Does evolution design robust food webs?

Theoretical works that use a dynamical approach to study the ability of ecological communities to resist perturbations are largely based on randomly generated ecosystem structures. By contrast, we ask here whether the evolutionary history of food webs matters for their robustness. Using a community evolution model, we first generate trophic networks by varying the level of energy supply (richness) of the environment in which species adapt and diversify. After placing our simulation outputs in perspective with present-day food webs empirical data, we highlight the complex, structuring role of this environmental condition during the evolutionary setting up of trophic networks. We then assess the robustness of food webs by studying their short-term ecological responses to swift changes in their customary environmental richness. We reveal that the past conditions have a crucial effect on the robustness of current food webs. Moreover, directly focusing on connectance of evolved food webs, it turns out that the most connected ones appear to be the least robust to sharp depletion in the environmental energy supply. Finally, we appraise the 'adaptation' of food webs themselves: generally poor, except in relation to a diversity of flux property.

[Placental chorioangioma. Two cases and review of the literature]. / Chorio-angiome placentaire. A propos de 2 cas et revue de la littérature.

Two cases of placental chorioangiomas were discovered, one echographically after in utero death at mid-term pregnancy and the second during the neonatal period associated with acute hydramniosis and a single umbilical artery. At 8 months, the new-born was in good health after persistent cholestasis at birth. A review of the literature of the macroscopic, histologic, echographic characteristics and the foetal-maternal complications of chorioangiomas revealed few cases of in utero death, especially so early in term.

[Pseudo-Horton disease caused by angiolymphoid hyperplasia with eosinophilia]. / Pseudo-maladie de Horton par hyperplasie angio-lymphoïde avec éosinophilie.

A case of angiolymphoid hyperplasia with intravascular eosinophilia is reported. The histologic pattern is characterized by an atypical vascular proliferation with an infiltrate composed of lymphocytes, eosinophils and mast cells. A possible intravascular proliferative process and histogenesis are discussed.

[Fetal pulmonary candidiasis complicating mycotic chorioamnionitis]. / Candidose pulmonaire foetale compliquant une chorioamniotite mycosique.

In relation to a case of pulmonary candidiasis in a seventeen week fetus, the authors review the cases of fetal candidiasis not resulting from contamination during delivery.

[Cervical thymic choristoma ]. / Chorista thymiques cervicaux.

Neck and thyroid tumors probably of thymic origin are more frequently reported since two years. It is therefore of interest to specify incidence and way of production of cervical ectopic tissue from they issue. So, authors studied 763 autopsies of fetus of various ages, newborns and infants and surgical pieces of 8 children and adults. Analysis of 72 cases of cervical thymic chorista.

[Malignant mixed mesodermal tumor of the ovary. A review of the literature apropos of a case with immunohistochemical study]. / Tumeur mixte mésodermique maligne de l'ovaire. Revue de la littérature à propos d'un cas avec étude immunohistochimique.

A very large left ovarian tumor in a 76 year old woman, on microscopic study, consisted of an epithelial component: both glandular and squamous, and a sarcomatous component: both cartilage and striated muscle. Epithelial and sarcomatous patterns were intermingled in a spindle-cell stroma. Immunohistochemical study revealed, in these spindle cells, cytokeratin-positive anaplastic epithelial structures and vimentin-positive mesenchymal structures. A review of the literature concerning this rare ovarian tumor especially including cases with a immunohistochemical study is added. However, immunohistochemical study does not allow histogenetic interpretation.