Plant phylogeny drives arboreal caterpillar assemblages across the Holarctic

1. Assemblages of insect herbivores are structured by plant traits such as nutrient content, secondary metabolites, physical traits, and phenology. Many of these traits are phylogenetically conserved, implying a decrease in trait similarity with increasing phylogenetic distance of the host plant taxa. Thus, a metric of phylogenetic distances and relationships can be considered a proxy for phylogenetically conserved plant traits and used to predict variation in herbivorous insect assemblages among co‐occurring plant species.
2. Using a Holarctic dataset of exposed‐feeding and shelter‐building caterpillars, we aimed at showing how phylogenetic relationships among host plants explain compositional changes and characteristics of herbivore assemblages.
3. Our plant–caterpillar network data derived from plot‐based samplings at three different continents included >28,000 individual caterpillar–plant interactions. We tested whether increasing phylogenetic distance of the host plants leads to a decrease in caterpillar assemblage overlap. We further investigated to what degree phylogenetic isolation of a host tree species within the local community explains abundance, density, richness, and mean specialization of its associated caterpillar assemblage.
4. The overlap of caterpillar assemblages decreased with increasing phylogenetic distance among the host tree species. Phylogenetic isolation of a host plant within the local plant community was correlated with lower richness and mean specialization of the associated caterpillar assemblages. Phylogenetic isolation had no effect on caterpillar abundance or density. The effects of plant phylogeny were consistent across exposed‐feeding and shelter‐building caterpillars.
5. Our study reveals that distance metrics obtained from host plant phylogeny are useful predictors to explain compositional turnover among hosts and host‐specific variations in richness and mean specialization of associated insect herbivore assemblages in temperate broadleaf forests. As phylogenetic information of plant communities is becoming increasingly available, further large‐scale studies are needed to investigate to what degree plant phylogeny structures herbivore assemblages in other biomes and ecosystems.

     

Functional rarefaction: estimating functional diversity from field data

Studies in biodiversity-ecosystem function and conservation biology have led to the development of diversity indices that take species' functional differences into account. We identify two broad classes of indices: those that monotonically increase with species richness (MSR indices) and those that weight the contribution of each species by abundance or occurrence (weighted indices). We argue that weighted indices are easier to estimate without bias but tend to ignore information provided by rare species. Conversely, MSR indices fully incorporate information provided by rare species but are nearly always underestimated when communities are not exhaustively surveyed. This is because of the well-studied fact that additional sampling of a community may reveal previously undiscovered species. We use the rarefaction technique from species richness studies to address sample-size-induced bias when estimating functional diversity indices. Rarefaction transforms any given MSR index into a family of unbiased weighted indices, each with a different level of sensitivity to rare species. Thus rarefaction simultaneously solves the problem of bias and the problem of sensitivity to rare species. We present formulae and algorithms for conducting a functional rarefaction analysis of the two most widely cited MSR indices: functional attribute diversity (FAD) and Petchey and Gaston's functional diversity (FD). These formulae also demonstrate a relationship between three seemingly unrelated functional diversity indices: FAD, FD and Rao's quadratic entropy. Statistical theory is also provided in order to prove that all desirable statistical properties of species richness rarefaction are preserved for functional rarefaction.     

Exclosure fences around nests of imperiled Florida Grasshopper Sparrows reduce rates of predation by mammals

Increasing nest survival by excluding predators is a goal of many bird conservation programs. However, new exclosure projects should be carefully evaluated to assess the potential risks of disturbance. We tested the effectiveness of predator exclosure fences (hereafter, fences) for nests of critically endangered Florida Grasshopper Sparrows (Ammodramus savannarum floridanus) at a dry prairie site (Three Lakes; 2015–2018) and a pasture site (the Ranch; 2015–2016) in Osceola County, Florida, USA. We installed fences at nests an average of 8 days after the start of incubation, and nest abandonment after fence installation was rare (2 of 149 installations). Predation was the leading cause of failure for unfenced nests at both sites (48–73%). At Three Lakes, nest cameras revealed that mammals and snakes were responsible for 61.5% and 38.5% of predation events, respectively, at unfenced nests. Fences reduced the daily probability of predation (0.016 for fenced nests vs. 0.074 for unfenced nests). The probability that a fenced nest would survive from discovery to fledging was more than double that of unfenced nests (60.4% vs. 27.7%). However, we found no difference in daily nest survival at the Ranch between the year before nests were fenced (2015; 0.874) and the year when all but one nest were fenced (2016; 0.867) because red imported fire ants (Solenopsis invicta) were responsible for 86% of predation events at fenced nests at the Ranch. The use of cameras at fenced nests revealed that site‐specific differences in nest predators explained variation in fence efficiency between sites. Our fence design may be useful for other species of grassland birds, but site‐specific predator communities and species‐specific response of target bird species to fences should be assessed before installing fences at other sites.     

Natural Occurrence of Left-Handed (Z) Regions in PM2 DNA

Abstract

Bacteriophage PM2 DNA, a ccc genome of high apparent superhelical density, contains left-handed (Z) regions as detected by competitive radioimmunoassay, agarose gel electrophoresis of DNA: antibody complexes and immunoelectron microscopy. The latter technique, in conjunction with partial blockage of restriction endonuclease sites by bound antibody, was used to map the left-handed regions along the DNA molecule. A cluster of four to five antibody molecules (approximately 25% of bound antibody) was located within map units 0.05–0.18 of the single Hpa II restriction site. Sequence analysis of part of this region showed the presence of several areas of high alternating purine-pyrimidine content. A strong correlation is observed between alternating pyrimidine-purine tracts of significant length and antibody binding sites.     

A nuclear specific glycoprotein representative of a unique pattern of glycosylation

Whole rat liver nuclei were reacted with UDP-[14C]galactose in the presence of bovine beta(1----4) galactosyltransferase. The reaction mixture was electrophoresed on a reducing sodium dodecyl sulfate-polyacrylamide gel. Autoradiograms of the gel demonstrated a major labeled broad band migrating with an apparent molecular weight of 65,000-66,000. A number of other less prominently labeled bands were also present. The labeled 65,000-66,000 band when cut from the gel and subjected to alkaline reduction while in the gel matrix exclusively yielded a 14C-labeled disaccharide that co-migrated with a [14C]Gal-GlcNAcol standard in descending paper chromatography. Treatment of this disaccharide with beta-galactosidase (beta-D-galactoside galactohydrolase; EC 3.2.1.23) from Aspergillus niger removed all the [14C]galactose label. Treatment of the labeled 65,000-66,000 polypeptide with Endoglycosidase F, however, did not remove the [14C]galactose label. Western transfer blots of sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels performed with horseradish peroxidase-labeled succinyl wheat germ agglutinin, a lectin specific for GlcNAc, on unlabeled nuclei revealed a dominant band at 63,000-64,000. Subjecting 14C-labeled nuclei to this procedure resulted in a shift of the major horseradish peroxidase-labeled succinyl wheat germ agglutinin band to 65,000-66,000. The shifted band was coincident with the [14C]galactose band as visualized on an autoradiogram. A survey of other rat tissue nuclei revealed the same spectrum of [14C]galactose acceptor proteins with a dominant 65,000-66,000 galactose-labeled band.     

Phosphorylation of rat heart glycogen synthase: studies in cardiomyocytes and in vitro phosphorylations with cAMP-dependent kinase and protein phosphatase-1

The phosphorylation of glycogen synthase has been studied in freshly isolated adult rat cardiomyocytes. Six peaks of 32P-labeled tryptic peptides are recovered via C-18 high performance liquid chromatography (HPLC) when synthase is immunoprecipitated from 32P-labeled cardiomyocytes and digested with trypsin. When epinephrine treated cells are used as a source of enzyme, the same HPLC profile is obtained with a dramatic enhancement of 32P recovered in two of the HPLC peaks. In vitro phosphorylation of rat heart synthase by cAMP-dependent protein kinase stimulates the conversion of synthase from the I to the D form and results in the recovery of the same tryptic peptides from the C-18 as is the case for synthase derived from cardiomyocytes. Treatment of cAMP-dependent kinase phosphorylated synthase with protein phosphatase-1 leads to a reactivation of the enzyme and a dephosphorylation of the same tryptic peptides that are selectively phosphorylated in epinephrine treated cardiomyocytes. These results are discussed in relation to hormonal control of glycogen metabolism in cardiac tissue.     

Cyclic AMP, the hyperresponsiveness factor from hog kidney

The isolation and identification of a material present in the plasma of hypertensive dogs and hypertensive human patients has been under study since 1972. The earliest experiments in relation to this work, noted that plasma from hypertensive dogs cause a hyperresponse to norepinephrine when both were administered by way of the vein. Employing a rat assay system that consisted of an anesthetized rat with polyethylene catheters in the vein for giving norepinephrine and the test fractions and a catheter in the artery for blood pressure monitoring, fractions from hog kidney were tested for hyperresponsiveness activity. The active material is very comparable to cyclic AMP in molecular weight, ultraviolet spectrum, paper chromatography, Enzyme hydrolysis and activity in the anesthetized rat system. This evidence indicates that the hyperresponsiveness factor of renal origin is cyclic AMP.