Fig. 2

Evolution of gonadal sex allocation (GSA) across 120 species of Macrostomum. Colors along the branches show results of an ancestral state reconstruction for GSA. Some clades are marked with Roman numerals (see the “Results” section), and species names are abbreviated (three letters for the genus, and three letters or a three-digit number, respectively, for named species and new species; see Additional file 1: Table S2 for full names). The three panels show, from left to right, residual testis size, residual ovary size, and GSA (i.e., testis area/(testis area + ovary area)), with dots representing species means and whiskers representing standard errors (no SEs are given for the former two since the residuals were calculated across all species using species means). Dot color indicates the inferred mating syndrome that the species are assigned to hypodermic (yellow), intermediate (light green), reciprocal (green), and unclear (gray). The last column (N) gives the number of specimens with a GSA estimate. Note that no SEs are drawn for species with one sample only (14 of 120) and in many cases the SEs are small and thus do not extend beyond the symbols