The protein content of tissues in cynipid galls (Hymenoptera: Cynipidae): Similarities between cynipid galls and seeds

Cynipid galls are examples of induced plant development, where the gall inducer is in control of cell differentiation and morphogenesis of a new plant organ. This study concentrates on the tissues of the larval chamber common to all cynipid galls. The protein content of the inner gall tissue was compared to that of non‐gall plant tissues. We investigated three oak and two rose galls and their respective host plants. Total protein signatures of inner gall tissues were different from those of non‐gall plant tissues, and among the five galls. N‐terminal sequences were obtained for two abundant proteins from the inner gall tissues of D. spinosa and A. quercuscalicis, which were common to all galls, at 62 and 43 kDa. Database queries suggest the 62 kDa protein to be homologous to a protein disulphide isomerase (PDI), and the 43 kDa protein to be homologous to NAD‐dependent formate dehydrogenase (FDH). A naturally biotinylated protein was detected at 33 kDa during Western analyses with streptavidin. Western analyses revealed the presence of the biotinylated protein and PDI in the inner gall tissues of all five galls, while FDH was only detected in A. quercuscalicis and A. fecundator. PDI was also common to all non‐gall tissues, while FDH was not detected in non‐gall tissues, and the biotinylated protein was only detected in seeds. The proteins identified in the inner gall tissue suggest that (a) inner gall tissues in some galls are under respiratory stress, and (b) cynipid gall formation might involve the ectopic expression of seed‐specific proteins.     

Interactions between oak tannins and parasite community structure: Unexpected benefits of tannins to cynipid gall-wasps

Plant species vary tremendously in the number of phytophagous species they support. May (1979) and Price (1980) proposed that some of this variation may be due to variation in biochemical defenses. We find that variation between oak species in leaf tannin levels is positively correlated with 1) variation in the numbers of species of leaf-galling cynipid wasps those trees host; and 2) the density of individual galls per oak leaf. We hypothesize that leaf and gall tannins serve a protective function for cynipids, decreasing the amount of cynipid larval mortality due to fungal infestation. This defensive function would explain the observed positive relationships between oak tannin levels and cynipid diversity as well as cynipid abundance.     

Dogwood borer (Lepidoptera: Sesiidae) infestation of horned oak galls

Pin oak, Quercus palustris Muenchhausen, is the primary host for the gall wasp Callirhytis cornigera (Osten Sacken). Woody stem galls formed by C. cornigera may be infested by the dogwood borer, Synanthedon scitula (Harris), an important pest of flowering dogwood, Cornus florida L. Previous research has shown that S. scitula has a bimodal seasonal flight pattern, with peaks in late spring and midsummer. We tested the hypothesis that moths emerging from dogwoods largely account for the first flight pulse, whereas emergence from stem galls contributes disproportionately to the second pulse. Seasonal flight activity of S. scitula was monitored with pheromone traps baited with Z,Z-3,13-octadecadien-1-ol acetate. Traps were hung near plantings of dogwoods in suburban landscapes or near heavily galled pin oaks. Borer emergence from dogwood was monitored by sampling infested trees for pupal exuviae, and from galls that were collected and held in outdoor rearing cages. The impact of S. scitula on C. cornigera larvae was assessed by weighing, measuring, and dissecting galls. Flight activity of S. scitula began on 5 May and ended on 13 October 1999, with peaks in late May and in late July to early August. The flight pattern was similar for the two types of trapping sites, and moths emerged from both hosts during both flight periods. Proportionately more moths emerged from dogwoods during the first flight pulse than during the second, but emergence from galls was nearly evenly divided between the two flight peaks. We therefore reject the hypothesis that emergence of borers from galls contributes disproportionately to the second flight period. Approximately 12-15% of stem galls (2-3 yr old) contained S. scitula larvae. Feeding and tunneling by borers contributed to gall desiccation and reduced horn development, but rarely killed C. cornigera larvae. This study has implications for management of S. scitula because borers emerging from horned oak galls may represent a threat to dogwood.     

Parasitoid and inquiline attack in the galls of four alien, cynipid gall wasps: host switches and the effect on parasitoid sex ratios

1. Four alien cynipid gall wasps of the genus Andricus are established and still spreading in the British Isles. The order, according to the northerliness of their distribution boundary, is: A. corruptrix→A. quercuscalicis→A. lignicola→A. kollari. All four aliens have a sexual generation in spring on Quercus cerris (introduced to Britain) and an agamic generation in autumn on native oak species. 2. For 2 years 1994 and 1995, galls of both generations of the four alien species were sampled at eight sites from the south of England to the north of Scotland to determine the parasitoid and inquiline species that attack the new galls. The spring generations of the invading species shared a parasitoid complex of four pteromalid species. Five species of inquilines and 11 species of parasitoids emerged from the autumn galls. 3. Two colonisation events were recorded for A. lignicola and A. corruptrix. On both occasions, the spring generations were found first at the new sites, indicating that the agamic generation provides the colonisers for these invading species. After colonisation, the galls of both species were attacked by parasitoids in their first season. 4. In spring, the invading species were among the most abundant cynipids at all eight sites. By sampling the whole local community of cynipid galls, it was found that the parasitoid species attacking the spring galls of the invaders seemed to have shifted their attack to the new hosts. 5. The secondary sex ratios of the parasitoid species emerging from the sexual galls of A. quercuscalicis (the smallest of the four) showed a strong and significant male bias at all sites and in both years. Parasitoid emergence from the galls of the sexual generations of the other three species (all about equal in size) was between 60 and 70% male, and variable among sites and between years.     

Light distribution and foliage structure in an oak canopy

 Leaf angle distribution and shoot bifurcation ratio were measured and related to photon flux density (PFD) distribution in an oak canopy. Leaf angle distribution deviated substantially from random and changed markedly throughout the canopy. The observed leaf angle distribution was described by an ellipsoidal function with the single parameter of the distribution, x, changing from 1.6 at the top of the canopy to 3.2 in the lowest branches. In vertically homogeneous canopies, the extinction coefficient for diffuse radiation is expected to decline with increasing leaf area index (LAI). However, in the canopy studied here, the leaf angle distribution changed with height such that the effective extinction coefficient remained constant. Both shoot bifurcation ratio and leaf number per shoot declined with decreasing PFD inside the canopy. Based on these observed relationships, a simple canopy growth model that assumes horizontal homogeneity of the canopy was constructed. Calculations showed that a steady state, when growth in the upper of the canopy is in equilibrium with decline of lower canopy, the total canopy LAI should equal to 4.3. This predicted value of equilibrium LAI is larger than that estimated from measurements of PFD transmission (LAI=3.3), but smaller than that directly determined by litter collection (LAI=6.2 in 1998). Possible reasons for these discrepancies are discussed. Received: 22 June 1998 / Accepted: 7 April 1999     

Origin of spatial genetic structure in an expanding oak population

Spatial genetic structure (SGS) results from the interplay of several demographical processes that are difficult to tease apart. In this study, we explore the specific effects of seed and pollen dispersal and of early postdispersal mortality on the SGS of a seedling cohort (N = 786) recruiting within and around an expanding pedunculate oak (Quercus robur) stand. Using data on dispersal (derived from parentage analysis) and mortality (monitored in the field through two growing seasons), we decompose the overall SGS of the cohort into its components by contrasting the SGS of dispersed (i.e. growing away from their mother tree) vs. nondispersed (i.e. growing beneath their mother tree) and initial vs. surviving seedlings. Patterns differ strongly between nondispersed and dispersed seedlings. Nondispersed seedlings are largely responsible for the positive kinship values observed at short distances in the studied population, whereas dispersed seedlings determine the overall SGS at distances beyond c. 30 m. The paternal alleles of nondispersed seedlings show weak yet significantly positive kinships up to c. 15 m, indicating some limitations in pollen flow that should further promote pedigree structures at short distances. Seedling mortality does not alter SGS, except for a slight increase in the nondispersed group. Field data reveal that mortality in this group is negatively density‐dependent, probably because of small‐scale variation in light conditions. Finally, we observe a remarkable similarity between the SGS of the dispersed seedlings and that of the adults, which probably reflects dispersal processes during the initial expansion of the population. Overall, this study demonstrates that incorporating individual‐level complementary information into analyses can greatly improve the detail and confidence of ecological inferences drawn from SGS.     

EPPS: mining the COG database by an extended phylogenetic patterns search

SUMMARY: EPPS runs under Microsoft Windows. It is an extended version of the phylogenetic patterns search (PPS). The output condition of PPS is the exact match of a user defined phylogenetic pattern with the pattern represented by the respective cluster of orthologous groups (COG). In contrast, the software described here is less restrictive. The user may define the accuracy of the search by the number of genomes that are allowed not to match the predefined phylogenetic pattern. Thus, EPPS has the advantage to detect COGs even if organisms defined to be included are not or organisms defined to be excluded are present in the output COGs.     

Heritable variation in an extended phenotype: the case of a parasitoid manipulated by a virus

In host-symbiont interactions, the genes of both host and symbiont can influence phenotypic traits. In the context of a conflict of interest, fitness-related traits are subjected to opposing selective pressures in the genomes of the partners. In the Drosophila parasitoid Leptopilina boulardi, females usually avoid laying eggs into already parasitized larvae. However, when infected by the virus LbFV, they readily lay additional eggs into parasitized larvae. Inducing superparasitism allows the virus to colonize uninfected parasitoid lineages but is usually maladaptive for the parasitoid. We tested for the presence of resistance genes to this behavioural manipulation in the parasitoid genotype by sampling 30 lines from five populations with contrasting viral prevalence, after infecting them with a reference viral isolate. No geographical differentiation was observed although some genotypes underwent less manipulation than others, and these differences were heritable across generations. The viral titre was not correlated with these differences although fecundity differed between extreme lines.     

Environmental change in Garry oak (Quercus garryana) ecosystems: the evolution of an eco-cultural landscape

Globally, colonialism resulted in the suppression of aboriginal land management practices, abetted by the concept of terra nullius, “belonging to no one”; the belief that aboriginal people had little influence on or ownership of the land. Until recently, this ideology was entrenched in resource management and policy. Traditional ecological knowledge, historical ecology, archaeology, and palaeoecological research have shown these assumptions to be wrong. In this paper we take a multidisciplinary approach (biogeography, paleoecology, dendrochronology, and bioclimatic envelope modeling) to better understand the role of climate and fire in the formation of eco-cultural landscapes. We synthesize results from pollen and charcoal analysis in Garry oak ecosystems that indicate there were continuous and frequent prescribed burning events, with more severe fires occurring every 26–41 years in southwest British Columbia throughout the Anthropocene (~last 250 years) that substantially altered forest structure and composition. These results are consistent with stand age reconstructions in BC and Washington with Garry oak establishment beginning ~1850 AD, corresponding with modern fire exclusion, aboriginal population decline, and end of the Little Ice Age. Douglas-fir recruitment has been continuous since ~1900, with succession of oak woodland to closed conifer forest at most sites. These findings indicate that the structure of many Garry oak ecosystems have been profoundly influenced by eco-cultural practices. Overwhelming evidence indicates that in many cases these ecosystems are dependent on prescribed fire for their open structure. In the absence of aboriginal land-management practices, active management will be necessary to maintain Garry oak woodland.     

Profiling the extended phenotype of plant pathogens

One of the most fundamental questions in plant pathology is what determines whether a pathogen grows within a plant? This question is frequently studied in terms of the role of elicitors and pathogenicity factors in the triggering or overcoming of host defences. However, this focus fails to address the basic question of how the environment in host tissues acts to support or restrict pathogen growth. Efforts to understand this aspect of host–pathogen interactions are commonly confounded by several issues, including the complexity of the plant environment, the artificial nature of many experimental infection systems and the fact that the physiological properties of a pathogen growing in association with a plant can be very different from the properties of the pathogen in culture. It is also important to recognize that the phenotype and evolution of pathogen and host are inextricably linked through their interactions, such that the environment experienced by a pathogen within a host, and its phenotype within the host, is a product of both its interaction with its host and its evolutionary history, including its co‐evolution with host plants. As the phenotypic properties of a pathogen within a host cannot be defined in isolation from the host, it may be appropriate to think of pathogens as having an ‘extended phenotype’ that is the product of their genotype, host interactions and population structure within the host environment. This article reflects on the challenge of defining and studying this extended phenotype, in relation to the questions posed below, and considers how knowledge of the phenotype of pathogens in the host environment could be used to improve disease control.

• What determines whether a pathogen grows within a plant?
• What aspects of pathogen biology should be considered in describing the extended phenotype of a pathogen within a host?
• How can we study the extended phenotype in ways that provide insights into the phenotypic properties of pathogens during natural infections?

     

Beyond DNA: integrating inclusive inheritance into an extended theory of evolution

Many biologists are calling for an 'extended evolutionary synthesis' that would 'modernize the modern synthesis' of evolution. Biological information is typically considered as being transmitted across generations by the DNA sequence alone, but accumulating evidence indicates that both genetic and non-genetic inheritance, and the interactions between them, have important effects on evolutionary outcomes. We review the evidence for such effects of epigenetic, ecological and cultural inheritance and parental effects, and outline methods that quantify the relative contributions of genetic and non-genetic heritability to the transmission of phenotypic variation across generations. These issues have implications for diverse areas, from the question of missing heritability in human complex-trait genetics to the basis of major evolutionary transitions.     

The structure of protein evolution and the evolution of protein structure

The observed distribution of protein structures can give us important clues about the underlying evolutionary process, imposing important constraints on possible models. The availability of results from an increasing number of genome projects has made the development of these models an active area of research. Models explaining the observed distribution of structures have focused on the inherent functional capabilities and structural properties of different folds and on the evolutionary dynamics. Increasingly, these elements are being combined.     

The evolution of the cortico-cerebellar complex in primates: anatomical connections predict patterns of correlated evolution

Investigations into the evolution of the primate brain have tended to neglect the role of connectivity in determining which brain structures have changed in size, focusing instead on changes in the size of the whole brain or of individual brain structures, such as the neocortex, in isolation. We show that the primate cerebellum, neocortex, vestibular nuclei and relays between them exhibit correlated volumetric evolution, even after removing the effects of change in other structures. The patterns of correlated evolution among individual nuclei correspond to their known patterns of connectivity. These results support the idea that the brain evolved by mosaic size change in arrays of functionally connected structures. Furthermore, they suggest that the much discussed expansion of the primate neocortex should be re-evaluated in the light of conjoint cerebellar expansion.     

The extended phenotype of Scots pine Pinus sylvestris structures the understorey assemblage

Heritable variation in plant secondary compounds in dominant species has been hypothesised to effect ecosystem function and the structure of associated assemblages of plants, microbes and animals. The functioning of this extended phenotype in relation to the understorey vegetation composition was tested within a boreal forest system dominated by Pinus sylvestris which contains a range of monoterpenes, the composition of which is largely under genetic control. A variance partitioning approach was adopted to identify the relative importance of tree chemistry, environment, spatial location and tree architecture in controlling the distribution of species in the ground flora under individual trees. The monoterpene composition of the pine needles appeared to contribute significantly to controlling understorey vegetation composition, but was less important than environmental factors, though similar to spatial factors. Thus there appears to be a link between variation in the chemical composition of the single, dominant tree species within this system and the pattern of occurrence and abundance in other species at the same trophic level.     

The extended evolutionary synthesis and the role of soft inheritance in evolution

In recent years, a number of researchers have advocated extending the modern synthesis in evolutionary biology. One of the core arguments made in favour of an extension comes from work on soft inheritance systems, including transgenerational epigenetic effects, cultural transmission and niche construction. In this study, we outline this claim and then take issue with it. We argue that the focus on soft inheritance has led to a conflation of proximate and ultimate causation, which has in turn obscured key questions about biological organization and calibration across the life span to maximize average lifetime inclusive fitness. We illustrate this by presenting hypotheses that we believe incorporate the core phenomena of soft inheritance and will aid in understanding them.     

The extended phenotype(s): a comparison with niche construction theory

While niche construction theory locates animal artefacts in their constructors’ environment, hence treating them as capable of exerting selective pressure on both the constructors and their descendants, the extended phenotype concept assimilates artefacts with their constructors’ genes. Analogous contrasts apply in the case of endoparasite and brood parasite genes influencing host behaviour. The explanatory power of these competing approaches are assessed by re-examining the core chapters of Richard Dawkins’ The Extended Phenotype. Because animal artefacts (chapter 11) have multiple evolutionary consequences for their constructors, the extra-body effects of a gene seemingly include feedback effects on multiple other genes, a result which is more consistent with niche construction theory than with selfish gene theory. In the case of endoparasite genes influencing host behaviour (chapter 12), Dawkins’ argument leaves out what appears to be the key explanatory component, namely the role of the host’s own bodily systems in making it possible for such genes to exist. For action at a distance (chapter 13), it is unclear whether the key genes have extended effects because they sit in the body of the manipulating organism, or alternatively do not have such effects because they sit in the body of its victim. It is argued that niche construction theory offers a superior explanation in all three cases, regardless of whether the extended phenotype concept is interpreted in selfish gene or selfish organism terms.