Isonymy and the genetic structure of Switzerland. I. The distributions of surnames.

The surname distribution of the population of Switzerland was studied using a sample of 1,702,000 private users registered for the year 1994 in the Helvetic Telephone Directory. These users were distributed in four linguistic areas, in 26 Cantons and 271 Communes of the Confederation. Estimates of unbiased random isonymy, of Fisher's alpha, an indicator of abundance of surnames converging to the allele effective number in standard genetic polymorphisms, and of Karlin-McGregor's v, an indicator of immigration rates, were calculated for each Commune, each Canton, each linguistic area and for the whole Confederation. The Commune with the highest value of alpha was Geneva (alpha = 5312) followed by Versoix (3713) and by the Communes of Vaud on the north shore of Lake Leman, Chavannes (3381), Montreux (3200), Nyon (3114) and Lausanne (3109). The Italian-speaking Communes of the Ticino were next. The lowest value (alpha = 29) was observed in Poschiavo, south of the Berninapass; alpha = 39 was observed in Einsiedeln (Schwyz); then Mels and Widnau (62 and 67, Canton of St Gallen), Frutingen in Bern (72), and Appenzell (80). Accordingly, the highest consanguinity values were observed in the Grisons and in the nucleus of the founding Cantons, while the lowest were observed in the Cantons of Geneva and Vaud, preferential areas of immigration to Switzerland from abroad. The effect of subdivision on isonymy is large at the Commune level, and decreases in Cantons and linguistic groups. French and Italian languages indicate minor, German and Romanisch major inbreeding.