The influence of age and sex on wing-tip pattern in adult Black-headed Gulls Larus ridibundus

A discriminant equation based on bill-depth and total head- and bill-length is provided to sex adult Black-headed Gulls Larus ridibundus . This equation is used to sex birds of known age. Relationships between age and morphometrics and between age and the black extent on the wing are then investigated both in males and females. Size of birds did not change with age but the black extent on the wing tended to decrease with age in both sexes. The tendency to become lighter with age may he an expression of senescence.     

Hidden diversity and endemism on seamounts: focus on poorly dispersive neogastropods

The seamounts chain offers a set of fragmented habitats in which species with poor dispersive ability may undergo divergence in allopatry. Such a scenario may explain the endemism often described on seamounts. In gastropods, it is possible to infer the mode of development of a species from the morphology of its larval shell. Accordingly, we examine the population genetics of several caenogastropods from the Norfolk and Lord Howe seamounts (south‐west Pacific) with contrasting modes of larval development. A prerequisite to our study was to clarify the taxonomic framework. The species delimitation was ruled using an integrative approach, based on both morphological and molecular evidence. Molecular data indicate an unexpected taxonomic diversity within the existing species names. Both the clarification of the taxonomic framework and the importance of the sampling effort allow us to confidently detect cryptic diversity and micro‐endemism. These results are discussed in relation to the dispersive capacities of the organisms. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 420–438.     

Involvement of thioredoxin y2 in the preservation of leaf methionine sulfoxide reductase capacity and growth under high light

Methionine (Met) in proteins can be oxidized to two diastereoisomers of methionine sulfoxide, Met‐S‐O and Met‐R‐O, which are reduced back to Met by two types of methionine sulfoxide reductases (MSRs), A and B, respectively. MSRs are generally supplied with reducing power by thioredoxins. Plants are characterized by a large number of thioredoxin isoforms, but those providing electrons to MSRs in vivo are not known. Three MSR isoforms, MSRA4, MSRB1 and MSRB2, are present in Arabidopsis thaliana chloroplasts. Under conditions of high light and long photoperiod, plants knockdown for each plastidial MSR type or for both display reduced growth. In contrast, overexpression of plastidial MSRBs is not associated with beneficial effects in terms of growth under high light. To identify the physiological reductants for plastidial MSRs, we analyzed a series of mutants deficient for thioredoxins f, m, x or y. We show that mutant lines lacking both thioredoxins y1 and y2 or only thioredoxin y2 specifically display a significantly reduced leaf MSR capacity (–25%) and growth characteristics under high light, related to those of plants lacking plastidial MSRs. We propose that thioredoxin y2 plays a physiological function in protein repair mechanisms as an electron donor to plastidial MSRs in photosynthetic organs.     

Cost of sexually embracing a large female offset by the number of eggs fertilized for small male Bufo bufo L.

When pairing with high quality females, a male increases its fitness through an increased number and/or quality of sired offsprings. In anurans, size has often been used as a measure of female quality. In the present study, we examined the effects of pairing with large females for small males in the common toad, Bufo bufo . For the first time in anurans, we show a fitness cost for males to maintain amplexus with a large female. Indeed, although we did not detect any effect of male size on male pairing success in a first breeding event in the presence of other competing males, when males that were successful in the first breeding event were tested for a second time, male pairing success strongly decreased when they had been first paired with a large female. However, the higher fecundity of large females (1.52-fold more than that of small females) may override this pairing cost, especially because high fertilization rate was not linked to male/female body size ratio. Indeed, we did not detect any difference in egg fertilization success between small males paired with large and small females. Our results suggest that predictable cues of female reproductive value exist in common toads, thus meeting a prerequisite of the occurrence of male mate choice. Male mate choice, probably underestimated in anurans, may be particularly important in species where the breeding season is short and the number of mating events for a male is limited. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 755–762.     

Predicting xylem phenology in black spruce under climate warming

In the next century, the boreal ecosystems are projected to experience greater rates of warming than most other regions of the world. As the boreal forest constitutes a reservoir of trees of huge ecological importance and only partially known economic potential, any possible climate‐related change in plant growth and dynamics has to be promptly predicted and evaluated. A model for assessing xylem phenology in black spruce [Picea mariana (Mill.) B.S.P.] using daily temperatures and thermal thresholds was defined and applied to predict changes in onset, ending and duration of xylem growth under different warming scenarios with temperatures rising by up to 3 °C. This was achieved by collecting and analyzing a dataset obtained from a 7‐year monitoring of cambium phenology and wood formation on a weekly time‐scale in trees growing in four sites at different latitudes and altitudes in the Saguenay‐Lac‐Saint‐Jean region (Quebec, Canada). The onset of xylem growth occurred between mid‐May and early June while the end ranged between mid‐September and early October, resulting in a growing season of 101–141 days. The model predicted longer duration of xylem growth at higher temperatures, with an increase of 8–11 days/ °C, because of an earlier onset and later ending of growth. With an increase of 3 °C in the mean temperature during the year, the duration of xylem growth changed on average from 125 to 160 days. The predicted changes in cambial phenology could significantly affect future wood production of the boreal ecosystems.     

Global change and root function

Global change includes land-use change, elevated CO₂ concentrations, increased temperature and increased rainfall variability. All four aspects by themselves and in combination will influence the role of roots in linking below- and above-ground ecosystem function via organic and inorganic resource flows. Root-mediated ecosystem functions which may be modified by global change include below-ground resource (water, nutrients) capture, creation and exploitation of spatial heterogeneity, buffering of temporal variations in above-ground factors, supply and storage of C and nutrients to the below-ground ecosystem, mobilization of nutrients and C from stored soil reserves, and gas exchange between soil and atmosphere including the emission from soil of greenhouse gases. The theory of a functional equilibrium between root and shoot allocation is used to explore predicted responses to elevated CO₂ in relation to water or nutrient supply as limiting root function. The theory predicts no change in root:shoot allocation where water uptake is the limiting root function, but substantial shifts where nutrient uptake is (or becomes) the limiting function. Root turnover will not likely be influenced by elevated CO₂, but by changes in regularity of water supply. A number of possible mechanisms for root-mediated N mineralization is discussed in the light of climate change factors. Rhizovory (root consumption) may increase under global change as the balance between plant chemical defense and adapted root consuming organisms may be modified during biome shifts in response to climate change. Root-mediated gas exchange allows oxygen to penetrate into soils and methane (CH₄) to escape from wetland soils of tundra ecosystems as well as tropical rice production systems. The effect on net greenhouse gas emissions of biome shifts (fens replacing bogs) as well as of agricultural land management will depend partly on aerenchyma in roots.     

Ruffed Grouse Winter Habitat Use in Mixed Softwood-Hardwood Forests,Québec,Canada

Abstract: Ruffed grouse (Bonasa umbellus) is a popular small game species in northeastern North America. We assessed female ruffed grouse habitat characteristics during winter of 2001-2002 and 2002-2003 in a region dominated by mixed softwood-hardwood forests by comparing used and random locations. We followed 23 radiotagged adult females in 2 forest sites of the Réserve faunique de Portneuf, Québec, Canada, from late November to mid-April. We described grouse habitat using ground surveys and identified selected habitat characteristics using analysis of variance and logistic regression. Females preferred mixed softwood-hardwood stands > 17 m tall and 61-120 years old. Compared with random locations, grouse locations had more well-developed total canopy cover (>4m;75%), canopy (>4m;35%), midstory (1-4 m tall; 35%), and lower-story (<1 m tall; 23%) coniferous cover, and higher coniferous stem density and tree basal area (dbh > 9 cm; 343 stems/ha and 9.0 m²/ha, respectively). Forest management should maintain mature mixed softwood-hardwood stands (50% coniferous), which are adequate winter habitat for ruffed grouse.     

Variation of carbon isotope fractionation in hydrogenotrophic methanogenic microbial cultures and environmental samples at different energy status

Methane is a major product of anaerobic degradation of organic matter and an important greenhouse gas. Its stable carbon isotope composition can be used to reveal active methanogenic pathways, if associated isotope fractionation factors are known. To clarify the causes that lead to the wide variation of fractionation factors of methanogenesis from H₂ plus CO₂ (), pure cultures and various cocultures were grown under different thermodynamic conditions. In syntrophic and obligate syntrophic cocultures thriving on different carbohydrate substrates, fermentative bacteria were coupled to three different species of hydrogenotrophic methanogens of the families Methanobacteriaceae and Methanomicrobiaceae. We found that C‐isotope fractionation was correlated to the Gibbs free energy change (ΔG) of CH₄ formation from H₂ plus CO₂ and that the relation can be described by a semi‐Gauss curve. The derived relationship was used to quantify the average ΔG that is available to hydrogenotrophic methanogenic archaea in their habitat, thus avoiding the problems encountered with measurement of low H₂ concentrations on a microscale. Boreal peat, rice field soil, and rumen fluid, which represent major sources of atmospheric CH₄, exhibited increasingly smaller , indicating that thermodynamic conditions for hydrogenotrophic methanogens became increasingly more favourable. Vice versa, we hypothesize that environments with similar energetic conditions will also exhibit similar isotope fractionation. Our results, thus, provide a mechanistic constraint for modelling the ¹³C flux from microbial sources of atmospheric CH₄.