Life-history traits display strong associations to genome size in annelids

Genome size, known also as the C-value, has been proposed as an important determinant of life-history variation in numerous animal taxa. We assessed the relationships between genome size and fitness-related life-history traits in six species of interstitial marine annelids of the genus Ophryotrocha. Life-history traits and genome size data obtained from 18 additional annelid species were included in our analyses to have a broader phylogenetic scope. Unexpectedly, genome sizes assessed here by flow cytometry in four Ophryotrocha species were three times larger than previously reported values obtained using Feulgen densitometry. This has implications for the hypothesis that harsh interstitial habitats select for small genomes in meiofaunal annelids. Within the genus Ophryotrocha, significant and positive relationships were found between genome size and nucleus size, and between genome size, age at first egg mass deposition, body size and lifespan. These relationships held up in the broader phylogenetic comparison. Our study provides evidence for the important role played by genome size in the evolution of life-history traits in annelids. -- Keywords : C-value ; Flow cytometry ; Ophryotrocha ; Body size ; Developmental rate ; Lifespan

Age Dependent Dysfunction of Mitochondrial and ROS Metabolism Induced by Mitonuclear Mismatch

Mitochondrial and nuclear genomes have to coevolve to ensure the proper functioning of the different mitochondrial complexes that are assembled from peptides encoded by both genomes. Mismatch between these genomes is believed to be strongly selected against due to the consequent impairments of mitochondrial functions and induction of oxidative stress. Here, we used a Drosophila model harboring an incompatibility between a mitochondrial tRNAtyr and its nuclear-encoded mitochondrial tyrosine synthetase to assess the cellular mechanisms affected by this incompatibility and to test the relative contribution of mitonuclear interactions and aging on the expression of impaired phenotypes. Our results show that the mitochondrial tRNA mutation caused a decrease in mitochondrial oxygen consumption in the incompatible nuclear background but no effect with the compatible nuclear background. Mitochondrial DNA copy number increased in the incompatible genotype but that increase failed to rescue mitochondrial functions. The flies harboring mismatch between nuclear and mitochondrial genomes had almost three times the relative mtDNA copy number and fifty percent higher rate of hydrogen peroxide production compared to other genome combinations at 25 days of age. We also found that aging exacerbated the mitochondrial dysfunctions. Our results reveal the tight interactions linking mitonuclear mismatch to mitochondrial dysfunction, mitochondrial DNA regulation, ROS production and aging

The invasive common reed (Phragmites australis) along roads in Quebec (Canada): a genetic and biogeographical analysis

During the last century, common reed (Phragmites australis) colonies expanded in marshes of north-eastern North America. This species is highly problematical because it has a strong impact on plant and animal diversity. In the province of Québec (Canada), the spread of common reed coincided with the expansion of the highway network from 1963 to 1984. We hypothesized that highways contributed to the spread of the common reed by creating dispersal corridors and favorable habitats for the growth of the species. To test this hypothesis, in 2003 we mapped the spatial distribution of common reed colonies along all Québec’s highways (2800 km). We also sampled 260 populations to determine whether common reed found along highways is native or exotic. Furthermore, in 2004 we mapped the spatial distribution of colonies along secondary roads in three large areas (485-810 km²), more specifically in regions where common reed colonies were particularly abundant. Globally, 24% of roadsides were invaded by common reed. Highest common reed densities were registered near the city of Montréal, in the south-western part of the province. In this region, the common reed formed hedges several kilometres long. The roadsides of secondary roads where also highly invaded, which suggests that the entire road network contributed to the spread of common reed. Genetic analyses indicated that 99% of common reed colonies found along highways were exotic (haplotype M from Eurasia). Only three out of 260 colonies were dominated by a North American genotype. The spread of common reed in Québec probably resulted from the introduction of an exotic genotype in the first part of the 20th century. This genotype likely benefited from the expansion of the highway network to establish new colonies in most regions of southern Québec. The maintenance of the highway network (ditch digging, roadside mowing) also probably contributed to the spread of common reed and to the improvement of growth conditions for the species

Sources and Export Fluxes of Inorganic and Organic Carbon and Nutrient Species From the Seasonally Ice-Covered Yukon River

Climate and environmental changes are having profound impacts on Arctic river basins, but the biogeochemical response remains poorly understood. To examine the effect of ice formation on temporal variations in composition and fluxes of carbon and nutrient species, monthly water and particulate samples collected from the lower Yukon River between July 2004 and September 2005 were measured for concentrations of organic and inorganic C, N, and P, dissolved silicate (Si(OH)4), and stable isotope composition (δD and δ18O). All organic carbon and nutrient species had the highest concentration during spring freshet and the lowest during the winter season under the ice, indicating dominant sources from snowmelt and flushing of soils in the drainage basin. In contrast, inorganic species such as dissolved inorganic carbon (DIC) and Si(OH)4 had the highest concentrations in winter and the lowest during spring freshet, suggesting dilution during snowmelt and sources from groundwater and leaching/weathering of mineral layer. The contrasting relation with discharge between organic, such as dissolved organic carbon (DOC), and inorganic, such as DIC and Si(OH)4, indicates hydrological control of solute concentration but different sources and transport mechanisms for organic and inorganic carbon and nutrient species. Concentration of DOC also shows an inter-annual variability with higher DOC in 2005 (higher stream flow) than 2004 (lower stream flow). Average inorganic N/P molar ratio was 110 ± A 124, with up to 442 under the ice and 38-70 during the ice-open season. While dissolved organic matter had a higher C/N ratio under the ice (45-62), the particulate C/N ratio was lower during winter (21-26) and spring freshet (19). Apparent fractionation factors of C, N, P, Si and δD and δ18O between ice and river water varied considerably, with high values for inorganic species such as DIC and Si(OH)4 (45 and 9550, respectively) but lower values for DOC (4.7). River ice formation may result in fractionation of inorganic and organic solutes and the repartitioning of seasonal flux of carbon and nutrient species. Annual export flux from the Yukon River basin was 1.6 x 1012 g-DOC, 4.4 x 1012 g-DIC, and 0.89 x 1012 g-POC during 2004-2005. Flux estimation without spring freshet sampling results in considerable underestimation for organic species but significant overestimation for inorganic species regardless of the flux estimation methods used. Without time-series sampling that includes frozen season, an over- or under-estimation in carbon and nutrient fluxes will occur depending on chemical species. Large differences in carbon export fluxes between studies and sampling years indicate that intensive sampling together with long-term observations are needed to determine the response of the Yukon River to a changing climate

Data from: Strategies for a successful plant invasion: the reproduction of Phragmites australis in northeastern North America

1. Knowing the relative contribution of vegetative propagation and sexual reproduction to the dispersal and establishment of exotic plants is crucial for devising efficient control strategies. This is particularly true for the common reed (Phragmites australis), one of the most invasive species in North America. 2. For the first time we combined in situ field observations and genetic evidence, based on two genotyping techniques, i.e., microsatellite markers (SSR) and genotyping-by-sequencing (GBS), to determine the propagation strategies of this invader at its northern distribution limit in North America, and especially in roadside ditches. 3. Field observations revealed that, in a region where the common reed is already abundant, both seeds and plant fragments contributed to the establishment of new populations. Newly established individuals originated mostly (84%) from seeds rather than fragments, but a larger proportion of individuals originating from fragments survived the second year compared to seedlings. 4. High genetic diversity among marsh and roadside common reed stands indicated the prime role of sexual reproduction for dispersal. The vast majority of genotypes were found in only one stand; such high genetic variability can only be explained by sexual reproduction. Half the surveyed stands comprised a single clone, suggesting that local expansion mainly occurred vegetatively. As the small proportion of SSR genotypes initially thought to be common between distant stands proved to be distinct (as revealed by GBS data), it is likely that all the stands examined were initially founded by genetically distinct individuals. 5. Synthesis. Our study suggests that long-distance dispersal by seeds is important for the common reed, in marshes and roadsides, while both seeds and plant fragments contribute to short-distance dispersal along roads, at least in regions where the species is already abundant. The success of this invader in North America seems to be attributable to a reproduction strategy combining the advantages of sexuality with those of vegetative propagation. Moreover, this study shows that the GBS approach strongly reduces uncertainties associated with the use of a limited number of markers. This approach is especially valuable for ecologists dealing with an ever increasing number of invaders, of which few have identified microsatellite markers

Évolution des programmes d'enseignement de 1861 à nos jours /

Bibliogr. à la fin de certains chap.Notes (part. bibliogr.) au bas des p

Sources and export fluxes of inorganic and organic carbon and nutrient species from the seasonally ice-covered Yukon River

National Science Foundation [0554781, 0436179, 0850957]; Frontier Research System for Global Change/Japan through the International Arctic Research Center at the University of Alaska Fairbanks; Northern Gulf Institute; University of Southern MississippiClimate and environmental changes are having profound impacts on Arctic river basins, but the biogeochemical response remains poorly understood. To examine the effect of ice formation on temporal variations in composition and fluxes of carbon and nutrient species, monthly water and particulate samples collected from the lower Yukon River between July 2004 and September 2005 were measured for concentrations of organic and inorganic C, N, and P, dissolved silicate (Si(OH)(4)), and stable isotope composition (delta D and delta(18)O). All organic carbon and nutrient species had the highest concentration during spring freshet and the lowest during the winter season under the ice, indicating dominant sources from snowmelt and flushing of soils in the drainage basin. In contrast, inorganic species such as dissolved inorganic carbon (DIC) and Si(OH)(4) had the highest concentrations in winter and the lowest during spring freshet, suggesting dilution during snowmelt and sources from groundwater and leaching/weathering of mineral layer. The contrasting relation with discharge between organic, such as dissolved organic carbon (DOC), and inorganic, such as DIC and Si(OH)(4), indicates hydrological control of solute concentration but different sources and transport mechanisms for organic and inorganic carbon and nutrient species. Concentration of DOC also shows an inter-annual variability with higher DOC in 2005 (higher stream flow) than 2004 (lower stream flow). Average inorganic N/P molar ratio was 110 +/- A 124, with up to 442 under the ice and 38-70 during the ice-open season. While dissolved organic matter had a higher C/N ratio under the ice (45-62), the particulate C/N ratio was lower during winter (21-26) and spring freshet (19). Apparent fractionation factors of C, N, P, Si and delta D and delta(18)O between ice and river water varied considerably, with high values for inorganic species such as DIC and Si(OH)(4) (45 and 9550, respectively) but lower values for DOC (4.7). River ice formation may result in fractionation of inorganic and organic solutes and the repartitioning of seasonal flux of carbon and nutrient species. Annual export flux from the Yukon River basin was 1.6 x 10(12) g-DOC, 4.4 x 10(12) g-DIC, and 0.89 x 10(12) g-POC during 2004-2005. Flux estimation without spring freshet sampling results in considerable underestimation for organic species but significant overestimation for inorganic species regardless of the flux estimation methods used. Without time-series sampling that includes frozen season, an over- or under-estimation in carbon and nutrient fluxes will occur depending on chemical species. Large differences in carbon export fluxes between studies and sampling years indicate that intensive sampling together with long-term observations are needed to determine the response of the Yukon River to a changing climate

Albert_etal_JEcol

Genetic data (SSR, SNP) from Phragmites australis populations sampled along highways and in marshes of southern Québec, Canad