Concordant morphological and molecular clines in a contact zone of the Common and Spined toad (Bufo bufo and B. spinosus) in the northwest of France.

BACKGROUND: Hybrid zones are regions where individuals of two species meet and produce hybrid progeny, and are often regarded as natural laboratories to understand the process of species formation. Two microevolutionary processes can take place in hybrid zones, with opposing effects on population differentiation. Hybridization tends to produce genetic homogenization, reducing species differences, whereas the presence of mechanisms of reproductive isolation result in barriers to gene flow, maintaining or increasing differences between taxa. RESULTS: Here we study a contact zone between two hybridizing toad species, Bufo bufo and B. spinosus, through a combination of molecular (12 polymorphic microsatellites, four nuclear and two mitochondrial SNP markers) and morphological data in a transect in the northwest of France. The results show largely concordant clines across markers, defining a narrow hybrid zone of ca. 30 km wide. Most hybrids in the centre of the contact zone are classified as F2 or backcrossed individuals, with no individuals assigned to the F1 hybrid class. CONCLUSIONS: We discuss the implications of these results for our understanding of the evolutionary history of these species. We anticipate that the toad contact zone here described will become an important asset in the study of hybrid zone dynamics and evolutionary biology because of its easy access and the abundance of the species involved.

Tratamiento de las anormalidades dentofaciales que acompañan al síndrome de Hallermann-Streiff / Treatment of the dentofacial abnormalitys that accompany sindrome by Hallermann-Streiff

El síndrome de Hallermann-Streiff es una enfermedad genética rara caracterizada entre otros signos, por discefalia, hipotricosis, microftalmia, cataratas, nariz picuda y enanismo proporcionado así como alteraciones en el desarrollo de los maxilares y en el número, tamaño, forma y estructura de los dientes. El caso que reportamos presentaba hipoplasia de ambos maxilares, hipodoncia, microdoncia, hipoplasia del esmalte y dientes con raices cortas, que en su conjunto alterabn la estética facial y la función masticatoria. El tratamiento de las alteraciones dentofaciales se realizó utilizando sobredentaduras habiéndose obtenido resultados estéticos y funcionales aceptables.