Personality interacts with habitat quality to govern individual mortality and dispersal patterns

Individual phenotypic differences are increasingly recognized as key drivers of ecological processes. However, studies examining the relative importance of these differences in comparison with environmental factors or how individual phenotype interacts across different environmental contexts remain lacking. We performed two field experiments to assess the concurrent roles of personality differences and habitat quality in mediating individual mortality and dispersal. We quantified the predator avoidance response of mud crabs, Panopeus herbstii, collected from low‐ and high‐quality oyster reefs and measured crab loss in a caging experiment. We simultaneously measured the distance crabs traveled as well as the stability of personalities across reef quality in a separate reciprocal transplant experiment. Habitat quality was the primary determinant of crab loss, although the distance crabs traveled was governed by personality which interacted with habitat quality to control the fate of crabs. Here, crabs on low‐quality reefs rapidly emigrated, starting with the boldest individuals, and experienced modest levels of predation regardless of personality. In contrast, both bold and shy crabs would remain on high‐quality reefs for months where bolder individuals experienced higher predation risk. These findings suggest that personalities could produce vastly different population dynamics across habitat quality and govern community responses to habitat degradation.     

Paracrystalline Sheets Reaggregated from Solubilized Exosporium of Bacillus cereus

Fragments of exosporium, isolated from dormant spores of Bacillus cereus, were disintegrated by treatment with sodium dodecyl sulfate (SDS) or with phenol and acetic acid. After centrifugation of each preparation, proteins in the supernatant fractions were resolved by disc gel electrophoresis into either two or eight bands, respectively. The SDS-solubilized fraction contained spheroidal particles 11 to 44 nm in diameter. When centrifuged until clear, this fraction after dialysis still gave rise to crystal-like sheets which had the same lattice symmetry and major chemical components (protein, lipid, and carbohydrate) as fragments of the native exosporium.     

Purification and crystallization of Pseudomonas aeruginosa chloramphenicol acetyltransferase

A chloramphenicol acetyltransferase from Pseudomonas aeruginosa genomic DNA has been overexpressed, refolded, purified, and crystallized. Crystals suitable for a three-dimensional x-ray structure determination were obtained from solutions of polyethyleneglycol methyl ether 2000 containing NiCl₂ at pH 8.5. These crystals belong to the cubic space group P4_1/332 (a = 154.8 Å) and diffract x-rays to ≈3.2 Å resolution. Proteins 28:298–300, 1997. © 1997 Wiley-Liss Inc.     

Habitat quality mediates personality through differences in social context

Assessing the stability of animal personalities has become a major goal of behavioral ecologists. Most personality studies have utilized solitary individuals, but little is known on the extent that individuals retain their personality across ecologically relevant group settings. We conducted a field survey which determined that mud crabs, Panopeus herbstii, remain scattered as isolated individuals on degraded oyster reefs while high quality reefs can sustain high crab densities (>10 m^?2). We examined the impact of these differences in social context on personality by quantifying the boldness of the same individual crabs when in isolation and in natural cohorts. Crabs were also exposed to either a treatment of predator cues or a control of no cue throughout the experiment to assess the strength of this behavioral reaction norm. Crabs were significantly bolder when in groups than as solitary individuals with predator cue treatments exhibiting severally reduced crab activity levels in comparison to corresponding treatments with no predator cues. Behavioral plasticity depended on the individual and was strongest in the presence of predator cues. While bold crabs largely maintained their personality in isolation and group settings, shy crabs would become substantially bolder when among conspecifics. These results imply that the shifts in crab boldness were a response to changes in perceived predation risk, and provide a mechanism for explaining variation in behavioral plasticity. Such findings suggest that habitat degradation may produce subpopulations with different behavioral patterns because of differing social interactions between individual animals.     

6-deoxyerythronolide B production through chromosomal localization of the deoxyerythronolide B synthase genes in E. coli

Chromosomal engineering was used to localize the deoxyerythronolide B synthase (DEBS) genes and propionyl-CoA carboxylase (PCC) genes to the BAP1 Escherichia coli chromosome creating the new strain YW9. YW9 then featured a plasmid-free heterologous pathway for the production of the polyketide product 6-deoxyerythronolide B (6dEB, a precursor to the antibiotic erythromycin) highlighted by the successful chromosomal integration of five genes total and three DEBS genes each approximately 10 kb in length. The new strain was tested for small-scale 6dEB biosynthesis and compared to 6dEB production from plasmid-derived gene expression at 22, 30, and 37 degrees C. YW9 produced 6dEB at each temperature tested; whereas, the current plasmid-based system could only produce 6dEB at 22 and 30 degrees C. As determined by MS analysis, average production levels for YW9 were 0.47 (22 degrees C), 0.52 (30 degrees C), and 0.11 (37 degrees C)mg/L.     

Inhibition between invasives: a newly introduced predator moderates the impacts of a previously established invasive predator

1. With continued globalization, species are being transported and introduced into novel habitats at an accelerating rate. Interactions between invasive species may provide important mechanisms that moderate their impacts on native species. 2. The European green crab Carcinus maenas is an aggressive predator that was introduced to the east coast of North America in the mid-1800 s and is capable of rapid consumption of bivalve prey. A newer invasive predator, the Asian shore crab Hemigrapsus sanguineus, was first discovered on the Atlantic coast in the 1980s, and now inhabits many of the same regions as C. maenas within the Gulf of Maine. Using a series of field and laboratory investigations, we examined the consequences of interactions between these predators. 3. Density patterns of these two species at different spatial scales are consistent with negative interactions. As a result of these interactions, C. maenas alters its diet to consume fewer mussels, its preferred prey, in the presence of H. sanguineus. Decreased mussel consumption in turn leads to lower growth rates for C. maenas, with potential detrimental effects on C. maenas populations. 4. Rather than an invasional meltdown, this study demonstrates that, within the Gulf of Maine, this new invasive predator can moderate the impacts of the older invasive predator.     

Environment,but not migration rate,influences extinction risk in experimental metapopulations

Ecological theory suggests that several demographic factors influence metapopulation extinction risk, including synchrony in population size between subpopulations, metapopulation size and the magnitude of fluctuations in population size. Theoretically, each of these is influenced by the rate of migration between subpopulations. Here we report on an experiment where we manipulated migration rate within metapopulations of the freshwater zooplankton Daphnia magna to examine how migration influenced each of these demographic variables, and subsequent effects on metapopulation extinction. In addition, our experimental procedures introduced unplanned but controlled differences between metapopulations in light intensity, enabling us to examine the relative influences of environmental and demographic factors. We found that increasing migration rate increased subpopulation synchrony. We failed to detect effects of migration on population size and fluctuations in population size at the metapopulation or subpopulation level, however. In contrast, light intensity did not influence synchrony, but was positively correlated with population size and negatively correlated with population fluctuation. Finally, synchrony did not influence time to extinction, while population size and the magnitude of fluctuations did. We conclude that environmental factors had a greater influence on extinction risk than demographic factors, and that metapopulation size and fluctuation were more important to extinction risk than metapopulation synchrony.     

Dioecy and the evolution of sex ratios in ants

Split sex ratios, when some colonies produce only male and others only female reproductives, is a common feature of social insects, especially ants. The most widely accepted explanation for split sex ratios was proposed by Boomsma and Grafen, and is driven by conflicts of interest among colonies that vary in relatedness. The predictions of the Boomsma–Grafen model have been confirmed in many cases, but contradicted in several others. We adapt a model for the evolution of dioecy in plants to make predictions about the evolution of split sex ratios in social insects. Reproductive specialization results from the instability of the evolutionarily stable strategy (ESS) sex ratio, and is independent of variation in relatedness. We test predictions of the model with data from a long-term study of harvester ants, and show that it correctly predicts the intermediate sex ratios we observe in our study species. The dioecy model provides a comprehensive framework for sex allocation that is based on the pay-offs to the colony via production of males and females, and is independent of the genetic variation among colonies. However, in populations where the conditions for the Boomsma–Grafen model hold, kin selection will still lead to an association between sex ratio and relatedness.     

Community impacts of two invasive crabs: the interactive roles of density, prey recruitment, and indirect effects

Assessing the implications of species invasion for native communities requires determining whether effects of invaders are novel, or are redundant with effects of species that are already present. Using a pair of field experiments conducted over two successive years, we examined factors that influence community impacts of a recent predatory crab invader (Hemigrapsus sanguineus) and a previously established invasive crab (Carcinus maenas) on New England coasts. We demonstrate that effects of these species differ temporally with changes in the ambient prey community, and are influenced by density differences between the two species and by different strengths and types of indirect effects that each elicits. Our study highlights the importance of including bottom-up processes (i.e., prey recruitment) when examining the redundancy of consumers.