Flag Leaf Anatomy of Triticum and Aegilops Species in Relation to Photosynthetic Rate

Quantitative anatomical and other measurements were made onfully expanded flag leaves of a series of diploid, tetraploidand hexaploid Triticum and Aegilops species, and photosyntheticrates per unit leaf area were measured at light saturation (P_max). Diploids had the highest P_max, hexaploids the lowest with tetraploidsbeing intermediate. The anatomical features of tetraploids andhexaploids were generally similar, but different from the diploids.The diploids had thinner leaves with less dry matter and chlorophyllper unit area. The surface area of the mesophyll cells per unitvolume of mesophyll tissue was similar for all ploidy levels,as was the ratio mesophyil cell surface area per unit leaf area.It is argued that while these anatomical features are unlikelyto account for the observed variation in Pmax, it is possiblethat other structural factors with which they are correlatedmay causally influence P_max. One such feature is the averagediffusion path length from the plasmalemma at the cell surfaceto the sites of carboxylation. Anatomy, photosynthesis, mesophyll, cell size, Triticum, Aegilops, polyploidy     

Weather-Related Indices of Autumn– Winter Dabbling Duck Abundance in Middle North America

ABSTRACT Research on effects of key weather stimuli influencing waterfowl migration during autumn and winter is limited. We investigated relationships between changes in relative abundances of mallard (Anas platyrhynchos) and other dabbling ducks (Anas spp.) and weather variables at midlatitude locations in North America. We used waterfowl survey data from Missouri Conservation Areas and temperature and snow cover data from the Historical Climatology Network to evaluate competing models to explain changes in relative abundance of ducks in Missouri, USA, during autumn-winter, 1995–2005. We found that a cumulative weather severity index model (CumulativeWSI; calculated as mean daily temp - degrees C + no. of consecutive days with mean temp ≤ 0° C + snow depth + no. of consecutive days with snow cover) had the greatest weight of evidence in explaining changes in relative abundance of ducks. We concluded the CumulativeWSI reflected current and cumulative effects of ambient temperatures on energy expenditure by ducks, and snow cover and wetland icing, on food availability for ducks. The CumulativeWSI may be useful in determining potential changes in autumn-winter distributions of North American waterfowl given different climate change projections and associated changes in habitat conservation needs. Future investigations should address interactions between CumulativeWSI and landscape habitat quality, regional waterfowl populations, hunter harvest, and other anthropogenic influences to increase understanding of waterfowl migration during autumn-winter.     

Survival of Wood Duck Ducklings and Broods in Mississippi and Alabama

ABSTRACT Although North American wood ducks (Aix sponsa) are well-studied throughout their range, researchers know little about demographic and environmental factors influencing survival of ducklings and broods, which is necessary information for population management. We studied radiomarked female and duckling wood ducks that used nest boxes and palustrine wetlands at Noxubee National Wildlife Refuge (NNWR) in Mississippi, USA, in 1996–1999, and riverine wetlands of the Tennessee-Tombigbee Rivers and Waterway (TTRW) system in Alabama in 1998–1999. We estimated survival of ducklings and broods and evaluated potentially important predictors of duckling survival, including age and body mass of brood-rearing females, hatch date of ducklings, duckling mass, brood size at nest departure, inter-day travel distance by ducklings, site and habitat use, and daily minimum air temperature and precipitation. At NNWR, survival of 300 radiomarked ducklings ranged from 0.15 (95% CI = 0.04-0.27) to 0.24 (95% CI = 0.13-0.38) and was 0.21 (95% CI = 0.15-0.28) for 1996–1999. Our overall estimate of brood survival was 0.64 (n = 91; 95% CI = 0.54-0.73). At TTRW, survival of 129 radiomarked ducklings was 0.29 in 1998 (95% CI = 0.20-0.41) and 1999 (95% CI = 0.13-0.45) and was 0.29 (95% CI = 0.20-0.40) for 1998–1999. Our overall estimate of brood survival was 0.71 (n = 38; 95% CI = 0.56-0.85). At NNWR, models that included all predictor variables best explained variation in duckling survival. Akaike weight (w_i) for the best model was 0.81, suggesting it was superior to other models (<0.01 < w_i < 0.18). We detected 4 competing models for duckling survival at TTRW. Inter-day distance traveled by ducklings was important as this variable appeared in all 4 models; duckling survival was positively related to this variable. Patterns of habitat-related survival were similar at both study areas. Ducklings in broods that used scrub-shrub habitats disjunct from wetlands containing aggregations of nest boxes had greater survival probabilities than birds remaining in wetlands with such nest structures. Managers may increase local wood duck recruitment by promoting availability of suitable brood habitats (e.g., scrub-shrub wetlands) without aggregations of nest boxes that may attract predators and by dispersing nest boxes amid or adjacent to these habitats. We did not determine an optimal density of nest boxes relative to local or regional population goals, which remains important research and conservation needs.     

A 5.8S nuclear ribosomal RNA gene sequence database: applications to ecology and evolution

We compiled a 5.8S nuclear ribosomal gene sequence database for animals, plants, and fungi using both newly generated and GenBank sequences. We demonstrate the utility of this database as an internal check to determine whether the target organism and not a contaminant has been sequenced, as a diagnostic tool for ecologists and evolutionary biologists to determine the placement of asexual fungi within larger taxonomic groups, and as a tool to help identify fungi that form ectomycorrhizae.     

Moist-Soil Seed Abundance in Managed Wetlands in the Mississippi Alluvial Valley

Abstract: Managed moist-soil units support early succession herbaceous vegetation that produces seeds, tubers, and other plant parts used by waterfowl in the Mississippi Alluvial Valley (MAV), USA. We conducted a stratified multi-stage sample survey on state and federal lands in the MAV of Arkansas, Louisiana, Mississippi, and Missouri during autumns 2002–2004 to generate a contemporary estimate of combined dry mass of seeds and tubers (herein seed abundance) in managed moist-soil units for use by the Lower Mississippi Valley Joint Venture (LMVJV) of the North American Waterfowl Management Plan. We also examined variation in mean seed abundance among moist-soil units in 2003 and 2004 in relation to management intensity (active or passive), soil pH and nutrient levels, proportional occurrence of plant life-forms (e.g., grass, flatsedge, and forb; vine; woody plants), and unit area. Estimates of mean seed abundance were similar in 2002 (x̄ = 537.1 kg/ha, SE = 100.1) and 2004 (x̄ = 555.2 kg/ha, SE = 105.2) but 35–40% less in 2003 (x̄ = 396.8 kg/ha, SE = 116.1). Averaged over years, seed abundance was 496.3 kg/ha (SE = 62.0; CV = 12.5%). Multiple regression analysis indicated seed abundance varied among moist-soil units inversely with proportional occurrence of woody vegetation and unit area and was greater in actively than passively managed units (R²_adj = 0.37). Species of early succession grasses occurred more frequently in actively than passively managed units (P ≤ 0.09), whereas mid- and late-succession plants occurred more often in passively managed units (P ≤ 0.02). We recommend the LMVJV consider 556 kg/ha as a measure of seed abundance for use in estimating carrying capacity in managed moist-soil units on public lands in the MAV. We recommend active management of moist-soil units to achieve maximum potential seed production and further research to determine recovery rates of seeds of various sizes from core samples and the relationship between seed abundance and unit area. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):707–714; 2008)