Differential profiling of selected defence‐related genes induced on challenge with Alternaria brassicicola in resistant white mustard and their comparative expression pattern in susceptible India mustard

The lack of availability of sources of resistance against Alternaria brassicicola within the family Brassicaceae has made oilseed mustard plants a target for one of the most damaging and widespread fungal diseases, Alternaria black spot. Of the other non‐host‐resistant/tolerant plants, Sinapis alba, white mustard, is considered to be the most important apart from Arabidopsis. To understand the defence response of S. alba upon incompatible interaction with this pathogen, a functional genomic approach using cDNA amplified fragment length polymorphism was performed. The highly reproducible bands, found to be either more amplified or uniquely present in infected S. alba plants compared with non‐infected plants, were further subjected to comparative reverse Northern analysis in the incompatible white mustard (S. alba) and compatible India mustard (Brassica juncea L.) plants. The suppression of 46% of the genes in the compatible background indicates the possibility of effective and specific recognition of Alternaria in S. alba. Analysis of the 118 genes up‐regulated specifically in infected S. alba compared with B. juncea showed that 98 genes have similarity to proteins such as receptor‐like protein kinase genes, genes involved with calcium‐mediated signalling and salicylic acid‐dependent genes as well as other genes of known function in Arabidopsis. The apparent expression profile data were further confirmed for selected genes by quantitative real‐time polymerase chain reaction analysis. Classification of these genes on the basis of their induction pattern in Arabidopsis indicates that the expression profile of several of these genes was distinct in S. alba compared with B. juncea.     

Variable temperature sensitivity of soil organic carbon in North American forests

We investigated mean residence time (MRT) for soil organic carbon (SOC) sampled from paired hardwood and pine forests located along a 22 °C mean annual temperature (MAT) gradient in North America. We used acid hydrolysis fractionation, radiocarbon analyses, long-term laboratory incubations (525-d), and a three-pool model to describe the size and kinetics of the acid insoluble C (AIC), active and slow SOC fractions in soil. We found that active SOC was 2 ± 0.2% (mean ± SE) of total SOC, with an MRT of 33 ± 6 days that decreased strongly with increasing MAT. In contrast, MRT for slow SOC and AIC (70 ± 6% and 27 ± 6% of total SOC, respectively) ranged from decades to thousands of years, and neither was significantly related to MAT. The accumulation of AIC (as a percent of total SOC) was greater in hardwood than pine stands (36% and 21%, respectively) although the MRT for AIC was longer in pine stands. Based on these results, we suggest that the responsiveness of most SOC decomposition in upland forests to global warming will be less than currently modeled, but any shifts in vegetation from hardwood to pine may alter the size and MRT of SOC fractions.     

Demography of Reintroduced Eastern Bluebirds and Brown-Headed Nuthatches

ABSTRACT Species reintroductions are used commonly as a tool for conservation, but rigorous, quantitative assessments of their outcome rarely occur. Such assessments are critical for determining success of the reintroduction and for identifying management actions needed to ensure persistence of reintroduced populations. We collected 9 years of demographic data on populations of brown-headed nuthatches (Sitta pusilla) and Eastern bluebirds (Sialia sialis) reintroduced via translocation into Long Pine Key, Everglades National Park, Florida, USA. Realized population growth of brown-headed nuthatches was positive in the first 3 years after cessation of translocations (λ₂₀₀₂ = 1.15, SE = 0.13; λ₂₀₀₃ = 1.28, SE = 0.12; λ₂₀₀₅ = 1.32, SE = 0.20) but became negative thereafter (λ₂₀₀₆ = 0.67, SE = 0.10; λ₂₀₀₇ = 0.77, SE = 0.13). Realized growth rate for the Eastern bluebird population did not vary among years and indicated either a stable or a slowly declining population (λ = 0.92, SE = 0.04). Reintroductions were a qualified success; they resulted in the re-establishment of populations of both species, but neither population grew to the extent expected and both remained at risk of extinction.     

Factors Influencing Reporting and Harvest Probabilities in North American Geese

ABSTRACT We assessed variation in reporting probabilities of standard bands among species, populations, harvest locations, and size classes of North American geese to enable estimation of unbiased harvest probabilities. We included reward (US$10, $20, $30, $50, or $100) and control ($0) banded geese from 16 recognized goose populations of 4 species: Canada (Branta canadensis), cackling (B. hutchinsii), Ross's (Chen rossii), and snow geese (C. caerulescens). We incorporated spatially explicit direct recoveries and live recaptures into a multinomial model to estimate reporting, harvest, and band-retention probabilities. We compared various models for estimating harvest probabilities at country (United States vs. Canada), flyway (5 administrative regions), and harvest area (i.e., flyways divided into northern and southern sections) scales. Mean reporting probability of standard bands was 0.73 (95% CI = 0.69–0.77). Point estimates of reporting probabilities for goose populations or spatial units varied from 0.52 to 0.93, but confidence intervals for individual estimates overlapped and model selection indicated that models with species, population, or spatial effects were less parsimonious than those without these effects. Our estimates were similar to recently reported estimates for mallards (Anas platyrhynchos). We provide current harvest probability estimates for these populations using our direct measures of reporting probability, improving the accuracy of previous estimates obtained from recovery probabilities alone. Goose managers and researchers throughout North America can use our reporting probabilities to correct recovery probabilities estimated from standard banding operations for deriving spatially explicit harvest probabilities.     

Inadvertent gene silencing of argininosuccinate synthase (bcass1) in Botrytis cinerea by the pLOB1 vector system

For several years, researchers working on the plant pathogen Botrytis cinerea and a number of other related fungi have routinely used the pLOB1 vector system, based on hygromycin resistance, under the control of the Aspergillus nidulans oliC promoter and what was reported to be the β‐tubulin (tubA) terminator. Recently, it has been demonstrated that this vector contains a 446‐bp portion of the B. cinerea argininosuccinate synthase gene (bcass1) rather than the tubA terminator. As argininosuccinate synthase is essential for the production of l ‐arginine, inadvertent gene silencing of bcass1 may result in partial l ‐arginine auxotrophy and, indeed, may lead to altered phenotypes in planta. In this article, we report our findings relating to possible problems arising from this incorrect plasmid construction. As an absolute baseline, gene disruption of bcass1 was carried out and generated a strict auxotroph, unable to grow without exogenous arginine supplementation. The knockout displayed an alteration in host range in planta, showing a reduction in pathogenicity on strawberries, French bean leaves and tomatoes, but maintained wild‐type growth on grape, which is in accordance with the reported arginine availability in such tissues. Deliberate gene silencing of bcass1 mirrored these effects, with strongly silenced lines showing reduced virulence. The degree of silencing as seen by partial auxotrophy was correlated with an observed reduction in virulence. We also showed that inadvertent silencing of bcass1 is possible when using the pLOB1 vector or derivatives thereof. Partial arginine auxotrophy and concomitant reductions in virulence were triggered in approximately 6% of transformants obtained when expressing enhanced green fluorescent protein, luciferase, monomeric red fluorescent protein or β‐glucuronidase using the pLOB1‐based expression system, which inadvertently contains 446 bp of the bcass1 coding sequence. We recommend the testing of transformants obtained using this vector system for arginine auxotrophy in order to provide assurance that any observed effects on the development or virulence are a result of the desired genetic alteration rather than accidental bcass1 silencing.     

Evapotranspiration and water use efficiency in a Chesapeake Bay wetland under carbon dioxide enrichment

Wetlands evapotranspire more water than other ecosystems, including agricultural, forest and grassland ecosystems. However, the effects of elevated atmospheric carbon dioxide (CO₂) concentration (C_a) on wetland evapotranspiration (ET) are largely unknown. Here, we present data on 12 years of measurements of ET, net ecosystem CO₂ exchange (NEE), and ecosystem water use efficiency (EWUE, i.e. NEE/ET) at 13:00–15:00 hours in July and August for a Scirpus olneyi (C3 sedge) community and a Spartina patens (C4 grass) community exposed to ambient and elevated (ambient+340 μmol mol^?1) C_a in a Chesapeake Bay wetland. Although a decrease in stomatal conductance at elevated C_a in the S. olneyi community was counteracted by an increase in leaf area index (LAI) to some extend, ET was still reduced by 19% on average over 12 years. In the S. patens community, LAI was not affected by elevated C_a and the reduction of ET was 34%, larger than in the S. olneyi community. For both communities, the relative reduction in ET by elevated C_a was directly proportional to precipitation due to a larger reduction in stomatal conductance in the control plants as precipitation decreased. NEE was stimulated about 36% at elevated C_a in the S. olneyi community but was not significantly affected by elevated C_a in S. patens community. A negative correlation between salinity and precipitation observed in the field indicated that precipitation affected ET through altered salinity and interacted with growth C_a. This proposed mechanism was supported by a greenhouse study that showed a greater C_a effect on ET in controlled low salinity conditions compared with high salinity. In spite of the differences between the two communities in their responses to elevated C_a, EWUE was increased about 83% by elevated C_a in both the S. olneyi and S. patens communities. These findings suggest that rising C_a could have significant impacts on the hydrologic cycles of coastal wetlands.     

The Proteaceous Pistil: Morphological and Anatomical Aspects of the Pollen Presenter and Style of Eight Species Across Five Genera

The morphology and anatomy of pollen presenters, styles andpollen of species ofBanksia, Dryandra, Hakea, IsopogonandMacadamiawerestudied. Serial sections of pistils and SEM images of pollenwere quantified to determine whether the low fertility observedin the Proteaceae has a structural basis. Pollen access to thestigma was investigated. There were three types of stigmaticcavity. A groove in which the stigmatic papillae were enclosedwas present inDryandra, BanksiaandHakea. Macadamiahad a groovewith protruding papillae, andIsopogonhad a tube which enclosedthe papillae. Anatomical studies showed the pollen presenterto be structurally complex but overall to have similar internalanatomy across the species studied. The species could be groupedaccording to presence or absence of transfer tissue and presenceor absence of sclerenchyma, but these groups were not mutuallyexclusive. In the pistil there were three structural filtersto pollen tube passage. The first was at the stigma, where pollengrain access could be limited by the diameter or length of thestigmatic groove or the capacity of the pollination chamberin relation to pollen volume. The second and third related toa narrowing of the transmitting tissue tract within the pollenpresenter and in the lower style which could influence pollentube passage to the ovule.Copyright 1999 Annals of Botany Company Proteaceae,Banksia coccinea, Banksia ericifolia, Dryandra formosa, Dryandra nana, Dryandra quercifolia, Hakea bucculenta, Isopogon cuneatus, Macadamia integrifolia,stigmatic cavity, fertility, pollen presenter, structural limitation, stigma, pollen grain, image analysis, transfer tissue.     

Male‐skewed adult sex ratio,survival, mating opportunity and annual productivity in the Snowy Plover Charadrius alexandrinus

Sex differences in adult mortality may be responsible for male‐skewed adult sex ratios and male‐skewed parental care in some birds. Because a surplus of breeding males has been reported in serially polyandrous populations of Snowy Plover Charadrius alexandrinus, we examined sex ratio, early‐season nesting opportunities, adult survival and annual reproductive success of a Snowy Plover population at Monterey Bay, California. We tested the hypotheses that male adult survival was greater than female survival and that a sex difference in adult survival led to a skewed adult sex ratio, different mating opportunities and different annual productivity between the sexes. Virtually all females left chicks from their first broods to the care of the male and re‐nested with a new mate. As a result, females had time to parent three successful nesting attempts during the lengthy breeding season, whereas males had time for only two successful attempts. Among years, the median population of nesting Plovers was 96 males and 84 females (median difference = 9), resulting in one extra male per eight pairs. The number of potential breeders without mates during the early nesting period each year was higher in males than in females. Adult male survival (0.734 ± 0.028 se) was higher than female survival (0.693 ± 0.030 se) in top‐ranked models. Annually, females parented more successful clutches and fledged more chicks than their first mates of the season. Our results suggest that in C. alexandrinus a sex difference in adult survival results in a male‐skewed sex ratio, which creates more nesting opportunities and greater annual productivity for females than for males.     

Monophyly and affinities of albanerpetontid amphibians (Temnospondyli; Lissamphibia)

The Albanerpetontidae are Middle Jurassic-Miocene amphibians that have variously been regarded as caudates (salamanders), a clade distinct from caudates, or incertae sedis lissamphibians. Here I test for monophyly of the Albanerpetontidae and examine the affinities of the group, within the framework of a more inclusive Temnospondyli, by performing a cladistic analysis using 59 informative characters scored for four non-lissamphibian temnospondyl genera, stem- and crown-clade caudates, salientians (frogs), gymnophionans (caecilians), and the two recognized albanerpetontid genera Albanerpeton and Celtedens . Monophyly of the Albanerpetontidae is corroborated. I interpret synapomorphies of the marginal teeth (non-pedicellate; crowns chisel like, labiolingually compressed, with three mesiodistally aligned cuspules) in albanerpetontids as being associated with a shearing bite. Other synapomorphies evidently strengthened and increased the mobility of the skull, mandible, and cervical region for burrowing, feeding, or both. Nested sets of synapomorphies place the Albanerpetontidae within the Lissamphibia, as the sistertaxon of Caudata plus Salientia. None of the 17 characters previously advanced as albanerpetontid-caudate synapomorphies convincingly places the Albanerpetontidae within the Caudata or allies the two groups as sistertaxa. Albanerpetontids are better interpreted not as aberrant caudates, but as a distinct clade of lissamphibians in which numerous apomorphies are superimposed upon an otherwise primitive lissamphibian body plan.