Atmospheric carbon dioxide: a driver of photosynthetic eukaryote evolution for over a billion years?

Exciting evidence from diverse fields, including physiology, evolutionary biology, palaeontology, geosciences and molecular genetics, is providing an increasingly secure basis for robustly formulating and evaluating hypotheses concerning the role of atmospheric carbon dioxide (CO(2)) in the evolution of photosynthetic eukaryotes. Such studies span over a billion years of evolutionary change, from the origins of eukaryotic algae through to the evolution of our present-day terrestrial floras, and have relevance for plant and ecosystem responses to future global CO(2) increases. The papers in this issue reflect the breadth and depth of approaches being adopted to address this issue. They reveal new discoveries pointing to deep evidence for the role of CO(2) in shaping evolutionary changes in plants and ecosystems, and establish an exciting cross-disciplinary research agenda for uncovering new insights into feedbacks between biology and the Earth system.     

Brachiopods from the Cisuralian–Guadalupian of Darvaz,Tajikistan and implications for Permian stratigraphic correlations

In this paper, we describe the upper Cisuralian Safetdara and Gundara formations of the Darvaz mountains, North Pamir, which were part of the Kunlun Arc, developed along the active Eurasian margin. The Safetdara Formation comprises massive limestones (mainly cyanobacterial, Tubiphytes and Archaeolithoporella boundstones) alternating with well-bedded bioclastic and oncoidal limestones and an interval of recessive shales. The formation crops out above the Chelamchi Formation consisting of turbiditic siltstones and sandstones with bioclastic silty limestones yielding massive limestone olistoliths. The Gundara Formation consists of fine sandstones at the base, followed by well-bedded marly bioclastic, oncoidal and microbial limestones, bearing a rich silicified brachiopod fauna in life-position. Two new taxa have been identified in this association: the cemented coralliform Gundaria insolita n. gen. n. sp. and the pedicle attached Hemileurus politus n. sp. The inferred environmental setting is that of shoal deposits of warm, shallow, high energy, clear marine waters for the Safetdara Formation. The agglutinated microbial reefs to cluster reefs of the Gundara Formation were probably growing in a muddier, quieter and probably slightly deeper setting.The foraminifers of the Brevaxina Zone suggest a Bolorian age for the top of the Chelamchi Formation, the Safetdara Formation and the base of the Gundara Formation. Kungurian conodonts have been found in the lower part of the Safetdara Formation. The biostratigraphic data from the sedimentary succession of North Pamir, integrated with those already obtained from Southeast Pamir, allow to refine the correlations between the Tethyan regional scale and the International Time Scale. In particular, it seems now clear that the Bolorian and the lower part of the Kubergandian correlate to the Kungurian.     

The evolution of signal–reward correlations in bee- and hummingbird-pollinated species of Salvia

Within-individual variation in floral advertising and reward traits is a feature experienced by pollinators that visit different flowers of the same plant. Pollinators can use advertising traits to gather information about the quality and amount of rewards, leading to the evolution of signal–reward correlations. As long as plants differ in the reliability of their signals and pollinators base their foraging decisions on this information, natural selection should act on within-individual correlations between signals and rewards. Because birds and bees differ in their cognitive capabilities, and use different floral traits as signals, we tested the occurrence of adaptive divergence of the within-individual signal–reward correlations among Salvia species that are pollinated either by bees or by hummingbirds. They are expected to use different floral advertising traits: frontal traits in the case of bees and side traits in the case of hummingbirds. We confirmed this expectation as bee- and hummingbird-pollinated species differed in which specific traits are predominantly associated with nectar reward at the within-individual level. Our findings highlight the adaptive value of within-individual variation and covariation patterns, commonly disregarded as ‘environmental noise’, and are consistent with the hypothesis that pollinator-mediated selection affects the correlation pattern among floral traits.     

A smörgåsbord of markers for avian ecology and evolution

The polymerase chain reaction has been a boon to the study of molecular ecology and population genetics of birds. But the nagging truth is that for many bird species, the number of polymerase chain reaction (PCR) primer pairs that one can pick off the shelf and expect to amplify their target loci with ease is frustratingly small. Now, studying DNA sequence variation in natural populations of birds just got a whole lot easier. This issue of Molecular Ecology reports a large-scale bioinformatics search for exonic sequences conserved between the chicken and zebra finch genomes and flanking polymorphic introns that has generated a staggering 242 PCR primer pairs that readily amplify their single-copy target loci in five avian species spanning ~100 million years of avian evolution ( Backström et al . 2008 ). As proof of principle, these primers have also been used to survey the genomic landscape in over 110 kb of intronic sequence in the collared flycatcher, a model species in ecology and evolution. These resources pave the way for easy multilocus study of evolving populations and lineages of birds, and bring the goal of quickly turning nonmodel species in to ecological genomic models tantalizingly close.     

Plant–animal interactions in suburban environments: implications for floral evolution

Plant interactions with mutualists and antagonists vary remarkably across space, and have played key roles in the ecology and evolution of flowering plants. One dominant form of spatial variation is human modification of the landscape, including urbanization and suburbanization. Our goal was to assess how suburbanization affected plant–animal interactions in Gelsemium sempervirens in the southeastern United States, including interactions with mutualists (pollination) and antagonists (nectar robbing and florivory). Based on differences in plant–animal interactions measured in multiple replicate sites, we then developed predictions for how these differences would affect patterns of natural selection, and we explored the patterns using measurements of floral and defensive traits in the field and in a common garden. We found that Gelsemium growing in suburban sites experienced more robbing and florivory as well as more heterospecific but not conspecific pollen transfer. Floral traits, particularly corolla length and width, influenced the susceptibility of plants to particular interactors. Observational data of floral traits measured in the field and in a common garden provided some supporting but also some conflicting evidence for the hypothesis that floral traits evolved in response to differences in species interactions in suburban vs. wild sites. However, the degree to which plants can respond to any one interactor may be constrained by correlations among floral morphological traits. Taken together, consideration of the broader geographic context in which organisms interact, in both suburban and wild areas, is fundamental to our understanding of the forces that shape contemporary plant–animal interactions and selection pressures in native species.     

History or ecology? Substrate type as a major driver of patial genetic structure in Alpine plants

Climatic history and ecology are considered the most important factors moulding the spatial pattern of genetic diversity. With the advent of molecular markers, species' historical fates have been widely explored. However, it has remained speculative what role ecological factors have played in shaping spatial genetic structures within species. With an unprecedented, dense large-scale sampling and genome-screening, we tested how ecological factors have influenced the spatial genetic structures in Alpine plants. Here, we show that species growing on similar substrate types, largely determined by the nature of bedrock, displayed highly congruent spatial genetic structures. As the heterogeneous and disjunctive distribution of bedrock types in the Alps, decisive for refugial survival during the ice ages, is temporally stable, concerted post-glacial migration routes emerged. Our multispecies study demonstrates the relevance of particular ecological factors in shaping genetic patterns, which should be considered when modelling species projective distributions under climate change scenarios.     

Barriers and Bridges to Prevention and Control of Dengue: The Need for a Social–Ecological Approach

This article critically examines how programs for the prevention and control of dengue fever have been conducted in the absence of an integrated approach, and considers the social and ecological factors influencing their effectiveness. Despite recognition of dengue fever as the most important arboviral disease affecting humans, and in spite of a greater emphasis on community-based control approaches, the burden placed on the communities, countries, and regions affected by this disease continues to rise. In considering historical experience in the Americas and the Asia-Pacific region, as well as the global forces that are exerting new pressures, the important elements of successful control programs are identified as community ownership, partnership with government, leadership, scalability, and control of immature mosquitoes. The key barriers to the exchange of knowledge and the transdisciplinary cooperation necessary for sustainable dengue control are rooted in differences in values among policy-makers, citizens, and scientists and are repeatedly expressed in technical, economic, cultural, geographic, and political dimensions. Through consideration of case studies in Cuba, Guatemala, Singapore, Thailand, Indonesia, and Vietnam, the limitations of control approaches that fail to take into account the complexities of ecological and social systems are presented. Bridges to effective control are identified as the basis for adaptability, both of control programs to the mosquito vector’s changing behavior and of education programs to public, regional and local particularities, as well as transdisciplinarity, community empowerment, the ability to scale local experiences up to the macro-level, and the capacity to learn from experience to achieve sustainability.     

The cichlid–Cichlidogyrus network: a blueprint for a model system of parasite evolution

Hydrobiologia - Species interactions are a key aspect of evolutionary biology. Parasites, specifically, are drivers of the evolution of species communities and impact biosecurity and public health....     

Effects of cytoplasmic genes on sperm viability and sperm morphology in a seed beetle: implications for sperm competition theory?

Sperm competition theory predicts that sperm traits influencing male fertilizing ability will evolve adaptively. However, it has been suggested that some sperm traits may be at least partly encoded by mitochondrial genes. If true, this may constrain the adaptive evolution of such traits because mitochondrial DNA (mtDNA) is maternally inherited and there is thus no selection on mtDNA in males. Phenotypic variation in such traits may nevertheless be high because mutations in mtDNA that have deleterious effects on male traits, but neutral or beneficial effects in females, may be maintained by random processes or selection in females. We used backcrossing to create introgression lines of seed beetles (Callosobruchus maculatus), carrying orthogonal combinations of distinct lineages of cytoplasmic and nuclear genes, and then assayed sperm viability and sperm length in all lines. We found sizeable cytoplasmic effects on both sperm traits and our analyses also suggested that the cytoplasmic effects varied across nuclear genetic backgrounds. We discuss some potential implications of these findings for sperm competition theory.     

Integrating genes and phenotype: a wheat–Arabidopsis–rice glycosyltransferase database for candidate gene analyses

Glycosyltransferases (GTs) constitute a very large multi-gene superfamily, containing several thousand members identified in sequenced organisms especially in plants. GTs are key enzymes involved in various biological processes such as cell wall formation, storage polysaccharides biosynthesis, and glycosylation of various metabolites. GTs have been identified in rice (Oryza sativa) and Arabidopsis thaliana, but their precise function has been demonstrated biochemically for only a few. In this work we have established a repertoire of virtually all the wheat (Triticum aestivum) GT sequences, using the large publicly available banks of expressed sequences. Based on sequence similarity with Arabidopsis and rice GTs compiled in the carbohydrate active enzyme database (CAZY), we have identified and classified these wheat sequences. The results were used to feed a searchable database available on the web () that can be used for initiating an exhaustive candidate gene survey in wheat applied to a particular biological process. This is illustrated through the identification of GT families which are expressed during cell wall formation in wheat grain maturation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. This work was funded by a grant of the French ministry of research.     

Differential δC and δN signatures among scallop tissues: implications for ecology and physiology

There have been several studies where the isotopic composition of organisms has been determined seasonally, but fewer have examined separate organs. In this context, separate organs (e.g. gonad, digestive gland and muscle) of a suspension-feeder, the scallop Pecten maximus, were used to assess seasonal changes of both stable isotopes and biochemical components. Our study used multiple indicators [stable carbon and nitrogen isotope ratios, biochemical components and seston chlorophyll-a (chl a)] to track nutritive activity and energy allocation in P. maximus from the Bay of Brest (France). In addition to seasonal variation in the isotopic composition of P. maximus tissues, we found strong differences in the mean isotopic signatures of different organs. This has serious implications for interpretation of animal diets and potential use in animal physiology. Furthermore, we present evidence that seasonal variations of metabolism will cause changes in the isotopic composition not related to changes in the diet. Interpretation of isotopic data may require consideration of values from several separate organs. Finally, δ¹⁵N appears powerful to track metabolite fates in the scallop P. maximus.     

Valentin Haecker (1864–1927) as a pioneer of phenogenetics: Building the bridge between genotype and phenotype

Valentin Haecker is one of the forerunners of experimental biology, genetics, and developmental physiology. Haecker introduced the term Phänogenetik (phenogenetics) in 1918 in Entwicklungsgeschichtliche Eigenschaftsanalyse (Evolutionary Analysis of Characters), in which he described the earliest stages in the development of the phenotype.¹ Haecker V. Entwicklungsgeschichtliche Eigenschaftsanalyse (Phänogenetik). Gemeinsame Aufgaben der Entwicklungsgeschichte, Vererbungs- und Rassenlehre. Jena: Gustav Fischer 1918. [Google Scholar] His major objective in this publication was to integrate the 2 most important concepts of Mendelian genetics—phenotype and genotype—within a well-articulated theory. Haecker realized that a proper analysis of how the genotype gives rise to the phenotype requires the integration of knowledge of morphology, physiology, and experimental embryology.     

Molecular links between X-inactivation and autosomal imprinting: X-inactivation as a driving force for the evolution of imprinting?

In classical Mendelian inheritance, each parent donates a set of chromosomes to its offspring so that maternally and paternally encoded information is expressed equally. The phenomena of X-chromosome inactivation (XCI) and autosomal imprinting in mammals violate this dogma of genetic equality. In XCI, one of the two female X chromosomes is silenced to equalize X-linked gene dosage between XX and XY individuals. In genomic imprinting, parental marks determine which of the embryo's two autosomal alleles will be expressed. Although XCI and imprinting appear distinct, molecular evidence now shows that they share a surprising number of features. Among them are cis-acting control centers, long-distance regulation and differential DNA methylation. Perhaps one of the most intriguing similarities between XCI and imprinting has been their association with noncoding and antisense RNAs. Very recent data also suggest the common involvement of histone modifications and chromatin-associated factors such as CTCF. Collectively, the evidence suggests that XCI and genomic imprinting may have a common origin. Here, I hypothesize that the need for X-linked dosage compensation was a major driving force in the evolution of genomic imprinting in mammals. I propose that imprinting was first fixed on the X chromosome for XCI and subsequently acquired by autosomes.     

The ecological role of moss in a polar desert: implications for aboveground–belowground and terrestrial–aquatic linkages

The McMurdo Dry Valleys of Antarctica is one of the coldest and driest habitats on the planet. As vascular plants are absent in this region, moss is the main form of aboveground primary production with a potentially important contribution to biogeochemical cycling, yet little is known about their ecological role. To determine the relationship between moss and soil properties relevant to biogeochemistry, we sampled both from a variety of locations in the Dry Valleys. Moss presence was compared to soil properties, and we measured the plasticity of moss stoichiometry (C:N:P) across gradients in nutrient availability. Results demonstrate that many soil properties significantly differed with moss presence, particularly conductivity and pH, but there is no strong evidence that this is caused by the moss presence and not the conditions inherent to the microsites where moss was found. There is great variability in moss stoichiometry, with some significant differences between sites, but generally variability within sites is larger than variation among sites. Results suggest that the main source of moss nutrients is from the soil, rather than water, but correlations with any one nutrient source are weak, suggesting a great deal of plasticity in moss stoichiometry and nutrient uptake.