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We sequenced genes coding for components of the SNARE complex (STX1A, VAMP2, SNAP25) and their regulatory proteins (STXBP1/Munc18-1, SYT1), which are essential for neurotransmission, in 95 patients with idiopathic mental retardation. We identified de novo mutations in STXBP1 (nonsense, p.R388X; splicing, c.169+1G>A) in two patients with severe mental retardation and nonsyndromic epilepsy. Reverse transcriptase polymerase chain reaction and sequencing showed that the splicing mutation creates a stop codon downstream of exon-3. No de novo or deleterious mutations in STXBP1 were found in 190 control subjects, or in 142 autistic patients. These results suggest that STXBP1 disruption is associated with autosomal dominant mental retardation and nonsyndromic epilepsy.

Interactions between headwater aquifers and peatlands have received limited scientific attention. Hydrological stresses, including those related to climate change, may adversely impact these interactions. In this study, the dynamics of a southern Québec headwater system where a peatland is present is simulated under current conditions and with climate change. The model is calibrated in steady state on field‐measured data and provides satisfactory results for transient‐state conditions. Under current conditions, simulations confirm that the peatland is fed by the fractured bedrock aquifer year‐round and provides continuous baseflow to its outlets. Climate change is simulated through its impact on groundwater recharge. Predicted precipitation and temperature data from a suite of regional climate model scenarios provide a net precipitation variation range from +10% to −30% for the 2041–2070 horizon. Calibrated recharge is modified within this range to perform a sensitivity analysis of the headwater model to recharge variations (+10%, −15% and −30%). Total contribution from the aquifer to rivers and streams varies from +14% to −44% of the baseline for +10% to −30% recharge changes from spring 2010 data, for example. With higher recharge, the peatland receives more groundwater, which could significantly change its vegetation pattern and eventually ecosystem functions. For a −30% recharge, the peatland becomes perched above the aquifer during the summer, fall and winter. Recharge reductions also induce sharp declines in groundwater levels and drying streams. Copyright © 2013 John Wiley & Sons, Ltd.

Summary 1The recent vegetation dynamics of 16 ombrotrophic mires in southern Québec (Canada) was studied through palaeoecological (dendrochronology, plant macrofossil and pollen analyses) and historical (aerial photograph analyses) techniques. 2 Plant macrofossil analyses show that prior to European colonization ( c . 1800), mires were predominately open environments dominated by Sphagnum mosses. Many sites subsequently became forested with little or no Sphagnum . 3 Aerial photograph analyses indicate that widespread forest expansion occurred in all mires between 1948 and 1995. The percentage of the total mire area occupied by forest increased from 22.5 to 56.5%, an overall gain of 137 ha of forest habitat. 4 A dry climatic period during the first part of the 20th century, drainage resulting from human activities, and fire events, seem to be the main causal factors of vegetation changes. 5 Forest expansion is expected to cause profound changes in bog ecosystems, such as altering hydrological conditions and organic accumulation processes, and to be detrimental to regional biodiversity and the carbon balance. 6 Overall, this study highlights the need to incorporate multiple approaches in reconstructing the vegetation dynamics of an ecosystem, and in determining causal factors of vegetation change.

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Aim:In urbanized areas, exotic invasions, native extinctions, and the alteration of habitats and natural processes drive homogenization, which is a form of biotic impoverishment. This study examines whether urbanization and flooding induce homogenization of herbaceous communities in riparian forests and quantifies the relationships between taxonomic and functional β-diversity.Location: Montréal, Québec, Canada.Methods: Inventories were conducted in 56 riparian forests. Taxonomic and functional β-diversity were calculated as between-site similarities in species or trait composition for three levels of urbanization and flooding. Differences among the disturbance levels were compared using tests for homogeneity in multivariate dispersions. We quantified the correlation between local species richness, exotic proportion, taxonomic and functional β-diversity. We also partitioned taxonomic β-diversity into species turnover and richness difference.Results: Urbanization led to taxonomic and functional differentiation, while increased flooding led to taxonomic and functional homogenization. We found a significant correlation between taxonomic and functional β-diversity. Changes in β-diversity were associated with species and trait turnover among both urbanization and flood levels, and with changes in species richness. Differentiation was associated with low species richness, and homogenization with high species richness. Exotic invasions tended to favour differentiation, but only at a low urbanization level. Main Conclusions:The effect of urbanization on plant diversity in riparian forests was twofold: first, it directly induced taxonomic and functional differentiation through its effect on species loss and turnover (higher β-diversity at high urbanization level); second, differentiation was indirectly favoured through the reduction in flooding (higher β-diversity at low flood level). Taxonomic and functional β-diversity followed similar patterns, likely because species invasions and extinctions are not random, but are related to species traits. Our results underline the need to move our focus from exotic species to the true underlying factors of biodiversity loss and homogenization, notably land use changes and human disturbances. K E Y W O R D S β-diversity, exotic species, flooding, functional traits, herbaceous species, multivariate dispersion, species richness difference, species turnover | 829 BRICE Et al. Funds came from the Natural Sciences and Engineering Research Council of Canada (scholarship to MH Brice, Discovery grant to S. Pellerin: RGPIN-2014-05367 and M. Poulin RGPIN-2014-05663), the Fonds de recherche Nature et technologies and the Quebec Centre for Biodiversity Science (scholarships to MH Brice). Our thanks municipalities and landowners for site access, to A. Langlois, A. Richer, J. S. Mignot, S. Pasquet and Y. Tendland for research assistance, P. Legendre, D. Borcard, E. Laliberté and P. Peres-Neto for statistical advice, K. Grislis and C. Brown for language editing, and Z.E. Taranu and three anonymous ...

Ground penetrating radar (GPR) is often used for investigating peat thickness. The quality of GPR measurements depends on electromagnetic wave (EMW) velocity estimates. The objective of this study is to determine the number of manual measurements required to minimize EMW velocity error in peatlands. A total of 175 manually measured peat thicknesses are used with a depthto-target method to assess EMW velocity in two southern Quebec peatlands. Mean measured EMW velocities are 0·040 and 0·039 m ns -1 with standard deviations of 0·013 and 0·008 m ns -1 . Statistical analyses show that at least 30 calibration points are required to minimize the EMW velocity error, regardless of the geological setting. Figure 1. Study sites of (a) the Lanoraie peatland complex and (b) the Covey Hill peatland, southern Quebec (Canada).