Pollen competition as an asymmetric reproductive barrier between two closely related Silene species.

Reproductive barriers are important determinants of gene flow between divergent populations or species. We studied pollen competition as a post-mating reproductive barrier between Silene dioica and S. latifolia. Gene flow between these species is extensive, but early-generation hybrids are rare. In an experiment with conspecific, heterospecific and 50 : 50 mixed pollinations in the two species, pollination treatments did not significantly affect seed set and seed weight. However, molecular determination of siring success after mixed pollinations showed that fewer than expected hybrids were produced in S. latifolia (18% hybrids) but not in S. dioica (51% hybrids). This constitutes an asymmetric post-mating reproductive barrier and likely contributes to the rarity of early-generation hybrids. Our study shows that pollen competition can be an effective barrier to hybridization between closely related species that likely acts in concert with other reproductive barriers.

Larval host plant origin modifies the adult oviposition preference of the female European grapevine moth Lobesia botrana.

According to the 'natal habitat preference induction' (NHPI) hypothesis, phytophagous insect females should prefer to lay their eggs on the host species on which they developed as larvae. We tested whether this hypothesis applies to the breeding behaviour of polyphagous European grapevine moth, Lobesia botrana, an important pest in European vineyards. We previously found that different grape cultivars affect several life history traits of the moth. Because the different cultivars of grapes are suspected to provide different plant quality, we tested the NHPI hypothesis by examining oviposition choice of L. botrana among three Vitis vinifera cultivars (Pinot, Chasselas and Chardonnay). In a choice situation, females of L. botrana that had never experienced grapes were able to discriminate between different grape cultivars and preferentially selected Pinot as an oviposition substrate. This 'naive' preference of oviposition could be modified by larval environment: Females raised on grapes as larvae preferred to lay eggs on the cultivar that they had experienced. Furthermore, experience of the host plant during adult emergence could be excluded because when pupae originating from our synthetic diet were exposed to grapes, the emerging adults did not show preference for the cultivar from which they emerged. The NHPI hypothesis that includes the two sub-hypothesis "Hopkins host selection principle" and "chemical legacy" may thus be relevant in this system.

[The influence of the masticatory muscles on craniofacial growth. A microsurgical study in the rat]. / L'effet des muscles masticateurs sur la croissance cranio-faciale. Etude micro-chirurgicale chez le rat.

Possible influence of masticatory muscles on facial growth was investigated in the rat by the formation of several experimental groups: excision of right masseter muscle of right temporal muscle, of both masseter muscles, of both temporal muscles and of both masseter and temporal muscles, section of inferior maxillary nerve and masseter transplantation. Results demonstrated that overall masticatory muscles provided equilibrium of masticatory function, any rupture of this equilibrium producing effects on mandibular growth and that of the facial mass.

[Experimental factors influencing the growth of the jaws]. / Etudes expérimentales des facteurs influençant la croissance des maxillaires.

An experimental study evaluated the effect of various surgical procedures on maxillary growth. Raising and excision of palatine muco-periosteum did not modify facial or palatine growth. Resection of the bony palate showed the non-essential nature of the medial palaxine suture during normal growth, even in the transverse direction. Coagulation of the two posterior palaxine arteries disturbed palaxine growth, but ligature of the external carotid artery failed to alter facial growth. Several tests were carried out to determine the importance of functional matrices: excision of facial nerve trunk did not affect bone growth, destruction of the trigeminal provoked obvious disturbance of craniofacial growth while obturation of a nasal fossa produced no observable anomaly. Enucleation demonstrated the need for an intact globe for normal orbital growth, and resection of the mandibular condyle showed the primordial role of cartilaginous centers in mandibular growth.

[Early excision and grafting in facial burns]. / L'excision-greffe précoce dans les brûlures de la face.

Early excision and graft surgery is now a routinely used procedure, but whereas its application for burns of the hand has been well determined it is employed less extensively for facial lesions. It is a heavy and very hemorrhagic surgery requiring close cooperation between surgeons and intensive care physicians. Its use for the face is not easy to define, difficulties arising because of the need to establish the depth of the burn, the hemorrhagic risk involved and the need for effective compression after graft surgery.