Nonparametric spatial regression of survival probability: visualization of population sinks in Eurasian woodcock

Both evolutionary ecologists and wildlife managers make inference based on how fitness and demography vary in space. Spatial variation in survival can be difficult to assess in the wild because (1) multisite study designs are not well suited to populations that are continuously distributed across a large area and (2) available statistical models accounting for detectability less than 1.0 do not easily cope with geographical coordinates. Here we use penalized splines within a Bayesian state-space modeling framework to estimate and visualize survival probability in two dimensions. The approach is flexible in that no parametric form for the relationship between survival and coordinates need be specified a priori. To illustrate our method, we study a game species, the Eurasian Woodcock Scolopax rusticola, based on band recovery data (5000 individuals) collected over a > 50 000-km2 area in west-central France with contrasted habitats and hunting pressures. We find that spatial variation in survival probability matches an index of hunting pressure and creates a mosaic of population sources and sinks. Such analyses could provide guidance concerning the spatial management of hunting intensity or could be used to identify pathways of spatial variation in fitness, for example, to study adaptation to changing landscape and climate.     

Genetic population structure in a commercial marine invertebrate with long-lived lecithotrophic larvae: <Emphasis Type="Italic">Cucumaria</Emphasis><Emphasis Type="Italic">frondosa</Emphasis> (Echinodermata: Holothuroidea)

The patterns of genetic diversity and connectivity were investigated in Cucumaria frondosa, the most abundant sea cucumber in the North Atlantic, to assist in the management and conservation of this ecologically important marine invertebrate, which is the target of an emerging fishery. Mitochondrial DNA COI sequences of 334 C. frondosa were obtained and analyzed, mainly from its western North Atlantic range, where the commercial fishery is being developed, with complementary sampling in the mid- and eastern North Atlantic. Analysis of molecular variance showed no significant (P > 0.05) differences among subpopulations in the western region suggesting that it constitutes one panmictic population. The same analysis showed low, but significant differences between eastern and western Atlantic populations. Coalescent analyses using isolation with migration models and a Bayesian skyline plot indicated historical divergence and a general increase in population size prior to the last glacial maximum and highly asymmetric gene flow (nearly 100 times lower from west to east) between sea cucumbers from North America and Norway. Results suggest that subpopulations of C. frondosa within the western North Atlantic have been highly connected. We propose that aided by the high-connectivity local subpopulations can recover rapidly from natural (i.e., ice ages) or anthropogenic (i.e., overfishing) population declines through recruitment from deep refugia.     

Economic Analysis of Summer Fallow Management to Reduce Take-All Disease and N Leaching in a Wheat Crop Rotation

This paper addresses the question of summer cover-crop adoption by farmers in presence of a risk of yield loss due to take-all disease and climate variability. To analyze the public incentives needed to encourage farmers to adopt summer cover crops as a means of reducing N leaching, we combine outputs from an economic, an epidemiological and an agronomic model. The economic model is a simple model of choice under risk. The farmer is assumed to choose among a range of summer fallow managements and input uses on the basis of the expected utility criterion (HARA assumption) in presence of both climate and take-all risks. The epidemiological model proposed by Ennaïfar et al. (Eur J Plant Pathol 118:127–143, 2007) is used to determine the impact of take all on yields and N uptake. The crop-soil model (STICS) is used to compute yield developments and N leaching under various management options and climatic conditions. The input parameters are chosen to match the conditions prevailing in Grignon, located in the main wheat-growing area in France. Eight management systems are examined: four summer fallow managements: ‘wheat volunteers’ (WV), ‘bare soil’ (BS), ‘early mustard’, ‘late mustard’, and two input intensities. We show that the optimal systems are BS (WV) when the take-all risk is (not) taken into account by agents. We then compute the minimum payment to each system such that it emerges in the optimum. We thus derive the required amounts of transfer needed to trigger catch-crop adoption. The results of the Monte Carlo sensitivity analysis show that the ranking of management systems is robust over a wide range of input parameters.     

Microbial activity and water-soluble trace element species in the rhizosphere of spring wheat (Triticum aestivum cv. USU-Perigee)

The influence of microbial activity on the concentration and speciation of trace elements (TEs) was assessed in a study on the bioavailability of TEs for edible plants. A growth chamber experiment with spring wheat (Triticum aestivum cv. USU-Perigee) was conducted and the bulk (Bk) and the rhizosphere (Rz) soil components were collected at maturity. A characterization of the microbial activity and population was made by measuring the microbial biomass, enzymes (acid phosphatase, arylsulfatase, dehydrogenase and urease) and 16S rDNA DGGE profiles. In soil water extracts, major solutes (H(+), Ca, Mg, Na, NH(4), K, Cl, NO(3), SO(4), total N, DON and DOC) and trace elements (Al, As, Cd, Ce, Cr, Cu, Fe, Pb, Tl, and Zn) including monomeric Al species, free Cu(2+) and labile Zn were determined. The partition of the variation indicated that 12.1% of the distribution of TEs in the Bk soil was significantly and exclusively explained by chemical properties while this value was less than 0.1% for the Rz soil. To the contrary, microbial properties contributed significantly to 12.3% of the distribution of TEs in the Rz soil whereas it explained less than 0.1% for the Bk soil. Detailed redundancy analyses identified several potential mechanisms (e.g. weathering of primary mineral, solubilisation of sesquioxides, bacterial effect on the redox status) explaining the fate of TEs in the Bk and Rz soils. This study revealed that microbial activity is strongly associated to the speciation of trace elements in the Rz of edible plants and points to some microbial processes influencing TE speciation.     

Escape migration decisions in Eurasian Woodcocks: insights from survival analyses using large-scale recovery data

During unpredictable adverse conditions, endotherms can engage in emergency behaviors (movement, torpor, hyperphagia) to maintain energy balance and reduce mortality hazards. Bird “escape migration” is one of the most visible of these behaviors. In this study, we focus on a Eurasian Woodcock Scolopax rusticola population. Seasonal migrations bring this population from its breeding grounds in Eastern and Northern Europe to its wintering grounds in France. A varying number of these birds are also regularly reported from Spain, supposedly during additional escape movements that occur in winter. Using models that account for the imperfect detection rate of individuals and a large (>44,000 individuals) dataset combining information from the wintering and breeding ranges, we show that severe winters significantly reduced survival probability, but that migration to Spain increased only during the most intense cold spell that occurred over the 20-year study period. This suggests that the decision to resume migration during the winter is submitted to a threshold mechanism, which we discuss in the light of current models of migratory behavior.     

Double-outlet right ventricle with absent left ventricle and mitral atresia in a fetus with a deletion 22q12

Interstitial deletions of chromosomal region 22q12 are rare. We report the prenatal diagnosis of a de novo interstitial deletion 22q12. The fetus was karyotyped because of a complex cardiac anomaly. Conventional and molecular cytogenetics showed a female karyotype with a de novo pericentric inversion of one chromosome 22 associated with a deletion of the chromosomal region 22q12 leading to a partial monosomy 22q12. At autopsy, the fetus showed double-outlet right ventricle (DORV) with absent left ventricle and mitral atresia. This observation suggests that one or several genes for the early looping step of heart development may reside in chromosomal region 22q12. Further studies are needed to identify these genes, and to search microdeletions of 22q12 region in patients with DORV. Copyright © 2004 John Wiley & Sons, Ltd.