Differential susceptibility to Eucalyptus secondary compounds explains feeding by the common ringtail (Pseudocheirus peregrinus) and common brushtail possum (Trichosurus vulpecula).

The effect of two plant secondary metabolites, tannins and formylated phloroglucinol compounds (FPCs), on the intake of Eucalyptus foliage by common ringtail (Pseudocheirus peregrinus) and common brushtail possums (Trichosurus vulpecula) was studied. We manipulated the amount of tannin that was free to bind with protein by coating foliage with polyethylene glycol 4000 (PEG) and relied on natural intraspecific variation in FPC concentrations. In contrast to ringtail possums, brushtail possums showed a greater tolerance to FPCs and ate more foliage when it was coated with PEG, suggesting that tannins limited their food intake. Brushtails detected the effects of tannins through immediate oral sensations rather than through systemic effects. Ringtail possums appeared highly tolerant of foliar tannins yet susceptible to low concentrations of FPCs. We could not detect any interaction between tannins and FPCs that affected the intake of Eucalyptus foliage by either species of possum. Although ringtail and brushtail possums are widely regarded as specialist and generalist folivores, respectively, their differential susceptibility to co-occurring secondary metabolites suggests greater complexity. Each possum species appears to be a specialist in its own right, which leads to a partitioning of available foliage. Brushtails avoid tannins and ringtails avoid FPCs.

The relationship of health locus of control and cardiac rehabilitation to mastery of illness-related stress.

The study examined the relationships among participation in outpatient rehabilitation, health locus of control, and mastery of stress with coronary artery disease completed the Master of Stress Instrument (MSI) and the Multidimensional Health Locus of Control Scale. One fourth of the sample had participated in the hospital's cardiac rehabilitation programme. Results showed no difference between cardiac-rehabilitation participants and nonparticipants on mastery, internal locus of control or stress. Demographic characteristics of age, education, race and gender revealed no significant correlation with either the total MSI score or its component measures. However, internal locus of control was significantly and positively correlated to both growth and total mastery. A stronger relationship was found between internal locus of control and change. This finding supports the hypothesis that health-internals achieve higher levels of mastery.