Adaptation of a quantitative trait to a changing environment: New analytical insights on the asexual and infinitesimal sexual models.

Predicting the adaptation of populations to a changing environment is crucial to assess the impact of human activities on biodiversity. Many theoretical studies have tackled this issue by modeling the evolution of quantitative traits subject to stabilizing selection around an optimal phenotype, whose value is shifted continuously through time. In this context, the population fate results from the equilibrium distribution of the trait, relative to the moving optimum. Such a distribution may vary with the shape of selection, the system of reproduction, the number of loci, the mutation kernel or their interactions. Here, we develop a methodology that provides quantitative measures of population maladaptation and potential of survival directly from the entire profile of the phenotypic distribution, without any a priori on its shape. We investigate two different systems of reproduction (asexual and infinitesimal sexual models of inheritance), with various forms of selection. In particular, we recover that fitness functions such that selection weakens away from the optimum lead to evolutionary tipping points, with an abrupt collapse of the population when the speed of environmental change is too high. Our unified framework allows deciphering the mechanisms that lead to this phenomenon. More generally, it allows discussing similarities and discrepancies between the two systems of reproduction, which are ultimately explained by different constraints on the evolution of the phenotypic variance. We demonstrate that the mean fitness in the population crucially depends on the shape of the selection function in the infinitesimal sexual model, in contrast with the asexual model. In the asexual model, we also investigate the effect of the mutation kernel and we show that kernels with higher kurtosis tend to reduce maladaptation and improve fitness, especially in fast changing environments.

[Pseudomyxoma peritonei. Apropos of 19 cases]. / Maladie gélatineuse du péritoine. A propos de 19 cas.

Nineteen patients, 15 women, 4 men, mean age 65 years, were treated for pseudomyxoma peritonei between 1971 and 1991. The clinical onset was generally insidious, predominant signs being ascites (9 cases), a mass (9 cases), distension (8 cases) and abdominal pain (8 cases). Diagnosis was assisted by scan imaging and alteration in serum ACE levels. The initial mucosecreting tumor was appendicular (12 cases), ovarian (11 cases) or both (4 cases). Histology was benign in 17 of the 19 patients. After surgical treatment in all cases, 10 patients relapsed, global survival at 5 years being 65% and at 10 years 49%.

[Contusions of the liver in adults. Initial non-operative management with computerized tomography follow-up is a reasonable therapeutic option. Report of 16 cases]. / Contusions du foie de l'adulte. L'abstention opératoire initiale sous contrôle tomodensitométrique est une option thérapeutique raisonnable. A propos de seize observations.

Nonoperative management of blunt liver injury in adults still remains controversial. From February 1985 through September 1989, 27 patients were treated for blunt hepatic trauma: 11 required immediate operation and 16 (59%) were initially managed nonoperatively after evaluation of intraabdominal injury by computerized tomography. All of these 16 patients were hemodynamically stable and had no significant peritoneal signs. CT criteria for nonoperative management included subcapsular and intrahepatic hematoma, capsular tear or unilobar fracture, absence of large hemoperitoneum, absence of large devitalized liver and absence of other intraabdominal organ injuries. Clinical follow-up, repeated radiologic examinations and surgery confirmed the accuracy of CT. Only 2 patients required delayed operation (12.5%). Serial abdominal CT studies are an integral part of the conservative treatment of blunt hepatic injuries and showed complete resolution of hepatic injuries in the fourteen nonoperated patients in less than six months. No death and no delayed septic or biliary complications were noted. Mean hospital stay was seventeen days for all of the patients (multiple injuries or not) and only ten days for isolated blunt liver injury. These good results depend on identification of candidates for nonoperative management on strict clinical and CT criteria. Nonoperative management of adult blunt liver injury based on these findings is a useful alternative in a selected group of hemodynamically stable patients and decreases the rate of non-therapeutic coeliotomy.