Inbreeding from isonymy and repeated pairs of surnames in the Ebro Delta region (Tarragona, Spain).

The aim of the study was to evaluate the levels of inbreeding calculated from isonymy with its random (Fr) and nonrandom (Fn) components, and repeated pairs of surnames (RP2) and their random component (RP2r) in the Ebro River Delta region (Tarragona, Spain). This region is made up of four parishes, and data correspond to the period 1939-1995. The global results are on the same levels as observed in other studies, but the values obtained in 3 of 4 parishes are relatively high. The Fn global value is higher than Fr, as opposed to what happens in each parish, so there is a clear Wahlund effect of subdivision of the region into parishes. Among the parishes there is a clear differentiation for Amposta, with values much lower than for the rest, due to the behavior of this population, i.e., a high immigration rate.