Autogamy in Allogromia laticollaris (Foraminifera)

SYNOPSIS. The life cycles of 2 strains of Allogromia laticollaris (CSH and TPA) raised on experimentally restricted diets have been studied. Cloned cultures of the strains differed in nutritional requirements for continuous reproduction. The TPA strain was more fecund. Both strains have a basically apogamic (asexual) life cycle; only occasionally were gamonts (sexually reproducing individuals) produced. They were autogamous (self-fertilizing) and fusion of the gametes took place within the parental test.
We found in CSH clones a regular alternation of vesicularly nucleated and compactly multinucleated diploid generations. The details of the life cycle of either strain are not known well enough to be able to construct life cycle diagrams more meaningful than that of Arnold. The 2 strains studied differ in cytologic and nuclear detail from each other and from the strain studied by Arnold.     

Molecular and morphological boundaries of the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae)

Neoseiulus californicus (McGregor) is a natural enemy of pest mites used worldwide in many crops. Its correct identification is thus essential to ensure biological control success. The present study aimed to characterize molecular and morphological intraspecific variations for assisting in the diagnosis of the species and to build baseline information about expected variations within a commercially important phytoseiid species. Morphological and molecular [12S rRNA, cytochrome b mitochondrial (mt)DNA, and internal transcribed spacer] analyses were carried out on fourteen populations collected worldwide and on one mass‐reared strain. The genetic distances between the specimens of N. californicus and another related species were high and no overlap was observed, sustaining the reliability of such molecular methods for assisting a specific diagnosis. Furthermore, the genetic distances between populations of N. californicus were very low and overlap between intra‐ and interpopulations distances was observed, except for two populations collected in France (Marsillargues and Midi‐Pyrénées). The high mitochondrial differentiation between these two latter populations and the others questions their specific status: do they belong to the species N. californicus or to another cryptic species? However, using nuclear DNA marker analyses, no distinct differences were observed. Furthermore, even if significant morphological differences were observed between the populations, these differences were very small and the standard errors within each population were very low. We thus concluded that all the populations studied belong to the species N. californicus, despite unexpected high mitochondrial variations. The present study thus displays the importance of an integrative taxonomic approach for avoiding misidentifications. A discussion on morphological and mtDNA variations in relation to diagnostic reliability is developped. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 393–406.     

Variability within a pea core collection of LEAM and HSP22, two mitochondrial seed proteins involved in stress tolerance

LEAM, a late embryogenesis abundant protein, and HSP22, a small heat shock protein, were shown to accumulate in the mitochondria during pea (Pisum sativum L.) seed development, where they are expected to contribute to desiccation tolerance. Here, their expression was examined in seeds of 89 pea genotypes by Western blot analysis. All genotypes expressed LEAM and HSP22 in similar amounts. In contrast with HSP22, LEAM displayed different isoforms according to apparent molecular mass. Each of the 89 genotypes harboured a single LEAM isoform. Genomic and RT‐PCR analysis revealed four LEAM genes differing by a small variable indel in the coding region. These variations were consistent with the apparent molecular mass of each isoform. Indels, which occurred in repeated domains, did not alter the main properties of LEAM. Structural modelling indicated that the class A α‐helix structure, which allows interactions with the mitochondrial inner membrane in the dry state, was preserved in all isoforms, suggesting functionality is maintained. The overall results point out the essential character of LEAM and HSP22 in pea seeds. LEAM variability is discussed in terms of pea breeding history as well as LEA gene evolution mechanisms.     

Reduced N cycling in response to elevated CO2, warming,and drought in a Danish heathland: Synthesizing results of the CLIMAITE project after two years of treatments

Field‐scale experiments simulating realistic future climate scenarios are important tools for investigating the effects of current and future climate changes on ecosystem functioning and biogeochemical cycling. We exposed a seminatural Danish heathland ecosystem to elevated atmospheric carbon dioxide (CO₂), warming, and extended summer drought in all combinations. Here, we report on the short‐term responses of the nitrogen (N) cycle after 2 years of treatments. Elevated CO₂ significantly affected aboveground stoichiometry by increasing the carbon to nitrogen (C/N) ratios in the leaves of both co‐dominant species (Calluna vulgaris and Deschampsia flexuosa), as well as the C/N ratios of Calluna flowers and by reducing the N concentration of Deschampsia litter. Belowground, elevated CO₂ had only minor effects, whereas warming increased N turnover, as indicated by increased rates of microbial NH₄⁺ consumption, gross mineralization, potential nitrification, denitrification and N₂O emissions. Drought reduced belowground gross N mineralization and decreased fauna N mass and fauna N mineralization. Leaching was unaffected by treatments but was significantly higher across all treatments in the second year than in the much drier first year indicating that ecosystem N loss is highly sensitive to changes and variability in amount and timing of precipitation. Interactions between treatments were common and although some synergistic effects were observed, antagonism dominated the interactive responses in treatment combinations, i.e. responses were smaller in combinations than in single treatments. Nonetheless, increased C/N ratios of photosynthetic tissue in response to elevated CO₂, as well as drought‐induced decreases in litter N production and fauna N mineralization prevailed in the full treatment combination. Overall, the simulated future climate scenario therefore lead to reduced N turnover, which could act to reduce the potential growth response of plants to elevated atmospheric CO₂ concentration.     

Experimental climate effect on seasonal variability of polyphenol/phenoloxidase interplay along a narrow fen–bog ecological gradient in Sphagnum fallax

Extracellular phenoloxidase enzymes play an important role in the stability of soil carbon storage by contributing to the cycling of complex recalcitrant phenolic compounds. Climate warming could affect peatland functioning through an alteration of polyphenol/phenoloxidase interplay, which could lead them to becoming weaker sinks of carbon. Here, we assessed the seasonal variability of total phenolics and phenoloxidases subjected to 2–3 °C increase in air temperature using open‐top chambers. The measurements were performed along a narrow fen–bog ecological gradient over one growing season. Climate warming had a weak effect on phenoloxidases, but reduced phenolics in both fen and bog areas. Multivariate analyses revealed a split between the areas and also showed that climate warming exacerbated the seasonal variability of polyphenols, culminating in a destabilization of the carbon cycle. A negative relationship between polyphenols and phenoloxidases was recorded in controls and climate treatments suggesting an inhibitory effect of phenolics on phenoloxidases. Any significant decrease of phenolics through repeatedly elevated temperature would greatly impact the ecosystem functioning and carbon cycle through an alteration of the interaction of polyphenols with microbial communities and the production of extracellular enzymes. Our climate treatments did not have the same impact along the fen–bog gradient and suggested that not all the peatland habitats would respond similarly to climate forcing.     

An analysis of population genetic differentiation and genotype–phenotype association across the hybrid zone of carrion and hooded crows using microsatellites and MC1R

The all black carrion crow ( Corvus corone corone ) and the grey and black hooded crow ( Corvus   corone cornix ) meet in a narrow hybrid zone across Europe. To evaluate the degree of genetic differentiation over the hybrid zone, we genotyped crows from the centre and edges of the zone, and from allopatric populations in northern (Scotland–Denmark–Sweden) and southern Europe (western–central northern Italy), at 18 microsatellites and at a plumage candidate gene, the MC1R gene. Allopatric and edge populations were significantly differentiated on microsatellites, and populations were isolated by distance over the hybrid zone in Italy. Single-locus analyses showed that one locus, CmeH9, differentiated populations on different sides of the zone at the same time as showing only weak separation of populations on the same side of the zone. Within the hybrid zone there was no differentiation of phenotypes at CmeH9 or at the set of microsatellites, no excess of heterozygotes among hybrids and low levels of linkage disequilibrium between markers. We did not detect any association between phenotypes and nucleotide variation at MC1R , and the two most common haplotypes occurred in very similar frequencies in carrion and hooded crows. That we found a similar degree of genetic differentiation between allopatric and edge populations irrespectively of their location in relation to the hybrid zone, no differentiation between phenotypes within the hybrid zone, and neither heterozygote excess nor consistent linkage disequilibrium in the hybrid zone, is striking considering that carrion and hooded crows are phenotypically distinct and sometimes recognised as separate species.