Asymmetric patterns of recovery in two habitat forming seagrass species following simulated overgrazing by urchins

The persistence of seagrass meadows reflects variation in factors that influence their productivity and consumption. Sea urchins (Amblypneustes pallidus) can over-graze seagrass (Amphibolis antarctica) to create sparse meadows in South Australia, but this effect is not observed in adjacent Posidonia sinuosa meadows despite greater densities of inhabiting urchins. To test the effect of urchin grazing on seagrass biomass, we elevated the density of urchins in meadows of A. antarctica and P. sinuosa and quantified seagrass decline. Urchins removed similar amounts of biomass from both seagrass species, but the loss of leaf meristems was 11-times greater in A. antarctica than in P. sinuosa. In a second experiment to assess the recovery of seagrass, we simulated urchin grazing by clipping seagrass to mimic impacts measured in the first experiment, as well as completely removing all above ground biomass in one treatment. Following simulated grazing, P. sinuosa showed a rapid trajectory toward recovery, while A. antarctica meadows continued to decline relative to control treatments. While both A. antarctica and P. sinuosa were susceptible to heavy grazing loss, consumption of the exposed meristems of A. antarctica appears to reduce its capacity to recover, which may increase its vulnerability to long-term habitat phase-shifts and associated cascading ecosystem changes. © 2013 Elsevier B.V.Owen W. Burnell, Sean D. Connell, Andrew D. Irving, Bayden D. Russel

Plant defence theory re-examined: nonlinear expectations based on the costs and benefits of resource mutualisms

1.  General theories of plant defence often fail to account for complex interactions between the resources required for defence expression. For example, the carbon that is used for carbon-based defence is acquired using nutrient-rich photosynthetic pigments, while nutrient gain itself requires substantial carbon allocation belowground. We should therefore expect the expression of plant defence to reflect the tight linkage between carbon and nutrient gain, yet mechanistic studies linking resource gain with plant defence theory have been slow to emerge. 2.  The overwhelming majority of plants participate in nutrition mutualisms with fungal or bacterial symbionts. We propose the resource exchange model of plant defence (REMPD) in which the costs and benefits associated with nutrition mutualisms affect plant resource status and allocation to growth and defence. The model predicts quadratic relationships between mutualist abundance and expression of defence. Within plant genotypes, both plant biomass and defence expression are maximized at optimal nutrient exchange among mutualistic partners, and as a consequence, the two are positively associated. 3.  We tested the model by growing Asclepias syriaca , the common milkweed, with two mycorrhizal fungal species in nine fungal abundance treatments. Plant growth and defence traits and mycorrhizal colonization were quantified after 14 weeks of plant growth. Linear, quadratic, saturating and exponential decay models were fit to curves relating the proportion of root colonized by mycorrhizal fungi to plant traits, and compared using AICc. 4.  As predicted by our model, increasing colonization by Scutellospora pellucida produced quadratic responses in plant growth, latex exudation and cardenolide production. In contrast, Glomus etunicatum appeared to act as a parasite of A. syriaca , causing exponential decline in both plant growth and latex exudation. As predicted by our model, plant growth was positively correlated with all defences quantified. 5.   Synthesis . The REMPD combines cost–benefit analysis of mutualisms with plant resource acquisition strategies to predict the expression of plant defence. The effects of S. pellucida and G. etunicatum on defence expression differ; however, both provide support for the model and suggest that resource mutualisms affect the expression of defence in a predictable nonlinear fashion.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79195/1/j.1365-2745.2010.01755.x.pd

Synthesis and application of photoproline - a photoactivatable derivative of proline

A convenient synthesis in optically pure form of a derivative of L-proline is described, called photoproline, containing a diazirine group at position-4 of the pyrrolidine ring, starting from L-4-hydroxyproline. The use of Fmoc-L-photoproline in the synthesis of a cyclic peptidomimetic antibiotic demonstrates that this photoprobe can be incorporated into synthetic peptides using solid-phase Fmoc chemistry. Photoproline may be of wide value in the preparation of diverse peptide-based photoaffinity probes

Behavioral approach with or without surgical intervention to the vulvar vestibulitis syndrome: A prospective randomized and non randomized study

This article describes the outcome of a behavioral approach with or without preceding surgical intervention in 48 women with the vulvar vestibulitis syndrome. In the first part of the study, 14 women with the vulvar vestibulitis syndrome were randomly assigned to one of two treatment programs: either a behavioral approach or a behavioral approach preceded by surgery In the second part of the study, 34 women and their partners were given a choice of treatment. Follow-lip data were gathered a mean of 3 and 2 1/2 years after treatment, respectively In the randomized patient population, the intervention had a positive effect on all of them: the complaints disappeared diminished or did not change but formed less of a problem. The difference in outcome between the two different treatments, a behavioral approach with or without preceding surgery, war not statistically significant. In the second non-randomized part of the study, 28 out of the 34 women (82%) chose the behavioral approach without preceding surgery. The difference in outcome between the two treatments was not statistically significant. Two out of the 28 women who chose behavioral treatment without preceding surgery had to be referred for psychiatry consultation because of serious psychosexual problems. In one woman, psychiatric treatment was successful. Three other women, whose behavioral treatment failed underwent additional surgery, which clearly helped them to overcome the deadlock in the behavioral approach. The behavioral approach should be the first choice of treatment for the vulvar vestibulitis syndrome. Surgical intervention should be considered as an additional form of treatment in some cases with the vulvar vestibulitis syndrome to facilitate breaking the vicious circle of irritation, pelvic floor muscle hypertonia and sexual maladaptive behavior