishes/spites the other type of player. Different updating rules in the evolutionary game produce different evolutionary outcomes: with one updating rule—the score-dependent viability model, in which a player dies with a probability inversely proportional to the game score and the resulting unoccupied site is colonized by one player chosen randomly—the evolution of spite/punishment is promoted more than with the other updating rule—the score-dependent fertility model, in which, after a player dies randomly, the site is colonized by a player with a higher game score. If the population has empty sites, spiteful players or punishers should have less chance to interact with others and then spite/punish others. Thus the presence of empty sites would affect the evolutionary dynamics of spite/punishment. Here, we investigated whether the presence of empty sites discourages the evolution of spite/punishment in both a lattice-structured population and a completely mixing population where players interact with others randomly, especially when the score-dependent viability model is adopted. In the lattice-structured population adopting this viability model, the presence of empty sites promoted the evolution of cooperation and did not reduce the effect of spite/punishment. In the completely mixing population, the presence of empty sites did not promote evolution of cooperation by punishment. The evolutionary dynamics of the score-dependent viability model with empty sites were close to those of the score-dependent fertility model.     

Resource distribution influences mating system in the bobuck (<Emphasis Type="Italic">Trichosurus cunninghami</Emphasis>: Marsupialia)

Mammalian mating systems are thought to be shaped by the spatial distribution and abundance of key resources, which in turn influence the spacing behaviour of individuals. In particular, female home range size is predicted to reflect the availability of key resources. We documented the availability and distribution of food and shelter resources for two neighbouring populations of bobucks, or mountain brushtail possums, Trichosurus cunninghami, that were characterised by different mating systems: our “forest population” was socially monogamous, whereas the “roadside population” was polygynous. Both silver wattle, Acacia dealbata, the main food resource for bobucks, and den-trees, which provided shelter, occurred at significantly higher density at the roadside site. The pattern of distribution of these two resources also differed between the sites. Both food and den-trees were scattered evenly throughout the roadside habitat. In contrast, den-trees were located predominantly at one end of the forest site, while silver wattle trees were located at the other. There was no significant difference in the amount of silver wattle, or in the number of den-trees, located within the home ranges of individual females at the two sites. However, forest females had home ranges, on average, almost three times the size of those of roadside females. At the roadside site, the size of female home ranges varied inversely with the density of silver wattle, indicating that these females ranged over as large an area as necessary to gain access to sufficient silver wattle trees. There was no such relationship among forest females. These populations provide a clear example of resource distribution determining female home range size. This influenced the number of female home ranges a male’s home range overlapped with, which in turn determined the mating system. Such clear links between resource availability and mating system have not previously been established in a marsupial.     

Nectar and hostplant scarcity limit populations of an endangered Oregon butterfly

As grassland habitats become degraded, declines in juvenile and adult food resources may limit populations of rare insects. Fender's blue butterfly (Icaricia icarioides fenderi), a species proposed for listing as endangered under the US Endangered Species Act, survives in remnants of upland prairie in western Oregon. We investigated the effects of limited larval hostplants and adult nectar sources on butterfly population size at four sites that encompass a range of resource densities. We used coarse and detailed estimates of resource abundance to test hypotheses relating resource quantity to population size. Coarse estimates of resources (percent cover of hostplant and density of nectar flowers) suggest that butterfly population size is not associated with resource availability. However, more detailed estimates of resources (density of hostplant leaves and quantity of nectar from native nectar sources) suggest that butterfly population size is strongly associated with resource availability. The results of this study suggest that restoring degraded habitat by augmenting adult and larval resources will play an important role in managing populations of this rare butterfly. Received: 20 June 1998 / Accepted: 25 November 1998     

Feeding of tropical freshwater fishes: seasonality in resource availability and resource use

Summary Food resources in the environment and in the diets of small fish inhabiting two water bodies in a tropical savanna were studied during both wet and dry seasons. During the wet season (high water, abundant food) most fish species in both habitats fed predominantly on vegetation-dwelling invertebrates. Most fish species switched to alternative foods (algae and detritus) following the drastic decline in invertebrate food available towards the end of the dry season. In one habitat, this change in diet was accompanied by an increase in the volume of food intake. In the second habitat, only two larger species foraged intensively, while smaller species showed low food intake or almost ceased feeding. These differences may be explained by the high risk of predation for small fish in the second habitat. Dietary overlaps among fish species were high at the end of the dry season and moderate in the wet season. However, critical analysis of such factors as food abundance, the size and number of shared prey, and diet breadth showed that all significant overlaps were ecologically unimportant i.e. there was only weak competition for food.     

Resource heterogeneity generated by shrubs and topography on coastal sand dunes

In early stages of primary succession, colonizing plants can create resource patches that influence the abundance and distribution of other species. To test whether different colonizing shrubs generate contrasting patches on coastal sand dunes, we compared soil characteristics and light availability under the nitrogen-fixing shrub Lupinus arboreus, under the non-nitrogen-fixing shrub Artemisia pycnocephala, and between shrubs on dunes at a site in northern California. Concentrations of inorganic nitrogen and net nitrogen mineralization rates were generally 1–10 times greater in soil under Lupinus than under Artemisia or between shrubs. Soil water content was mostly lower under shrubs. Mean photon flux density near ground level was reduced by at least 80% at 35 cm inside shrub canopies. Topography appeared to have more effect on soil moisture but less direct effect on nitrogen availability than did Lupinus. However, Lupinus probably increases nitrogen levels more on higher, drier dunes. Microhabitats under and between nitrogen-fixing shrubs constitute a mosaic of individually poor but complementary patches in which high levels of light and moderate levels of soil nitrogen are present but tend not to occur together.     

Captive breeding reveals larval performance and adult body size differences between two geographical populations of the stag beetle Aegus chelifer chelifer (Coleoptera: Lucanidae)

Stag beetles usually have great intraspecific variation in their body sizes, which can be affected by both environmental and genetic factors. However, direct studies on wild-caught specimens may be insufficient to clarify such variation due to the confounding effects of ecological variance in natural habitats. To evaluate this, the stag beetle Aegus chelifer chelifer MacLeay, 1819 was collected from within two localities (Bangkok metropolitan area and Chanthaburi province) in Thailand and then reared under the same condition to investigate the differences in morphological characteristics between the wild-caught and captive-bred beetles and between the two geographical populations. Narrow-sense heritabilities (h²) of the observed traits in adults were not significant. Variation in the body size of captive-bred specimens was less than in the wild-caught specimens and the overlap of the body size variation between the two populations was lower in the captive-bred beetles. The Chanthaburi population had a significantly larger body size than the Bangkok population. Allometric slopes and intercepts were also significantly different between the two geographic populations. Captive-bred larvae showed similar relative growth rates, but male larvae from the Chanthaburi population had a longer feeding period, and so a larger adult body size, than those from the Bangkok population. The differences between the two populations could be explained by adaptation through larval performances and body size in order to respond to their habitats.     

Solution structure of the isolated Pelle death domain

The interaction between the death domains (DDs) of Tube and the protein kinase Pelle is an important component of the Toll pathway. Published crystallographic data suggests that the Pelle-Tube DD interface is plastic and implies that in addition to the two predominant Pelle-Tube interfaces, a third interaction is possible. We present the NMR solution structure of the isolated death domain of Pelle and a study of the interaction between the DDs of Pelle and Tube. Our data suggests the solution structure of the isolated Pelle DD is similar to that of Pelle DD in complex with Tube. Additionally, they suggest that the plasticity observed in the crystal structure may not be relevant in the functioning death domain complex.     

Evidence of complex formation between FADD and c-FLIP death effector domains for the death inducing signaling complex

Adaptor protein FADD forms the death inducing signaling complex (DISC) by recruiting the initiating caspases-8 and -10 through homotypic death effector domain (DED) interactions. Cellular FLICE-inhibitory protein (c-FLIP) is an inhibitor of death ligand-induced apoptosis downstream of death receptors, and FADD competes with procaspase-8/10 for recruitment for DISC. However, the mechanism of action of FADD and c-FLIP proteins remain poorly understood at the molecular level. In this study, we provide evidence indicating that the death effector domain (DED) of FADD interacts directly with the death effector domain of human c-FLIP. In addition, we use homology modeling to develop a molecular docking model of FADD and c-FLIP proteins. We also find that four structure-based mutants (E80A, L84A, K169A and Y171A) of c-FLIP DEDs disturb the interaction with FADD DED, and that these mutations lower the stability of the c-FLIP DED. [BMB Reports 2014; 47(9): 488-493]     

The size distribution of insertions and deletions in human and rodent pseudogenes suggests the logarithmic gap penalty for sequence alignment

The size distributions of deletions, insertions, and indels (i.e., insertions or deletions) were studied, using 78 human processed pseudogenes and other published data sets. The following results were obtained: (1) Deletions occur more frequently than do insertions in sequence evolution; none of the pseudogenes studied shows significantly more insertions than deletions. (2) Empirically, the size distributions of deletions, insertions, and indels can be described well by a power law, i.e., f _k = Ck ^–b , where f _k is the frequency of deletion, insertion, or indel with gap length k, b is the power parameter, and C is the normalization factor. (3) The estimates of b for deletions and insertions from the same data set are approximately equal to each other, indicating that the size distributions for deletions and insertions are approximately identical. (4) The variation in the estimates of b among various data sets is small, indicating that the effect of local structure exists but only plays a secondary role in the size distribution of deletions and insertions. (5) The linear gap penalty, which is most commonly used in sequence alignment, is not supported by our analysis; rather, the power law for the size distribution of indels suggests that an appropriate gap penalty is w _k = a + b ln k, where a is the gap creation cost and blnk is the gap extension cost. (6) The higher frequency of deletion over insertion suggests that the gap creation cost of insertion (a _i ) should be larger than that of deletion (a _d ); that is, a _i – a _d = In R, where R is the frequency ratio of deletions to insertions. Correspondence to: W.-H. Li     

Upon intracellular processing, the C-terminal death domain-containing fragment of the p53-inducible PIDD/LRDD protein translocates to the nucleoli and interacts with nucleolin

The p53-inducible and death domain-containing PIDD/LRDD protein has been described as an adaptor protein, which forms large protein complexes with RAIDD, another death domain-containing protein, leading to recruitment, and activation of the initiator caspase-2, and p53-mediated apoptosis. Here, we describe in further detail the proteolytic processing of PIDD/LRDD that occurs in healthy cells before induction of apoptosis. We could demonstrate that the C-terminal fragment containing the PIDD death domain shuttles into the nucleoli. This translocation is mediated by or leads to the interaction of the PIDD death domain with nucleolin, a protein important for rRNA processing within nucleoli and possibly involved in the DNA damage response. Ectopically expressed LRDD and endogenous nucleolin co-localized within the nucleoli, and overexpression of both full-length LRDD and the LRDD death domain sensitized cells for UV-induced apoptosis. When expressed alone, the PIDD/LRDD death domain tended to form large filamentous structures resembling so-called death filaments. The functional consequences of the identified PIDD/nucleolin interaction remain to be elucidated, but may be related to a recently discovered new role for PIDD in the activation of NF-kappaB upon genotoxic stress.     

Differential response of trees and shrubs to browsing and pruning: the effects on Pistacia growth and gall-inducing aphids

The effects of long term browsing on growth and morphology of P. atlantica trees and P. palaestina shrubs, and on the colonization of these hosts by their respective gall-inducing aphid guilds, were studied in natural vegetation pastures in Israel. To simulate apical dominance release by browsing, trees and shrubs were pruned and observed one year later. P. atlantica responded strongly to browsing, producing a crown of dense and sharp dry branches and thorn-like shoots, and pruning, compensating or overcompensating for the lost biomass in the studied morphological variables. Morphological responses of P. palaestina were less evident: we found no compensation in most variables. Three species of aphids produced more galls on browsed than on control shoots of P. atlantica. Two species induced more galls on pruned shoots. The five aphid species on P. palaestina colonized browsed and unbrowsed shoots equally, and produced fewer galls on pruned shoots. The role of apical dominance in architectural responses of trees and shrubs to browsing and pruning, as related to resource availability and timing, is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of forest canopy composition on soil nutrients and dynamics of the understorey: mixed canopies serve neither vascular nor bryophyte strata

Question: The effect of overstorey composition on above‐ground dynamics of understorey vegetation is poorly understood. This study examines the understorey biomass, production and turnover rates of vascular and non‐vascular plants along a conifer–broadleaf gradient of resource availability and heterogeneity. Location: Canadian boreal forests of northwest Quebec and Ontario. Methods: We sampled mature stands containing various proportions of black spruce (Picea mariana (Mill.) BSP), trembling aspen (Populus tremuloides Michx.) and jack pine (Pinus banksiana Lamb.). Above‐ground biomass of the understorey vegetation was assessed through harvesting; annual growth rates were calculated as the differences between biomass in 2007 and 2008, as estimated by allometric relationships, and turnover rates were estimated as net primary production divided by the biomass in 2007. Results: Higher aspen presence, linked to greater nutrient availability in the forest floor, was generally associated with higher vascular biomass and production in the understorey. This effect was less pronounced in sites of high intrinsic fertility. In contrast, bryophyte biomass was positively associated with conifer abundance, particularly in wet sites of the Quebec study area. Non‐linear responses resulted in total understorey biomass being lower under mixed canopies than under pure aspen or pure conifer canopies. Turnover rates did not differ with overstorey composition. Conclusions: While resource availability is a main driver of understorey productivity, resources as drivers appear to differ with differences in understorey strata components, i.e. vascular versus non‐vascular plants. Resource heterogeneity induced by a mixed canopy had overall negative effects on understorey above‐ground productivity, as this productivity seemed to rely on species adapted to the specific conditions induced by a pure canopy.     

A Dynamical Model of Biological Population Under the Variation of Resource and Its Numerical Analysis

1IntroductionTheLogisticequationofpopulationgroanisaclassicalmodeld~bingthePOPulationdy~cs,itisconSiderasthefundamentalthaiofPOPulationd~cs(May,1974).Inthebeisticmodel,thegrowth~ourofpopulationdependsonthebiolodedspeCies'intrinsicrateofincreaseandthe~lugCapaCityofenvironxnent.Therearetwoqueshonswoadinvestigatingfabler.First,dasapopulationreachitSintrinsicrateonlywhenthePOPulatonsizeisequaltozero?hand,isthe~lugcapadtyofenvironmentaconStantwhichcanbedet~nedinadvance?Infact,anypopulationc…     

Resource polyphenism increases species richness: a test of the hypothesis

A major goal of evolutionary biology is to identify the causes of diversification and to ascertain why some evolutionary lineages are especially diverse. Evolutionary biologists have long speculated that polyphenism—where a single genome produces alternative phenotypes in response to different environmental stimuli—facilitates speciation, especially when these alternative phenotypes differ in resource or habitat use, i.e. resource polyphenism. Here, we present a series of replicated sister-group comparisons showing that fishes and amphibian clades in which resource polyphenism has evolved are more species rich, and have broader geographical ranges, than closely related clades lacking resource polyphenism. Resource polyphenism may promote diversification by facilitating each of the different stages of the speciation process (isolation, divergence, reproductive isolation) and/or by reducing a lineage''s risk of extinction. Generally, resource polyphenism may play a key role in fostering diversity, and species in which resource polyphenism has evolved may be predisposed to diversify.     

Caspase-8 and Bid: Caught in the act between death receptors and mitochondria

Mitochondria play a central role in maintaining cells alive, but are also important mediators of cell death. The main event in mitochondrial signalling and control of apoptosis is the permeabilisation of the outer mitochondrial membrane and the release of pro-apoptotic proteins into the cytosol from the mitochondrial intermembrane space. With respect to death receptor-mediated apoptosis, the activation of the mitochondrial pathway is required for apoptosis induction in cells which are described as “type II” cells whereas “type I” cells do not require it. In type I cells, activation of the extrinsic pathway is sufficient to induce apoptosis. This review deals with the events that enable cell death in type II cells, i.e., the signals that lead from death receptor stimulation to permeabilisation of the outer mitochondrial membrane. Caspase-8 and Bid are the known procurers of the death signal in this part of the apoptotic pathway. Currently many exciting new findings are emerging concerning the regulation of caspase-8 and Bid function and activation. We will take you on a journey through these new developments and point out what we consider the major unknowns in this field. We end our review on an up-to-date discussion of the determinants of the type I-type II cell distinction. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.     

Differences in foliage quality of young jack pine (Pinus banksiana Lamb.) on burned and clearcut sites: effects on jack pine budworm (Choristoneura pinus pinus Freeman)

Summary Suitability of young jack pine as a host for jack pine budworm was examined on similarly-aged trees growing on two areas previously burned in wildfires and on two previously clearcut areas in northwest Wisconsin. Nitrogen, monoterpenes, and moisture levels of foliage, and xylem water potential were measured and related to larval survival and pupal weight of caged jack pine budworm larvae. Nitrogen, monoterpenes, needle weight, and needle moisture were higher in trees growing on clearcut sites than on burned area trees. Surival of budworms to early and late instar, pupation, and adult eclosion was greater for larvae caged on clearcut-area trees than on burned-area trees. Female pupal weight differed between older (ca 10 years old) and younger (ca 8 years old) trees, but not between clearcut and burned areas. Mean female pupal weight was greatest on lownitrogen trees, where larval survival was lowest. Foliar nitrogen was consistently included as a significant predictor in budworm survival regressions. Regressions indicated larval survival and pupal weight may be associated with different tree- and foliage-related traits. Results suggest long-lasting effects of previous forest disturbance may subsequently affect herbivorous insects such as jack pine budworm.