Inter‐annual variability of fruit timing and quantity at Nouragues (French Guiana): insights from hierarchical Bayesian analyses

The timing and quantity of fruit production are major determinants of the functioning of a forest community, but simultaneous analyses of both are rare. We analyzed a ten‐year dataset (2001–2011) of fruit production for 45 tree and liana species from the Nouragues rain forest, French Guiana. We developed a hierarchical Bayesian approach to determine variation in the timing and quantity of fruit production. Our analysis accommodates missing censuses and quantifies variation at seasonal and inter‐annual scales. The fruiting peak of 22 of 45 species occurred during the peak of the rainy season, which is typical for central and eastern Amazon. The timing and quantity of fruit production varied substantially across years in most species, with greater variation in quantity than in timing. The timing of fruit production varied from continuously fruiting species to mast fruiting species that had two or more consecutive years without fruit production. Fully 40% of species were mast fruiting species. The seasonal timing and inter‐annual variation in fruiting were unrelated to seed dispersal mode across species. We saw no evidence for directional change in the level of fruit production, the timing of fruit production, or their variances; however, 10 yr is a short record for such analyses.     

Maintenance of the inner cell mass in human blastocysts from fragmented embryos

The degree of fragmentation during early cleavage is universally used as an indicator of embryo quality during human in vitro fertilization treatment. Extensive fragmentation has been associated with reduced blastocyst formation and implantation. We examined the relationship between early fragmentation and subsequent allocation of cells to the trophectoderm and inner cell mass in the human blastocyst. We retrospectively analyzed data from 363 monospermic human embryos that exhibited varying degrees of fragmentation on Day 2. Embryos were cultured from Day 2 to Day 6 in Earle balanced salt solution with 1 mM glucose and human serum albumin. Rates of development and blastocyst formation were measured. The number of cells in the trophectoderm and inner cell mass and the incidence of apoptosis were assessed following differential labeling with polynucleotide-specific fluorochromes. Increasing fragmentation resulted in reduced blastocyst formation and lower blastocyst cell numbers. For minimal and moderate levels of fragmentation, the reduction in cell numbers was confined largely to the trophectoderm and a steady number of inner cell mass cells was maintained. However, with extensive fragmentation of more than 25%, cell numbers in both lineages were reduced in the few embryos that formed blastocysts. Apoptotic nuclei were present in both the trophectoderm and inner cell mass, with the lowest incidence in blastocysts that had developed from embryos with minor (5-10%) fragmentation. Paradoxically, higher levels of apoptosis were seen in embryos of excellent morphology, suggesting a possible role in regulation of cell number.     

Rapid detection of microbial contamination in frozen vegetables by automated impedance measurements.

Automated impedance measurements can be used to rapidly assess whether a sample of frozen vegetables contains greater or less than 10(5) organisms per g. Microorganisms growing pureed food samples cause a change in the impedance of the medium when the organisms reach a threshold concentration of between 10(6) and 10(7) organisms per ml. Estimates of the concentration of microorganisms initially present in the food sample can be made by recording the time required for the organisms in the sample to replicate to threshold levels. In this study, the detection times for 357 samples of frozen vegetables were compared with standard plate counts for each sample. The agreement between the two methods in distinguishing samples containing more than 10(5) organisms per g was 92.6% for 257 assorted frozen vegetables and somewhat higher (93 to 96%) when separate cutoff times were used for each type of vegetable. The time required for analysis was about 5 h, compared to the 48 to 72 h required for standard plate counts.     

A Framework for Evaluating Heterogeneity and Landscape-Level Impacts of Non-native Aquatic Species

Non-native species are a major component of global environmental change, and aquatic systems are especially vulnerable to non-native species impacts. Much of the research on aquatic non-native species impact has occurred at the local or site level. In reality, non-native species impacts play out across multiple spatial scales on heterogeneous landscapes. How can we ‘scale up’ our understanding of site-level impacts to the broader landscape scale? To address this disconnect, we synthesize our current understanding of key components of landscape-scale non-native species impacts: geographic range, abundance, and local impacts. Most aquatic non-native species have small ranges, while a few have large ranges. However, aquatic non-native species are often far from saturated on landscapes, and occurrence records are often woefully incomplete. Aquatic non-native species are often at low abundances where they are present, reaching high abundance in a small number of locations. Finally, local-scale impact can be estimated from abundance, but this requires knowledge of the abundance–impact relationship. Considering these multiple components enables understanding of non-native species impacts at broader spatial scales. Although the landscape-level impacts of aquatic non-native species may be high, the spatial distribution of site-level impacts is uneven, and highly impacted sites may be relatively uncommon. This heterogeneity in impacts provides an opportunity to optimize and prioritize non-native species management and prevention efforts.     

Testing and interpreting the shared space‐environment fraction in variation partitioning analyses of ecological data

Variation partitioning analyses combined with spatial predictors (Moran's eigenvector maps, MEM) are commonly used in ecology to test the fractions of species abundance variation purely explained by environment and space. However, while these pure fractions can be tested using a classical residuals permutation procedure, no specific method has been developed to test the shared space‐environment fraction (SSEF). Yet, the SSEF is expected to encompass a major driver of community assembly, that is, an induced spatial dependence effect (ISD; i.e. the reflection of a spatially structured habitat filter on a species distribution). A reliable test of this fraction is therefore crucial to properly test the presence of an ISD on ecological data. To bridge the gap, we propose to test the SSEF through spatially‐constrained null models: torus‐translations, and Moran spectral randomisations. We investigated the type I error rate and statistical power of our method based on two real environmental datasets and simulations of tree distributions. Ten types of tree distribution displaying contrasted aggregation properties were simulated, and their abundances were sampled in 153 regularly‐distributed 20 × 20 m quadrats. The SSEF was tested for 1000 simulated tree distributions either unrelated to the environment, or filtered by environmental variables displaying contrasting spatial structures. The method proposed provided a correct type I error rate (< 0.05). The statistical power was high (> 0.9) when abundances were filtered by an environmental variable structured at broad scale. However, the spatial resolution allowed by the sampling design limited the power of the method when using a fine‐scale filtering variable. This highlighted that an ISD can be properly detected providing that the spatial pattern of the filtering process is correctly captured by the sampling design of the study. An R function to apply the SSEF testing method is provided and detailed in a tutorial.     

Metabolism of gibberellins by immature barley grain

Gibberellins A₁, A₄, A₉, A₁₂-aldehyde, A₂₀ and A₅₁, each labelled with both a radioactive and stable isotope were fed to immature barley grain by injection into the endosperm. After 7 d, extensive metabolism of all substrates had occurred, and metabolites were identified by combined capillary gas chromatography-mass spectrometry. A proposed scheme of gibberellin metabolism in immature barley grain is presented.Abbreviations GA_n gibberellin A_n - GC-MS combined gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography