The Nature of Selection on the Major Histocompatibility Complex.

Only natural selection can account for the extreme genetic diversity of genes of the major histocompatibility complex (MHC). Although the structure and function of classic MHC genes is well understood at the molecular and cellular levels, there is controversy about how MHC diversity is selectively maintained. The diversifying selection can be driven by pathogen interactions and inbreeding avoidance mechanisms.

Phylogenetic and ecological determinants of the neotropical dawn chorus.

The concentration of avian song at first light (i.e. the dawn chorus) is widely appreciated, but has an enigmatic functional significance.

Serum immunoglobulin G levels are positively related to reproductive performance in a long-lived seabird, the common tern (Sterna hirundo).

The evolution of longevity requires a low risk of mortality from extrinsic factors, relative to intrinsic factors, so that individuals that differentially invest in physiological self-maintenance and minimize their annual reproductive costs will maximize lifetime fitness through a prolonged reproductive lifespan. The trade-off between reproductive effort and self-maintenance, as measured by immune function, has been well documented in short-lived birds, but is difficult to demonstrate in long-lived birds. To assess self-maintenance in a long-lived seabird, we measured serum protein levels, including immunoglobulin G (IgG = IgY), in 30 breeding pairs of common terns (Sterna hirundo) and their first-hatched (A) chicks.

Restricting fluid intake during a single meal did not affect food intake in older adults.

Restricting fluid intake has been shown to decrease ad libitum food intake in animals and young adult humans. The purpose of this study was to determine if restricting fluid intake during a meal affects food intake in older adults. In a crossover counterbalanced design, 24 subjects (11 m, 13 f), 61-95 years, received lunch at a congregate meal site.

Ecological correlates of single-seededness in a woody tropical flora.

A reduction in seed number per fruit is recognized as a common evolutionary trend among flowering plants. In order to evaluate the ecological role of single-seededness and its possible adaptive significance, we used van Roosmalen's (1985) descriptions of fruits for woody species in the Guianan flora to identify fruit and seed characters and dispersal syndromes associated with the single-seeded trait. We coded the following characters: seed number (one seed or more than one seed), fleshiness (dry or fleshy), dehiscence (dehiscent or indehiscent), dispersal syndrome, seed size (length), and fruit size (length).