Towards robust evolutionary inference with integral projection models.

Integral projection models (IPMs) are extremely flexible tools for ecological and evolutionary inference. IPMs track the distribution of phenotype in populations through time, using functions describing phenotype-dependent development, inheritance, survival and fecundity. For evolutionary inference, two important features of any model are the ability to (i) characterize relationships among traits (including values of the same traits across ages) within individuals, and (ii) characterize similarity between individuals and their descendants. In IPM analyses, the former depends on regressions of observed trait values at each age on values at the previous age (development functions), and the latter on regressions of offspring values at birth on parent values as adults (inheritance functions). We show analytically that development functions, characterized this way, will typically underestimate covariances of trait values across ages, due to compounding of regression to the mean across projection steps. Similarly, we show that inheritance, characterized this way, is inconsistent with a modern understanding of inheritance, and underestimates the degree to which relatives are phenotypically similar. Additionally, we show that the use of a constant biometric inheritance function, particularly with a constant intercept, is incompatible with evolution. Consequently, current implementations of IPMs will predict little or no phenotypic evolution, purely as artefacts of their construction. We present alternative approaches to constructing development and inheritance functions, based on a quantitative genetic approach, and show analytically and through an empirical example on a population of bighorn sheep how they can potentially recover patterns that are critical to evolutionary inference.

Postlaminectomy arteriovenous fistula: the Brazilian experience.

Arteriovenous fistula is an infrequent complication of lumbar disc surgery. It is often not suspected, and the symptoms are diagnosed as deep venous thrombosis or heart failure. As a result of our review of the Brazilian literature and a survey of 3,500 Brazilian physicians, 5 cases of post-laminectomy arteriovenous fistula are added to the literature. A review of these cases shows that: (1) the right common iliac artery was injured in most cases, (2) the vena cava was frequently injured, and (3) direct repair was possible when the vena cava and the aorta were injured. A vascular prosthesis was necessary when the iliac arteries were damaged. The correct diagnosis is usually made by detection of an abdominal bruit in a patient with a history of lumbar disc surgery and is confirmed by arteriogram. Surgical treatment, either by suture or bypass, is the treatment of choice and results in cure.