Figure 1. Europe-wide distribution, reproductive pathways and contact zone in Odra R. basin of studied species.

(a) Distribution area of C. tanaitica (blue circles), C. taenia (red area), and C. elongatoides (yellow area), with the directions of postglacial colonization of Europe by C. taenia (red arrows) and C. elongatoides (yellow arrow). Secondary contact zones are indicated by zigzag symbols, and the dispersal of clonal lineages is indicated by dotted arrows (modified from [13], [46], [64]); (b) inferred reproductive pathways in Cobitis complex. Sperm at straight arrow indicates true fertilization, whereas sperm at round arrow indicates a triggering the egǵs development without paternal genetic contribution to the offspring; (c) Sampling sites in the Odra R. hybrid zone. For each locality, the presence of C. taenia and C. elongatoides is indicated by red and yellow dots, respectively and we indicate co-occurring hybrid biotypes, and their number in parentheses, if more than one. For each biotype on a given sample site, we list the presence of clones (MLL) and their absolute frequencies in parentheses, if more than one.